Replacing conventional with brown midrib corn silage in a total mixed ration: the impact on early and late lactation dairy cow intake, milk yield and composition, and milk fatty acids profile

摘要

Brown midrib corn silage (BMRS) is used as an alternative to conventional corn silage (CS) to increase milk yield because of its higher neutral detergent fibre digestibility (NDFD) and DM intake (DMI). Forty Holstein dairy cows were used in a completely randomised design with a 2 x 2 factorial arrangement. Two groups of 13 cows in early lactation (EL) and 7 in late lactation (LL) were fed with a total mixed ration including brown midrib (BMR) or conventional corn silage (C), for a period of 42 days. The cows were milked twice a day, milk yield and DMI were recorded, and NDFD was estimated. Milk composition was measured twice a week and milk fatty acid profile was quantified on the final week of the experiment. In EL, BMR diet increased DMI, NDFD, milk and protein yield whereas milk fat content and yield were decreased. Concentrations of trans-10 C18:1 and trans-10, cis-12 C18:2 in milk were higher in BMR. In LL cows DMI was similar between BMR and C whereas milk and fat yields tended to be higher in C. Fat-corrected milk yield was greater in the C diet. The effect of the BMRS on DMI and milk yield depended on stage of lactation, justifying its use in early lactation. The lower milk fat concentration, observed when BMRS was included in the diets, could be explained in part by an increased concentration of trans-10 C18:1 and trans-10, cis-12 C18:2.