RUMEN-PROTECTED METHIONINE OR LYSINE SUPPLEMENTATION OF COMISANA EWESDIETS - EFFECTS ON MILK FATTY-ACID COMPOSITION

The effect of graded levels of dietary rumen-protected methionine (rp- Met) or lysine (rp-Lys) on the fatty acid composition of Comisana ewes ' milk was investigated. The animals lambed in autumn and were separat ed from their lambs 7 weeks after parturition; they were divided into five groups of nine which were given different rations. The control gr oup was fed on a mixture of vetch and oat hay with a pelleted concentr ate; the other groups were given the control ration supplemented with rp-Met (3.5 or 7.0 g/kg) or rp-Lys (10.5 or 21.0 g/kg). Milk fatty aci d composition was determined by gas chromatography, and these values w ere subjected to principal components analysis. A correlation was foun d between fatty acid composition and diet. We demonstrated that giving the experimental diets significantly affected milk fat, to an extent that was independent of the levels of the supplementary amino acids. T he milk fat of the control group contained largely caprylic, capric an d lauric acids, whereas that of the groups given the supplementary ami no acids contained largely palmitic: palmitoleic, stearic and oleic ac ids. Thus supplementation resulted in an increase in the proportion of 16:0-18:3 (primarily palmitic and stearic) and a reduction in the pro portion of 4:0-12:0 fatty acids. There was also a modest increase in t he unsaturated: saturated fatty acid ratio.