Advancement of ovulation and oestrus after temporary calf removal and FSH supplementation in postpartum beef cows
Additional Document Info
To evaluate the effect of temporary calf removal and/or FSH supplementation on post-partum ovarian and oestrous activity, 40 anoestrous multiparous Aberdeen Angus cows under grazing conditions were used. The animals were allocated, on the basis of calving date and body condition, to four initially similar groups according to a 2 2 factorial design (ten animals per group) involving a 72 h calf removal (TCR) and exogenous follicle stimulating hormone supplementation (FSH). Anoestrus was determined by measuring plasma progesterone concentrations before treatments, which began at 29.6 4.9 days postpartum. Total FSH supplementation (12 mg, porcine FSH) was performed by six intramuscular decreasing doses (3, 3, 2, 2, 1 and 1 mg, respectively) distributed at 12 h intervals, beginning 24 h before TCR. Oestrus detection (twice daily) and blood sample collection (every 2-3 days) were performed from 7 days before the start of treatments and for 45 days thereafter. The TCR plus FSH group had higher oestrous and ovulation rates at 40 days postpartum (control, 10% and 10%; TCR, 10% and 10%; FSH, 10% and 10%; TCR plus FSH, 60% and 60%) and 60 days postpartum (control, 30% and 30%; TCR, 50% and 50%; FSH, 40% and 50%; TCR plus FSH, 80% and 100%). These differences were significant (P < 0.05) for oestrous rates at 40 days postpartum and for ovulation rates at 40 and 60 days postpartum. TCR plus FSH significantly shortened (P < 0.05) the intervals (mean s.e.m., days) from calving to first ovulation (control, 61.2 5.5; TCR, 62.8 4.6; FSH, 61.6 3.8 and TCR plus FSH, 43.4 3.1) and a similar trend (P > 0.05) was observed for the intervals from calving to first oestrus (control, 61.2 5.5; TCR, 62.3 5.4; FSH, 63.4 3.9 and TCR + FSH, 47.7 5.2). The rate of short first luteal phases ( 10 days) was: control, 40%; TCR, 33%; FSH, 43%; TCR plus FSH, 89% (P < 0.12). In summary, TCR plus FSH resulted in increased ovulation and oestrus rates, shorter postpartum intervals, but subnormal corpora lutea were formed following the first ovulation in early postpartum beef cows. 1994.