Short-term studies on the response of grazing dairy cows to dietary supplementation

Abstract

Milk production of grazing dairy cows receiving 3 kg per day of wheat, sorghum, maize, oats or barley was measured. In general, only small differences were observed in the yield and composition of milk produced from cows consuming the different grains. Two experiments were conducted to investigate the relationship between the milk response of grazing dairy cows to 3 kg supplement and their level of production, stage of lactation, and age. Similar mean responses to supplementation were found in both experiments but no consistent relationship between response and either level of production, stage of lactation or age was found. A further experiment examined the response of grazing dairy cows, grouped into four groups according to their level of production, to 3, 4.1/3 5.2/3, 7 or 8.5 kg supplement per day. These treatments had a non-significant effect on milk composition; as the rate of supplementation increased, the yield of milk and its constituents first increased then commenced to decrease. The response obtained from both low and high producing cows was similar. It was thus concluded that in the short-term neither the type of grain fed, the cow's age, level of production nor stage of lactation affected its response to supplementation. The dichotomy between this conclusion and the widespread view that high producers respond better to supplementation is discussed.