Effects of stocking rate and energy supplementation on milk production from tropical grass-legume pasture

Abstract

Forty Friesian cows were grazed continuously on a green panic (Panicum maximum var. trichoglume)/glycine (Glycine wightii cv. Tinaroo) pasture at stocking rates of 1.3, 1.6, 1.9 and 2.5 cows ha-1 for two years on the Atherton Tableland, Queensland. A supplement of 3.6 kg crushed maize cow-1 day-1 was fed for 50 days post-partum to half the cows in each group in both years. Milk yield per cow was reduced from 3811 kg lactation-1 at 1.3 cows ha-l to 3289 kg lactation-1 at 2.5 cows ha-1. With increasing stocking rate milk yield per hectare increased linearly to 8309 kg ha-1 at 2.5 cows ha-1. At 1.9 and 2.5 cows ha-1 cows lost weight over the two years and in late lactation levels of milk solids were often low. Also at these stocking rates cows had to be supplemented for up to 60 days during the main dry season. Legume content of the pasture declined linearly (P < 0.05) with increasing stocking rates. Maize feeding in early lactation increased milk yield over the total lactation by approximately 12 per cent, the response being 2.3 kg milk per kg maize fed, Response was greater at lighter stocking rates as cows in the heavier stocking rate treatments dried off prematurely. It was concluded that per hectare milk production from tropical grass/legume pastures can approach that from temperate pastures and that energy supplementation early in lactation would substantially increase per cow production.