EFFECTS OF WHOLE COTTONSEED, COTTONSEED OIL OR ANIMAL FAT ON DIGESTIBILITY OF WHEAT STRAW DIETS BY STEERS'

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1 EFFECTS OF WHOLE COTTONSEED, COTTONSEED OIL OR ANIMAL FAT ON DIGESTIBILITY OF WHEAT STRAW DIETS BY STEERS' J. A. Moore, R. S. Swingle and W. H. Hale University of Arizona 2, Tucson ABSTRACT Two completely random digestion trials were conducted, each with 12 beef steers (325 kg initial weight), to measure changes in digestibilities of fat and of forage components when fat was added to diets containing 62 to 76% wheat straw. Trial 1 diets contained either no added fat or 6.3% added fat from whole cottonseed (30% of the diet), cottonseed oil or animal fat; diets were formulated to contain equal levels of cottonseed hulls and cottonseed meal. Trial 2 diets contained 0, 2, 4 or 8% added animal fat. In all forms and at all levels, added fat increased apparent digestibility of dietary lipid (P<.05). However, estimated true digestibility of lipid decreased (from 94 to 71%) as added fat was increased from 0 to 8% (P<.05). Up to 6.3% added fat increased digestible energy (DE) content of the diet. Fat additions of 2 and 4% increased daily DE intake (P<.05) and did not depress digestibility of diet components (P>.05). Fat additions of 6.3% or greater, either as free fats or as whole cottonseed, reduced (P<.05) mean acid detergent fiber digestibility from 40 to 28%~ In addition to depressing fiber digestibility, 8% added fat reduced (P<.05) digestibilities of dry matter (from 54 to 47%), organic matter (60 to 52%) and gross energy (60 to 51%). Oil fed as whole cottonseed caused digestibility depressions similar to free fat addition at the same level. These data are interpreted to show that up to 4% fat may be added to low quality forage diets without depressing digestion of diet components. Addition of 2 to 4% fat may be expected to stimulate feed intake and increase DE intake by steers. Attempts to increase caloric density of low quality forage diets by fat additions greater than 4% may be counterproductive. (Key Words: Animal Fats, Cottonseed, Wheat Straw, Digestibility, Cattle.) Introduction Addition of fat to diets containing chopped forages reduces feed dustiness and increases gross energy content, but may have negative effects on digestibility of diet components (Erwin et al., 1956; Bohman and Lesperance, 1962). Most research with fat additions to ruminant diets has been conducted using sheep or dairy cows; few reports are available with data from beef cattle on high-forage diets. Available studies indicate additions of 5 to 7% fat in high-forage diets depresses dry matter and fiber digestibilities by steers (Erwin et al., 1956; Murphy and Morgan, 1983; Jenkins and Palmquist, 1984), but not by sheep (Grainger et al., 1957; White et al., 1958; Dijkstra, 1969) or lactating dairy cows (Palmquist and Conrad, 1 Arizona Agr. Exp. Sta. Journal Article No Dept. of Anim. Sci. Received October 9, Accepted April 23, , 1980; Jenkins and Palmquist, 1984). Up to 25% whole cottonseed in diets for lactating dairy cows increased digestibility of N, ether extract and energy without depressing fiber digestibility (Smith et al., 1981), but information concerning the response of beef cattle on low quality forage diets to this high (20%) fat feedstuff is not available. If the energy density of diets high in wheat straw could be elevated by addition of fat or whole cottonseed, levels of animal performance might be increased and cost of gains reduced. The purposes of this study were: 1) to compare three fat sources (animal fat, whole cottonseed and cottonseed oil) in high-forage diets and 2) to study incremental additions of animal fat to diets high in wheat straw for beef steers. Materials and Methods Two digestion trials were conducted, each with 12 beef steers of mixed breeding (mean initial weight 325 kg). In trial 1 (comparison of different types of added fat), diets high in wheat straw contained either no added fat or 1267 j. Anim. Sci :

2 1268 MOORE ET AL. 6.3% added fat from whole cottonseed (30% of the diet), cottonseed oil or animal fat (table 1); diets were formulated to contain equal levels of cottonseed hulls and cottonseed meal. For trial 2 (increasing levels of added fat), steers from trial 1 were reassigned to four groups, with the restriction that no group would have more than one steer from a previous treatment, and randomly allotted to wheat straw diets with O, 2, 4 or 8% added animal fat (table 2). Diets in both trials were formulated to contain equal levels of protein and Ca. Wheat straw was chopped through a 2.54-cm screen in a hay mill before mixing with other diet ingredients. Cottonseed oil and animal fat (melted) were added to the diets at the time of mixing. Steers were individually fed in m pens with concrete floors. Each digestion trial consisted of a 21-d preliminary period, followed by 7 d total fecal collection. Steers had ad libitum access to feed for the first 18 d, then feed intake was kept constant for the remainder of the period at a level judged to be maximum for each steer. Steers were fed equal portions twice daily, at 0800 and Feed samples and refusals were taken daily. Fecal samples were dried at 50 C in a forced-air oven, and all samples were ground through a l-ram screen before analyses. Nitrogen (using a Technieon Autoanalyzer), dry matter (DM) and organic matter (OM) analyses were performed according to AOAC (1980). Gross energy (GE) was determined by isoperibol operation of a Parr oxygen bomb calorimeter (Parr Instrument Co., 1982); acid detergent fiber (ADF) was measured according to Goering and Van Soest (1970). Lipid was extracted using both chloroform-methanol (CM) and chloroform-methanol-hydrochloric acid (CMH) by the method of Heath and Hill (1969) as adapted by Marchello et al. (1971). Insoluble saponified fatty acids in the feces (fecal soaps) were calculated as the difference between CMH and CM extracts as suggested by Figroid (1971). Feed samples were analyzed for P (Technicon Autoanalyzer) and Ca (atomic absorption speetrophotometry) according to AOAC (1980). TABLE 1. INGREDIENT COMPOSITION AND CHEMICAL ANALYSES OF TRIAL 1 DIETS (AS-FED BASIS) Control Diet Whole cotton- Cotton- Animal seed seed oil fat Ingredient Chopped wheat straw, % Whole cottonseed, % Cottonseed oil, % Animal fat, % Cottonseed hulls, % Cottonseed meal, % Cane molasses, % Urea, % Diealcium phosphate, % Limestone, % Salt, % Vitamin A, IU/kg ,300 3,300 3,300 3,300 Analysis Dry matter, % Acid detergent fiber, % Chloroform-methanol lipid, % acid lipid, Gross energy, Mcal/kg Crude protein, % Calcium, % Phosphorus, %

3 FAT IN WHEAT STRAW DIETS FOR STEERS 1269 TABLE 2. INGREDIENT COMPOSITION AND CHEMICAL ANALYSES OF TRIAL 2 DIETS (AS-FED BASIS) Ingredient Chopped wheat straw, % Animal fat, % Cottonseed meal, % Cane molasses, % Urea, % Dicalcium phosphate, % Limestone, % Salt, % Vitamin A, IU/kg Percent added fat ,300 3,300 3,300 3,300 Analysis Dry matter, % Acid detergent fiber, % Chloroform-methanol lipid, % acid lipid, % Gross energy, Mcal/kg Crude protein, % Calcium, % Phosphorus, % Data from both trials were subjected to analysis of variance for a completely random design (Steel and Torrie, 1960). In trial 1, the diet effect was partitioned into orthogonal single degree of freedom contasts for control vs all forms of added fat, whole cottonseed vs free fats (cottonseed oil and animal fat) and cottonseed oil vs animal fat. In trial 2, Duncan's Multiple Range Test was used to locate differences between treatment means following a significant F-test. Results and Discussion Trial 1. Digestible energy concentration was higher (P<.05) in the diets with added fat than in the control diet (table 3). However, DE intake was not higher on the added fat diets because DM intake tended to be lower on these diets compared with the control. All forms of added fat depressed ADF digestibility (P<.05) and increased apparent digestibility of lipid, whether determined by extraction with CM or CMH (P<.05). Dry matter, OM and GE digestibilities were not different (P>.10) between control and added fat diets and digestibilities of OM and GE were not different among sources of added fat. Digestibility of DM was higher (P<.05) for the whole cottonseed diet than for the diets containing free fats. Crude protein (CP) digestibility was highest in the whole cottonseed diet, which may have been due to its higher CP content (table 1). Saponified fecal lipid (table 3) tended to be higher for the diets containing added fat than for the control (P<.10), but was not different among the added fat diets. Trial 2. Digestible energy content of the diet and DM intake/kg body weight "Ts tended to be higher for the diets with 2 or 4% added fat than for those wih 0 or 8% added fat (table 4). Daily DE intake was higher (P<.05) for steers fed the 4% fat diet than for those fed the 0 or 8% fat diets. Digestibilities of ADF, DM, OM and GE were not affected by additions of 2 or 4% fat, but were depressed (P<.05) by the highest level of added fat. Apparent lipid digestibility determined by CM extraction increased with each increment of fat addition (P<.05). Diets with added fat also had higher apparent digestibility coefficients for CMH-lipid than the control diet, but apparent digestibility of CMH-lipid did not increase (P>.05) when added fat was increased from 4 to 8%. Saponified lipid in the feces increased nearly twofold as the dietary fat level increased from 4 to 8% (P<.05).

4 1270 MOORE ET AL. TABLE 3. INTAKES AND APPARENT DIGESTION COEFFICIENTS AS AFFECTED BY SOURCE OF FAT (TRIAL 1) a Diet Whole cotton- Cotton- Animal Control seed seed oil fat SE b Initial wt, kg Digestible energy, Mcal/kg diet dry matter c Intake/day Dry matter, g/kg body wt "~s Digestible energy, Mcal Apparent digestion coefficients, % Acid detergent fiber c Chloroform-methanol lipid c acid lipid c Dry matter d (DM) Organic matter Gross energy Crude protein ode Saponified fecal lipid, % DM aeach value is the mean of three steers. bstandard error of the mean. CControl vs all added fat (P<.05). dwhole cottonseed vs cottonseed oil and animal fat (P<.05). ecottonseed oil vs animal fat (P<.05). Daily intake and fecal excretion of CMHlipid increased (P<.05) as level of added fat in the diet increased (table 5). Fecal CMH-lipid excreted/100 g DM intake was similar for diets containing 0 to 4% added fat, but was much higher (P<.05) for the diet with 8% fat. Simple linear regression of fecal CMH-lipid/100 g DM intake vs CMH-lipid intake by steers on 0, 2 and 4% fat diets (r=.93) was used to estimate metabolic fecal fat (3.10 g CMH/100 g DM intake) in order to calculate true digestion coefficients for dietary CMH-lipid. There was a sharp decrease (P<.05) in the estimated true digestion coefficient for CMH-lipid when the level of added fat was increased from 4 to 8%. As a result, and despite the 170 g/d greater CMHlipid intake on the 8% fat diet, daily absorption of CMH-lipid (estimated by multiplying daily lipid intakes by the calculated true digestion coefficient) was not different between the 4 and 8% fat diets. Discussion Results of this study are consistent with available published data in demonstrating that utilization of high-forage diets is depressed when fat additions exceed approximately 5%, although diet composition and ruminant species used for evaluation may influence the level at which fat additions have detrimental effects. In the current study, addition of up to 4% fat to wheat straw diets for steers was beneficial, since DE intake was higher and digestibilities of major diet fractions were not depressed. The indication that 6.3% fat is above the optimal level to add to wheat straw diets for steers (even when the fat is fed as whole cottonseed) is reflected in the depression of ADF digestibility for all diets with added fat in trial 1 (table 3) and for the 8% added fat diet in trial 2 (table 4). Similar results have been reported with beef steers fed forage diets with 7% animal fat (Erwin et al., 1956) or.23 kg

5 FAT IN WHEAT STRAW DIETS FOR STEERS 1271 TABLE 4. INTAKES AND APPARENT DIGESTION COEFFICIENTS AS AFFECTED BY LEVEL OF ADDED FAT (TRIAL 2) a Percent added animal fat SE b Initial wt, kg Digestible energy, Mcal/kg diet dry matter Intake/day Dry matter, g/kg body wt "~s Digestible energy, Meal 11.5 c 13.4 cd 16. ld 11.8 e Apparent digestion coefficients, % Acid detergent fiber 42.5 c 42.5 c 40.1 c 26.7 d 1.49 Chloroform-methanol lipid 53.1c 72.3 d 80.9 e 88.4 f 1.68 acid lipid 25.3c 42.0 d 53.1 e 49.5 e 1.89 Dry matter (DM) 54.4 c 52.6 c 53.1 c 46.8 d 1.06 Organic matter 59.9 c 59.9 c 60.6 c 52.1 d 1.18 Gross energy 57.7 c 58.6 c 60.0 c 51.4 d 1.17 Crude protein 64.6 c 58.4 d 59.1 d 67.6 c.95 Saponified fecal lipid, % DM 5.6 c 5.3 c 6.1 c 11.0 d.32 aeach value is the mean of three steers. bstandard error of the mean. c'd'e'fmeans within a row with superscripts that do not have a common letter differ (P<.05). TABLE 5. INTAKE, FECAL EXCRETION, ESTIMATED TRUE DIGESTIBILITY AND ABSORPTION OF CHLOROFORM-METHANOL ACID LIPID AS AFFECTED BY LEVEL OF ADDED FAT (TRIAL 2) a Percent added animal fat SE b CMH-lipid intake, g/d c d e f CMH-lipid in feces g/d c cd d e g/lo0 g DM intake 3.51 c 3.81 c 4.23 c 7.41 d Estimated true digestibility CMH-lipid, % 93.5 c 89.6 c 87.7 c 71.1 d Estimated true absorption CMH-lipid, g/d c d e e , aeach value is the mean of three steers. bstandard error of the mean. c'd'e'fmeans within a row with superscripts that do not have a common letter differ (P~.05).

6 1272 MOORE ET AL. animal fat/d (Bohman and Lesperance, 1962) and with dairy steers fed 5% animal fat in 50% hay diets (Murphy and Morgan, 1983 ; Jenkins and Palmquist, 1984). Fiber digestibility was not depressed when 5% fat was added to the concentrate portion of diets for lactating dairy cows (Palmquist and Conrad, 1978, 1980). In another digestion study with dairy cows, no depression in fiber digestibility was observed with up to 25% whole cottonseed in 50% alfalfa hay diets (Smith et al., 1981), which would be equivalent to approximately 5% added fat. Sheep on high-roughage diets appear to tolerate higher dietary fat than steers, since 5 to 7% corn oil does not depress cellulose digestibility if calcium in the diet is adequate (Grainger et al., 1957, 1961 ; White et al., 1958; Davison and Woods, 1961, 1963). The absence of depressed digestibilities of DM, OM and GE in trial 2 (table 4) when fat was added at up to 4% of the diet is consistent with most studies with steers on concentrate or 50% hay diets. In studies where 4 to 4.5% fat was added to concentrate diets, no depressions in DM or GE digestibilities were observed (Esplin et al., 1963; Roberts and McKirdy, 1964; Hale et al., 1965). Jenkins and Palmquist (1984) observed no depression in DM digestibility when 4.5% tallow fatty acids were added to 50% hay diets for Holstein steers, but 5% added tallow depressed DM digestibility by steers on 50% hay diets (Murphy and Morgan, 1983). Interpretation of published lipid digestibilities is complicated because the method used for lipid extraction influences the digestibility coefficient. The most common method is ether extraction, but high levels of dietary fat can result in the formation of fecal soaps that are insoluble in ether (Bohman and Lesperance, 1962; Roberts and McKirdy, 1964; Dijkstra, 1969; Figroid, 1971). If fatty acids combined in fecal soaps are not detected, lipid digestion coefficients will be artificially high, as can be seen by comparing apparent digestion coefficients for CM- and CMHqipid in tables 3 and 4. In studies where lipid digestibilities were determined by ether extraction, digestion coefficients increased with addition of fat to diets (Bohman and Lesperance, 1962; Esplin et al., 1963; Roberts and McKirdy, 1964; Hale et al., 1965). Correcting these lipid digestibilities for fecal soaps lowered digestion coefficients, but the trend toward higher apparent digestibilities for lipid in diets with added fat was similar whether corrected or not (Bohman and Lesperance, 1962), as it was in trial 2 (table 4) with up to 4% added fat in the diet. The determination that true digestion coefficients for dietary lipid decreased as fat level increased is in agreement with an earlier report by Palmquist and Conrad (1978). These investigators calculated a true digestibility for dietary fat of 81% when ether extract in the diet was less than 6%, but only 56% when dietary ether extract level was between 6 and 10%. The effect of lipid intake on lipid absorption noted in this study (table 5) supports the suggestion of Palmquist and Conrad (1978) that the capacity of the bovine small intestine for lipid absorption may be exceeded at high levels of dietary fat. In the current study, low level (2 or 4%) additions of fat to chopped wheat straw diets tended to stimulate DM intake by steers and did not adversely affect diet digestibility. When fat additions were greater than 4%, even in the form of whole cottonseed, fiber digestion was decreased and DE intake by steers was not improved over diets without added fat. Fat absorption appeared to decline sharply when lipid intake exceeded about 600 g/d. Literature Cited AOAC Official Methods of Analysis (13th Ed.). Association of Official Analytical Chemists, Washington, De. Bohman, V. R. and A. L. Lesperance Effect of dietary fat on the digestion and blood composition of cattle. Proc. West. Sec. Amer. Soc. Anita. Prod. 13:IX--1. Davison, K. L. and W. Woods Calcium and corn oil interrelationships as influencing ration utilization by lambs. J. Anim. Sci. 20:532. Davison, K. L. and W. Woods Effect of calcium and magnesium upon digestibility of a ration containing corn oil by lambs. J. Anim. Sci. 22:27. Dijkstra, N. D Influence of supplemental animal fats upon digestibility of ration components by ruminants. Neth. J. Agr. Sci. 17:27. Erwin, E. S., I. A. Dyer and M. E. Ensminger Effects of chlortetracycline, inedible animal fat, stilbestrol, and high and low quality roughage on performance of yearling steers. II. 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7 FAT IN WHEAT STRAW DIETS FOR STEERS 1273 Goering, H. K. and P. J. Van Soest Forage fiber analyses (apparatus, reagents, procedures, and some applications). ARS, USDA Handbook No Grainger, R. B., M. C. Bell, J. W. Stroud and F. H. Baker Effects of various cations and corn oil on crude cellulose digestibility by sheep. J. Anita. Sci. 20:319. Grainger, R. B., T. W. White, F. H. Baker and J. W. Stroud The interrelationship between calcium and fat in ruminant digestion. J. Anita. Sci. 16:1086 (Abstr.). Haie, W. H., E. C. Thiel, W. J. Saba, B. Taylor and B. Theurer Influence of calcium and phosphorus levels of the ration on tallow utilization by fattening steers. Proc. West. Sec. Amer. Soc. Anim. Sci. 19:LII-1. Heath, T, J. and L. N. Hill Dietary and endogenous long-chain fatty acids in the intestine of sheep, with an appendix on their estimation in feeds, bile, and feces. Aust. J. Biol. Sci. 22:1015. Jenkins, T. C. and D. L. Palmquist Effect of fatty acids or calcium soaps on rumen and total nutrient digestibility of dairy rations. J. Dairy Sci. 67:978. Marchello, J. A., R. D. Dryden and W. H. Hale Bovine serum lipids. I. The influence of added animal fat to the ration. J. Anim. Sci. 32:1008. Murphy, J. J. and D. J. Morgan Effect of inclu- sion of protected and unprotected tallow in the supplement on the performance of lactating dairy cows. Anim. Prod. 37:203. Palmquist, D. L. and H. R. Conrad High fat rations for dairy cows. Effects on feed intake, milk and fat production, and plasma metabolites. J. Dairy Sci. 61:890. Palmquist, D. L. and H. R. Conrad High fat rations for dairy cows. Tallow and hydrolyzed blended fat at two intakes. J. Dairy Sci. 63:391. Parr Instrument Co Manual No. 164, Instructions for the Parr 1710 calorimeter controller. Parr Instrument Co., Moline, IL. Roberts, W. K. and J. A. McKirdy Weight gains, carcass fat characteristics, and ration digestibility in steers as affected by dietary rapeseed oil, sunflowerseed oil, and animal tallow. J. Anim, Sci. 23:682. Smith, N. E., L. S. Collar, D. L. Bath, W. L. Dunkley and A. A. Franke Digestibility and effects of whole cottonseed fed to lactating cows. J. Dairy Sci. 64:2209. Steel, R.G.D. and J. H. Torrie Principles and Procedures of Statistics. McGraw-HiU Book Co., Inc., New York. White, T. W., R. B. Grainger, F. H. Baker and J. W. Stroud Effect of supplemental fat on digestion and the ruminal calcium requirement of sheep. J. Anim. Sei. 17:797.