Effect of concentrate level and stocking rate on performance of dairy cows calving in late winter

Abstract

SUMMARYA 2 × 2 factorial design experiment was conducted for 2 years using 72 British Friesian cows to assess the effects of two levels of concentrate input (822 and 610 ± 13·7 kg/cow) and two stocking rates (6·4 and 4·9 cows/ha) on animal performance. The animals, which had a mean calving date of 22 January, were blocked according to calving date and allocated at random to treatments within each block.All concentrates were given during the post-partum, indoor-feeding period in addition toad libitumgrass silage. All animals received equal concentrate inputs/kg milk produced for the first 4 weeks after calving following which the input to the low concentrate animals was reduced. The animals went to pasture during mid-April and were rotationally grazed for a 24-week period. The pasture received 450 kg N/ha. No interaction between concentrate input and stocking rate was found. The mean milk outputs during the winter period were 2064 and 1971 ±23·9 kg, during the grazing period 2679 and 2739 ± 53·2 kg, and during the total lactation 4991 and 4984 ± 78·8 kg for the high and low concentrate groups respectively. The mean live weights for the two groups were 515 and 496 + 3·1 kg at the end of the winter period and 549 and 537 ± 4·1 kg at the end of the grazing season. The mean values for the high and low stocking rates respectively were: output/cow at pasture, 2571 and 2847 ± 53·2 kg; total lactation yield, 4804 and 5170 + 78·8 kg; live weight at end of grazing season, 529 and 558 + 4·1 kg. Milk composition data are also presented.