DIETARY FIBER FOR DOGS: II. ISO-TOTAL DIETARY FIBER (TDF) ADDITIONS OF DIVERGENT FIBER SOURCES TO DOG DIETS AND THEIR EFFECTS ON NUTRIENT INTAKE, DIGESTIBILITY, METABOLIZABLE ENERGY AND DIGESTA MEAN RETENTION TIME G. C. Fahey, Jr.l, N. R. Merchen', J. E. Corbin', A. K. Hamilton', K. A. Serb1 and D. A. Hirakawa2 University of Illinois, Urbana 61801 and The Iams Co., Lewisburg, OH 45338 ABSTRACT
The objectives of this study were to examine widely divergent fiber sources for their efficacy as ingredients in a meat-based dog diet and to determine the effects of these fibers on fecal excretion responses and mean retention time of marked fiber in the gastrointestinal tract of the dog. Fiber sources tested included beet pulp (BP),tomato pomace (TP),peanut hulls (PH), wheat bran (WB) and alkaline hydrogen peroxide-treated wheat straw (AHPWS). Diets were isonitrogenous (5.3% JY) and iso-total dietary fiber (TDE 12.5%). Thirty female English Pointers (fivehatment) were used in the experiment. Intakes of DM and OM were similar among treatments, The highest intakes of ether extract (EE) occurred on the TP, PH and WB treatments. Dogs fed PH ingested the most crude fiber (23.6 gld), NDF (53.5 g/d), ADF (34.3 gld) and TDF (59.7 g/d). Digestibilities of DM and OM for all fiber treatments were lower than the control (87.6 vs 81.8% for DM; 90.2 vs 85.4% for OM), but values were similar among fiber sources. The highest EE and N digestibilities occurred on the control and AHPWS treatments. No differences were noted among exogenous fibercontaining treatments in fiber component digestibility. Digestible energy and ME values generally were similar among treatments. Among fiber sources, BP resulted in the greatest amount of wet feces excreted (270 g/d) and the lowest fecal DM (30.3%). No differences among fiber sources were noted in frequency of defecation or mean retention time. Iso-TDF diets (containing, on average, 12.5% TDF) appear to be utilized similarly, regardless of the diversity in sources of fiber tested. (Key Words: Dogs, Fiber, Meat Byproduct, Digestibility, Metabolizable Energy.) J. Anim. Sci. 1990. 68:42294235
Introduction Dietary fiber is a generic term that includes a number of substrates of unique chemical structure, characteristic physical properties and individual physiological effects (Kritchevsky, 1988). Most fibers are fermented to some extent by the microbial population residing in various compartments of the gastrointestinal
'Dept. of Anim. Sci. 2Duector of Res. and Tech. Services, The Iams Co., P.O. Box 862. Received January 23, 1990. Accepted M a y 1, 1990.
tract. The products of this digestion are hydrogen, methane, carbon dioxide-and certain shortchain fatty acids (acetate, propionate and butyrate, primarily). Mowat (1980) noted that as a result of the processing of human foods and beverages, byproducts unsuitable for human consumption are generated. These byproducts have potential use in animal feeds, especially as sources of dietary fiber. Although dogs belong to the mammalian order Carnivora, they are widely believed to be omnivorous in dietary habits and digestive capabilities (Kronfeld, 1972). Ostensibly, they should be provided with a source of dietary fiber for the same reasons
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FAHEY ET AL.
material was prepared and dogs were dosed as described by Fahey et al. (1990). Beginning 4 h postdosing and every 4 h until 60 h postdosing, any feces excreted by any dog was collected and weighed and time of collection (hour post-dosing) was recorded. Collection time was extended to 60 h post-dosing due to incomplete recoveries of the marker dose in Materialsand Methods many dogs in the previous experiment. Fecal Six diets were fed in this experiment. samples were processed and analyzed as Besides the negative control diet, which described by Fahey et at. (1990), and mean contained no exogenous fiber, and the positive retention time of Cr-mordanted fiber was control diet, which contained 7.5% beet pulp calculated using the same approach cited by (BP), other fiber sources fed included tomato Fahey et al. (1990). pomace (TP), peanut hulls (PH), wheat bran (WB) and alkaline hydrogen peroxide-treated Results and Discussion wheat straw (AHPWS). Each replaced dietary cornstarch. Beet pulp, TP, PH and W B were Ingredient composition of diets fed to dogs obtained from ingredient suppliers and is presented in Table 1. Fiber sources were AHPWS was made as follows: approximately added at the expense of the cornstarch 91 kg wheat straw, 2,274 liters water and 68 component of the diet. To maintain the isoliters of 35% hydrogen peroxide were placed TDF characteristic of all exogenous fiberin a 3,790-liter stainless steel vat equipped containing diets, various amounts of the fiber with a shaft-driven stirrer. Sodium hydroxide sources were added (7.50% BP, 8.66% TP, (approximately 32 liters of a 50% d w t 6.70% PH, 12.77% WB and 6.23% AHPWS) solution) was added until mixture pH was replacing cornstarch. All other dietary ingredi11.5. Reaction pH was monitored every 30 ents were constant across treatments. Starch and cell wall concentrations of fiber min and maintained at 11.5 f .2. Approximately 11 liters of concentrated hydrochloric sources fed to dogs are presented in Table 2. acid were needed to maintain the slurry at this Beet pulp, TP, PH and AHPWS contained pH. The reaction was terminated after 5.5 h by essentially no starch. Wheat bran, on the other bringing pH to 7.0 f .5 using an additional 15 hand, contained 14.5% starch. Fiber compoliters concentrated hydrochloric acid The nent concentrations varied widely. Crude fiber treated wheat straw was washed and partially (CF) values ranged from 9.6% for wheat bran dewatered using a modified Fourdrinier wire to 60.5% for peanut hulls. No CF value for filtration unit equipped with four spray show- AHE'WS is available. Wheat bran had the ers. The washed wheat straw was dried at W C lowest concentrations of TDF (45.1%), NDF in a forced-air oven for 48 h. (45.7%) and ADF (11.5%). Alkaline hydrogen Exogenous fiber-containing diets were peroxidetreated wheat straw had the highest balanced to be iso-total dietary fiber (TDF); concentrations of TDF, NDF and ADF, folthe level of TDF selected was 12.5%. This lowed by PH, TP and BP. Tomato pomace and level was selected based on the results of PH had very high ADL concentrations (31.8 and 27.3%, respectively), followed by AHPWS Fahey et al. (1990). Dogs used, experimental conditions, experi- (7.6%), WB (4.3%) and BP (3.3%). Comparmental procedures and chemical analyses of ison of TDF with NDF values indicates that diets and excreta were as described by Fahey the largest discrepancy occurred for BP (as et al. (1990). Statistical analyses were by least noted by Fahey et al. [1990]). Peanut hulls and squares ANOVA using the GLM procedure of AHPWS contained approximately five percentSAS (1982). Comparisons among treatments age units more TDF and NDF. Wheat bran were made by the F-test-protected least signifi- contained the same amount of each. Beet pulp cant difference test (Carmer and Swanson, and W B contained the highest percentage of 1973). hemicellulose (31.4 and 34.2%, respectively; In the case of the mean retention time NDF minus ADF) of all fiber sources tested. measurement, Cr-mordanted NDF isolated Chemical composition of diets fed to dogs from BP was used as a marker. The mordanted is reported in Table 3. All diets contained that humans are urged to consider fiber as a standard component of their normal diet. The purpose of this study was to evaluate widely divergent fiber sources as components of meat-based dog diets by examining intake, digestion, ME and retention time responses.
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FIBER IN DOG DIETS
TABLE 1. INGREDIENT COMPOSITION OP DIETS FED TO DOGS Dieta ~~~
Ingredient
~
Control
~~
TP
BP
PH
WB
mws
.9 47.7 18.7 8.9 6.4 12.77 2.0 1.35 .70 .67
6.6 47.7 18.7 8.9 6.4 6.23 2 .o 1.35 .70 .67
.48 20
QDMbasis Comsmh Animal proteinb Corn Poultry fat Rice Fiber source Brewer’s dried yeast Egg Potassium chloride Monosodium phosphate Vitamh/mhed premixc DLmethionine Sodium chloride ~~
~
~
12.8 47.7 18.7 8.9 6.4 0 2.0 1.35 .70 .67 .48 .20 .10
5.3 47.7 18.7 8.9 6.4 7.50 2.0 1.35 .70 .67
4.1 47.7 18.7 8.9 6.4 8.66 2.0 1.35 .70 .67
6.1 47.7 18.7 8.9 6.4 6.70 2.0 1.35 .70 .67
.48
.48
.48
.48
.20
.20
.20
.20 .10
.IO
~
.IO
.10 ~
~~
.10 ~~
%P = beet pulp; TP = tomato pomace; PH = peanut hulls; WB = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw. bA combination of poultry byproduct meal, chicken and meat meal. ‘Provided per kg diet: vitamin A, 2 5 , m Iu,vitamin E, 130 Iu,vitamin D3, 1,747.2 N, menadione, 3.4 mg, thiamin, 15.7 m g riboflavin, 9.6 mg; niacin, 16 mg. pantothenic acid, 29.8 m& biotin, .4 mg;folic acid, 1.4 mg;choline, 670 q, Vitamin 812, .2 mg; Mn, 44.2 q;Zn, 76.8 mg; Cu, 50.4 mg; Co, .5 mg. I, 2.9 mg; and Se, .1 mg.
approximately 94% DM, 92% OM and 7.5% ing BP to 5.2% for the diet containing PH). ash. Starch concentration was highest for the Neutral detergent fiber concentrations were, in control diet (31.3%) vs approximately 22.5% all cases, lower than TDF values. Acid for the exogenous fiber-containing diets. Crude detergent fiber values were somewhat variable, protein concentration was similar among diets as were ADL values, the latter being consis(average value, 33.2%), as was the percentage tently low (less than 1%) across treatments. EE (average value, 22.1%). The fact that TDF values were so similar Fiber composition of experimental diets across treatments allows a comparison of also is reported in Table 3. All exogenous digestive responses to different sources of fibercontaining diets had similar levels of dietary fiber when fed at levels providing TDF (range, 11.8% for the diet containing BP similar amounts of “total” fiber. Intake and digestibility data are presented in to 13.2% for the diet containing AHPWS). As expected, CF levels were much lower than Table 4. No differences were noted among TDF levels (range, 2.3% for the diet contain- treatments in amount of DM or OM ingested.
TABLE 2. STARCH AND CELL WALL CONCENTRATIONS OF mBER SOURCES FED TO DOGS Fiber sourcea Item Slarch
Crude fiber Total dietary fibex NDF ADF
ADL
BP
TP
0
0 39.1 66.5 61.9 47.9 31.8
19.0 76.8 60.1 28.7 3.3
PH %DMbasis 0 60.5 86.0 75.6 66.4 27.3
WB 14.5 9.6 45.1 45.7 11.5 4.3
mws 1.2 b 92.5 83.2 71.8 7.6
m
%P = beet pulp; TP = tomato pomace; PH = peanut hulls; WB = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw. %ot determined.
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FAHEY ET AL. TABLE 3. CHEMICAL COMPOSITION OF DIETS
PED TO DOGS
Dieta Item
Control
BP
TP
PH
WB
AHPWS
93.8
94.7
94.7
94.2
94.4
94.5
92.5 7.5 31.3 33.3 20.6 .7 6.1 5.6 3.0 .23
92.0 8.O 22.5 33.3 21.5 2.3 11.8 8.4 5.2 .41
92.4 7.6 22.3 33.4 23.2 4.0 12.2 10.8 6.9 .56
92.0 8.O 22.0 33.9 23.3 2.4 12.1 9.9 4.5 .29
92.3 7.7 23.3 32.1 22.1 4.3 13.2 10.2 7.8 .70
% DM basis
OM Ash Starch
CP Ether extract Crude fiber Total dietary fiber NDF ADF
92.4 7.7 22.6 33.3 22.1 5.2 13.1 11.7 8.1
ADL .84 'BP = beet pulp; TP = tomato pomace; PH = peanut hulls; WB = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw.
Intake of EE was, in general, highest for dogs No differences were noted in DM or OM fed diets containing TP, PH and W B vs those digestibility by dogs fed supplemental fiber fed control, BP and AHPWS diets. Nitrogen sources. In both cases, however, values were intake was lowest for dogs fed the diet lower than those for control dogs. Ether extract containing APHWS. Cmde fiber, NDF and digestion was highest for dogs fed the AHPWS ADF intakes varied widely among treatments, diet and lowest for dogs fed diets containing whereas TDF intakes were similar for dogs fed BP and TP, although EE digestibilities were diets containing exogenous fiber. very high for all treatments. Nitrogen digesti-
TABLE 4. INTAKE AND DIGESTIBILITY DATA FOR DOGS FED VARIOUS FIBER SOURCES Diet' Itemb
Control
BP
TP
PH
WB
AHPWS
SEM
DM Intake,!?/d OM N
441.8 408.8 23.5'' 91.0' 2.9' 24.68 12.88 27.0a
445.6 409.8 23.7' 95.6& 1o.2e 37.3f 2 1.4' 52.7'
449.0 414.8 24.v 104.v 17.9' 48.5' 28.8' 54.9
456.6 421.8 24.3' 100.8'' 23.e 53.5' 34.3' 59.7
461.2 424.2 25.v 107.3' 10.9 45.F 19.3' 56.P'
429.4 395.8 22.0d 94.9" 18.3' 43.7e 30.Ed 57.0''
13.30 12.22 .67 2.94 .49 1.29 .82 1.61
83.1d 86.3' 86.7' 94.16 24.8 41.6' 30.5' 37.4Cd
83.6d 86.5' 88.5' 95.6' 12.5 33.3d 32.4'' 34.1''
1.33 1.12 1.20
EE CF NDF ADF TDF Digestibility, % DM OM N EE
CF NDF ADP
TDF
87.6' 90.2' 85.1Cd 95.2'' 9.9 57.2' 47.1' 44.4'
81.6d 85.6' 82.T 93.3= 18.2 39.4d 3l.e' 37.2"
80Sd 84.2' 80.7 93.4= 5.3 35.5' 19.4' 31.3Cd
80.4' 84.2d 83.6& 94.7' 9.8 36.$ 2 1.2' 29.2*
.44 6.92 5.14 5.71 5.17
%P = beet pulp; TP = tomato pomace; PH = peanut hulls; WB = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw. %E = ether extract; CF = crude fibeq TDF = total dietary fiber. c*4e*'*8Meamin the same row without a common letter in their superscript differ (P < .05).
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FIBER IN DOG DIETS TABLE 5. DIGESTIBLE AND METABOLIZABLE ENERGY CONTENT OF DOGS DIETS CONTAINING VARIOUS mBER SOURCES Die? Item
Control
BP
TP
m
WB
AHPWS
SEM
GE intake, kcal/d GE in feces, kcaYd GE in urine,kcal/d Digestible energy kdd k d g DM intake % of GE intake
2,O39.Ob 167.2b 73.8
2,252.abC 274.2' 64.6
2,370.4' 363.8d 90.4
2,348.0c 331.8Cd 101.6
2,367.6' 297.8Cd 95.6
2,202.2bc 269.2' 98 .O
91.79 23.85 14.91
1,871.8 4.59b 91.8b
1,978.4 4.44' 879
2,006.6 4.4T 84.7d
2,010.2 4.M 85.6Cd
2,069.8 1,933.0 4.4gbC 4.51bC 87.5' 87.p
78.11 .041 .80
1,798.0 4.42b S8.4b 96.2
1,913.8 1,916.2 4.30bC 4.27k 85.v 80.gd 96.7 95.5
1,9011.6 4.18' 81.3d 94.9
1,974.2 4.28& 83.4Cd 95.4
74.08 .057 1.11 .7 1
ME kdd k W g DM intake % of GE intake 46 of DE
1,835.0 428bC 83.4Cd 94.9
B P = beet pulp; TP = tomato pomace; PH = peanut hulls; W B = wheat bran; and A H P W S = alkaline hydrogen peroxide-treat4 wheat straw. b*c*dh4eans in the same row without a common letter in their superscript differ (P < .05).
bility values ranged from 80.7%(") to 88.5% (AHPWS). No differences among treatments were noted for CF digestibility; coefficients varied markedly among treatments. Neutral detergent fiber digestibility did not differ among treatments containing fiber (average 37.3%); all values were less than that for the control. A similar pattern occurred for ADF digestion. Total dietary fiber digestibility coefficients were highest (44.4%) for control dogs and lowest (29.2%) for dogs fed the diet containing PH. Reasonably good agreement between NDF and TDF digestibility coefficients occurred for diets containing supplemental fiber. Data indicate that although fiber inclusion in the diet lowers nutrient digestibility, fiber source plays only a minor role in this regard, at least at the levels fed in this study. Digestibile energy and ME values are presented in Table 5. Gross energy intake (kcad) was higher for diets containing fiber than the control, probably because of higher EE concentrations and intakes for treatments containing fiber. Fecal energy excretion followed a similar trend. No differences in urinary energy excretion were detected. Digestible energy intake (kcad) was not different among treatments. When expressed in kcal/g DM intake, the highest DE values were for control dogs and those fed WE3 and AHPWS. When expressed as a percentage of GE intake, the highest value was for control dogs, followed by values for dogs fed diets containing BP, WE+ and AHPWS. With regard to DE, ME intake (kcad) did not differ among treatments. Expressed in kcal/
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g DM intake, values were highest for dogs fed the control diet and lowest for dogs whose diet contained PH. As a percentage of GE intake, ME values again were highest for control dogs. Among fiber sources, dogs fed diets containing BP had the highest values, whereas dogs fed diets containing TP and PH had the lowest values. Metabolizable energy, expressed as a percentage of DE, was not different among treatments. Again, a difference between control and fiber-supplemented diets was detected, but differences among fiber sources were minor. In trials in which extruded corn and extruded soybean meal made up nearly 85% of the DM in a dog diet, Allen et al. (1981) found that DM digestibility decreased linearly as level of beet pulp supplementation (6 and 12%) increased, but no significant differences in energy or CP digestibilities were noted among treatments. Inclusion of 8% TP in their diet resulted in reductions in DM, energy and CP digestibilities, but not in ADF digestibility. Pomaces contain pectins and many types of gums that reduce fat and CP digestibilities (Viola et al., 1970). Fecal excretion data and estimates of mean retention time of Cr-mordanted NDF are presented in Table 6. Quantity of wet feces excreted (g/d) was highest (P < .05) for dogs fed BP and lowest (P < .05) for those fed the control diet. Wet fecal excretion values for dogs fed the other fiber sources were intermediate to and different (P < .05) from those two treatments. Percentage DM of feces was higher (P < .05) for dogs fed the control, Tp and PH
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FAHEY ET AL. TABLE 6. FECAL EXCRETION AND MEAN RETENTION TIME DATA FOR DOGS FED VARIOUS FIBER SOURCES Dieta
Item
Control
BP
TP
PH
WB
AHPWS
SEM
Wet feces,g/d Pecal DM, 9% Requency of defecation, Mean retention time, h
125.7b 40.Sb 1.LIb 32.7
269.e 30.3' 2.F 24.5
205.gd 42.gb 2.5bc 29.4
208.4d 42.gb
218.6d 36.1d 2.3bc 24.4
217.4d 32.3Cd 2.3bc 29.8
14.5 1.47 .30 3.10
n0.m h
2.8'
28.9
%P = beet pulp; TP = tomato pomace; PH = peanut hulls; WE3 = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw. b.c*dm in the same row without a common letter in their superscript differ (P < .05).
diets than for those fed BP. AHPWS and WB diets. In the case of AHPWS,the increase in wet feces excreted is due more to increased water content of feces than to dramatic reductions in digestibility, although total fecal DM output increased. Dogs fed BP or WB excreted more wet feces than those fed the control diet both because of decreased fecal DM percentage and because of some reduction in digestibility, whereas dogs fed 'IF and PH had increased excretion of wet feces due primarily to decreased DM digestibilities (Table 4). Frequency of defecation increased (P < .05) for dogs fed BP and PH compared to dogs fed the control diet. Although other differences were not significant ( P > .05), mean values for frequency of defecation generally indicated that dogs fed any of the fiber sources needed to defecate more frequently than dogs fed the control diet. Mean retention time of Cr-mordanted NDF was unaffected (P > .05) by diet in this study. Fahey et al. (1990) showed that mean retention times were not decreased until dietary fiber level exceeded 10%.Values for mean retention times in this study were markedly higher than those reported by Fahey et al. (1990). Although differences in diets and animals probably account for some of this discrepancy, increasing the length of the collection period from 36 h to 60 h postdosing was largely responsible for the difference between the experiments. Many dogs had marker in the feces as late as 48 to 56 h postdosing, and recovery of marker at these later times resulted in much of the increase in estimates of mean retention time. Average recovery of marker was higher and less variable (90.8 ? 12.5% after 60 h) in this experiment than in the previous study (Fahey et al., l W ) , in which a collection period of 36 h was used.
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Bueno et al. (1981) noted that including fiber in dog diets alters small intestinal transit, digesta flow and motility. In their studies, effects seemed to differ for different fibers. The physical form of the fiber seemed to be of particular importance; certain fibers similar in chemical composition had very different effects on digesta flow. Several conclusions may be drawn from this data set. First, high-protein, high-fat diets contain components that analyze as TDF. In the case of the fiber sources used in this experiment, quantitative additions are possible such that diets may be made iso-TDF. Second, no acceptability problems occurred with the addition of these fiber sources to dog diets. However, dogs fed the diet containing M W S required 2 to 3 d before complete consumption of the diet was realized. Third, alkaline hydrogen peroxide treatment successfully converted low-quality agricultural residues into an acceptable fiber source that heretofore would not have been considered as components of dog diets. By using this treatment procedure, the opportunity exists for the manufacture of a "standard" fiber source from many different types of lignocellulosic substrates. Fourth, nutrient digestibilities were similar among fiber sources. Fifth, DE and ME intakes were similar across treatments, indicating that fiber additions had no negative influence on the energy status of the dog. Finally, although frequency of defecation was increased by fiber additions, mean retention times were not different among treatments. Implications
Inclusion of divergent fiber sources into meat-based, extruded dog diets at the 12.5% iso-total dietary fiber level (approximately 6% from basal dietary ingredients and 6% from
FIBER IN DOG DIETS
4235
1981. Effect of dietary fiber on gastrointestinal exogenous fiber sources) results in slightly motility and jejunal transit time in dogs. Gastroenterollower nutrient digestibilities and lower digestiogy 80:701. ble and metabolizable energy values (when Carmer, S. G. and M. R. Swanson. 1973. An evaluation of expressed as a percentage of gross energy ten pair-wise multiple comparison procedures by Monte Carlo methods. J. Am. Stat. Assoc. 18:66. intake). However, few differences existed among fiber sources in this regard. Choice of a Fahey, G. C., Jr., N. R. Merchen, J. E. Corbin, A. K. Hamilton, K. A. Serbe, S. M. Lewis and D. A. fiber source might be dictated by economic Hirakawa 1990. Dietary fiber for dogs: I. Effects of considerations. The alkaline hydrogen peroxide graded levels of dietary beet pulp on nutrient intake, treatment may have a place in dog nutrition in digestibility, metabolizable energy and digesta mean retention time. J. Anim. Sci. 68:4221. that many lowquality agricultural residues Kritchevsky,D. 1988.Dietaryfiber.AMU.Rev.Nutr. 8:301. could be treated using this procedure, resulting Kronfeld, D. S. 1972. Canine Nutxition. Univ. of Pennsylvain a similar fiber product regardless of starting nia, Philadelphia substrate. SAS. 1982. SAS User’s Guide: Stalistics. SAS Inst., Inc.,
Literature Cited Allen, S. E., G. C. Fahey, Jr., J. E. Corbin, J. L. Pugh and R.
A. pranklin. 1981. Evaluation of by-product feedstuffs as dietary W e n t s for dogs. J. Anim. Sci. 53:1538. Bueno, L., F. Praddaude. J. Fioramonti and Y.Ruckebusch.
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Gary. NC. Mowat, D. N. 1980. Opportnnity feeds for animals.
Feedstuffs 52:32. Viola, S., G. Zimmermatm and S. Makady. 1970. Effect of pectin and algin upon protein utilization, digestibility of nutrients and energy in young rats.Nutr. Rep.Int. 1: 367.
The objectives of this study were to examine widely divergent fiber sources for their efficacy as ingredients in a meat-based dog diet and to determine the effects of these fibers on fecal excretion responses and mean retention time of marked fiber in the gastrointestinal tract of the dog. Fiber sources tested included beet pulp (BP),tomato pomace (TP),peanut hulls (PH), wheat bran (WB) and alkaline hydrogen peroxide-treated wheat straw (AHPWS). Diets were isonitrogenous (5.3% JY) and iso-total dietary fiber (TDE 12.5%). Thirty female English Pointers (fivehatment) were used in the experiment. Intakes of DM and OM were similar among treatments, The highest intakes of ether extract (EE) occurred on the TP, PH and WB treatments. Dogs fed PH ingested the most crude fiber (23.6 gld), NDF (53.5 g/d), ADF (34.3 gld) and TDF (59.7 g/d). Digestibilities of DM and OM for all fiber treatments were lower than the control (87.6 vs 81.8% for DM; 90.2 vs 85.4% for OM), but values were similar among fiber sources. The highest EE and N digestibilities occurred on the control and AHPWS treatments. No differences were noted among exogenous fibercontaining treatments in fiber component digestibility. Digestible energy and ME values generally were similar among treatments. Among fiber sources, BP resulted in the greatest amount of wet feces excreted (270 g/d) and the lowest fecal DM (30.3%). No differences among fiber sources were noted in frequency of defecation or mean retention time. Iso-TDF diets (containing, on average, 12.5% TDF) appear to be utilized similarly, regardless of the diversity in sources of fiber tested. (Key Words: Dogs, Fiber, Meat Byproduct, Digestibility, Metabolizable Energy.) J. Anim. Sci. 1990. 68:42294235
Introduction Dietary fiber is a generic term that includes a number of substrates of unique chemical structure, characteristic physical properties and individual physiological effects (Kritchevsky, 1988). Most fibers are fermented to some extent by the microbial population residing in various compartments of the gastrointestinal
'Dept. of Anim. Sci. 2Duector of Res. and Tech. Services, The Iams Co., P.O. Box 862. Received January 23, 1990. Accepted M a y 1, 1990.
tract. The products of this digestion are hydrogen, methane, carbon dioxide-and certain shortchain fatty acids (acetate, propionate and butyrate, primarily). Mowat (1980) noted that as a result of the processing of human foods and beverages, byproducts unsuitable for human consumption are generated. These byproducts have potential use in animal feeds, especially as sources of dietary fiber. Although dogs belong to the mammalian order Carnivora, they are widely believed to be omnivorous in dietary habits and digestive capabilities (Kronfeld, 1972). Ostensibly, they should be provided with a source of dietary fiber for the same reasons
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FAHEY ET AL.
material was prepared and dogs were dosed as described by Fahey et al. (1990). Beginning 4 h postdosing and every 4 h until 60 h postdosing, any feces excreted by any dog was collected and weighed and time of collection (hour post-dosing) was recorded. Collection time was extended to 60 h post-dosing due to incomplete recoveries of the marker dose in Materialsand Methods many dogs in the previous experiment. Fecal Six diets were fed in this experiment. samples were processed and analyzed as Besides the negative control diet, which described by Fahey et at. (1990), and mean contained no exogenous fiber, and the positive retention time of Cr-mordanted fiber was control diet, which contained 7.5% beet pulp calculated using the same approach cited by (BP), other fiber sources fed included tomato Fahey et al. (1990). pomace (TP), peanut hulls (PH), wheat bran (WB) and alkaline hydrogen peroxide-treated Results and Discussion wheat straw (AHPWS). Each replaced dietary cornstarch. Beet pulp, TP, PH and W B were Ingredient composition of diets fed to dogs obtained from ingredient suppliers and is presented in Table 1. Fiber sources were AHPWS was made as follows: approximately added at the expense of the cornstarch 91 kg wheat straw, 2,274 liters water and 68 component of the diet. To maintain the isoliters of 35% hydrogen peroxide were placed TDF characteristic of all exogenous fiberin a 3,790-liter stainless steel vat equipped containing diets, various amounts of the fiber with a shaft-driven stirrer. Sodium hydroxide sources were added (7.50% BP, 8.66% TP, (approximately 32 liters of a 50% d w t 6.70% PH, 12.77% WB and 6.23% AHPWS) solution) was added until mixture pH was replacing cornstarch. All other dietary ingredi11.5. Reaction pH was monitored every 30 ents were constant across treatments. Starch and cell wall concentrations of fiber min and maintained at 11.5 f .2. Approximately 11 liters of concentrated hydrochloric sources fed to dogs are presented in Table 2. acid were needed to maintain the slurry at this Beet pulp, TP, PH and AHPWS contained pH. The reaction was terminated after 5.5 h by essentially no starch. Wheat bran, on the other bringing pH to 7.0 f .5 using an additional 15 hand, contained 14.5% starch. Fiber compoliters concentrated hydrochloric acid The nent concentrations varied widely. Crude fiber treated wheat straw was washed and partially (CF) values ranged from 9.6% for wheat bran dewatered using a modified Fourdrinier wire to 60.5% for peanut hulls. No CF value for filtration unit equipped with four spray show- AHE'WS is available. Wheat bran had the ers. The washed wheat straw was dried at W C lowest concentrations of TDF (45.1%), NDF in a forced-air oven for 48 h. (45.7%) and ADF (11.5%). Alkaline hydrogen Exogenous fiber-containing diets were peroxidetreated wheat straw had the highest balanced to be iso-total dietary fiber (TDF); concentrations of TDF, NDF and ADF, folthe level of TDF selected was 12.5%. This lowed by PH, TP and BP. Tomato pomace and level was selected based on the results of PH had very high ADL concentrations (31.8 and 27.3%, respectively), followed by AHPWS Fahey et al. (1990). Dogs used, experimental conditions, experi- (7.6%), WB (4.3%) and BP (3.3%). Comparmental procedures and chemical analyses of ison of TDF with NDF values indicates that diets and excreta were as described by Fahey the largest discrepancy occurred for BP (as et al. (1990). Statistical analyses were by least noted by Fahey et al. [1990]). Peanut hulls and squares ANOVA using the GLM procedure of AHPWS contained approximately five percentSAS (1982). Comparisons among treatments age units more TDF and NDF. Wheat bran were made by the F-test-protected least signifi- contained the same amount of each. Beet pulp cant difference test (Carmer and Swanson, and W B contained the highest percentage of 1973). hemicellulose (31.4 and 34.2%, respectively; In the case of the mean retention time NDF minus ADF) of all fiber sources tested. measurement, Cr-mordanted NDF isolated Chemical composition of diets fed to dogs from BP was used as a marker. The mordanted is reported in Table 3. All diets contained that humans are urged to consider fiber as a standard component of their normal diet. The purpose of this study was to evaluate widely divergent fiber sources as components of meat-based dog diets by examining intake, digestion, ME and retention time responses.
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4231
FIBER IN DOG DIETS
TABLE 1. INGREDIENT COMPOSITION OP DIETS FED TO DOGS Dieta ~~~
Ingredient
~
Control
~~
TP
BP
PH
WB
mws
.9 47.7 18.7 8.9 6.4 12.77 2.0 1.35 .70 .67
6.6 47.7 18.7 8.9 6.4 6.23 2 .o 1.35 .70 .67
.48 20
QDMbasis Comsmh Animal proteinb Corn Poultry fat Rice Fiber source Brewer’s dried yeast Egg Potassium chloride Monosodium phosphate Vitamh/mhed premixc DLmethionine Sodium chloride ~~
~
~
12.8 47.7 18.7 8.9 6.4 0 2.0 1.35 .70 .67 .48 .20 .10
5.3 47.7 18.7 8.9 6.4 7.50 2.0 1.35 .70 .67
4.1 47.7 18.7 8.9 6.4 8.66 2.0 1.35 .70 .67
6.1 47.7 18.7 8.9 6.4 6.70 2.0 1.35 .70 .67
.48
.48
.48
.48
.20
.20
.20
.20 .10
.IO
~
.IO
.10 ~
~~
.10 ~~
%P = beet pulp; TP = tomato pomace; PH = peanut hulls; WB = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw. bA combination of poultry byproduct meal, chicken and meat meal. ‘Provided per kg diet: vitamin A, 2 5 , m Iu,vitamin E, 130 Iu,vitamin D3, 1,747.2 N, menadione, 3.4 mg, thiamin, 15.7 m g riboflavin, 9.6 mg; niacin, 16 mg. pantothenic acid, 29.8 m& biotin, .4 mg;folic acid, 1.4 mg;choline, 670 q, Vitamin 812, .2 mg; Mn, 44.2 q;Zn, 76.8 mg; Cu, 50.4 mg; Co, .5 mg. I, 2.9 mg; and Se, .1 mg.
approximately 94% DM, 92% OM and 7.5% ing BP to 5.2% for the diet containing PH). ash. Starch concentration was highest for the Neutral detergent fiber concentrations were, in control diet (31.3%) vs approximately 22.5% all cases, lower than TDF values. Acid for the exogenous fiber-containing diets. Crude detergent fiber values were somewhat variable, protein concentration was similar among diets as were ADL values, the latter being consis(average value, 33.2%), as was the percentage tently low (less than 1%) across treatments. EE (average value, 22.1%). The fact that TDF values were so similar Fiber composition of experimental diets across treatments allows a comparison of also is reported in Table 3. All exogenous digestive responses to different sources of fibercontaining diets had similar levels of dietary fiber when fed at levels providing TDF (range, 11.8% for the diet containing BP similar amounts of “total” fiber. Intake and digestibility data are presented in to 13.2% for the diet containing AHPWS). As expected, CF levels were much lower than Table 4. No differences were noted among TDF levels (range, 2.3% for the diet contain- treatments in amount of DM or OM ingested.
TABLE 2. STARCH AND CELL WALL CONCENTRATIONS OF mBER SOURCES FED TO DOGS Fiber sourcea Item Slarch
Crude fiber Total dietary fibex NDF ADF
ADL
BP
TP
0
0 39.1 66.5 61.9 47.9 31.8
19.0 76.8 60.1 28.7 3.3
PH %DMbasis 0 60.5 86.0 75.6 66.4 27.3
WB 14.5 9.6 45.1 45.7 11.5 4.3
mws 1.2 b 92.5 83.2 71.8 7.6
m
%P = beet pulp; TP = tomato pomace; PH = peanut hulls; WB = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw. %ot determined.
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4232
FAHEY ET AL. TABLE 3. CHEMICAL COMPOSITION OF DIETS
PED TO DOGS
Dieta Item
Control
BP
TP
PH
WB
AHPWS
93.8
94.7
94.7
94.2
94.4
94.5
92.5 7.5 31.3 33.3 20.6 .7 6.1 5.6 3.0 .23
92.0 8.O 22.5 33.3 21.5 2.3 11.8 8.4 5.2 .41
92.4 7.6 22.3 33.4 23.2 4.0 12.2 10.8 6.9 .56
92.0 8.O 22.0 33.9 23.3 2.4 12.1 9.9 4.5 .29
92.3 7.7 23.3 32.1 22.1 4.3 13.2 10.2 7.8 .70
% DM basis
OM Ash Starch
CP Ether extract Crude fiber Total dietary fiber NDF ADF
92.4 7.7 22.6 33.3 22.1 5.2 13.1 11.7 8.1
ADL .84 'BP = beet pulp; TP = tomato pomace; PH = peanut hulls; WB = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw.
Intake of EE was, in general, highest for dogs No differences were noted in DM or OM fed diets containing TP, PH and W B vs those digestibility by dogs fed supplemental fiber fed control, BP and AHPWS diets. Nitrogen sources. In both cases, however, values were intake was lowest for dogs fed the diet lower than those for control dogs. Ether extract containing APHWS. Cmde fiber, NDF and digestion was highest for dogs fed the AHPWS ADF intakes varied widely among treatments, diet and lowest for dogs fed diets containing whereas TDF intakes were similar for dogs fed BP and TP, although EE digestibilities were diets containing exogenous fiber. very high for all treatments. Nitrogen digesti-
TABLE 4. INTAKE AND DIGESTIBILITY DATA FOR DOGS FED VARIOUS FIBER SOURCES Diet' Itemb
Control
BP
TP
PH
WB
AHPWS
SEM
DM Intake,!?/d OM N
441.8 408.8 23.5'' 91.0' 2.9' 24.68 12.88 27.0a
445.6 409.8 23.7' 95.6& 1o.2e 37.3f 2 1.4' 52.7'
449.0 414.8 24.v 104.v 17.9' 48.5' 28.8' 54.9
456.6 421.8 24.3' 100.8'' 23.e 53.5' 34.3' 59.7
461.2 424.2 25.v 107.3' 10.9 45.F 19.3' 56.P'
429.4 395.8 22.0d 94.9" 18.3' 43.7e 30.Ed 57.0''
13.30 12.22 .67 2.94 .49 1.29 .82 1.61
83.1d 86.3' 86.7' 94.16 24.8 41.6' 30.5' 37.4Cd
83.6d 86.5' 88.5' 95.6' 12.5 33.3d 32.4'' 34.1''
1.33 1.12 1.20
EE CF NDF ADF TDF Digestibility, % DM OM N EE
CF NDF ADP
TDF
87.6' 90.2' 85.1Cd 95.2'' 9.9 57.2' 47.1' 44.4'
81.6d 85.6' 82.T 93.3= 18.2 39.4d 3l.e' 37.2"
80Sd 84.2' 80.7 93.4= 5.3 35.5' 19.4' 31.3Cd
80.4' 84.2d 83.6& 94.7' 9.8 36.$ 2 1.2' 29.2*
.44 6.92 5.14 5.71 5.17
%P = beet pulp; TP = tomato pomace; PH = peanut hulls; WB = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw. %E = ether extract; CF = crude fibeq TDF = total dietary fiber. c*4e*'*8Meamin the same row without a common letter in their superscript differ (P < .05).
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4233
FIBER IN DOG DIETS TABLE 5. DIGESTIBLE AND METABOLIZABLE ENERGY CONTENT OF DOGS DIETS CONTAINING VARIOUS mBER SOURCES Die? Item
Control
BP
TP
m
WB
AHPWS
SEM
GE intake, kcal/d GE in feces, kcaYd GE in urine,kcal/d Digestible energy kdd k d g DM intake % of GE intake
2,O39.Ob 167.2b 73.8
2,252.abC 274.2' 64.6
2,370.4' 363.8d 90.4
2,348.0c 331.8Cd 101.6
2,367.6' 297.8Cd 95.6
2,202.2bc 269.2' 98 .O
91.79 23.85 14.91
1,871.8 4.59b 91.8b
1,978.4 4.44' 879
2,006.6 4.4T 84.7d
2,010.2 4.M 85.6Cd
2,069.8 1,933.0 4.4gbC 4.51bC 87.5' 87.p
78.11 .041 .80
1,798.0 4.42b S8.4b 96.2
1,913.8 1,916.2 4.30bC 4.27k 85.v 80.gd 96.7 95.5
1,9011.6 4.18' 81.3d 94.9
1,974.2 4.28& 83.4Cd 95.4
74.08 .057 1.11 .7 1
ME kdd k W g DM intake % of GE intake 46 of DE
1,835.0 428bC 83.4Cd 94.9
B P = beet pulp; TP = tomato pomace; PH = peanut hulls; W B = wheat bran; and A H P W S = alkaline hydrogen peroxide-treat4 wheat straw. b*c*dh4eans in the same row without a common letter in their superscript differ (P < .05).
bility values ranged from 80.7%(") to 88.5% (AHPWS). No differences among treatments were noted for CF digestibility; coefficients varied markedly among treatments. Neutral detergent fiber digestibility did not differ among treatments containing fiber (average 37.3%); all values were less than that for the control. A similar pattern occurred for ADF digestion. Total dietary fiber digestibility coefficients were highest (44.4%) for control dogs and lowest (29.2%) for dogs fed the diet containing PH. Reasonably good agreement between NDF and TDF digestibility coefficients occurred for diets containing supplemental fiber. Data indicate that although fiber inclusion in the diet lowers nutrient digestibility, fiber source plays only a minor role in this regard, at least at the levels fed in this study. Digestibile energy and ME values are presented in Table 5. Gross energy intake (kcad) was higher for diets containing fiber than the control, probably because of higher EE concentrations and intakes for treatments containing fiber. Fecal energy excretion followed a similar trend. No differences in urinary energy excretion were detected. Digestible energy intake (kcad) was not different among treatments. When expressed in kcal/g DM intake, the highest DE values were for control dogs and those fed WE3 and AHPWS. When expressed as a percentage of GE intake, the highest value was for control dogs, followed by values for dogs fed diets containing BP, WE+ and AHPWS. With regard to DE, ME intake (kcad) did not differ among treatments. Expressed in kcal/
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g DM intake, values were highest for dogs fed the control diet and lowest for dogs whose diet contained PH. As a percentage of GE intake, ME values again were highest for control dogs. Among fiber sources, dogs fed diets containing BP had the highest values, whereas dogs fed diets containing TP and PH had the lowest values. Metabolizable energy, expressed as a percentage of DE, was not different among treatments. Again, a difference between control and fiber-supplemented diets was detected, but differences among fiber sources were minor. In trials in which extruded corn and extruded soybean meal made up nearly 85% of the DM in a dog diet, Allen et al. (1981) found that DM digestibility decreased linearly as level of beet pulp supplementation (6 and 12%) increased, but no significant differences in energy or CP digestibilities were noted among treatments. Inclusion of 8% TP in their diet resulted in reductions in DM, energy and CP digestibilities, but not in ADF digestibility. Pomaces contain pectins and many types of gums that reduce fat and CP digestibilities (Viola et al., 1970). Fecal excretion data and estimates of mean retention time of Cr-mordanted NDF are presented in Table 6. Quantity of wet feces excreted (g/d) was highest (P < .05) for dogs fed BP and lowest (P < .05) for those fed the control diet. Wet fecal excretion values for dogs fed the other fiber sources were intermediate to and different (P < .05) from those two treatments. Percentage DM of feces was higher (P < .05) for dogs fed the control, Tp and PH
4234
FAHEY ET AL. TABLE 6. FECAL EXCRETION AND MEAN RETENTION TIME DATA FOR DOGS FED VARIOUS FIBER SOURCES Dieta
Item
Control
BP
TP
PH
WB
AHPWS
SEM
Wet feces,g/d Pecal DM, 9% Requency of defecation, Mean retention time, h
125.7b 40.Sb 1.LIb 32.7
269.e 30.3' 2.F 24.5
205.gd 42.gb 2.5bc 29.4
208.4d 42.gb
218.6d 36.1d 2.3bc 24.4
217.4d 32.3Cd 2.3bc 29.8
14.5 1.47 .30 3.10
n0.m h
2.8'
28.9
%P = beet pulp; TP = tomato pomace; PH = peanut hulls; WE3 = wheat bran; and AHPWS = alkaline hydrogen peroxide-treated wheat straw. b.c*dm in the same row without a common letter in their superscript differ (P < .05).
diets than for those fed BP. AHPWS and WB diets. In the case of AHPWS,the increase in wet feces excreted is due more to increased water content of feces than to dramatic reductions in digestibility, although total fecal DM output increased. Dogs fed BP or WB excreted more wet feces than those fed the control diet both because of decreased fecal DM percentage and because of some reduction in digestibility, whereas dogs fed 'IF and PH had increased excretion of wet feces due primarily to decreased DM digestibilities (Table 4). Frequency of defecation increased (P < .05) for dogs fed BP and PH compared to dogs fed the control diet. Although other differences were not significant ( P > .05), mean values for frequency of defecation generally indicated that dogs fed any of the fiber sources needed to defecate more frequently than dogs fed the control diet. Mean retention time of Cr-mordanted NDF was unaffected (P > .05) by diet in this study. Fahey et al. (1990) showed that mean retention times were not decreased until dietary fiber level exceeded 10%.Values for mean retention times in this study were markedly higher than those reported by Fahey et al. (1990). Although differences in diets and animals probably account for some of this discrepancy, increasing the length of the collection period from 36 h to 60 h postdosing was largely responsible for the difference between the experiments. Many dogs had marker in the feces as late as 48 to 56 h postdosing, and recovery of marker at these later times resulted in much of the increase in estimates of mean retention time. Average recovery of marker was higher and less variable (90.8 ? 12.5% after 60 h) in this experiment than in the previous study (Fahey et al., l W ) , in which a collection period of 36 h was used.
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Bueno et al. (1981) noted that including fiber in dog diets alters small intestinal transit, digesta flow and motility. In their studies, effects seemed to differ for different fibers. The physical form of the fiber seemed to be of particular importance; certain fibers similar in chemical composition had very different effects on digesta flow. Several conclusions may be drawn from this data set. First, high-protein, high-fat diets contain components that analyze as TDF. In the case of the fiber sources used in this experiment, quantitative additions are possible such that diets may be made iso-TDF. Second, no acceptability problems occurred with the addition of these fiber sources to dog diets. However, dogs fed the diet containing M W S required 2 to 3 d before complete consumption of the diet was realized. Third, alkaline hydrogen peroxide treatment successfully converted low-quality agricultural residues into an acceptable fiber source that heretofore would not have been considered as components of dog diets. By using this treatment procedure, the opportunity exists for the manufacture of a "standard" fiber source from many different types of lignocellulosic substrates. Fourth, nutrient digestibilities were similar among fiber sources. Fifth, DE and ME intakes were similar across treatments, indicating that fiber additions had no negative influence on the energy status of the dog. Finally, although frequency of defecation was increased by fiber additions, mean retention times were not different among treatments. Implications
Inclusion of divergent fiber sources into meat-based, extruded dog diets at the 12.5% iso-total dietary fiber level (approximately 6% from basal dietary ingredients and 6% from
FIBER IN DOG DIETS
4235
1981. Effect of dietary fiber on gastrointestinal exogenous fiber sources) results in slightly motility and jejunal transit time in dogs. Gastroenterollower nutrient digestibilities and lower digestiogy 80:701. ble and metabolizable energy values (when Carmer, S. G. and M. R. Swanson. 1973. An evaluation of expressed as a percentage of gross energy ten pair-wise multiple comparison procedures by Monte Carlo methods. J. Am. Stat. Assoc. 18:66. intake). However, few differences existed among fiber sources in this regard. Choice of a Fahey, G. C., Jr., N. R. Merchen, J. E. Corbin, A. K. Hamilton, K. A. Serbe, S. M. Lewis and D. A. fiber source might be dictated by economic Hirakawa 1990. Dietary fiber for dogs: I. Effects of considerations. The alkaline hydrogen peroxide graded levels of dietary beet pulp on nutrient intake, treatment may have a place in dog nutrition in digestibility, metabolizable energy and digesta mean retention time. J. Anim. Sci. 68:4221. that many lowquality agricultural residues Kritchevsky,D. 1988.Dietaryfiber.AMU.Rev.Nutr. 8:301. could be treated using this procedure, resulting Kronfeld, D. S. 1972. Canine Nutxition. Univ. of Pennsylvain a similar fiber product regardless of starting nia, Philadelphia substrate. SAS. 1982. SAS User’s Guide: Stalistics. SAS Inst., Inc.,
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A. pranklin. 1981. Evaluation of by-product feedstuffs as dietary W e n t s for dogs. J. Anim. Sci. 53:1538. Bueno, L., F. Praddaude. J. Fioramonti and Y.Ruckebusch.
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Gary. NC. Mowat, D. N. 1980. Opportnnity feeds for animals.
Feedstuffs 52:32. Viola, S., G. Zimmermatm and S. Makady. 1970. Effect of pectin and algin upon protein utilization, digestibility of nutrients and energy in young rats.Nutr. Rep.Int. 1: 367.
