Effects of post-grazing herbage height and concentrate feeding on milk production and major milk fatty acids of dairy cows in mid-lactation

Abstract

Milk fatty acids (FA) were compared in mid-lactation dairy cows in four feeding systems combining grazing management and supplementation. The four treatments were factorial combinations of compressed herbage grazed to 3·7 or 4·6 cm post-grazing height, with or without concentrate feeding (3·6 kg cow−1 d−1). Milk yield and composition were measured for four groups of eight Friesian × Jersey dairy cows over 3 weeks in mid-lactation for cows that had grazed treatments for 64 d from early spring. Milk yield was higher in cows fed concentrate plus herbage (23·9 kg d−1 cow−1) than cows fed herbage only (20·3 kg d−1 cow−1). Milk fat percentage was higher in cows fed herbage only (5·5%) than that fed herbage plus concentrate (5·1%). Milk protein percentage was higher in cows fed herbage plus concentrate (4·0%) than that fed herbage only (3·7%). The concentrations of conjugated linoleic acids c9, t11, C18:0, C18:1 t11 and C18:2 t9, c12 FA were lower where concentrate was fed. The concentrations of C18:1 t10, C18:1 t5, t8 and C18:2 c9, c12 FA were higher where concentrate was fed. The concentrations of C18:1 c6, C18:1 c9, C18:1 t9 and C18:3 c6,9,15 were unaffected by concentrate feeding. Post-grazing herbage height had no significant effect on milk yield or concentration of milk FA. Provided dairy cows are harvesting leafy material of similar nutrient and FA concentration, post-grazing herbage height does not appear to alter milk FA and the supply of high energy concentrates is more influential on milk FA profiles.