EFFECTS OF GRADED-LEVELS OF DIETARY RUMEN-PROTECTED FAT ON MILK CHARACTERISTICS OF COMISANA EWES

Comisana ewes (27) were divided into three groups of nine. Control gro up was fed a vetch and oat hay and a pelleted concentrate. The other t wo groups were given the control ration supplemented with 4 and 8% rum en-protected fat. The feeding treatment caused significant variations in the characteristics of milk, and these variations showed a good cor relation with the level of protected lipids in diets. Caproic acid (C- 6:0), caprylic acid (C-8:0), capric acid (C-10:0), lauric acid (C-12:0 ) and myristic acid (C-14:0) contributed mostly in the control group, while palmitic acid (C-16:0), oleic acid (C-18:1) and linoleic acid (C -18:2) were predominant in the groups fed with the supplemental rumen- protected fat. Also, a significant increase in the ratio between mediu m- and long-chain fatty acids (C-16:0+C-18:1+C-18:2) and short-chain f atty acids (C-6:0+C-8:0) was found to be a major source of variation r elated to the rumen-protected fat supplementation. Dietary lipid suppl ementation was effective in improving the unsaturated-to-saturated fat ty acid ratio in milk (P<0.01), but had a detrimental effect on milk p rotein content (P<0.01). Therefore, these results suggest that the add ition of rumen-protected fat in diets for lactating ewes may improve t he composition of milk fat, but it should be associated with supplemen tal dietary protein or, better still, rumen-protected amino acids to a lleviate the decrease in milk protein due to fat supplementation. (C) 1998 Elsevier Science B.V. All rights reserved.