Colostrum and milk fatty acids of dairy cows as influenced by extruded linseed supplementation during the transition period

Abstract

The effects of precalving fat sources on fatty acid (FA) profile of colostrum and milk and on metabolic parameters in early lactation were determined. Two fat supplements (target: 21% fat, DM basis) fed at 1.8 kg DM d -1 were compared: Control (C; containing fractionated palm oil rich in 16:0) and Linseed (L; containing extruded linseed, rich in 18:3n-3). Sixteen dry Holstein (n = 7) and Brown Swiss (n = 9) cows were assigned to four groups receiving the supplements from 5 wk pre- to 4 wk post-calving in different sequences: CC, CL, LC and LL. Treatments did not affect metabolic parameters, milk yield or composition. Linseed supplementation increased proportions of 18:0, 18:1, 18:2 and 18:3 in colostrum and milk (except 18:1 for colostrum). The highest n-3 FA proportion was observed in milk of LL cows. For most 16 and 18 FA, a fast response occurred within the first week of lactation for cows that switched treatments over calving. Carry-over to milk of 18:3 and its biohydrogenation products from linseed fed precalving was low. Pre-calving feeding strategies to favour incorporation of these FA into early lactation milk were not successful, but the reasons for this failure remain unclear.Key words: Linseed, omega-3 fatty acids, transition period, milk, colostrum, dairy cows