The interaction between breed and diet on CLA and fatty acids content of milk fat of four sheep breeds kept indoors or at grass

摘要

An experiment was conducted with the objective to study the interaction between breed and diet on conjugated linoleic acid (CLA) and fatty acids profile (FA) content of milk fat of four pure of dairy sheep breeds (Awassi, Lacaune, Friesland and Chios). All sheep used in this study were kept in one flock under the same management. During the winter months (from October to March) all sheep were kept indoors and fed with alfalfa hay and concentrates without any grazing and from April onwards were grazing native pastures without any supplementary feed. A total of 160 individual milk samples were taken from the four breeds at two sampling times: in January (n = 80) and in May (n = 80), when the ewes were in average, on 62 and 185 days in milk. These milk samples were analyzed for FA profile. The results of this experiment showed that the sheep breed had no effect on milk FA profile or on atherogenicity index (AI). The only significant effect was on Delta(-9) desaturase activity index expressed as C-18:1/C-18:0. On the contrary, the diet affected significantly the FA profile of all ewes milk fat, with pasture to cause lower proportions of saturated and higher proportions of unsaturated FA, compared with those of sheep kept and fed indoors. The interaction between breed and diet was significant for the FA C-10:0, C-14:0, C-15:0, C-16:0, C-17:1, C-18:1, C-18:2n6c, C-18:2n6t, C-18:3n6 and CLA and for FA groups SCFA, MCFA, LCFA and MUFA. The S/U FA ratio and the Delta(-9) desaturase indexes (C-14:1/C-14:0 and C-18:1/C-18:0) were also affected by the breed x diet interaction. In conclusion, pasture feeding when compared with supplementary diet, induce large variation in the milk FA profile. In addition pasture increases FA in milk fat which has potential interest for human health. Breed has small effect on milk FA profile, but it can be ignored as it is shown from the interaction breed x diet. (C) 2007 Elsevier B.V. All rights reserved.