Effect of Sometribove on Rumen Fermentation, Rate of Passage, Digestibility, and Milk Production Responses in Dairy Cows M. D. WINSRYG, M. J. ARAMBEL,' B. A. KENT, and J. L. WALTERS Department of Animal Science Utah State University Logan 84322-4815
ages of CP, a-amino N, and N H 3 N content in duodenal samples were unaffected by treatment. Total tract apparent digestibility of nutrients and mean daily DMI were unaffected by treatment. (Key words: sometribove, milk yield, ruminal parameters)
ABSTRACT
Six ruminally and duodenally fistulated Holstein cows 60 d postpartum were assigned randomly to each of two treatments in a single reversal design. Treatments consisted of placebo or 25 mg of sometribove injected daily. Twatments were initiated at 60 d f 7 postpartum and maintained for 6 wk with a 3-wk adjustment between treatment periods. All cows received a TMR consisting of 16% CP and 1.67 Mcal of NEfig of DM. Influence of bST on rumen fermentation characteristics, digesta rate of passage, apparent nutrient digestibility, and milk production was evaluated. Milk yield of treated animals was 4.0 kg/d higher than controls. The 3.5% FCM and milk production efficiency (3.5% FCMDMI) were significantly higher in treated animals than in controls (29.0 vs. 25.4 kgld and 1.38 vs. 1.21 kg/ kg, respectively). Percentage of rumen cellulolytic bacteria (of total viable bacteria) was not significantly different for bST-treated animals (6.4 vs. 3.4%). Total number of rumen protozoa tended to be higher (7.25 VS. 6.55 x 1@/d) in bST-treated animals. Ruminal percentages of CP, N H 3 N, a-amino N, W A , and pH were unaffected by treatment. Sometnibove treatment did not significantly affect liquid dilution or solids turnover rates. Percent-
INTRODUCTION
Effects of bST in lactating dairy cows have been a subject of interest for many years. Asimov and Krouze (2) first demonstrated that
Received March 25, 1991. Accepted May 31, 1991. 'This paper is pnblisbed with the approval of the director, Utah A~piculturalExperimmt Station, Utah State University, Logan as Journal Paper Number 4033. *Repl.int requests. 1991 J Dairy Sci 74351S3523
injections of crude pituitary extracts increased milk production in dajl cows. These findings were the beginnings of research to determine the feasibility of large-scale utilization of the hormone (11). When injected, bST supplements the cows' naturally occurring somatotropin and improves milk production efficiency. The bST supplements can be used in various doses and given a number of ways. Amounts administered ranged from 12.5 to 60 mgld, and routes of administration included continuous infusion and daily and biweekly subcutaneous and intramuscular injections (3, 11, 15). Responses to bST injections also have varied, in a dose-dependent fashion, from 10 to 40% increases in milk yield (4, 7) and 5 to 15% increases in feed efficiency (8, 19). Milk constituents also are affwted with increased percentages of milk fat from 1 to 13% and protein yield from 1 to 10% (3, 11). However, the percentage of milk constituents depends on the animals' energy and protein status (4, 5, 7, 14). Consequently, it has been repor&edin some studies that the percentage of milk protein was decreased with cows in negative energy balance (10, 11, 23). The response to bST is progressive and persists as long as treatment continues (12). The voluntary feed intake of bST-treated animals increases in response to increased nutrient requirements of greater milk yield (21,
3518
3519
SOMETRIBOVE AND RUMEN AND PRODUCTION PARAMETERS
22). This results in an increase in production efficiency from dilution of the maintenance requirement and could result in an increase in rate of passage of nutrients from the gastrointestinal tract and altered rumen fermentation patterns. The objectives of this study were to compare the effect of administering sometribove on rumen fermentation characteristics, passage rate of nutrients through the gastrointestinal tract, apparent digestibility of nutrients, and milk production response. MATERIALS AND METHODS
Six primiparous Holstein cows, surgically equipped with rumen fistulas and proximal duodenal Tcannulas, were assigned to each of two treatments in a switchback design. Treatments were control (2.5 ml, daily subcutanemus injection of 75 mM NaHCO3, placebo) and treatment (subcutaneous daily injection of 2.5 ml of 10 W/mI of bST). Sometribove (119 mg) was solubilized in 11.9 ml of bacteriostatic water for injection. Of that 11.9 ml of bacteriostatic water and 119 mg of bST of solution, 2.5 ml or 25 mg of bST were administered in one of four alternating sites (either within the area of the left and right border of the scapular cartilage or between the sacrum and ossa pelvis) at approximately 1200 h daily. Any solubilized hormone not used immediately was stored (48 h maximum) at 5'C. Treatments were initiated at 60 d f 7 postpartum and maintained for 6 wk with a 3-wk readjustment period, at which time the animals received no injections, were housed in the same facility as the trial, and were fed TMR. During the 6th wk of the trial, collections were made for 7 d. Cows were housed in tie stalls and had free access to water. They were fed for ad libitum intake a TMR (Table 1) twice daily at 0700 and 1500 h. The diet was offered in amounts calculated to provide 120% of the NRC recommended amount (17). Feed refusals were recorded once daily. Feed was sampled once weekly, composited monthly, dried (1). and ground through a Wiley mill (Thomas-Wdey LaboratorieS, Swedesboro, NJ) using a 1-mm screen. Samples were a n a l y d for DM (l), CP (13), ADF and NDF (28), and ADF ash (27) (Table 1). Milk yield was recorded twice daily at 0300 and 1500 h; samples from consecutive (am.-
TABLE 1. Composition and nutrient content of total mixed ration.
Iogredients and comuosition
(DM basis)
Alfalfa haylage Corn silage Chopped alfalfa hay Rolled barley Cottonseed, whole -t pulp Brcwas dried Beet molasses Vitamin-premix1
8.50 14.80 26.80 18.80 11.40 9.60 7.80 .90 1.40
e, ?6
15.00
NDF, % ADF, % NEL, McavlEg
a%
P. % ~~
~
49.70 32.50 1.67 .70 .46 -~
~~
~
'Consisted of NaCI, 99.445% Mn, .2%;Fe, .30%;Zn, .01%; I, .007%; co, .005%; 2000 Iu vitamin A, 2000 Iu vitamin D and .2 ru vitamin Wg.
p.m.) millrings were composited once weekly and analyzed for percentages of lactose, fat, protein, and SNF and for SCC using a Multispec M infrared analyzer (Wheldrake, York, Engl.). Rumen Fermentation At 2.5 h after the morning feeding (lo00 h) on the 4th d of collection, 300 ml of rumen digesta were collected from the midventral sac and analyzed for viable cellulolytic and total bacteria using habitat-stimulating media in anaerobic roll tubes as described by Leedle and Hespell (16). Samples of whole digesta were strained through four layers of cheesecloth and placed in a Waring blender (PGC Scientific Co., Gaithersburg, MD), flushed with COz, agitated 1 min, and serially diluted with anaerobic dilution solution. Roll tubes for total viable bacteria contained a total carbohydratebased medium and rumen fluid at dilutions of lO-'O/ml and lV/ml.and roll tubes for cellulose bacteria contained cellulose and cellobiose-based medium and rumen fluid at dilutions of 10%d and 10-8/ml. Roll tubes were incubated at 39'C for at least 7 d, and individual colonies were counted. Rumen samples were diluted 1:l with a 50% formalin solution and placed in scintillation vials for total protozoa Journal of Dairy Science Vol. 74, No. 10, 1991
3520
WLNSRYG ET AL.
counts (9). A 1-ml aliquot of the preserved sample was pipetted into a test tube and mixed with two drops of 2% brilliant green. Samples were allowed to stand for at least 4 h; 9 ml of a 30% glycerol solution were then added. If further dilutions were necessary to facilitate counting of protozoa, the 30% glycerol solution was used. A 1-ml aliquot was pipetted into a Sedgwick-Rafter counting chamber (Hausser Scientific, Blue Bell, PA), ad total protozoa were counted after 5 min. On d 5 of the collection period, rumen digesta samples were collected at 0, 2,4, 6, 8, 10, and 12 h after the a.m. feeding. Rumen samples were collected from the midventral sac and separated into liquid and solids fractions by centrifuging the sample at 7000 x g for 15 min. The solids portion was lyophilized and ground through a Wiley mill using a 1-mm mesh screen. Samples were analyzed for CP (13). The liquid portion of the rumen sample was analyzed for a-amino N (18), N H 3 N (samples were acidified and frozen before analysis) (13), pH determined at sampling time (Fisher Accumet Digital p w o n Meter, model 425), and VFA using a Hewlett-Packard 5890 gas chromatograph (Avondale, PA) with an Alltech carbowax 20 M capillary column (Deerlield, IL) with a IO-mm x .53-mm x 1 . 3 3 - p film thickness. Duodenal Digesta
On d 5 through 7 of collections, Cr-mordanted straw was made using a modified procedure of Uden et al. (26) and added to the rumen via the fistula before feeding (O600 h). The modified mordant4 straw, consisting of 500 g of chopped straw, 40 g of sodium dichromate, and 4 L of deionized water, was used to determine particulate rate of passage. Cobalt-EDTA was made according to Teeter and Owens (24) and also added to the rumen via the fistula 6 h after the am. feeding. Duodenal digesta were collected at 0, 2,4, 6, 8, 10, 12, 15, 18,24,30,36,42,48,60, and 72 h postdosing with Cr-mordanted straw. The samples were separated into liquid and solid fractions by centrifuging at 7000 x g for 15 min. The solid portion was lyophilized and ground through a Wiley mill using a 1-mm screen. Samples were analyzed for Cr using a Journal of Dairy Science Vol. 74, No. 10, 1991
Buck 200 atomic absorption spectrophotometer (Buck East Noma&, CT') to determine rate of particulate passage through the duodenum according to Uden et al. (26). Crude protein (13) also was measured as previously described. The liquid portion (6 through 72 h) was analyzed for Co using a Buck 200 atomic absorption spectrophotometer to determine liquid dilution rates. Ammonia N (13) and a-amino N (18) also were analyzed. Nutrlent Dlgestlblllty
On d 1 through 5 of the collections, fecal grab samples were obtained prior to the am. and p.m. feedings, composited, dried in a W C oven for 48 h, ground through a Wiley mill using a 1-mm mesh screen, and analyzed for DM (2). CP (13), ADF and NDF (28), and ADF ash (27). The ADF ash was used as a marker to determine total tract apparent nutrient digestibility. Analysls of Data
The data were analyzed by the least squares procedures according to a hierarchical model with correlations nested within treatment effects. Feed intake was included in the model as a covariate. The dependent variables were daily milk and feed intakes, 3.5% FCM, and milk components (20). Significance was declared at P c .05 unless otherwise noted.
TABLE 2. Effect of bST treatment on mean daily DMI, milk yield and components, and production efficiency. Treatment ItCUl
DMI, kgld Milk yield, kgld 35% FCM, kgid Pat, 96 Rotein, 96 Lactose, % SNF, %
SCC, l o a o ~
Control
bST
21.00
21.10 26.60b 30.w 25.4ob 29.W 3.23 3.25 2.8gb 2.98' 4.79 4.77 8.38 8.44 154.44 93.24
SEM
.30 .37 .94
.os .a? .17
.25 52.50
Production efficiency, 3.5% pchy DMI
1.21b
1.38'
.02
3521
SOMETRZBOVE AND RUMEN AND PRODUCI'ION PARAMETERS TABLE 3. Effect of bST treatment on rumen microbial
rmmbcrs. Treatment _
Item
Control
Bacteria Total, x 101o/ml Celldolytic, x I@/ ml Celldo€ytic, % htozoa. x ld/ml
_
_
~
bST
SEM
10.70
10.40
.60
3.42 3.40 6.55
4.83 6.39 7.28
2.76 2.33 .80
Injections of bST did not influence DMI. Previous work (3, 8, 21, 22) showed that feed intake would be increased, therefore, affecting milk production as well as altering rumen fermentation. The lack of increase in feed intake observed in this study could be a function of stage of lactation. In studies begun later in lactation (90 d in lactation), feed intake increased (3, IO). Dry matter intake, yields of 3.5% FCM and milk components, and production efficiency are shown in Table 2. Milk yield increased 4 kg/d with daily injections of bST, which was similar to yield increases reported in other studies (7, 8, 11). In accordance with previous work (8, l l ) , 3.5% FCM and production efficiency of bST-treated animals increased significantly. The observed decrease in percentage of milk protein in bST-treated cows may have
TABLE 4. Effect of bST treatment on rumen fermentation characteristics. Treatment
ConrrOl
a.%
17.49 &Amino N, jmol/dl 587.62 4.67 NH3 N. mg/dl 5.46 PH Total WA, m o l & 155.92
bST
-
Acetic (A) Ropionic (P) Isobutyric Butyric Isovaleric Valeric A P Ratio
61.28 22.91 .79 12.05 1.12 1.83 2.67
SEM
3.75 30.60 .87 .90 154.50 3.93 (mol/lOO mol) 62.43 1.07 21.99 .82 .82 .M .46 11.58 1.24 .12 .14 2.02 2.84 .82 17.82 563.43 6.33 5.51
Treatment
~
RESULTS AND DISCUSSION
Itcm
TABLE 5. Effect of bST treatment on duodenal digesta flow kimtics.
Item
Control bST
Liquid dilution rate, %b 7.30 6.09 Fkticdate rate of pasw e , %m 3.49 351 m, 46 15.57 16.28 NH3 N, mg/a 1.91 1.61 amino N, pmol/dl 471.18 442.13
SEM 1.90 1.42 1.89 .37 30.11
been a result of limited feed intake and the greater negative energy balance stimulated by higher milk production (10, 11, 23). The effects of daily injections of bST during early lactation on rumen total viable bacte ria, cellulolytic bacteria, percentage of cellulolytic bacteria and protozoal numbers are in Table 3. The percentage of cellulolytic bacteria tended to be higher for the treatment group. Evidence indicates that DMI improves with bST administration (10, 21, 22), which could increase the rate of passage of those nutrients. This could in turn change rumen fermentation patterns and increasing microbial populations. In our study, however, DMI and rate of passage were similar for both groups, resulting in similar microbial numbers. Content of ruminal (Table 4) and duodenal samples (Table 5 ) for CP, a-amino N, and N H 3 N would not be expected to differ with animals fed the same diet, unless intake was varied (19) to alter rate of feed passage. These parameters were not significantly different between treatments nor were they dissimilar over time. It was proposed that if an increase in DMI was observed, nutrient digestibilities could be affected (23). Total tract apparent digestibility of nutrients of the ration was unaffected by
TABLE 6. of bST treatment on total tract nutrient - apparem digestibility. Flffect
Treatment Itcm
Control
bST
SEM
0, %
61.72 4256 48.50
62.18 44.62 49.97
2.91 6.43 6.91
ADP, 96 NDF, %
J o d of Dairy Science Vol. 74, No. 10, 1991
3522
WJNSRYG ET AL.
daily bST injections (Table 6). probably because there were no differences in intake (25).
In conclusion, milk production was increased by 4.0 kg/d with bST injections, confirming previous work (4, 11, 19). but further research is necessary to determine whether bST injections in late lactation in conjunction with increased feed intake would affect rumen fermentation parameters. Such research could be conducted in late lactation, when degree and duration of a negative energy balance would be diminished, therefore, rumen data would be more representative. It is accepted that bST does not directly affect rumen fermentation parameters; rather, increased mobilization of nutrients available to the mammary gland stimulates milk production and alters nutrient partitioning (12). Many key regulatory enzymes probably increase the synthesis rate of nutrients but do not directly affect the microbial environment or change microbial populations unless an increase in DMI occurs. Therefore, a possible mechanism by which bST could affect the ruminal or duodenal parametes indirectly would be through increased feed intake to meet increased energy demands, thus, altering fermentation patterns. ACKNOWLEDGMENTS
Appreciation is expressed to the Monsanto Company for their support of this project, with a special thanks to Gary Hartnell. Appreciation also is expressed to Rob Callan and Mark Olsen for their help and support throughout the entire project.
P. J. Eppad, and S. J. Sechcn. 1985. Sources of variation and prospects for improvement of productive efficiency in the dairy cow: a review. J. Anim. Sci. 60583. 6 chalnp8, W.1982. Responses to dairy COWS to Somatotropin. J. Dairy Sci. 65(Suppl. 1):216.(Abstr.) 7IQlahrP4 W.,and P. L. Schneider. 1986. Bovine somatotropin: physioiogy. lactational nspofses aad implications for the dairy industq. Prof. Anrm. Sci. 227. 8 Chalup4 W.,B. Vecchiarelli, P. Schneider, and R. G. Eggert. 1986. Long-term responses of l a c t a w cows to daily injection of ncnnbioant somatotropin. J. Dairy Sci. 69(Suppl. 1):151.(Abslr.) 9 Dehority, B.A. 1974. Rumen ciliate fauna of A l a s h moose (Ovibos rmcscharus) and Dall mountain sheep (&is &lis). J. Protoml. 21:26. lOEmight, W.I., L. T. chapin, W.M. Moseley, S. A. Zirm. and H. A. Tucker. 1986. Growth hormone releasing factor stimulates milk produaion and sustains growth hornone release in Holstein cows. J. Dairy Sci. 6 9 3 4 . llpronk, T. J., C. J. Peel, D. E. Bauman, and R. C. Gorewit. 1983. Comparison of different pattcms of exogenous p w t h hormone administration on milk production in Holstein wws. J. Anim. Sci. 57:699. 12 Gluckman, P.D., B. H.Breier, and S. R Davis. 1987. Physiology of the somatotropic axis with particular reference to the ntminant J. Dahy Sci. 70:442. 13Hach, C. C., S. V. Brayton, and A. B. Kopelove. 1985. A Powerfal KjeMahl nitrogen method using peroxysulfuric acid. I. A@. Food Chem. 33:1117. 14Huber, J. T., and L. Kung, Jr. 1981. Rotein and nonprotein nitrogen utilization in dairy catlle. J. Dairy Sci. 64:1170. 15 Hutchison, C. F.,J. E.Tomlinson, and W.H.M c h . 1986. The. effects of wrogenous recombinant or pituitary extracted bovine growth hormone on performance of dairy cows.J. Dairy Sci. 69(Suppl. 1):152.(Abstr.) 16Lecdle, JAZ., and R. B. Hespell. 1980. Differential carbohydrate media and auaerobic replica plating tshniques in delineating carbhydrabutiliziog subp u p s in Nmen bacterial populations. Appl. Enviuon. Microbial. 39:709. 17National Research Council. 1978. Nutrient requirements of dairy cattle. 5th ed. Natl. Acad. Sci., Washington.
REFERENCES 1Association of official Analytical Chemists. 1980. Official methods of analysis 12th ed. AOAC. Washiagton,
Dc.
2Asimov, G. I., and N. K. Krouze. 1937. The lactogenic preparations from the anterior pituitary and the increase of milk yield in cows. J. Dairy Sci. 20289. 3 Bauman. D. E., P. J. Eppard, M.I. DeGeeter. and 0. M.Lanza. 1985. RCS~OIECS Of high-producing dairy cows to long-term lreatment with pituitary somaw tropin and recombinant somatotropin. J. Dairy Sci. 68: 1352. 4Bauman, D. E., and S.N. McCutcheon. 1985. Page in Proc. 6th Int. Symp. Ruminant Physiol. L.E. MiUigan, W. L. Grovum, and A. Dobson, ed. Rcston h b l . Co.. Inc., Reston, VA. 5Bauman. D. E.,S. N. McCutcheon, W.D. Steinhour,
Journal of Dairy Science Vol. 74, No. 10, 1991
Dc.
18PaImeq D. W., and T. Peters, 1969. Alpha amino nitrogen procedure. Clin. cbrm 15:891. 19Pcel. C. 1.. T. J. Fro&, D. E. Bauman, and R. C. Gorewit. 1983. Effect of exogenous growth hormone in early and late lactation on lactational performaace of dairy cows. I. Dairy Sci. W776. 20 Sncdecor, G. W., and W.G. Cochraa 1967. Statistical mtttaods. 6th ed. Iowa state press, Ames. 21 Sodaholm, C. G., D. E. Otterby, F. R. Ehle, J. G. Linn, W. P. Hamen, and R. I. Amexstad. 1986. Effects of different doses of recombinant bovine somatompin (rbSTH) on milk production, body wmposition, and condition score in lactating cows. J. Dairy Sci. 69(SuppI. 1):152.(Abstr.) 22Sode&olm, C. G., D. E. Otterby, J. G. Lion, J. E. whcaton, W.P.Hamen, and R J. Annwstad. 1986. Effects of different doses of ncombinant bovine somatotropin (rbSlli) on circulating metabolites, b-
SOMETRIBOVE AND RUMEN AND PRODUCTION PARAh4ETERS
mons, and physiological parameters in lactating cows. J. Dairy Sci. 69(Suppl. 1):152.(Abstr.) 23 Staples, C. R, H. H. Head, and D. E. Dauda 1988. Short-term adminisbation of bovine somatotropin to lactating dairy cows in a subtropical mvironment. 1988. J. Dairy Sci. 71:3274. 24Ttcter, R. G., and P.N.Owens. 1983. auaactcnS * tics of water soluble markers for m e y r i n g . ~ m nliquid volume and dilution rate. J. Anus Sci. 56717. = w e l l , €3. P.,A.C.G. Brown, P. J. Reynolds, G. L. Haalaed.D.E.Bauman,C.J.Peel,andW.D.Stcinhour. 1988. Effect of bovine somatotropin on m e t a b lism of lactating dairy cows: energy and nitrogen
3523
utilizatiw. as determhed by respiration calorimetry. J. Nutr. 1181024. 26Uden. P., P. E. Colucci, and P. J. Van Soest 1980. Investigationof chromium, cerium and cobalt as markers in digesta, rate of passage sludies. J. Sci. Food Agric. 31:625. 27Undersander. D. I., N. A. Cole, and C. H. Nayor. 1987. D i g e s t i i by lambs of water-stressed alfalfa as detumined by total collection or internal markers. J. Dairy Sci. 7a1719. 28 Van Soesb P. I. 1%7. Development of a comprehensive system of feed analysis and its application to forages. J. Anim. Sci. 26:119.
Journal of Dairy Science Vol. 74, No. 10, 1991
ages of CP, a-amino N, and N H 3 N content in duodenal samples were unaffected by treatment. Total tract apparent digestibility of nutrients and mean daily DMI were unaffected by treatment. (Key words: sometribove, milk yield, ruminal parameters)
ABSTRACT
Six ruminally and duodenally fistulated Holstein cows 60 d postpartum were assigned randomly to each of two treatments in a single reversal design. Treatments consisted of placebo or 25 mg of sometribove injected daily. Twatments were initiated at 60 d f 7 postpartum and maintained for 6 wk with a 3-wk adjustment between treatment periods. All cows received a TMR consisting of 16% CP and 1.67 Mcal of NEfig of DM. Influence of bST on rumen fermentation characteristics, digesta rate of passage, apparent nutrient digestibility, and milk production was evaluated. Milk yield of treated animals was 4.0 kg/d higher than controls. The 3.5% FCM and milk production efficiency (3.5% FCMDMI) were significantly higher in treated animals than in controls (29.0 vs. 25.4 kgld and 1.38 vs. 1.21 kg/ kg, respectively). Percentage of rumen cellulolytic bacteria (of total viable bacteria) was not significantly different for bST-treated animals (6.4 vs. 3.4%). Total number of rumen protozoa tended to be higher (7.25 VS. 6.55 x 1@/d) in bST-treated animals. Ruminal percentages of CP, N H 3 N, a-amino N, W A , and pH were unaffected by treatment. Sometnibove treatment did not significantly affect liquid dilution or solids turnover rates. Percent-
INTRODUCTION
Effects of bST in lactating dairy cows have been a subject of interest for many years. Asimov and Krouze (2) first demonstrated that
Received March 25, 1991. Accepted May 31, 1991. 'This paper is pnblisbed with the approval of the director, Utah A~piculturalExperimmt Station, Utah State University, Logan as Journal Paper Number 4033. *Repl.int requests. 1991 J Dairy Sci 74351S3523
injections of crude pituitary extracts increased milk production in dajl cows. These findings were the beginnings of research to determine the feasibility of large-scale utilization of the hormone (11). When injected, bST supplements the cows' naturally occurring somatotropin and improves milk production efficiency. The bST supplements can be used in various doses and given a number of ways. Amounts administered ranged from 12.5 to 60 mgld, and routes of administration included continuous infusion and daily and biweekly subcutaneous and intramuscular injections (3, 11, 15). Responses to bST injections also have varied, in a dose-dependent fashion, from 10 to 40% increases in milk yield (4, 7) and 5 to 15% increases in feed efficiency (8, 19). Milk constituents also are affwted with increased percentages of milk fat from 1 to 13% and protein yield from 1 to 10% (3, 11). However, the percentage of milk constituents depends on the animals' energy and protein status (4, 5, 7, 14). Consequently, it has been repor&edin some studies that the percentage of milk protein was decreased with cows in negative energy balance (10, 11, 23). The response to bST is progressive and persists as long as treatment continues (12). The voluntary feed intake of bST-treated animals increases in response to increased nutrient requirements of greater milk yield (21,
3518
3519
SOMETRIBOVE AND RUMEN AND PRODUCTION PARAMETERS
22). This results in an increase in production efficiency from dilution of the maintenance requirement and could result in an increase in rate of passage of nutrients from the gastrointestinal tract and altered rumen fermentation patterns. The objectives of this study were to compare the effect of administering sometribove on rumen fermentation characteristics, passage rate of nutrients through the gastrointestinal tract, apparent digestibility of nutrients, and milk production response. MATERIALS AND METHODS
Six primiparous Holstein cows, surgically equipped with rumen fistulas and proximal duodenal Tcannulas, were assigned to each of two treatments in a switchback design. Treatments were control (2.5 ml, daily subcutanemus injection of 75 mM NaHCO3, placebo) and treatment (subcutaneous daily injection of 2.5 ml of 10 W/mI of bST). Sometribove (119 mg) was solubilized in 11.9 ml of bacteriostatic water for injection. Of that 11.9 ml of bacteriostatic water and 119 mg of bST of solution, 2.5 ml or 25 mg of bST were administered in one of four alternating sites (either within the area of the left and right border of the scapular cartilage or between the sacrum and ossa pelvis) at approximately 1200 h daily. Any solubilized hormone not used immediately was stored (48 h maximum) at 5'C. Treatments were initiated at 60 d f 7 postpartum and maintained for 6 wk with a 3-wk readjustment period, at which time the animals received no injections, were housed in the same facility as the trial, and were fed TMR. During the 6th wk of the trial, collections were made for 7 d. Cows were housed in tie stalls and had free access to water. They were fed for ad libitum intake a TMR (Table 1) twice daily at 0700 and 1500 h. The diet was offered in amounts calculated to provide 120% of the NRC recommended amount (17). Feed refusals were recorded once daily. Feed was sampled once weekly, composited monthly, dried (1). and ground through a Wiley mill (Thomas-Wdey LaboratorieS, Swedesboro, NJ) using a 1-mm screen. Samples were a n a l y d for DM (l), CP (13), ADF and NDF (28), and ADF ash (27) (Table 1). Milk yield was recorded twice daily at 0300 and 1500 h; samples from consecutive (am.-
TABLE 1. Composition and nutrient content of total mixed ration.
Iogredients and comuosition
(DM basis)
Alfalfa haylage Corn silage Chopped alfalfa hay Rolled barley Cottonseed, whole -t pulp Brcwas dried Beet molasses Vitamin-premix1
8.50 14.80 26.80 18.80 11.40 9.60 7.80 .90 1.40
e, ?6
15.00
NDF, % ADF, % NEL, McavlEg
a%
P. % ~~
~
49.70 32.50 1.67 .70 .46 -~
~~
~
'Consisted of NaCI, 99.445% Mn, .2%;Fe, .30%;Zn, .01%; I, .007%; co, .005%; 2000 Iu vitamin A, 2000 Iu vitamin D and .2 ru vitamin Wg.
p.m.) millrings were composited once weekly and analyzed for percentages of lactose, fat, protein, and SNF and for SCC using a Multispec M infrared analyzer (Wheldrake, York, Engl.). Rumen Fermentation At 2.5 h after the morning feeding (lo00 h) on the 4th d of collection, 300 ml of rumen digesta were collected from the midventral sac and analyzed for viable cellulolytic and total bacteria using habitat-stimulating media in anaerobic roll tubes as described by Leedle and Hespell (16). Samples of whole digesta were strained through four layers of cheesecloth and placed in a Waring blender (PGC Scientific Co., Gaithersburg, MD), flushed with COz, agitated 1 min, and serially diluted with anaerobic dilution solution. Roll tubes for total viable bacteria contained a total carbohydratebased medium and rumen fluid at dilutions of lO-'O/ml and lV/ml.and roll tubes for cellulose bacteria contained cellulose and cellobiose-based medium and rumen fluid at dilutions of 10%d and 10-8/ml. Roll tubes were incubated at 39'C for at least 7 d, and individual colonies were counted. Rumen samples were diluted 1:l with a 50% formalin solution and placed in scintillation vials for total protozoa Journal of Dairy Science Vol. 74, No. 10, 1991
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WLNSRYG ET AL.
counts (9). A 1-ml aliquot of the preserved sample was pipetted into a test tube and mixed with two drops of 2% brilliant green. Samples were allowed to stand for at least 4 h; 9 ml of a 30% glycerol solution were then added. If further dilutions were necessary to facilitate counting of protozoa, the 30% glycerol solution was used. A 1-ml aliquot was pipetted into a Sedgwick-Rafter counting chamber (Hausser Scientific, Blue Bell, PA), ad total protozoa were counted after 5 min. On d 5 of the collection period, rumen digesta samples were collected at 0, 2,4, 6, 8, 10, and 12 h after the a.m. feeding. Rumen samples were collected from the midventral sac and separated into liquid and solids fractions by centrifuging the sample at 7000 x g for 15 min. The solids portion was lyophilized and ground through a Wiley mill using a 1-mm mesh screen. Samples were analyzed for CP (13). The liquid portion of the rumen sample was analyzed for a-amino N (18), N H 3 N (samples were acidified and frozen before analysis) (13), pH determined at sampling time (Fisher Accumet Digital p w o n Meter, model 425), and VFA using a Hewlett-Packard 5890 gas chromatograph (Avondale, PA) with an Alltech carbowax 20 M capillary column (Deerlield, IL) with a IO-mm x .53-mm x 1 . 3 3 - p film thickness. Duodenal Digesta
On d 5 through 7 of collections, Cr-mordanted straw was made using a modified procedure of Uden et al. (26) and added to the rumen via the fistula before feeding (O600 h). The modified mordant4 straw, consisting of 500 g of chopped straw, 40 g of sodium dichromate, and 4 L of deionized water, was used to determine particulate rate of passage. Cobalt-EDTA was made according to Teeter and Owens (24) and also added to the rumen via the fistula 6 h after the am. feeding. Duodenal digesta were collected at 0, 2,4, 6, 8, 10, 12, 15, 18,24,30,36,42,48,60, and 72 h postdosing with Cr-mordanted straw. The samples were separated into liquid and solid fractions by centrifuging at 7000 x g for 15 min. The solid portion was lyophilized and ground through a Wiley mill using a 1-mm screen. Samples were analyzed for Cr using a Journal of Dairy Science Vol. 74, No. 10, 1991
Buck 200 atomic absorption spectrophotometer (Buck East Noma&, CT') to determine rate of particulate passage through the duodenum according to Uden et al. (26). Crude protein (13) also was measured as previously described. The liquid portion (6 through 72 h) was analyzed for Co using a Buck 200 atomic absorption spectrophotometer to determine liquid dilution rates. Ammonia N (13) and a-amino N (18) also were analyzed. Nutrlent Dlgestlblllty
On d 1 through 5 of the collections, fecal grab samples were obtained prior to the am. and p.m. feedings, composited, dried in a W C oven for 48 h, ground through a Wiley mill using a 1-mm mesh screen, and analyzed for DM (2). CP (13), ADF and NDF (28), and ADF ash (27). The ADF ash was used as a marker to determine total tract apparent nutrient digestibility. Analysls of Data
The data were analyzed by the least squares procedures according to a hierarchical model with correlations nested within treatment effects. Feed intake was included in the model as a covariate. The dependent variables were daily milk and feed intakes, 3.5% FCM, and milk components (20). Significance was declared at P c .05 unless otherwise noted.
TABLE 2. Effect of bST treatment on mean daily DMI, milk yield and components, and production efficiency. Treatment ItCUl
DMI, kgld Milk yield, kgld 35% FCM, kgid Pat, 96 Rotein, 96 Lactose, % SNF, %
SCC, l o a o ~
Control
bST
21.00
21.10 26.60b 30.w 25.4ob 29.W 3.23 3.25 2.8gb 2.98' 4.79 4.77 8.38 8.44 154.44 93.24
SEM
.30 .37 .94
.os .a? .17
.25 52.50
Production efficiency, 3.5% pchy DMI
1.21b
1.38'
.02
3521
SOMETRZBOVE AND RUMEN AND PRODUCI'ION PARAMETERS TABLE 3. Effect of bST treatment on rumen microbial
rmmbcrs. Treatment _
Item
Control
Bacteria Total, x 101o/ml Celldolytic, x I@/ ml Celldo€ytic, % htozoa. x ld/ml
_
_
~
bST
SEM
10.70
10.40
.60
3.42 3.40 6.55
4.83 6.39 7.28
2.76 2.33 .80
Injections of bST did not influence DMI. Previous work (3, 8, 21, 22) showed that feed intake would be increased, therefore, affecting milk production as well as altering rumen fermentation. The lack of increase in feed intake observed in this study could be a function of stage of lactation. In studies begun later in lactation (90 d in lactation), feed intake increased (3, IO). Dry matter intake, yields of 3.5% FCM and milk components, and production efficiency are shown in Table 2. Milk yield increased 4 kg/d with daily injections of bST, which was similar to yield increases reported in other studies (7, 8, 11). In accordance with previous work (8, l l ) , 3.5% FCM and production efficiency of bST-treated animals increased significantly. The observed decrease in percentage of milk protein in bST-treated cows may have
TABLE 4. Effect of bST treatment on rumen fermentation characteristics. Treatment
ConrrOl
a.%
17.49 &Amino N, jmol/dl 587.62 4.67 NH3 N. mg/dl 5.46 PH Total WA, m o l & 155.92
bST
-
Acetic (A) Ropionic (P) Isobutyric Butyric Isovaleric Valeric A P Ratio
61.28 22.91 .79 12.05 1.12 1.83 2.67
SEM
3.75 30.60 .87 .90 154.50 3.93 (mol/lOO mol) 62.43 1.07 21.99 .82 .82 .M .46 11.58 1.24 .12 .14 2.02 2.84 .82 17.82 563.43 6.33 5.51
Treatment
~
RESULTS AND DISCUSSION
Itcm
TABLE 5. Effect of bST treatment on duodenal digesta flow kimtics.
Item
Control bST
Liquid dilution rate, %b 7.30 6.09 Fkticdate rate of pasw e , %m 3.49 351 m, 46 15.57 16.28 NH3 N, mg/a 1.91 1.61 amino N, pmol/dl 471.18 442.13
SEM 1.90 1.42 1.89 .37 30.11
been a result of limited feed intake and the greater negative energy balance stimulated by higher milk production (10, 11, 23). The effects of daily injections of bST during early lactation on rumen total viable bacte ria, cellulolytic bacteria, percentage of cellulolytic bacteria and protozoal numbers are in Table 3. The percentage of cellulolytic bacteria tended to be higher for the treatment group. Evidence indicates that DMI improves with bST administration (10, 21, 22), which could increase the rate of passage of those nutrients. This could in turn change rumen fermentation patterns and increasing microbial populations. In our study, however, DMI and rate of passage were similar for both groups, resulting in similar microbial numbers. Content of ruminal (Table 4) and duodenal samples (Table 5 ) for CP, a-amino N, and N H 3 N would not be expected to differ with animals fed the same diet, unless intake was varied (19) to alter rate of feed passage. These parameters were not significantly different between treatments nor were they dissimilar over time. It was proposed that if an increase in DMI was observed, nutrient digestibilities could be affected (23). Total tract apparent digestibility of nutrients of the ration was unaffected by
TABLE 6. of bST treatment on total tract nutrient - apparem digestibility. Flffect
Treatment Itcm
Control
bST
SEM
0, %
61.72 4256 48.50
62.18 44.62 49.97
2.91 6.43 6.91
ADP, 96 NDF, %
J o d of Dairy Science Vol. 74, No. 10, 1991
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WJNSRYG ET AL.
daily bST injections (Table 6). probably because there were no differences in intake (25).
In conclusion, milk production was increased by 4.0 kg/d with bST injections, confirming previous work (4, 11, 19). but further research is necessary to determine whether bST injections in late lactation in conjunction with increased feed intake would affect rumen fermentation parameters. Such research could be conducted in late lactation, when degree and duration of a negative energy balance would be diminished, therefore, rumen data would be more representative. It is accepted that bST does not directly affect rumen fermentation parameters; rather, increased mobilization of nutrients available to the mammary gland stimulates milk production and alters nutrient partitioning (12). Many key regulatory enzymes probably increase the synthesis rate of nutrients but do not directly affect the microbial environment or change microbial populations unless an increase in DMI occurs. Therefore, a possible mechanism by which bST could affect the ruminal or duodenal parametes indirectly would be through increased feed intake to meet increased energy demands, thus, altering fermentation patterns. ACKNOWLEDGMENTS
Appreciation is expressed to the Monsanto Company for their support of this project, with a special thanks to Gary Hartnell. Appreciation also is expressed to Rob Callan and Mark Olsen for their help and support throughout the entire project.
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