Forage mixtures for dairy cows: the effect on dry matter intake and milk production of incorporating different proportions of maize silage into diets based on grass silages of differing energy value

Abstract

SUMMARYDuring weeks 3–23 of lactation, 63 multiparous and 28 primiparous Friesian cows were offered ad libitum access to grass silage of either average (A)(ME 10·6 MJ/kg DM; CP 158 g/kg DM) or low (L)(ME 9·9 MJ/kg DM; CP 154 g/kg DM) energy value, either alone or in mixtures consisting of one of these grass silages with 25, 50 or 75% of the forage DM as maize silage. In addition, all cows received 7·2 kg DM/day of concentrate (ME 12·9 MJ/kg DM; CP 202 g/kg DM). There was a significant (P < 0·001) linear relationship between silage DM intake and percentage maize inclusion with grass silage. For grass silage A, DM intake of the mixture of grass and maize in a 1:1 DM ratio was significantly (P < 0·001) higher that at other inclusion levels. There was a significant (P < 0·05) overall linear effect of proportion of maize on milk yield, with a regression coefficient of 0·022 ± 0·009 kg/day per percentage maize proportion. Although milk composition was unaffected by treatment, there was a significant (P < 0·01) linear effect of maize proportion on protein yield for grass silage L, the regression coefficient being 0·8±0·03 g/day/percentage maize proportion. The mixture of grass silage A and maize silage in a 1:1 DM ratio produced the highest yield of milk protein.