Production performance and milk composition of dairy cows fed different concentrations of flax hulls

A total of 45 lactating Holstein cows averaging 617 kg of body weight (SE = 20.6) were allotted at week 20 of lactation to five groups of nine cows blocked for similar days in milk to determine the effects of feeding different concentrations of flax hulls on dry matter (DM) intake, milk production, milk composition, digestion, and milk concentration of the mammalian lignan enterolactone. Cows within each block were assigned to one of the five isoenergetic total mixed diets containing either 0, 50, 100, 150, or 200 g/kg DM flax hulls (FHs). The experiment was carried out from wk 20 to 24 of lactation and diets were fed for ad libitum intake. Concentration of FH in the diet had no effect on milk yield, proportions of protein and fat and yields of protein, fat and lactose. There was a linear increase in proportion of lactose in milk and a quadratic effect of feeding level of flax hulls on somatic cell count. Total tract apparent digestibility of DM, acid detergent fiber (ADF), and neutral detergent fiber (aNDF) was similar among diets. Total tract apparent digestibility of ether extract increased with higher proportions of flax hulls in the diet and the increase was more important from 0 to 50 g/kg DM flax hulls. Moreover, milk proportions of total trans, monounsaturated and polyunsaturated fatty acids and concentration of the mammalian lignan enterolactone increased with greater concentration of flax hulls in the diet while the inverse was observed for proportions of saturated fatty acids. Flax hull supplementation may then contribute to the modification of milk composition for better human health with no detrimental effect on productivity of dairy cows.