Intake, digestibility, milk production and kinetics of digestion and passage for diets based on maize or grass silage fed to late lactation dairy cows

Abstract

This experiment compares maize and grass silage in relation to dry matter (DM) intake, milk production and the kinetics of digestion and passage for both forages. Twenty-two multiparous late lactation dairy cows were fed diets based on maize or grass silage (diets MS and GS, respectively) for a period of 7 weeks. Milk production was determined over 4 weeks ( n=11 per treatment) with total diet digestibility, forage DM intake and rumen outflow rate being determined in tie stalls ( n=7 per treatment). Forage degradability characteristics were determined using three fistulated steers. The difference in forage DM intake between treatments was highly significant ( P<0.001) with a higher forage DM intake realised for the MS diet (13.54 vs. 9.49 kg/day). Milk yield did not differ significantly with treatment ( P>0.05). However, cows fed the MS diet had a significantly higher milk fat and milk protein content and milk fat yield ( P<0.01). When rumen fill was estimated using the degradability characteristics for forage NDF and the determined rumen outflow rates (2.45 and 2.02% per hour for the grass and maize silage, respectively), the maize silage NDF caused a higher rumen fill than the grass silage NDF (6.83 vs. 4.83 kg of NDF). These results suggest that rumen fill proceeds to a greater degree for cows fed maize silage and that under the conditions of this experiment, extra production from the increased forage DM intake was realised in milk fat and protein content and milk fat yield.