Effects of ewe feeding system (grass vs concentrate) on milk fatty acid composition

the aim of this work was to investigate whether and how the feeding system could effect ewe milk fatty acids. Twenty pregnat Comisana ewes were divided into two groups of ten one month before lambing and allowed two different systems: Pasture group (P) grazed on a vetch pasture; stall group (S) was given hay, a commercial concentrate and a mixture of barley and faba bean. After lambing, individual milk samples were teken weekley and analysed for fatty acid composition. The trial went on for 38 days. Milk from P ewes was poorer in lauric (C12:0), myristic (C14:0) and palmitic (C16:0) acids than milk from S ewes (P<0.05, P<0.001 and P=0.001 respectively). Trans-vaccenic acid (C18:1 trans 11) was significantly higher (P<0.001) in milk from P animals compared to S ewes. Linoleic acid (C18:2 n-6) tended to be higher (P=0.06) im milk from S ewes while linolenic acid (C18:3 n-3) was significantly higher (P<0.001) im milk from P animals (1.72 vs 0.79% total fatty acids). Conjugated linoleic acid (C18:2 cis 9-trans11) was almost double in mik form P ewes compared to S animals (2.53 vs 1.33 % total fatty acids, P<0.001). The ratio between linoleic and linolenic acids was higher (P=0.001) in milk from stall-fed ewes. These results indicate that the ewe feeding system strongly affects milk fatty acid profile and, particularly, that grass feeding enhances milk dietetic quality.