Effects of Whole Cottonseed, Cottonseed Oil or Animal Fat on Digestibility of Wheat Straw Diets by Steers

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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. Copyright © 1986. American Society of Animal Science . Copyright 1986 by American Society of Animal Science.

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