The effects of feeding maize silage at different times prior to an herbage meal on dry matter intake, milksolids production and nitrogen excretion in late-lactation dairy cows

Abstract

The objective of this study was to determine the effect of feeding maize silage at different times before the herbage meal on dry matter (DM) intake, milksolids (MS) production and nitrogen (N) excretion of late lactation dairy cows. In an indoor study, nine Friesian × Jersey dairy cows were assigned to three treatments: (1) herbage only (control); (2) supplemented with 3 kg DM of maize silage after morning milking approximately nine hours before the herbage meal (9BH); and (3) supplemented with 3 kg DM of maize silage after afternoon milking approximately one hour before the herbage meal (1BH). Cows were offered ad libitum cut herbage (perennial ryegrass-white clover) for five hours from 1530 to 2030 h. Herbage DM intake was greater (P=0.03) for control than 1BH cows, but did not differ between control and 9BH or between 1BH and 9BH cows (13.71, 11.96 and 12.74 kg DM/cow/ day for control, 1BH and 9BH, respectively). The substitution of herbage by maize silage was greater (P=0.05) for 1BH than 9BH cows (0.56 vs 0.31 kg DM herbage per kg DM maize silage, respectively). Milksolids production did not differ between treatments (overall mean 1.33 kg MS/cow/day). Nitrogen concentration in faeces and estimated urinary-N excretion (g/day) were lower in supplemented than control cows. Under herbage restriction, it is important to consider time of maize silage supplementation relative to the herbage meal for managing substitution rate and urinary-N excretion.