The effect on milk production of replacing grass silage with maize silage in the diet of dairy cows

Abstract

This experiment examined the effects of replacing high digestibility grass silage (GS) with maize silage (MS) grown under marginal climatic conditions on milk production and forage intake of Friesian cows. Fifty-six cows were fed 6 kg/d (fresh weight) of concentrates and one of four forages: (1) all GS, (2) 67:33 GS:MS, (3) 33:67 GS:MS, and (4) all MS. Concentrate crude protein (CP) level was varied to equalise total dietary CP. The analysis of the GS and MS were: DM (g/kg) 223 and 257, pH 3.91 and 3.98, and CP (g/kg DM) 155 and 91. The MS contained 219 g starch/kg DM. In vivo OM digestibilities were 0.782 and 0.674 (s.e.m.=0.0063, P<0.001) for the GS and MS respectively. Silage DM intakes were 8.8, 9.7, 10.4, and 10.7 (s.e.m.=0.35) kg DM/d for treatments 1 to 4, respectively. The intake on treatment 1 was significantly lower than on treatments 3 and 4 ( P<0.01 and P<0.001, respectively). Milk yields were 21.4, 23.0, 23.1, and 22.7 (s.e.m.=0.48) kg/d for treatment 1 to 4, respectively. The differences in milk yield between the GS only and the two GS:MS mixtures were significant ( P<0.05). Maximum milk protein concentration (31.6 g/kg) and yield of fat and protein (1.59 kg/d) were achieved on the mixed forage diet containing 67% maize silage. These results show that moderate quality maize silage can successfully replace a high proportion of high digestibility grass silage in dairy cow diets.