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High Fat Rations for Ruminants. I. The Addition of Saturated and Unsaturated Fats to High Roughage and High Concentrate Rations¹

Ohio Agricultural Research and Development Center, Wooster 44691

Abstract

A growth and tissue analysis study involving 172 lambs, two digestion trials and an absorption trial were utilized to study the effects of additions of saturated and unsaturated fats to high roughage and high grain rations. Lambs fed high corn rations gained faster (P<.05) than those fed the high roughage ration without fat but not faster than those fed the high roughage ration plus fat. Over the entire group of high grain rations studied, additional fat (6% HEF fat or corn oil) did not stimulate faster gains and 8% HEF fat depressed gains. Lambs fed steam flaked corn rations gained faster than those fed ground shelled corn. The addition of fat did not significantly (P>.05) affect digestibilities of the high roughage or the high grain rations. Fat additions did not affect molar proportions of volatile fatty acids but proportions of propionate, butyrate and valerate were significantly higher (P<.05) in rumen liquor from lambs fed high grain rations compared to high roughage fed lambs.

Proportions of long chain fatty acids in the rumen content lipids reflected the dietary lipids. Rumen lipids from high grain fed lambs contained higher proportions of stearic, oleic and linoleic acids and less linolenic acid than rumen lipids from roughage fed animals. The addition of the hydrogenated feeding fat increased proportions of oleic acid and decreased the polyunsaturated acids. Consumption of additional corn oil further increased linoleic acid. Evidence of biohydrogenation in the rumen was confirmed. Blood lipids from grain fed animals contained lower proportions of stearic, linoleic and linolenic acids and higher proportions of oleic and arachidonic acids compared to blood from roughage fed animals. No significant (P>.05) effect of time after feeding was observed in blood lipid fatty acids. Additions of fat to the lamb rations had little effect on fatty acid composition of the liver on muscle lipids. Linolenic acid was higher in the subcutaneous fat from animals fed high roughage rations.

¹ Approved for publication as Journal Article No. 98-70 by the Associate Director of the Ohio Agricultural Research and Development Center, Wooster.

² Present address: Department of Animal Sciences and Industry, Oklahoma State University, Stillwater.

³ The authors acknowledge the assistance of R. P. Kraus and R. Stall in care of the animals, S. Foley in the lipid analyses and C. R. Weaver in statistical analyses.