Effect of feeding system on unsaturated fatty acid level in milk of dairy cows

Abstract

In recent years, consumer attitudes toward fat of animal origin have changed owing to findings that some milk fatty acids (FAs) are positive for human health, especially conjugated linolenic acid and n-3 FAs. Accordingly, the manipulation of the fat content and FA composition of cows’ milk via nutritional strategies has been an important target for the dairy industry in many countries. Twenty commercial Holstein–Friesian dairy herds of Asturias (northern Spain) with 1106 dairy cows were examined in order to evaluate milk FA profiles under different management systems. These herds were divided into three groups according to management: (1) indoor herds: cows feeding indoors, (2) mixed herds: indoor management system but with at least 6 h of grazing outdoors and (3) outdoor herds: cows allowed 6–18 h of grazing per day. Milk from the indoor herds exhibited the highest concentration of fat (3.57%; PO0.01), protein (3.14%; PO0.001), lactose (4.76%; PO0.01) and urea (29.4 mg dl-1; PO0.01). The milk of outdoor herds had a lower (PO0.05) content of short-chain FAs than that of the indoor and mixed herds (10.89 versus 11.52 and 11.35 g 100 g-1 FA). The milk of the indoor herds had higher concentrations of saturated fatty acids (SFA) (67.56 g 100 g-1 FA; PO0.001) and palmitic and palmitoleic acids (30.16 and 1.82 g 100 g-1 FA, respectively), while that of the mixed and outdoors herds had higher concentrations of unsaturated fatty acids (UFA) (34.58 g 100 g-1 FA; PO0.001) and long-chain FAs, especially stearic (13.89 g 100 g-1 FA; PO0.01), vaccenic (2.77 g 100 g-1 FA; PO0.001), conjugated linoleic (0.92 g 100 g - 1 FA; PO0.001) and linolenic (0.42 g 100 g-1 FA; PO0.001) acids. Results from this study suggest that the incorporation of forage and pasture in the diet of dairy cows can improve the FA profile of milk.