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Digestion and Performance Responses to Lasalocid and Concentrate Supplements by Beef Cattle Fed Bermudagrass Hay a
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D. S. Hubbell , Dr. A. L. Goetsch , D. L. Galloway Sr. , L. a
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A. Forster Jr. , W. Sun & Dr. K. F. Harrison
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University of Arkansas , Fayetteville, AR, 72701, USA Published online: 08 Sep 2009.
To cite this article: D. S. Hubbell , Dr. A. L. Goetsch , D. L. Galloway Sr. , L. A. Forster Jr. , W. Sun & Dr. K. F. Harrison (1992) Digestion and Performance Responses to Lasalocid and Concentrate Supplements by Beef Cattle Fed Bermudagrass Hay, Archiv für Tierernaehrung, 42:1, 79-92, DOI: 10.1080/17450399209428532 To link to this article: http://dx.doi.org/10.1080/17450399209428532
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Arch. Anim. Nutr.• 1992, Vo1.42. pp. 79-92 Reprints available directly from the publisher Photocopying permitted by license only University of Arkansas, Fayeueville. AR 7270t. USA
D. S. HUBBELL, A. L. GOETSCH*, D. L. GALLOWAY sr., L. A. FORsTERjr., W. SUN and K. F. HARRISON
Digestion and perfonnance responses to lasalocid and concentrate supplements by beef cattle fed bennudagrass hay**
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KEY WORDS Digestion, Lasalocid, beef cattle, Burmudagrass hay
I.
Introduction
Ionophores are routinely used in high-grain diets to improve feed efficiency and live weight gain (GALYEAN and HUBBERT, 1989).. With forage-based diets, ionophores generally affect performance positively, but changes are more variable than those with grain-based diets (FAULKNER et aI., 1985; GALYEAN and HUBBERT, 1989). Overall, impro vements in live-weight gain of grazing cattle with ionophores increase with increasing forage quality (COOMBE et aI., 1979; WILKINSON et aI., 1980; SPROTT et aI., 1988):Warm season grasses are usually considered to be relatively low quality. Nonetheless, OLIVER (1975) and ROUQUETTE et aI. (1980) increa~e9 performance of beef calves ingesting ber mudagrass by supplementing with monensin. Ionophores improve animal performance by increasing efficiency of energy metabo lism in the rumen and (or) animal, improving nitrogen metabolism and decreasing inci dence of digestive disorders (BERGEN, 1986). MINSON (1990) summarized that acetate: propionate in ruminal fluid is usually greater for warm- than cool-season grasses because of the low -level of nonstructural carbohydrates in warm-season grasses. Because of this and factors such as the high fibre level, low availability of glucose or associated metaboJites such as NADPH 2, glycerol phosphate and (or) oxaloacetate may limit the efficiency of energy metabolism by growing ruminants ingesting warm-season grass (MACRAE et aI., 1985; BLACK et aI., 1987a, b). Hence, an increased glucose supply with grain supplementation via increased propionate production and ruminal escape of grain starch and protein or when an ionophore is given through increased propionate and pos sibly enhanced ruminal escape of feed protein should contribute to improvements in animal performance. Low readily fermentable substrate content, cell wall degradability and voluntary con sumption of warm-season grasses relative to cool-season grasses and high ruminal degradability of forage proteins can yield insufficient availability of amino acids for high live-weight gain of growing beef cattle (MCCOLLUM and HORN, 1990). Thus, increased microbial protein synthesis and (or) ruminal outflow of feed protein by grain or protein meal supplementation could increase live-weight gain. Ionophores lower duodenal microbial protein flow in some cases and, therefore, may not increase performance if a
* **
Reprint requests. Published with the approval of the Director of the Arkansas Agricultural Experiment Station.
79
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80
D.S. HUBBELL ET AL.
depression in microbial protein synthesis outweighs enhanced ruminal outflow of undegraded feed protein with decreased ruminal proteolysis (VAN NEVEL and DEMEYER, 1977). Supplementation with a low level of com (e.g. less than 0.5 % of live weight) generally only slightly impairs bermudagrass fibre digestion (FORSTER et aI., 1990; GAL LOWAY et aL, 1991; SUN et aI., 1991). Ionophores have de'pressed fibre digestion with high-forage diets in many cases (ELLIS et aI., 1983), and postruminal fibre digestion can not compensate if the ruminal depression is severe. The likelihood and magnitude of depressed fibre digestion with ionophores is greater with mature or low-quality forage than with immature or high-quality forage (ZORRILLA-RIOS et aI., 1985). Concentrate supplements such as com, protein meals and ionophores can affect similar animal conditions (e.g. volatile fatty acid levels, supplies of glucose and amino acids and fibre digestion). Hence, supplementation and supplement composition may alter effects of an ionophore on digestion and performance by beef cattle. This study was conducted to determine if supplementing beef cattle ingesting bermudagrass hay with a low level of com alone or plus a mix of protein meals would change e.ffects of lasalocid on digestion . and performance.
2.
Materials and methods
2.1.
Experiment 1, digestion
2.1.1.
Animals and diets
Six beef cows (average initial and final live weights of 477 and 502 kg, respectively; Angus, Hereford or Angus x Hereford) fitted with ruminal and duodenal cannulae were used in a digestion study with 14-day periods in a 6 x 6 Latin square design. Cows were housed in 3.1 m x 4.6 m pens and given free access to water. COWS received a basal ration of bermudagrass hay (Basal, B) or were supplemented with ground com (C) or com plus a mix of protein meals (CP). Approximately 0.25 % of live-weight of com was supplemented; the protein meal mix consisted of 50 % hydrolyz ed feather meal, 25 % blood meal and 25 % soybean meal and was fed at approximately 0.048 % of live-weight (dry matter basis). In addition, cows received a mixed mineral supplement supplying 11.0 g NaCl and 3.7 g trace mineral mix alone or with 1.33 g Bovatec®~·· (providing 200 mg lasalocid daily; L). Trace mineral mix was comprised of 12 % Zn, 10 % Fe, 8 % Mn, 5 % K, 2.5 Mg, 1.5 % Ca, 0.3 % I, 0.1 % Co and 0.02 % Se. Mineral supplements were fed alone or mixed with other concentrates and given in small buckets. Supplements were given at 10.00 h and consumed in less than 15 minutes. Bermudagrass (Table 1; Cynodon dactylon) hay (second harvest, cut in the mid- to full bloom growth stage in late-summer and drought-stressed) was fed in two equal meals at 07.00 hand 16.00 h so that total daily dry matter (DM) intake approximated 1.25 % of live-weight/day. Very small hay refusals occurred occasionally and were measured.
***
Hoffman-La Roche, Inc., Nutley, NJ.
LASALOXID AND CONCENTRATE SUPPLEMENTS
81
Table 1
Feedstuff composition (% dry matter)
Experiment 1 Corn CP*
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Item Dry maller** Ash Crude protein Neutral detergent fibre Acid detergent fibre Acid detergent lignin Cellulose Hemicellulose Potassium Sodium
87.4 1.5
10.3 1l.8 2.9
0.29 0.00
88.2 1.9 22.8 18.3 5.0
0.36 0.02
Hay 93.7 7.3 12.8 72.8 33.6 5.1 26.8 39.1 1.90 0.10
Experiment 2 Corn CP* 86.3 1.5 11.0
0.28 0.00
87.1 2.0 22.1
0.33 0,0\
Hay 94.3 6.9 10.7
81.3 38.2 5;5 31.8 43.1 1.73 0.02
* Corn + protein meals ** % air-dry
2.1.2.
Sampling procedures
Each experimental day began at the 07.00 h meal. On day 12, 100 ml of cobalt-ethylene diaminetetraacetic acid (UDEN et aI., 1980) was dosed into the rumen immediately prior to the 07.00 h meal. Ruminal fluid was sampled (450 ml) at 16.00 and 01.00 h on day 12 and at 10.00, 19.00 and 04.00 h on day 13. The pH was measured immediately, and sam ples were strained through eight layers of cheesecloth. For each cow, approximately 250 ml of each sample was composited in a saline-formalin solution (MERCHEN and SAlTER, 1983), and the other 200 ml was frozen after adding 2 ml of 20 % (volume/vol ume) sulfuric acid solution. Duodenal (spot sample) and faecal (grab) samples were obtained at the same times ~s ruminal fluid at 07.00 h on day 12 (immediately before the meal) and on day 14 at 13.00 and 22.00 h. Composites of duodenal and faecal samples were formed (wet basis) for each 'cow and period and stored frozen. Duodenal samples were divided into two portions, one being lyophilized and the other being refrozen. Fae cal samples were lyophilized and ground through a I-mm screen. Hay compos~tes for each period were constructed by sampling daily on day 10 to 14, and supplements were sampled once during this period.
2.1.3.
Analytical procedures
Composite samples of feed and duodenal and faecal digesta were analyzed for DM, ash, Kjeldahl nitrogen (N; AOAC 1975), neutral detergent fibre (NDF; ROBERTSON and VAN SOEST, 1981), acid detergent fibre (ADF; GOERING and VAN SOEST, 1970) and acid insoluble ash (AlA; VAN KEULEN and YOUNG, 1977). Feeds were analyzed for acid deter gent lignin (GOERING and VAN SOEST, 1970). Neutral detergent fibre and ADF analyses were conducted on air-dry samples, cellulose was estimated as weight loss upon sulfuric acid treatment and hemicellulose was calculated by subtracting ADF from NDF. Amylase
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D.S. HUBBELL ET AL.
was used in supplement NDF analysis (CHERNEY et aI., 1989). Dry duodenal composites were analyzed for purines with ribonucleic acid as a standard (ZINN and OWENS, 1986). Wet duodenal digesta was assayed for ammonia-N (BRODERICK and KANG, 1980) and for DM. A composite of each feedstuff was analyzed for potassium and sodium (HUANG and SCHULTE, 1985; ZARCINAS et aI., 1987). Bacterial cells isolated by differential centrifugation (MERCHEN and SATTER, 1983) of ruminal fluid stored in saline-formalin were lyophilized, crushed and analyzed for DM, ash, N and purines. Frozen ruminal fluid samples were thawed at room temperature, and portions were centrifuged at 10000 x g for 10 minutes. The supernatant was analyzed for cobalt by atomic absorption spectroscopy. Ammonia-N concentration for ruminal fluid samples at 10.00 and 16.00 h was measured, and a portion of supernatant from these sam ples was recentrifuged and analyzed for volatile fatty acids (VFA; ERWIN et aI., 1961). Acid insoluble ash was used as an internal marker for digestion estimation. The per centage of microbial N in duodenal digesta was obtained by dividing duodenal digesta nucleic acid concentration by the ratio of nucleic acids to total N in bacterial cells, and microbial organic matter (OM) was derived by use of bacterial cell N and OM concentra tions. Ruminal microbial growth efficiency was estimated as g microbial N/kg OM fer mented, adjusted for microbial OM. Subtracting microbial Nand ammonia-N from total N at the duodenum yielded apparent feed N. Ruminal digestibilities are given unadjusted (apparent) and adjusted (true) for non-feed constituents. Fluid dilution rate was estimated by regressing'the natural logarithm of marker concentration against time after administra tion. Volume was calculated by dividing marker dose by the extrapolated concentration at time zero, and outflow rate arose from multiplying dilution rate by volume.
2.104.
Statistical analyses
Data were analyzed by analysis of variance with animal, period and treatment in the statistical model. Orthogonal contrasts were made to test for effects of supplementation (B and B-'-L vs other treatments), supplement type (C and C-L vs CP and CP-L), lasalo cid (B, C and CP vs B-L, C-L and CP-L) and interactions between lasalocid and supple mentation and supplement type. For ruminal fluid pH and concentrations of ammonia-N and VFA, effects of sampling time and the time by treatment interaction were determin ed. Values averaged over time were presented when the time by treatment interaction was not significant (P> .10). Analyses were conducted by procedures outlined by Statistical Analysis System (SAS, 1985).
2.2.
Experiment 2
2.2.1.
Animals and diets
Sixty Brangus-crossbred heifers (236.2 ± 2.36 kg) and 60 steers (236.8 ± 2.38 kg) were used in an experiment at the University of Arkansas Livestock and Forestry Research Station near Batesville. Calves were born from 22 February 1988 to 12 April 1988, weaned on 14 October 1988 and fed a small amount of supplemental concentrate from weaning until trial initiation. Calves were treated for internal and external parasites at
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LASALOXID AND CONCENTRATE SUPPLEMENTS
83
weaning and had not previously consumed grain or received a growth stimulant. The trial began on 8 November 1988 when calves were approximately 7.5 months old. Calves were weighed (unfasted) early in the morning on days 1, 21, 42, 63 and 84. On day 1, steers were implanted with 200 mg progesterone and 20 mg estradiol benzoate (Syno vex-S®***) and allotted to 12 groups (5 heifers and 5 steers/group) for similar mean and variation in live-weight. Two groups of calves were assigned to each of the treatments in Experiment 1, except that feeding rates were 0.35 % live weight for corn and 0.067 % live weight for the pro tein meal mix (OM basis). Concentrate amounts were based on 21-day live-weight meas ures, and supplements were given at 09.00-10.00 h. Concentrate consumption was com plete in less than 30 minutes. However, Band B-L calves did not completely consume mineral supplements (92 and 83 % consumption, respectively), resulting in lasalocid in take of 145 mg/head and day for B-L calves. In addition, 35.4 g/head and day of dicalci urn phosphate was offered in a separate feeder; consumption averaged 16.9 g/head/day. Animals were placed in 12 2.0-hectare paddocks consisting predominately of common . bermudagrass, with some tall fescue (Festllca arundinacea) and weed species. Growing herbage was minimal throughout the study, and consumption of paddock herbage appear ed negligible. All paddocks contained a feeder in which large round bales of Tifton-44 bermudagrass hay (Table 1) were offered ad libitum. Bales were weighed, samples were taken before placement in feeders, ·and residual hay was weighed at the end of the study. Feedstuffs were analyzed as in Experiment 1.
2.2.2.
Statistical analyses
Data were analyzed with a split-plot design, with supplement treatment as the main plot and sex as the subplot. Contrasts used in Experiment 1 were employed. Feed intake and feed efficiency (calculated from average group intakes and live-weight gain) were analyzed with treatment in the model and the same contrasts.
3.
Results
3.1.
Experiment I, digestion
3.1.1.
Diets and digesta composition
Feedstuff composition is in Table 1. Ruminal pH, VFA molar proportions and total VFA concentration were not affected by the time by treatment interaction (P > 0.10). Lasalocid increased pH in unsupplemented cows but had little effect with supplementation (interac tion, P < 0.08; Table 2). The molar proportion of acetate (Table 2) was lower with than without lasalocid (P < 0.07) and that of propionate was higher (P < 0.10) with lasalocid, resulting in an effect of lasalocid on the acetate: propionate ratio (P < 0.06). The butyrate molar proportion was lower without than with supplementation (P < 0.05). Total VFA concentration in ruminal fluid was similar among treatments (P > 0.10). As expected,
*** Syntex Agribusiness, Inc., West Des Moines, lA, USA.
D.S. HUBBELL ET AL.
84 Table 2
Effects of supplementation with different concentrates and lasalocid on ruminal fluid characteristics for beef cows consuming berrnudagrass hay, experiment I
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Item
Treatment* B-L B
pH 6.56 VFA *** (molar %) Acetate 76.8 14.1 Propionate Isobutyrate 0.5 Butyrate 8.5 Isovalerate 0.6 Valerate 0.6 Total VFA (mMII) 101.6 Acetate: propionate 5.39 Ammonia-nitrogen (mg/dl) 10.00h 8.5 16.00h 5.0 Dilution rate (%!h) 6.48 Volume (I) 68.1 Outflow (ljh) 4.18
C-L
C
CP
CP-L
SE
E**
6.64
6.50
6.50
6.54
6.52
0.030
5,s -I
73.7 15.7 0.6 8.7 0.8 0.5 100.9 4.67
74.3 14.1 0.6 9.7 0.6 0.7 100.9 5.26
73.6 15.1 0.6 9.5 0.7 0.5 102.3 4.85
74.1 14.5 0.6 9.3 0.7 0.7 91.7 5.12
71.9 16.5 0.8 9.3 0.6 0.6 99.1 4.55
1.02 1.07 0.06 0.24 0.10 0.09 7.00 0.352
I
9.4 4.0 5.27 89.0 4.46
8.5 2.3 6.11 73.7 4.25
12.6 3.1 7.11 53.8 3.63
10.0 3.9 7.11 55.8 3.76
9.1 5.3 5.84 79.5 4.42
1.23 0.67 0.443 7.53 0.291
I
5, t 5 I
t-l T, s-l s, T-L s, T-L T-L
B =basal, no supplementation; C =supplementation with com; CP =supplementation with com plus protein meals; L = lasalocid ** Effect: 5 and s = supplementation (P < 0.05 and 0.10, respectively); T and t = supplement type (P < 0.05 and 0.06, respectively); 1= lasalocid (P < 0.1 0); s - I interaction between supplemen tation and lasalocid (P < 0.09); T - Land t -I =interaction between supplement type and lasalo cid (P < 0.05 and 0.06, respectively) *** Volatile fatty acids
*
sampling time and treatment tended to interact (P < 0.11) in ruminal ammonia-N concen tration. At 10.00 h adding lasalocid to corn alone increased the concentration whereas a slight depression occurred when lasalocid was added to com plus protein meals (interac tion, P < 0.06; Table 2). The level of ammonia-N at 16.00 h was lower (P < 0.05) for com when given alone than with the protein meals; lasalocid decreased the concentration without supplementation and increased the level with concentrate. Lasalocid increased fluid dilution rate and decreased volume and outflow rate with corn given ;Ilone but decreased dilution rate and increased volume and outflow rate when com plus protein meals were supplemented (interactions, P < 0.05; Table 2). Percentages of N (9.2-9.6) and nucleic acids (8.3-8.7) in bacterial cells were similar among treat ments (P > 0.10).
3.1.2.
Digestion
Com alone and plus protein meals comprised 21 and 25 % of total OM intake, respectively (Table 3). Flows of total, microbial and nonmicrobial OM and apparent and true ruminal OM digestibilities were similar among treatments (P> 0.10). Faecal. OM was lower with than without supplementation, and postruminal and total tract OM digest
85
LASALOXID AND CONCENTRATE SUPPLEMENTS
Table 3 Effects of supplementation with different concentrates and lasalocid on organic matter digestion in beef cows consuming bermudagrass hay, experiment I
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Item Passage, kg/day Intake Supplement Hay Total Duodenum Total Microbial Nonmicrobial Faeces Digestion, % Apparent ruminal True ruminal Postruminal Total tract
Treatment* B B-L
0.00
5041 5041 2.68
DAD 2.28 2.37 49.9 57.7 6.0 56.0
C
C-L
CP
CP-L
0.00 5.43 5.43
1.15 4.28 5.43
1.15 4.35 5.50
1.35 4.16 5.51
1.37 4.17 5.53
2.68 0.40 2.28 2.42
2.73 0.43 2.30 2.04
2.85 0.41
2.67
0041
2.83 0.45 2.39 2.04"
50.3 57.8 5.0 55.3
49.8 57.7 12.4 62.1
2044 2.09 48.9 56.2 13.2 62.1
2.26 2.09
5104 58.9 10.6 6-2.0
48.7 56.8 14.1 62.8
SE
Eb
0.160 0.030 0.142 0.058
S
2.68 2.40 2.56 0.93
S S
* B =basal, no supplementation; C =supplementation with com; CP =supplementation with com plus protein meals; L = lasalocid ** Effect: S = supplementation (P < 0.05) ibilities were greater with supplementation (P < 0.05). Postruminal digestion as a percen tage of OM at the duodenum was 11.6,9.2,21.7,24.7,2004 and 26.8 % (SE 3.99) for B, B-L, C, C-L, CP and CP-L, respectively. Ruminal NDF digestion was lower with than without supplementation (P < 0.05; Table 4). Ruminal NDF and ADF digestibilities were depressed (P < 0.10) by lasalocid. Treatment did not affect total tract digestion of NDF and ADF, indicating compensatory postruminal fibre digestion (Iasalocid effects: NDF, P < 0.06; ADF, P < 0.08). The degree to which total duodenal N (Table 5) was lower than intake was similar among treatments in g/day and as a percentage of intake. Microbial N flow was similar among treatments; Apparent feed N (feed plus endogenous) at the duodenum was affected by supplementation and was greater (P < 0.05) for supplementation with com plus protein meals than for supplementation with com alone. Rumen microbial growth efficiency was similar among treatments (P> 0.10), ranging from 13.5 to 15.1 g mi crobial N/kg OM fermented (SE lAO). Ammonia-N at the duodenum in this study vari ed with supplementation (P < 0.05), supplement type (P < 0,06) and the supplementa tion by lasalocid interaction (P < 0.05). The interaction coincides with that for ruminal ammonia-N at 16.00 h. The only effect of treatment on N digestion was a depression in true ruminal disappearance with supplementation (P < 0.09; Table 5). By applying ruminal digestibilities of hay crude protein for Band B-L to supplement treat ments (within lasalocid group), lasalocid appeared to slightly depress ruminal N disappearance of supplement and (or) hay. Postruminal N disappearance as a percentage of N at the duodenum was not affected by treatment (P > 0.10; 54.0-5804 %, SE 2.30).
86
D.S. HUBBELL ET AL.
Table 4 Effects of supplementation with different concentrates and lasalocid on digestion of neu tral detergent fibre (NDF) and acid detergent fibre (ADF) in beef cows consuming ber mudagrass hay, experiment 1
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Item NDF passage (kg/d) Intake Duodenum Faeces NDF digestion (%) Ruminal Postruminal Total tract ADF passage (kg/d) Intake Duodenum Faeces ADF digestion (%) Ruminal Postruminal Total tract
Treatment* B-L B
C
C-L
CP
CP-L
4.24
4.27
3.49
3.55
3.52
3.51
1.71 1.72
1.86 1.74
1.47 1.42
1.65 1.45
1.50 1.45
1.62 1.40
59.9 -0.6 59.2 1.96 0.90 0.91 54.3 -1.3 53.0
56.5 2.6 59.1
58.1 0.9 59.0
1.98 0.95 0.93 51.6 0.8 52.4
1.59 0.75 0.74 52.4 0.3 52.7
54.9 4.1 59.0 1.60 0.86 0.76 47.5 5.2 52.7
57.2 1.6 58.8 1.58 0.77 0.76 51.0 0.7 51.7
53.9 6.0 59.9 1.57 0.81 0.74 48.3 4.4 52.7
SE
E**
0.082 0.041
S,L S
2.26 2.15 1.03 0.039 0.019
S,I S
2.46 2.36 1.08
* B:o basal, no supplementation; C:o supplementation with com; CP:o supplementation with com plus protein meals; L:o lasalocid . ** Effect: S :0 supplementation (P < 0.05); L and 1:0 lasalocid (P < 0.05 and 0.10, respectively) Table 5 Effects of supplementation with different concentrates and lasalocid on nitrogen disap pearance in beef cows consuming bermudagrass hay, experiment 1 Item
Treatment* B-L B
Passage (g/d) Intake
Supplement 0.0 Hay 119.6 Total 119.6 Duodenum Total 102.3 Microbial 42.1 Nonmicrobial 53.3 Ammonia 7.0 Faeces 44.8 Digestion, % Apparent ruminal 11.2 True rumin"al 53.6 Postruminal 50.6 Total tract 61.8
SE
E**
129.0 45.6 77.3 6.1 53.2
6.29 3.01 4.42 0.37 1.99
S,T
9.2 45.6 53.5 62.7
4.41 3.23 4.12 1.31
C
C-L
CP
CP-L
0.0 118.9 118.9
19.3 94.0 113.3
19.3. 97.7 117.0
50.2 91.7 141.9
50.6
93.8
144.4
101.9 41.0 54.7 6.2 46.9
102.4 43.8 54.9 4.7 45.6
107.5 42.9 59.1 5.4 45.5
120.7 42.2 72.9 5.5 54.6
12.6 52.8 48.0 60.6
8.0 51.3 51.5 .59.4
7.2 48.2 53.6 60.9
14.4 48.0 47.2 61.7
S,T S,t,SoL S,T s
* B:obasal, no supplementation; C:osupplementation with com; CP:osupplementation with com plus protein meals; L:o lasalocid ** Effect: Sand S:o supplementation (P < 0.05 and 0.09, respectively); T and t:o supplement type (P < 0.05 and 0.06, respectively); SoL interaction between supplementation and lasalocid (P 0.10). Response to concentrate supplementation was fairly similar among treatments for the 42-day periods, but the change in live-weight gain when the protein meal mix was added to supplemental com was larger on day 1-42 (supplement type effect; P < 0.05) than on day 43-84 (P > 0.10). Table 6 Effects of supplementation with different concentrates and lasalocid on live-weight gain, dry matter (DM) intake and gain: feed DM for beef calves consuming bermudagrass, experiment 2 Item
Treatment*
Daily gain (kg) Day 1-42 Day 43-84 Day 1-84 DM intake (kg/d) Supplement Hay Total Gain: feed DM Hay Total feed
B
B-L
C
C-L
CP
CP-L
SE
0.29 0.60 0.44
0.27 0.52 0.39
0.42 0.75 0.59
0.45 0.72 0.59
0.54 0.82 0.68
0.64 0.78 0.71
0.060 0.098 0.059
S,T .S S
0.00 5.13 5.13
0.00 5.45 5.45
0.88 4.97 5.84
0.88 4.58 5.46
1.06 4.99 6.05
1.06 5.04 6.11
0.207 0.210
s S, t
0.088 0.088
0.072 0.072
0.118 0.100
0.129 0.108
0.136 0.112
0.141 0.116
0.013 0.012
S S
E**
* B::: basal, no supplementation; C =supplementation with com; CP =supplementation with com plus protein meals; L =lasalocid ** Effect: Sand s =supplementation (P < 0.05 and 0.08, respectively); T and t =supplement type (P < 0.05 and 0.10, respectively) For the entire study, adding the protein meal mix to com tended (P < 0.12) to improve live-weight gain. Feed conversion was more efficient (P < 0.05) with than without supplementation. Supplementation decreased hay intake (P < 0.08) and increased total DM consumption (P < 0.10; Table 6). Daily live-weight gain was greater for implanted steers than for nonimplanted heifers on day 1-42 (P < 0.05), day 43-84 (P < 0.06) and day 1-84 (P < 0.05; 0.62 vs 0.52 kg). Sex did not interact with treatment in live-weight gain (P> 0.10).
4.
Discussion
4.1.
Digesta characteristics
Only a small effect of supplementation in Experiment 1 on ruminal pH may relate to the low amount of concentrate given and high saliva flow caused by the high NDF level in hay. An explanation for the supplementation x lasalocid interaction in ruminal pH is not
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apparent. Restricted feeding probably limited magnitudes of change in VFA levels with lasalocid and contributed to the lack of effect of supplement treatments. Effects of lasalocid on ruminal ammonia-N concentration in Experiment I differed with supplement treatmertt, suggesting that changes in the microbial population affecting proteolysis and deamination with lasalocid varied with supplement treatment. Treatment effects on ruminal fluid volume (Table 2) may have been involved as well. Ionophores often decrease ruminal ammonia-N concentration (VAN NEVEL and DEMEYER, 1977; however, GADO et al. (1986) increased ruminal ammonia-N concentration in beef steers fed 20 or 80 % concentrate diets by giving 300 mg lasalocid. Reasons for interactions in Experiment 1 between lasalocid and supplement treatments in fluid dilution rate, volume and outflow rate are not apparent. Ionophores have decreas ed digesta passage rate with depressed feed intake (Pmm and ELLIS, 1979; Pmm et aI., 1980). However, in one trial POND and ELLIS (1979) supplemented heifers grazing ber mudagrass with monensin and increased feed intake while decreasing digesta passage. DESWYSEN et al. (1987) observed less ruminal contractions and motility with monensin supplementation. Similar effects of lasalocid have not been shown yet, and lasalocid may have less effect on host metabolism than monensin (ARMSTRONG and SPEARS,1988).
4.2.
Supplementation and supplement type
In Experiment 2, increased overall live-weight gain with com was probably in response to an improved energy, glucose and (or) amino acid status. Results in Experiment 1 suggest that com did not markedly affect VFA levels. The trend for increased live-weight gain when the protein meal mix was added to com may be because of the trend for higher total DM intake, possibly in relation to an improved amino acid status (EGAN, 1977), although increased feed intake would not necessarily be solely responsible (MCCOLLUM and HORN, 1990). High postruminal digestion in supplemented animals in Experiment I appeared largely a function of digestion of concentrate escaping ruminal degradation. Grain supplementa tion can shift fibre digestion postruminally, but only a small change seems likely in Experiment I with the low dietary concentrate level, restricted feed intake and the resul tant high ruminal pH. Alternatively, a greater effect seems possible in Experiment 2. Microbial N flow to the intestines in Experiment 2 may have been increased with com, although results of Experiment I and steady total intake when com was offered in Exper iment 2 suggest that any such change was not large. No effect of com on ruminal capture of forage N in Experiment I probably relates to restricted, constant feed intake. However, the higher level of NDF in bermudagrass in Experiment 2 than in Experiment I would have provided greater opportunity for the increased quantity of fcrmentable OM with com addition to incrcase microbial growth.
4.3.
Lasalocid effccts and interactions
Lasalocid did not affect live-weight gain in Experiment 2. Lasalocid has increased per formance of beef cattle consuming diets based on forage of higher quality than this ber mudagrass hay (WILKINSON et aI., 1980; GALYEAN and HUBBERT, 1989). But, OLIVER
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(1975) increased live-weight gain of beef steers grazing bennudagrass of unknown quali ty by adding different levels of monensin to 0.91 kg (air-dry) of com. Furthennore, live weight gain by beef calves grazing bennudagrass in two trials was increased by supple menting with 200 mg daily of monensin, but quality of grazed forage was higher than of bennudagrass hay in Experiment 2 (ROUQUETIE et aI., 1980). No effect on live-weight gain of lasalocid or interaction with supplementation treat ment in Experiment 2 coincide with constant total tract digestion and postruminal N flow and only small changes in VFA proportions in Experiment ~. Ad libitum forage intake and fast digesta passage from the rumen in Experiment 2 may have led to a greater effect of lasalocid on fibre digestion relative to that in Experiment I. Perhaps shorter residence of digesta in the gut with high feed intake in Experiment 2 prevented high and compensa tory postruminal digestion. Negative effects of ionophoreson fibrolytic capacity of rumi nal microbes may hinder efficacious use of ionophores to increase live-weight gain by growing animals consuming low quality forage (COO~lBE et aI., 1979; WALLACE etal., 1981; BOGAERT et aI., 1989). Full complements of fibrolytic microbes and activities seem more imperative to high forage digestion and animal perfonnance with low-·than high quality forage. Lower total tract fibre digestion with than without lasalocid in Exper iment 2 could have countered the increased capture of feed energy in y'FA and more effi cient host metabolism with lasalocid as a consequence of the altered digestion product array (WALLACE et aI., 1981; BERGEN, 1986; GALYEAN and HUBBERT, 1989). The lack of effect of lasalocid on live-weight gain in Experiment 2 suggests that glu cose precursors with all supplement treatments were adequate to achieve potential rates of live-weight gain and accretion of tissue detennined by the rate and pattern of energy derivation from microbial and host digestion. Conversely, the increased supply of glucose precursors with lasalocid may have been offset by the lower total energy status with depressed fibre digestion. Because live-weight gain tended to increase when the protein meal mix was added to com but did not rise further when lasalocid was added, amino acids spared from breakdown with lasalocid did not seem stimulatory to live-weight gain, perhaps because of similar energy available for live-weight gain regardless of lasalocid addition. The lack of interaction in live-weight gain of sex and lasalocid implies that dif ferences between sexes in nutrient needs because of varying body composition were not great (e.g. higher glucose demand for NADPH 2 and glycerol phosphate needed for fat synthesis for nonimplanted heifers than for implanted steers; MCCOLLUM and HORN, 1990), perhaps in relation to young animal age and similar pre-trial treatment. Or, greater total live-weight gain and protein accreation by implanted steers may have compensated for a higher percentage of fat in tissue accreted by heifers. Other factors that may have influenced these results include dietary levels of minerals and the ionophore. Concentrations of potassium in bennudagrass hays were considerably higher than in most high-grain diets. BERGEN (1986) and GALYEAN and HUBBERT (1989) discussed effects of dietary mineral levels on bacterial cell membrane ion gradients and ionophore effectiveness. A relatively high dietary potassium level can minimize effects of lasalocid. Perhaps this was responsible for the disparity between results with lasalocid in Experiment 2 and those of OLIVER (1975) and ROUQUETIE et al. (1984) with monensin. However, consistent effects of lasalocid with different supplement treatments in Experi ment 2 indicate that dietary potassium level did not have a large effect on lasalocid actions. In addition, the level of lasalocid in high-forage diets can affect perfonnance (THoNNEY et aI., 1981; GUTIERREZ et aI., 1982), as also has been noted for monensin
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(OLIVER, 1975; FAULKNER et aI., 1985). Quadratic responses in live-weight gain to increasing lasalocid level may result from reduced feed intake and (or) digestion at high levels (THONNEY et aI., 1981; GUTIERREZ et aI., 1982). Conversely, ANDERSON and HORN (1987) increased live-weight gain by heifers grazing wheat forage with 200 mg lasalocid but not with 100 mg. The lack of effect of lasalocid onfeed intake in Experiment 2 sug gests that feed intake was not involved in steady live-weight gain. Supplementing beef cattle consuming bermudagrass hay with lasalocid did not im prove performance regardless of concentrate supplementation or supplement type. Some interactions occurred between lasalocid and supplement treatment in characteristics of ruminal fluid but not in digestion. Perhaps impaired digestion with lasalocid coupled with minor changes in VFA production prevented effects of the ionophore on performance, similar to findings of COOMBE et al. (1979) as.suggested by WALLACE et al. (1981). Pos sible compensatory changes in digestion and metabolism with lasalocid apparently did not vary with concentrate supplement treatment or differences in animal performance induced by supplement treatment and animal type. Further research should be conducted to determine characteristics of forages, animals and ionophore administration which govern effects of ionophores on performance of growing cattle consuming forage.
Summary Beef cattle consuming bermudagrass hay were not supplemented or received a limited amount of ground com alone or with a mix of protein meals to determine influences of concentrate supplementation on digestion and performance when the ionophore lasalocid (200 mg daily) was given. With limited feed intake, supplement treatment did not change the acetate to propionate shift in beef cows occurring with lasalocid (P < 0.06). Lasalocid did not affect sites of digestion of organic matter or nitrogen with any supplement treat ment. However, lasalocid decreased (P < 0.10) ruminal digestion of neutral and acid detergent fibre. Live-weight "gain by growing beef calves ingesting bermudagrass hay ad libitum was higher (P < 0.05) with than without supplementation and tended (P < 0.12) to be greater for com plus protein meals than for com alone. Lasalocid did not affect or interact with supplement treatment in feed intake or live-weight gain of heifers (236 kg; no growth stimulant) or steers (237 kg; treated with 200 mg progesterone and 20 mg estradiol benzoate). Lasalocid at 200 mg daily did not improve digestion characteristics or influence performance by beef cattle consuming a Basal diet of bermudagrass hay. Further, effects of lasalocid were not modulated by supplementation with concentrate, concentrate type or sex or growth stimulant usage.
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Zusammenfassung D. S. HUBBELL, A. L. GOETSCH, D. L. GALLOWAY sen., L. A. FORsTERjun., W. SUN und K. F. HARRISON
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Auswirkung von Lasalocid- und Konzentratzusatzen zu' Bermudagrasheura tionen auf die Verdauung und die Leistung von Fleischrindem Die Bermudagrasheurationen fUr Fleischrinder erhielten keine Zusatze oder nur eine begrenzte Menge Maismehl oder ein Gemisch von Proteinmehl, urn die Auswirkung des Zusatzes von Konzentrat auf die Verdauung und die Leistung zu bestimmen, wenn das Ionophor Lasalocid zugesetzt wurde (200 mg/d). Bei limitierter Futteraufnahme wandelte der Zusatz das Azetat in den Fleischktihen nicht zu Propionat urn, wie es bei Lasalocid geschieht (P < 0,06). Lasalocid beeintriichtigte durch keinen Zusatz den Verdauungsort von organischer Substanz oder Stickstoff, jedoch verringerte Lasalocid (P < 0,10) die Verdauung von neutralen oder sauren Detergenzfasem im Pansen. Die Lebendmasse zunahme von wachsenden Fleischkalbem bei ad-libitum-Aufnahme von Bermudagrasheu war' mit Supplementierung heher (P < 0,05) als ohne und envies sich fUr Mais- und Pro teinmehl hoher als fUr Mais allein. Lasalocid reagierte nicht mit anderen Zusatzen tlnd beeintrachtigte nicht die Futteraufnahme oder die. Lebendmassezunahme von Farsen (236 kg; keine Wachstumsstimulanzien) oder Bullen (237 kg; behandel.t mit 200 mg Pro gesteron und 20 mg Estradiolbenzoat). Eine Dosis von 200 mg/d verbesserte die Ver dauungseigenschaften nicht und hatte keinen EinfluB 'auf die Leistung von Fleisch rindem, die eine Basalration von Bermudagrasheu erbielten. Damber hinaus wurden die Auswirkungen von Lasalocid nieht durch den Zusatz von Konzentrat, die Art des 15:on zentrats, das Geschlecht der Tie!C oder den Gebrauch von Wachstumsstimulanzien modu liert.
References ANDERSO:-l, M. A. and G. W. HORN: J. Anim. Sci. 65, 865 (1987)
AOAC: Official Methods of Analysis (12th edn.): Association of Official Analytical Chemists.
Washington, DC (1975) ARMSTRO"G, J. D. and J. W. SPEARS: J. Anim. Sci. 66, 1807 (1988) BERGEN, W. G.: Michigan State Res. Resp. 473, 52 (1986) BLACK, J. L., M. GILL, D. E. BEEVER, J. H. M. THORNLEY and J. D. OLDHAM: J. Nutr. 117, 105 (l987a) BLACK, J. L., M. GILL, D. E. BEEVER, J. H. M. THORI'LEY and J. D. OLDHAM: J. Nutr. 117, 116 (I 987b) BOGAERT, C., L. Gm.IEZ, J. P. JOUANY and G. JE:\IINET: Anim. Feed Sci. Techno!. 27, I (1989) BRODERICK, G. A. and J. H. KANG: J. Dairy Sci. 63, 64 (1980) CHERNEY, D. J. R.; J. A. PATTERSO:-l and J. H. CHERNEY: J. Dairy Sci. 72, 3079 (1989) COm.IBE, J. B., D. A. DINIUS, H. K. GOERING and R. R. OLTJEN: J. Anim. Sci. 48, 1223 (1979) DESWYSEN, A. G., W. C. ELLIS, K. R. PO"D, W. L. JENKINS and J. CO:-lNELLY: J. Anim. Sci. 64, 827 (1987) . EGAN, A. R.: Aust. J. Agric. Res. 28, 907 (1977) ELLIS, W. C., G. W. HORN, D. DELANEY and K. R. PO:-lD: In: G. W. Hom (Ed.) Proc. National Wheat Pasture Symposium. Oklahoma Agric. Exp. Sta. MP-115, 343 (1983) ERWI:'-l, E. S., G. T. MARCO and E. M. E~IERY: J. Dairy Sci. 44,1768 (1961)
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FAULKNER, D. B., T. J. KLOPFENSTEI:-
Archiv für Tierernaehrung Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gaan19
Digestion and Performance Responses to Lasalocid and Concentrate Supplements by Beef Cattle Fed Bermudagrass Hay a
a
a
D. S. Hubbell , Dr. A. L. Goetsch , D. L. Galloway Sr. , L. a
a
A. Forster Jr. , W. Sun & Dr. K. F. Harrison
a
a
University of Arkansas , Fayetteville, AR, 72701, USA Published online: 08 Sep 2009.
To cite this article: D. S. Hubbell , Dr. A. L. Goetsch , D. L. Galloway Sr. , L. A. Forster Jr. , W. Sun & Dr. K. F. Harrison (1992) Digestion and Performance Responses to Lasalocid and Concentrate Supplements by Beef Cattle Fed Bermudagrass Hay, Archiv für Tierernaehrung, 42:1, 79-92, DOI: 10.1080/17450399209428532 To link to this article: http://dx.doi.org/10.1080/17450399209428532
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Arch. Anim. Nutr.• 1992, Vo1.42. pp. 79-92 Reprints available directly from the publisher Photocopying permitted by license only University of Arkansas, Fayeueville. AR 7270t. USA
D. S. HUBBELL, A. L. GOETSCH*, D. L. GALLOWAY sr., L. A. FORsTERjr., W. SUN and K. F. HARRISON
Digestion and perfonnance responses to lasalocid and concentrate supplements by beef cattle fed bennudagrass hay**
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KEY WORDS Digestion, Lasalocid, beef cattle, Burmudagrass hay
I.
Introduction
Ionophores are routinely used in high-grain diets to improve feed efficiency and live weight gain (GALYEAN and HUBBERT, 1989).. With forage-based diets, ionophores generally affect performance positively, but changes are more variable than those with grain-based diets (FAULKNER et aI., 1985; GALYEAN and HUBBERT, 1989). Overall, impro vements in live-weight gain of grazing cattle with ionophores increase with increasing forage quality (COOMBE et aI., 1979; WILKINSON et aI., 1980; SPROTT et aI., 1988):Warm season grasses are usually considered to be relatively low quality. Nonetheless, OLIVER (1975) and ROUQUETTE et aI. (1980) increa~e9 performance of beef calves ingesting ber mudagrass by supplementing with monensin. Ionophores improve animal performance by increasing efficiency of energy metabo lism in the rumen and (or) animal, improving nitrogen metabolism and decreasing inci dence of digestive disorders (BERGEN, 1986). MINSON (1990) summarized that acetate: propionate in ruminal fluid is usually greater for warm- than cool-season grasses because of the low -level of nonstructural carbohydrates in warm-season grasses. Because of this and factors such as the high fibre level, low availability of glucose or associated metaboJites such as NADPH 2, glycerol phosphate and (or) oxaloacetate may limit the efficiency of energy metabolism by growing ruminants ingesting warm-season grass (MACRAE et aI., 1985; BLACK et aI., 1987a, b). Hence, an increased glucose supply with grain supplementation via increased propionate production and ruminal escape of grain starch and protein or when an ionophore is given through increased propionate and pos sibly enhanced ruminal escape of feed protein should contribute to improvements in animal performance. Low readily fermentable substrate content, cell wall degradability and voluntary con sumption of warm-season grasses relative to cool-season grasses and high ruminal degradability of forage proteins can yield insufficient availability of amino acids for high live-weight gain of growing beef cattle (MCCOLLUM and HORN, 1990). Thus, increased microbial protein synthesis and (or) ruminal outflow of feed protein by grain or protein meal supplementation could increase live-weight gain. Ionophores lower duodenal microbial protein flow in some cases and, therefore, may not increase performance if a
* **
Reprint requests. Published with the approval of the Director of the Arkansas Agricultural Experiment Station.
79
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depression in microbial protein synthesis outweighs enhanced ruminal outflow of undegraded feed protein with decreased ruminal proteolysis (VAN NEVEL and DEMEYER, 1977). Supplementation with a low level of com (e.g. less than 0.5 % of live weight) generally only slightly impairs bermudagrass fibre digestion (FORSTER et aI., 1990; GAL LOWAY et aL, 1991; SUN et aI., 1991). Ionophores have de'pressed fibre digestion with high-forage diets in many cases (ELLIS et aI., 1983), and postruminal fibre digestion can not compensate if the ruminal depression is severe. The likelihood and magnitude of depressed fibre digestion with ionophores is greater with mature or low-quality forage than with immature or high-quality forage (ZORRILLA-RIOS et aI., 1985). Concentrate supplements such as com, protein meals and ionophores can affect similar animal conditions (e.g. volatile fatty acid levels, supplies of glucose and amino acids and fibre digestion). Hence, supplementation and supplement composition may alter effects of an ionophore on digestion and performance by beef cattle. This study was conducted to determine if supplementing beef cattle ingesting bermudagrass hay with a low level of com alone or plus a mix of protein meals would change e.ffects of lasalocid on digestion . and performance.
2.
Materials and methods
2.1.
Experiment 1, digestion
2.1.1.
Animals and diets
Six beef cows (average initial and final live weights of 477 and 502 kg, respectively; Angus, Hereford or Angus x Hereford) fitted with ruminal and duodenal cannulae were used in a digestion study with 14-day periods in a 6 x 6 Latin square design. Cows were housed in 3.1 m x 4.6 m pens and given free access to water. COWS received a basal ration of bermudagrass hay (Basal, B) or were supplemented with ground com (C) or com plus a mix of protein meals (CP). Approximately 0.25 % of live-weight of com was supplemented; the protein meal mix consisted of 50 % hydrolyz ed feather meal, 25 % blood meal and 25 % soybean meal and was fed at approximately 0.048 % of live-weight (dry matter basis). In addition, cows received a mixed mineral supplement supplying 11.0 g NaCl and 3.7 g trace mineral mix alone or with 1.33 g Bovatec®~·· (providing 200 mg lasalocid daily; L). Trace mineral mix was comprised of 12 % Zn, 10 % Fe, 8 % Mn, 5 % K, 2.5 Mg, 1.5 % Ca, 0.3 % I, 0.1 % Co and 0.02 % Se. Mineral supplements were fed alone or mixed with other concentrates and given in small buckets. Supplements were given at 10.00 h and consumed in less than 15 minutes. Bermudagrass (Table 1; Cynodon dactylon) hay (second harvest, cut in the mid- to full bloom growth stage in late-summer and drought-stressed) was fed in two equal meals at 07.00 hand 16.00 h so that total daily dry matter (DM) intake approximated 1.25 % of live-weight/day. Very small hay refusals occurred occasionally and were measured.
***
Hoffman-La Roche, Inc., Nutley, NJ.
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Table 1
Feedstuff composition (% dry matter)
Experiment 1 Corn CP*
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Item Dry maller** Ash Crude protein Neutral detergent fibre Acid detergent fibre Acid detergent lignin Cellulose Hemicellulose Potassium Sodium
87.4 1.5
10.3 1l.8 2.9
0.29 0.00
88.2 1.9 22.8 18.3 5.0
0.36 0.02
Hay 93.7 7.3 12.8 72.8 33.6 5.1 26.8 39.1 1.90 0.10
Experiment 2 Corn CP* 86.3 1.5 11.0
0.28 0.00
87.1 2.0 22.1
0.33 0,0\
Hay 94.3 6.9 10.7
81.3 38.2 5;5 31.8 43.1 1.73 0.02
* Corn + protein meals ** % air-dry
2.1.2.
Sampling procedures
Each experimental day began at the 07.00 h meal. On day 12, 100 ml of cobalt-ethylene diaminetetraacetic acid (UDEN et aI., 1980) was dosed into the rumen immediately prior to the 07.00 h meal. Ruminal fluid was sampled (450 ml) at 16.00 and 01.00 h on day 12 and at 10.00, 19.00 and 04.00 h on day 13. The pH was measured immediately, and sam ples were strained through eight layers of cheesecloth. For each cow, approximately 250 ml of each sample was composited in a saline-formalin solution (MERCHEN and SAlTER, 1983), and the other 200 ml was frozen after adding 2 ml of 20 % (volume/vol ume) sulfuric acid solution. Duodenal (spot sample) and faecal (grab) samples were obtained at the same times ~s ruminal fluid at 07.00 h on day 12 (immediately before the meal) and on day 14 at 13.00 and 22.00 h. Composites of duodenal and faecal samples were formed (wet basis) for each 'cow and period and stored frozen. Duodenal samples were divided into two portions, one being lyophilized and the other being refrozen. Fae cal samples were lyophilized and ground through a I-mm screen. Hay compos~tes for each period were constructed by sampling daily on day 10 to 14, and supplements were sampled once during this period.
2.1.3.
Analytical procedures
Composite samples of feed and duodenal and faecal digesta were analyzed for DM, ash, Kjeldahl nitrogen (N; AOAC 1975), neutral detergent fibre (NDF; ROBERTSON and VAN SOEST, 1981), acid detergent fibre (ADF; GOERING and VAN SOEST, 1970) and acid insoluble ash (AlA; VAN KEULEN and YOUNG, 1977). Feeds were analyzed for acid deter gent lignin (GOERING and VAN SOEST, 1970). Neutral detergent fibre and ADF analyses were conducted on air-dry samples, cellulose was estimated as weight loss upon sulfuric acid treatment and hemicellulose was calculated by subtracting ADF from NDF. Amylase
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was used in supplement NDF analysis (CHERNEY et aI., 1989). Dry duodenal composites were analyzed for purines with ribonucleic acid as a standard (ZINN and OWENS, 1986). Wet duodenal digesta was assayed for ammonia-N (BRODERICK and KANG, 1980) and for DM. A composite of each feedstuff was analyzed for potassium and sodium (HUANG and SCHULTE, 1985; ZARCINAS et aI., 1987). Bacterial cells isolated by differential centrifugation (MERCHEN and SATTER, 1983) of ruminal fluid stored in saline-formalin were lyophilized, crushed and analyzed for DM, ash, N and purines. Frozen ruminal fluid samples were thawed at room temperature, and portions were centrifuged at 10000 x g for 10 minutes. The supernatant was analyzed for cobalt by atomic absorption spectroscopy. Ammonia-N concentration for ruminal fluid samples at 10.00 and 16.00 h was measured, and a portion of supernatant from these sam ples was recentrifuged and analyzed for volatile fatty acids (VFA; ERWIN et aI., 1961). Acid insoluble ash was used as an internal marker for digestion estimation. The per centage of microbial N in duodenal digesta was obtained by dividing duodenal digesta nucleic acid concentration by the ratio of nucleic acids to total N in bacterial cells, and microbial organic matter (OM) was derived by use of bacterial cell N and OM concentra tions. Ruminal microbial growth efficiency was estimated as g microbial N/kg OM fer mented, adjusted for microbial OM. Subtracting microbial Nand ammonia-N from total N at the duodenum yielded apparent feed N. Ruminal digestibilities are given unadjusted (apparent) and adjusted (true) for non-feed constituents. Fluid dilution rate was estimated by regressing'the natural logarithm of marker concentration against time after administra tion. Volume was calculated by dividing marker dose by the extrapolated concentration at time zero, and outflow rate arose from multiplying dilution rate by volume.
2.104.
Statistical analyses
Data were analyzed by analysis of variance with animal, period and treatment in the statistical model. Orthogonal contrasts were made to test for effects of supplementation (B and B-'-L vs other treatments), supplement type (C and C-L vs CP and CP-L), lasalo cid (B, C and CP vs B-L, C-L and CP-L) and interactions between lasalocid and supple mentation and supplement type. For ruminal fluid pH and concentrations of ammonia-N and VFA, effects of sampling time and the time by treatment interaction were determin ed. Values averaged over time were presented when the time by treatment interaction was not significant (P> .10). Analyses were conducted by procedures outlined by Statistical Analysis System (SAS, 1985).
2.2.
Experiment 2
2.2.1.
Animals and diets
Sixty Brangus-crossbred heifers (236.2 ± 2.36 kg) and 60 steers (236.8 ± 2.38 kg) were used in an experiment at the University of Arkansas Livestock and Forestry Research Station near Batesville. Calves were born from 22 February 1988 to 12 April 1988, weaned on 14 October 1988 and fed a small amount of supplemental concentrate from weaning until trial initiation. Calves were treated for internal and external parasites at
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weaning and had not previously consumed grain or received a growth stimulant. The trial began on 8 November 1988 when calves were approximately 7.5 months old. Calves were weighed (unfasted) early in the morning on days 1, 21, 42, 63 and 84. On day 1, steers were implanted with 200 mg progesterone and 20 mg estradiol benzoate (Syno vex-S®***) and allotted to 12 groups (5 heifers and 5 steers/group) for similar mean and variation in live-weight. Two groups of calves were assigned to each of the treatments in Experiment 1, except that feeding rates were 0.35 % live weight for corn and 0.067 % live weight for the pro tein meal mix (OM basis). Concentrate amounts were based on 21-day live-weight meas ures, and supplements were given at 09.00-10.00 h. Concentrate consumption was com plete in less than 30 minutes. However, Band B-L calves did not completely consume mineral supplements (92 and 83 % consumption, respectively), resulting in lasalocid in take of 145 mg/head and day for B-L calves. In addition, 35.4 g/head and day of dicalci urn phosphate was offered in a separate feeder; consumption averaged 16.9 g/head/day. Animals were placed in 12 2.0-hectare paddocks consisting predominately of common . bermudagrass, with some tall fescue (Festllca arundinacea) and weed species. Growing herbage was minimal throughout the study, and consumption of paddock herbage appear ed negligible. All paddocks contained a feeder in which large round bales of Tifton-44 bermudagrass hay (Table 1) were offered ad libitum. Bales were weighed, samples were taken before placement in feeders, ·and residual hay was weighed at the end of the study. Feedstuffs were analyzed as in Experiment 1.
2.2.2.
Statistical analyses
Data were analyzed with a split-plot design, with supplement treatment as the main plot and sex as the subplot. Contrasts used in Experiment 1 were employed. Feed intake and feed efficiency (calculated from average group intakes and live-weight gain) were analyzed with treatment in the model and the same contrasts.
3.
Results
3.1.
Experiment I, digestion
3.1.1.
Diets and digesta composition
Feedstuff composition is in Table 1. Ruminal pH, VFA molar proportions and total VFA concentration were not affected by the time by treatment interaction (P > 0.10). Lasalocid increased pH in unsupplemented cows but had little effect with supplementation (interac tion, P < 0.08; Table 2). The molar proportion of acetate (Table 2) was lower with than without lasalocid (P < 0.07) and that of propionate was higher (P < 0.10) with lasalocid, resulting in an effect of lasalocid on the acetate: propionate ratio (P < 0.06). The butyrate molar proportion was lower without than with supplementation (P < 0.05). Total VFA concentration in ruminal fluid was similar among treatments (P > 0.10). As expected,
*** Syntex Agribusiness, Inc., West Des Moines, lA, USA.
D.S. HUBBELL ET AL.
84 Table 2
Effects of supplementation with different concentrates and lasalocid on ruminal fluid characteristics for beef cows consuming berrnudagrass hay, experiment I
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Item
Treatment* B-L B
pH 6.56 VFA *** (molar %) Acetate 76.8 14.1 Propionate Isobutyrate 0.5 Butyrate 8.5 Isovalerate 0.6 Valerate 0.6 Total VFA (mMII) 101.6 Acetate: propionate 5.39 Ammonia-nitrogen (mg/dl) 10.00h 8.5 16.00h 5.0 Dilution rate (%!h) 6.48 Volume (I) 68.1 Outflow (ljh) 4.18
C-L
C
CP
CP-L
SE
E**
6.64
6.50
6.50
6.54
6.52
0.030
5,s -I
73.7 15.7 0.6 8.7 0.8 0.5 100.9 4.67
74.3 14.1 0.6 9.7 0.6 0.7 100.9 5.26
73.6 15.1 0.6 9.5 0.7 0.5 102.3 4.85
74.1 14.5 0.6 9.3 0.7 0.7 91.7 5.12
71.9 16.5 0.8 9.3 0.6 0.6 99.1 4.55
1.02 1.07 0.06 0.24 0.10 0.09 7.00 0.352
I
9.4 4.0 5.27 89.0 4.46
8.5 2.3 6.11 73.7 4.25
12.6 3.1 7.11 53.8 3.63
10.0 3.9 7.11 55.8 3.76
9.1 5.3 5.84 79.5 4.42
1.23 0.67 0.443 7.53 0.291
I
5, t 5 I
t-l T, s-l s, T-L s, T-L T-L
B =basal, no supplementation; C =supplementation with com; CP =supplementation with com plus protein meals; L = lasalocid ** Effect: 5 and s = supplementation (P < 0.05 and 0.10, respectively); T and t = supplement type (P < 0.05 and 0.06, respectively); 1= lasalocid (P < 0.1 0); s - I interaction between supplemen tation and lasalocid (P < 0.09); T - Land t -I =interaction between supplement type and lasalo cid (P < 0.05 and 0.06, respectively) *** Volatile fatty acids
*
sampling time and treatment tended to interact (P < 0.11) in ruminal ammonia-N concen tration. At 10.00 h adding lasalocid to corn alone increased the concentration whereas a slight depression occurred when lasalocid was added to com plus protein meals (interac tion, P < 0.06; Table 2). The level of ammonia-N at 16.00 h was lower (P < 0.05) for com when given alone than with the protein meals; lasalocid decreased the concentration without supplementation and increased the level with concentrate. Lasalocid increased fluid dilution rate and decreased volume and outflow rate with corn given ;Ilone but decreased dilution rate and increased volume and outflow rate when com plus protein meals were supplemented (interactions, P < 0.05; Table 2). Percentages of N (9.2-9.6) and nucleic acids (8.3-8.7) in bacterial cells were similar among treat ments (P > 0.10).
3.1.2.
Digestion
Com alone and plus protein meals comprised 21 and 25 % of total OM intake, respectively (Table 3). Flows of total, microbial and nonmicrobial OM and apparent and true ruminal OM digestibilities were similar among treatments (P> 0.10). Faecal. OM was lower with than without supplementation, and postruminal and total tract OM digest
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Table 3 Effects of supplementation with different concentrates and lasalocid on organic matter digestion in beef cows consuming bermudagrass hay, experiment I
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Item Passage, kg/day Intake Supplement Hay Total Duodenum Total Microbial Nonmicrobial Faeces Digestion, % Apparent ruminal True ruminal Postruminal Total tract
Treatment* B B-L
0.00
5041 5041 2.68
DAD 2.28 2.37 49.9 57.7 6.0 56.0
C
C-L
CP
CP-L
0.00 5.43 5.43
1.15 4.28 5.43
1.15 4.35 5.50
1.35 4.16 5.51
1.37 4.17 5.53
2.68 0.40 2.28 2.42
2.73 0.43 2.30 2.04
2.85 0.41
2.67
0041
2.83 0.45 2.39 2.04"
50.3 57.8 5.0 55.3
49.8 57.7 12.4 62.1
2044 2.09 48.9 56.2 13.2 62.1
2.26 2.09
5104 58.9 10.6 6-2.0
48.7 56.8 14.1 62.8
SE
Eb
0.160 0.030 0.142 0.058
S
2.68 2.40 2.56 0.93
S S
* B =basal, no supplementation; C =supplementation with com; CP =supplementation with com plus protein meals; L = lasalocid ** Effect: S = supplementation (P < 0.05) ibilities were greater with supplementation (P < 0.05). Postruminal digestion as a percen tage of OM at the duodenum was 11.6,9.2,21.7,24.7,2004 and 26.8 % (SE 3.99) for B, B-L, C, C-L, CP and CP-L, respectively. Ruminal NDF digestion was lower with than without supplementation (P < 0.05; Table 4). Ruminal NDF and ADF digestibilities were depressed (P < 0.10) by lasalocid. Treatment did not affect total tract digestion of NDF and ADF, indicating compensatory postruminal fibre digestion (Iasalocid effects: NDF, P < 0.06; ADF, P < 0.08). The degree to which total duodenal N (Table 5) was lower than intake was similar among treatments in g/day and as a percentage of intake. Microbial N flow was similar among treatments; Apparent feed N (feed plus endogenous) at the duodenum was affected by supplementation and was greater (P < 0.05) for supplementation with com plus protein meals than for supplementation with com alone. Rumen microbial growth efficiency was similar among treatments (P> 0.10), ranging from 13.5 to 15.1 g mi crobial N/kg OM fermented (SE lAO). Ammonia-N at the duodenum in this study vari ed with supplementation (P < 0.05), supplement type (P < 0,06) and the supplementa tion by lasalocid interaction (P < 0.05). The interaction coincides with that for ruminal ammonia-N at 16.00 h. The only effect of treatment on N digestion was a depression in true ruminal disappearance with supplementation (P < 0.09; Table 5). By applying ruminal digestibilities of hay crude protein for Band B-L to supplement treat ments (within lasalocid group), lasalocid appeared to slightly depress ruminal N disappearance of supplement and (or) hay. Postruminal N disappearance as a percentage of N at the duodenum was not affected by treatment (P > 0.10; 54.0-5804 %, SE 2.30).
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Table 4 Effects of supplementation with different concentrates and lasalocid on digestion of neu tral detergent fibre (NDF) and acid detergent fibre (ADF) in beef cows consuming ber mudagrass hay, experiment 1
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Item NDF passage (kg/d) Intake Duodenum Faeces NDF digestion (%) Ruminal Postruminal Total tract ADF passage (kg/d) Intake Duodenum Faeces ADF digestion (%) Ruminal Postruminal Total tract
Treatment* B-L B
C
C-L
CP
CP-L
4.24
4.27
3.49
3.55
3.52
3.51
1.71 1.72
1.86 1.74
1.47 1.42
1.65 1.45
1.50 1.45
1.62 1.40
59.9 -0.6 59.2 1.96 0.90 0.91 54.3 -1.3 53.0
56.5 2.6 59.1
58.1 0.9 59.0
1.98 0.95 0.93 51.6 0.8 52.4
1.59 0.75 0.74 52.4 0.3 52.7
54.9 4.1 59.0 1.60 0.86 0.76 47.5 5.2 52.7
57.2 1.6 58.8 1.58 0.77 0.76 51.0 0.7 51.7
53.9 6.0 59.9 1.57 0.81 0.74 48.3 4.4 52.7
SE
E**
0.082 0.041
S,L S
2.26 2.15 1.03 0.039 0.019
S,I S
2.46 2.36 1.08
* B:o basal, no supplementation; C:o supplementation with com; CP:o supplementation with com plus protein meals; L:o lasalocid . ** Effect: S :0 supplementation (P < 0.05); L and 1:0 lasalocid (P < 0.05 and 0.10, respectively) Table 5 Effects of supplementation with different concentrates and lasalocid on nitrogen disap pearance in beef cows consuming bermudagrass hay, experiment 1 Item
Treatment* B-L B
Passage (g/d) Intake
Supplement 0.0 Hay 119.6 Total 119.6 Duodenum Total 102.3 Microbial 42.1 Nonmicrobial 53.3 Ammonia 7.0 Faeces 44.8 Digestion, % Apparent ruminal 11.2 True rumin"al 53.6 Postruminal 50.6 Total tract 61.8
SE
E**
129.0 45.6 77.3 6.1 53.2
6.29 3.01 4.42 0.37 1.99
S,T
9.2 45.6 53.5 62.7
4.41 3.23 4.12 1.31
C
C-L
CP
CP-L
0.0 118.9 118.9
19.3 94.0 113.3
19.3. 97.7 117.0
50.2 91.7 141.9
50.6
93.8
144.4
101.9 41.0 54.7 6.2 46.9
102.4 43.8 54.9 4.7 45.6
107.5 42.9 59.1 5.4 45.5
120.7 42.2 72.9 5.5 54.6
12.6 52.8 48.0 60.6
8.0 51.3 51.5 .59.4
7.2 48.2 53.6 60.9
14.4 48.0 47.2 61.7
S,T S,t,SoL S,T s
* B:obasal, no supplementation; C:osupplementation with com; CP:osupplementation with com plus protein meals; L:o lasalocid ** Effect: Sand S:o supplementation (P < 0.05 and 0.09, respectively); T and t:o supplement type (P < 0.05 and 0.06, respectively); SoL interaction between supplementation and lasalocid (P 0.10). Response to concentrate supplementation was fairly similar among treatments for the 42-day periods, but the change in live-weight gain when the protein meal mix was added to supplemental com was larger on day 1-42 (supplement type effect; P < 0.05) than on day 43-84 (P > 0.10). Table 6 Effects of supplementation with different concentrates and lasalocid on live-weight gain, dry matter (DM) intake and gain: feed DM for beef calves consuming bermudagrass, experiment 2 Item
Treatment*
Daily gain (kg) Day 1-42 Day 43-84 Day 1-84 DM intake (kg/d) Supplement Hay Total Gain: feed DM Hay Total feed
B
B-L
C
C-L
CP
CP-L
SE
0.29 0.60 0.44
0.27 0.52 0.39
0.42 0.75 0.59
0.45 0.72 0.59
0.54 0.82 0.68
0.64 0.78 0.71
0.060 0.098 0.059
S,T .S S
0.00 5.13 5.13
0.00 5.45 5.45
0.88 4.97 5.84
0.88 4.58 5.46
1.06 4.99 6.05
1.06 5.04 6.11
0.207 0.210
s S, t
0.088 0.088
0.072 0.072
0.118 0.100
0.129 0.108
0.136 0.112
0.141 0.116
0.013 0.012
S S
E**
* B::: basal, no supplementation; C =supplementation with com; CP =supplementation with com plus protein meals; L =lasalocid ** Effect: Sand s =supplementation (P < 0.05 and 0.08, respectively); T and t =supplement type (P < 0.05 and 0.10, respectively) For the entire study, adding the protein meal mix to com tended (P < 0.12) to improve live-weight gain. Feed conversion was more efficient (P < 0.05) with than without supplementation. Supplementation decreased hay intake (P < 0.08) and increased total DM consumption (P < 0.10; Table 6). Daily live-weight gain was greater for implanted steers than for nonimplanted heifers on day 1-42 (P < 0.05), day 43-84 (P < 0.06) and day 1-84 (P < 0.05; 0.62 vs 0.52 kg). Sex did not interact with treatment in live-weight gain (P> 0.10).
4.
Discussion
4.1.
Digesta characteristics
Only a small effect of supplementation in Experiment 1 on ruminal pH may relate to the low amount of concentrate given and high saliva flow caused by the high NDF level in hay. An explanation for the supplementation x lasalocid interaction in ruminal pH is not
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apparent. Restricted feeding probably limited magnitudes of change in VFA levels with lasalocid and contributed to the lack of effect of supplement treatments. Effects of lasalocid on ruminal ammonia-N concentration in Experiment I differed with supplement treatmertt, suggesting that changes in the microbial population affecting proteolysis and deamination with lasalocid varied with supplement treatment. Treatment effects on ruminal fluid volume (Table 2) may have been involved as well. Ionophores often decrease ruminal ammonia-N concentration (VAN NEVEL and DEMEYER, 1977; however, GADO et al. (1986) increased ruminal ammonia-N concentration in beef steers fed 20 or 80 % concentrate diets by giving 300 mg lasalocid. Reasons for interactions in Experiment 1 between lasalocid and supplement treatments in fluid dilution rate, volume and outflow rate are not apparent. Ionophores have decreas ed digesta passage rate with depressed feed intake (Pmm and ELLIS, 1979; Pmm et aI., 1980). However, in one trial POND and ELLIS (1979) supplemented heifers grazing ber mudagrass with monensin and increased feed intake while decreasing digesta passage. DESWYSEN et al. (1987) observed less ruminal contractions and motility with monensin supplementation. Similar effects of lasalocid have not been shown yet, and lasalocid may have less effect on host metabolism than monensin (ARMSTRONG and SPEARS,1988).
4.2.
Supplementation and supplement type
In Experiment 2, increased overall live-weight gain with com was probably in response to an improved energy, glucose and (or) amino acid status. Results in Experiment 1 suggest that com did not markedly affect VFA levels. The trend for increased live-weight gain when the protein meal mix was added to com may be because of the trend for higher total DM intake, possibly in relation to an improved amino acid status (EGAN, 1977), although increased feed intake would not necessarily be solely responsible (MCCOLLUM and HORN, 1990). High postruminal digestion in supplemented animals in Experiment I appeared largely a function of digestion of concentrate escaping ruminal degradation. Grain supplementa tion can shift fibre digestion postruminally, but only a small change seems likely in Experiment I with the low dietary concentrate level, restricted feed intake and the resul tant high ruminal pH. Alternatively, a greater effect seems possible in Experiment 2. Microbial N flow to the intestines in Experiment 2 may have been increased with com, although results of Experiment I and steady total intake when com was offered in Exper iment 2 suggest that any such change was not large. No effect of com on ruminal capture of forage N in Experiment I probably relates to restricted, constant feed intake. However, the higher level of NDF in bermudagrass in Experiment 2 than in Experiment I would have provided greater opportunity for the increased quantity of fcrmentable OM with com addition to incrcase microbial growth.
4.3.
Lasalocid effccts and interactions
Lasalocid did not affect live-weight gain in Experiment 2. Lasalocid has increased per formance of beef cattle consuming diets based on forage of higher quality than this ber mudagrass hay (WILKINSON et aI., 1980; GALYEAN and HUBBERT, 1989). But, OLIVER
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89
(1975) increased live-weight gain of beef steers grazing bennudagrass of unknown quali ty by adding different levels of monensin to 0.91 kg (air-dry) of com. Furthennore, live weight gain by beef calves grazing bennudagrass in two trials was increased by supple menting with 200 mg daily of monensin, but quality of grazed forage was higher than of bennudagrass hay in Experiment 2 (ROUQUETIE et aI., 1980). No effect on live-weight gain of lasalocid or interaction with supplementation treat ment in Experiment 2 coincide with constant total tract digestion and postruminal N flow and only small changes in VFA proportions in Experiment ~. Ad libitum forage intake and fast digesta passage from the rumen in Experiment 2 may have led to a greater effect of lasalocid on fibre digestion relative to that in Experiment I. Perhaps shorter residence of digesta in the gut with high feed intake in Experiment 2 prevented high and compensa tory postruminal digestion. Negative effects of ionophoreson fibrolytic capacity of rumi nal microbes may hinder efficacious use of ionophores to increase live-weight gain by growing animals consuming low quality forage (COO~lBE et aI., 1979; WALLACE etal., 1981; BOGAERT et aI., 1989). Full complements of fibrolytic microbes and activities seem more imperative to high forage digestion and animal perfonnance with low-·than high quality forage. Lower total tract fibre digestion with than without lasalocid in Exper iment 2 could have countered the increased capture of feed energy in y'FA and more effi cient host metabolism with lasalocid as a consequence of the altered digestion product array (WALLACE et aI., 1981; BERGEN, 1986; GALYEAN and HUBBERT, 1989). The lack of effect of lasalocid on live-weight gain in Experiment 2 suggests that glu cose precursors with all supplement treatments were adequate to achieve potential rates of live-weight gain and accretion of tissue detennined by the rate and pattern of energy derivation from microbial and host digestion. Conversely, the increased supply of glucose precursors with lasalocid may have been offset by the lower total energy status with depressed fibre digestion. Because live-weight gain tended to increase when the protein meal mix was added to com but did not rise further when lasalocid was added, amino acids spared from breakdown with lasalocid did not seem stimulatory to live-weight gain, perhaps because of similar energy available for live-weight gain regardless of lasalocid addition. The lack of interaction in live-weight gain of sex and lasalocid implies that dif ferences between sexes in nutrient needs because of varying body composition were not great (e.g. higher glucose demand for NADPH 2 and glycerol phosphate needed for fat synthesis for nonimplanted heifers than for implanted steers; MCCOLLUM and HORN, 1990), perhaps in relation to young animal age and similar pre-trial treatment. Or, greater total live-weight gain and protein accreation by implanted steers may have compensated for a higher percentage of fat in tissue accreted by heifers. Other factors that may have influenced these results include dietary levels of minerals and the ionophore. Concentrations of potassium in bennudagrass hays were considerably higher than in most high-grain diets. BERGEN (1986) and GALYEAN and HUBBERT (1989) discussed effects of dietary mineral levels on bacterial cell membrane ion gradients and ionophore effectiveness. A relatively high dietary potassium level can minimize effects of lasalocid. Perhaps this was responsible for the disparity between results with lasalocid in Experiment 2 and those of OLIVER (1975) and ROUQUETIE et al. (1984) with monensin. However, consistent effects of lasalocid with different supplement treatments in Experi ment 2 indicate that dietary potassium level did not have a large effect on lasalocid actions. In addition, the level of lasalocid in high-forage diets can affect perfonnance (THoNNEY et aI., 1981; GUTIERREZ et aI., 1982), as also has been noted for monensin
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(OLIVER, 1975; FAULKNER et aI., 1985). Quadratic responses in live-weight gain to increasing lasalocid level may result from reduced feed intake and (or) digestion at high levels (THONNEY et aI., 1981; GUTIERREZ et aI., 1982). Conversely, ANDERSON and HORN (1987) increased live-weight gain by heifers grazing wheat forage with 200 mg lasalocid but not with 100 mg. The lack of effect of lasalocid onfeed intake in Experiment 2 sug gests that feed intake was not involved in steady live-weight gain. Supplementing beef cattle consuming bermudagrass hay with lasalocid did not im prove performance regardless of concentrate supplementation or supplement type. Some interactions occurred between lasalocid and supplement treatment in characteristics of ruminal fluid but not in digestion. Perhaps impaired digestion with lasalocid coupled with minor changes in VFA production prevented effects of the ionophore on performance, similar to findings of COOMBE et al. (1979) as.suggested by WALLACE et al. (1981). Pos sible compensatory changes in digestion and metabolism with lasalocid apparently did not vary with concentrate supplement treatment or differences in animal performance induced by supplement treatment and animal type. Further research should be conducted to determine characteristics of forages, animals and ionophore administration which govern effects of ionophores on performance of growing cattle consuming forage.
Summary Beef cattle consuming bermudagrass hay were not supplemented or received a limited amount of ground com alone or with a mix of protein meals to determine influences of concentrate supplementation on digestion and performance when the ionophore lasalocid (200 mg daily) was given. With limited feed intake, supplement treatment did not change the acetate to propionate shift in beef cows occurring with lasalocid (P < 0.06). Lasalocid did not affect sites of digestion of organic matter or nitrogen with any supplement treat ment. However, lasalocid decreased (P < 0.10) ruminal digestion of neutral and acid detergent fibre. Live-weight "gain by growing beef calves ingesting bermudagrass hay ad libitum was higher (P < 0.05) with than without supplementation and tended (P < 0.12) to be greater for com plus protein meals than for com alone. Lasalocid did not affect or interact with supplement treatment in feed intake or live-weight gain of heifers (236 kg; no growth stimulant) or steers (237 kg; treated with 200 mg progesterone and 20 mg estradiol benzoate). Lasalocid at 200 mg daily did not improve digestion characteristics or influence performance by beef cattle consuming a Basal diet of bermudagrass hay. Further, effects of lasalocid were not modulated by supplementation with concentrate, concentrate type or sex or growth stimulant usage.
LASALOXlD AND CONCENTRATE SUPPLEMENTS
91
Zusammenfassung D. S. HUBBELL, A. L. GOETSCH, D. L. GALLOWAY sen., L. A. FORsTERjun., W. SUN und K. F. HARRISON
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Auswirkung von Lasalocid- und Konzentratzusatzen zu' Bermudagrasheura tionen auf die Verdauung und die Leistung von Fleischrindem Die Bermudagrasheurationen fUr Fleischrinder erhielten keine Zusatze oder nur eine begrenzte Menge Maismehl oder ein Gemisch von Proteinmehl, urn die Auswirkung des Zusatzes von Konzentrat auf die Verdauung und die Leistung zu bestimmen, wenn das Ionophor Lasalocid zugesetzt wurde (200 mg/d). Bei limitierter Futteraufnahme wandelte der Zusatz das Azetat in den Fleischktihen nicht zu Propionat urn, wie es bei Lasalocid geschieht (P < 0,06). Lasalocid beeintriichtigte durch keinen Zusatz den Verdauungsort von organischer Substanz oder Stickstoff, jedoch verringerte Lasalocid (P < 0,10) die Verdauung von neutralen oder sauren Detergenzfasem im Pansen. Die Lebendmasse zunahme von wachsenden Fleischkalbem bei ad-libitum-Aufnahme von Bermudagrasheu war' mit Supplementierung heher (P < 0,05) als ohne und envies sich fUr Mais- und Pro teinmehl hoher als fUr Mais allein. Lasalocid reagierte nicht mit anderen Zusatzen tlnd beeintrachtigte nicht die Futteraufnahme oder die. Lebendmassezunahme von Farsen (236 kg; keine Wachstumsstimulanzien) oder Bullen (237 kg; behandel.t mit 200 mg Pro gesteron und 20 mg Estradiolbenzoat). Eine Dosis von 200 mg/d verbesserte die Ver dauungseigenschaften nicht und hatte keinen EinfluB 'auf die Leistung von Fleisch rindem, die eine Basalration von Bermudagrasheu erbielten. Damber hinaus wurden die Auswirkungen von Lasalocid nieht durch den Zusatz von Konzentrat, die Art des 15:on zentrats, das Geschlecht der Tie!C oder den Gebrauch von Wachstumsstimulanzien modu liert.
References ANDERSO:-l, M. A. and G. W. HORN: J. Anim. Sci. 65, 865 (1987)
AOAC: Official Methods of Analysis (12th edn.): Association of Official Analytical Chemists.
Washington, DC (1975) ARMSTRO"G, J. D. and J. W. SPEARS: J. Anim. Sci. 66, 1807 (1988) BERGEN, W. G.: Michigan State Res. Resp. 473, 52 (1986) BLACK, J. L., M. GILL, D. E. BEEVER, J. H. M. THORNLEY and J. D. OLDHAM: J. Nutr. 117, 105 (l987a) BLACK, J. L., M. GILL, D. E. BEEVER, J. H. M. THORI'LEY and J. D. OLDHAM: J. Nutr. 117, 116 (I 987b) BOGAERT, C., L. Gm.IEZ, J. P. JOUANY and G. JE:\IINET: Anim. Feed Sci. Techno!. 27, I (1989) BRODERICK, G. A. and J. H. KANG: J. Dairy Sci. 63, 64 (1980) CHERNEY, D. J. R.; J. A. PATTERSO:-l and J. H. CHERNEY: J. Dairy Sci. 72, 3079 (1989) COm.IBE, J. B., D. A. DINIUS, H. K. GOERING and R. R. OLTJEN: J. Anim. Sci. 48, 1223 (1979) DESWYSEN, A. G., W. C. ELLIS, K. R. PO"D, W. L. JENKINS and J. CO:-lNELLY: J. Anim. Sci. 64, 827 (1987) . EGAN, A. R.: Aust. J. Agric. Res. 28, 907 (1977) ELLIS, W. C., G. W. HORN, D. DELANEY and K. R. PO:-lD: In: G. W. Hom (Ed.) Proc. National Wheat Pasture Symposium. Oklahoma Agric. Exp. Sta. MP-115, 343 (1983) ERWI:'-l, E. S., G. T. MARCO and E. M. E~IERY: J. Dairy Sci. 44,1768 (1961)
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FAULKNER, D. B., T. J. KLOPFENSTEI:-
