The production and composition of milk from dairy cows fed hay and supplemented with either brewers' grains or rolled barley grain

Abstract

Four groups of seven Friesian cows were offered 70% of their calculated metabolizable energy requirements as pasture hay and either 2.4, 4.8 or 7.2 kg/d of dry matter (DM) as wet brewers' grains or 3.9 kg DM/d as rolled barley. A further group of cows received no supplement. The quantities of brewers' grains offered were calculated from in vitro digestible DM content to provide lo%, 20% and 30%, respectively, of metabolizable energy requirements and the rolled barley 30% of metabolizable energy requirements. The cows consumed a mean of 2.2,4.3 and 6.1 kg DM/d, respectively, as brewers' grains and 3.9 kg DM/d as rolled barley. The daily yields of milk (litres), protein (kg) and solids not fat (kg), respectively, were greater (P < 0.05) for the cows offered brewers' grains at 4.8 kg DM/d (1 5.6,0.49, 1.36) and 7.2 kg DM/d (16.4, 0.54, 1.45) than for the cows offered rolled barley (13.3, 0.45, 1.21). Daily yields of milk fat from the cows offered either 4.8 or 7.2 kg DM/d of brewers' grains or rolled barley did not differ significantly. There were no significant differences between treatments in liveweight change. It was concluded that wet brewers' grains and rolled barley offered as supplements to dairy cows fed hay have similar nutritive values for milk production. It was calculated that for milk fat production the break even landed price ratio of brewers' grains to barley is 1:1.26.