Enhancing pasture-based dairying with supplementary feeds

New Zealand dairy farmers are increasingly using supplementary feeds in an attempt to overcome the quantitative and nutritional limitations of pasture. The use of rolled maize grain and pasture silage supplements was evaluated on a farmlet basis for two seasons. Supplementary feeding resulted in 88 and 82 g milksolids (MS)/kg dry matter (DM) at stocking rates of 3.24 and 4.48 Friesian cows/ha respectively. At the lower stocking rate the responses during spring, summer and autumn were 11, 53 and 113 g MS/kg DM respectively. Small spring responses were attributed to poor use of the spared pasture and cow condition that resulted from supplementary feeding. Large autumn responses were due to extending lactation length. Responses were less variable at the high stocking rate. If large amounts of supplements are used, the stocking rate must be sufficient to ensure high rates of pasture utilisation are maintained. A second farmlet trial compared rolled maize grain, maize silage, and a nutritionally balanced ration at 4.41 Friesian cows/ha. Offering 1.04-l .23 t DM/cow of supplement increased annual pasture net herbage accumulation by 1.8 t DM/ha, and MS production .-.~-.by up to 96kglcoW (32%)X4iGze gram resulted m the largest response, although responses to maize grain and maize silage were similar when the differences in metabolisable energy (ME) content were accounted for. The balanced ration produced the lowest response, both to DM and ME, and was 20% less than that predicted by the CNCPS nutrition model. ME content is the key nutritional parameter which will determine the likely MS response to supplements.