The Fatty Acids Composition and Health Lipid Indices in the Sheep Raw Milk Under a Pasture-Based Dairy System

This research was conducted to study fatty acids composition, especially content of n-3 FA; c9,t11-CLA (rumenic acid) and t11-C18:1 (vaccenic acid) and health lipid indices of milk according to the feeding practices in sheep. The exeperimental diets consisted of: P - pasture without any diet supplementation, PC - pasture + standard concentrate (500 g/d), PCs - pasture + fat-enriched concentrate (camelina seed-based concentrate: 500 g/d). Camelina seeds (Cs - Camelina sativa L) were used to increase the beneficial FA concentration in milk fat. PC diet as compared to P diet increases daily milk yield and the content of milk fat, but it adversely affects the quality of milk fats. Fat in the milk of PC ewes had a higher content of hypercholesterolemic FA, while the polyunsaturated FA (PUFA) concentration decreased (p [ 0.001). The use Cs in the concentrate mixture (PCs diet) increased by more than double the c9,t11-CLA, C20:5n-3 (EPA), C22:6n-3 (DHA), C18:3n-3 (ALA) and t11-C18:1 (VA) (p [ 0.001) in milk fat, without any negative effects on milk yield and composition. Beneficial changes of health lipid indices milk fat (atherogenic index, thrombogenic index, n-6/n-3 FA) were detected when the diet of ewes was supplemented with fat-enriched concentrate (PCs group) because of high concentration of c9,t11-CLA, n-3 FA which has sanogenic properties. It is concluded that, when pasture quality and availability do not limit dairy production, supplementation of grazing ewes with concentrate mixture is not recommended, because compromised the milk FA profile. The using camelina seeds in strategies for supplementing the diet of ewes on pastures is a good choice both for the daily milk yield and even more so for the sanogenetic quality of milk fats.