Extruded linseed in the diet of dairy ewes: Effect on fatty acid composition of milk and cheese

Ovine milk is naturally richer in short chain but poorer in mid and long chain saturated fatty acids than bovine milk. It results healthier also because as a human food it is characterized by more vaccenic and the conjugated linoleic acid isomer, rumenic acid. The concentration of the major beneficial components, rumenic (RA) and vaccenic (VA) acids, is very sensitive to the quality of the diet, because both RA and VA are metabolic intermediates of the rumen biohydrogenation of linoleic acid (LA) and VA only of α-linolenic acid (α-LNA). Aim of the trial was to study the effect of extruded linseed in the diet of ewes as a means to enhance the concentration of beneficial fatty acids in milk and in the derived cheese. Two groups of 24 Sarda ewes each have been monitored for milk fatty acid composition for 10 weeks after weaning. The diet of the experimental group was supplemented with 200 g/head/day extruded linseed. Butyric acid (BA) was not influenced by the dietary supplement. Monounsaturated acids (MUFA) resulted depressed (58 vs. 48%) by linseed, whereas ω-3 polyunsaturated acids (PUFA n-3) were increased (1 vs. 2.1%), both starting from the second week of lactation. VA was increased more than threefold from the third week on (1.7 vs. 5.9%) and RA almost threefold from the second week on (0.9 vs. 2.3%). All differences resulted significant (P<0.01). The beneficial acids were slightly lost with cheese making, still the cheese from treated ewes resulted decidedly healthier.