A note on the effects of 72-hour calf removal and/or bull exposure upon post-partum reproductive performance of angus cows

The objective of the present study was to determine whether short-term calf removal (SCR) and/or bull exposure (BE) could improve post-partum reproductive performance. The trial was conducted during the spring and early summer when forage availability was optimum. Sixty-four Angus multiparous cows in good body condition were allotted according to a 2 × 2 factorial design involving SCR and BE. At 33 days post partum calves were removed for 72 h from the SCR and SCR + BE groups, and a vasectomized bull was introduced to the BE and SCR + BE groups and remained with the cows until the end of the experiment. Oestrous detection was performed daily based only on the homosexual behaviour of the cows. Cows were bred by natural service by two fertile bulls. Blood samples for progesterone analysis were collected alternatively every 3 and 4 days from 26 to 120 days post partum. There were no significant differences (P > 0·05) among groups in the ovulation, oestrus, and pregnancy rates during the breeding period, in conception rates, nor in the intervals from calving to first ovulation, to first oestrus, and to conception. Under the conditions of this experiment 72 h calf removal and/or bull exposure did not improve post-partum reproductive performance.