Influence of pre- and post-calving pasture allowance on hill country beef cow and calf performance

Abstract

Sixty pregnant beef cows of Friesian, 7/8 Friesian X Jersey, and Angus genotypes 3 years of age and older were used. At 56 days before calving, each cow was allocated to 1 of 2 daily pasture DM allowance levels: 20 (“20”) and 8 (“8”) kg DM per cow. At calving cows were re-assigned to daily pasture allowances of 20 (“20-20” and “8-20”) or 8 (“20-8” and 8-8”) kg DM per cow for 56 days post-partum. At 56 days after calving, the cows were grouped into a single mob and given a daily allowance of 18 kg DM per cow throughout mating and until weaning. Despite similar pre-calving weights, “20” cows were 36 kg heavier (P < 0.01) immediately after calving than “8” cows. Forty-two days after calving the visually assessed condition scores of “20” cows remained consistently higher (P < 0.05) than the score of “8” cows. Mean DM intakes (kg/cow/day) for “20” and “8” cows before calving were 9.5 and 6.3 respectively. Mean DM intakes (kg/cow/day) (and % DM utilisation rates) for “20” and “8” cows before calving were 9.5 kg (47.6%) and 6.3 kg (78.2%) respectively. At 56 days after calving, “20-20” and “8-20” cows weighed 520 kg and 502 kg respectively and were heavier (P < 0.01) than “20-8” and “8-8” cows (340 kg and 392 kg); condition scores were significantly different (P < 0.05) at 6.8, 6.0, 3.4, and 2.5 respectively. Treatments did not affect calf weights until 56 days of age when calves of “20-20” (76 kg) and “8-20” (81 kg) cows were heavier (P < 0.05) than those of “8-8” cows (67 kg) ; calves out of “20-8” cows (74 kg) were intermediate. Intakes (kg DM/cow/day) for “20-20”, “8-20”, “20-8”, and “8-8” cows during the 56 days after calving were 10.5, 11.7, 6.8, and 7.0 kg respectively. From 56 days post-partum until weaning, gains in cow live weight (and condition score) were − 5 kg (− 0.2) , 44 kg (2.0), 4 kg (−0.1), and 58 kg (2.7) for “20-20”, “20-8”, “8-20”, and “8-8” cows respectively. Corresponding calf weight gains (kg) were 81, 83, 83, and 83. The mean intervals (days) from calving to first oestrus were 72, 80, and 69 for “20-20”, “20-8”, and “8-20” cows respectively, shorter (P < 0.05) than the 97 days of “8-8” cows. Pre-calving pasture allowance had no effect on interval from calving to first oestrus or pregnancy rate, but both these traits were affected by post-calving allowance.