Induction of ovulatory oestrus in true anoestrous buffaloes during low breeding season

A fertility treatment trial of anoestrous buffaloes was undertaken on a well managed dairy farm in the low breeding season. Forty lactating buffaloes, 12 each from first and second parity and 16 from third or higher parity, not seen in oestrus for at least 3 to 5 months were diagnosed anoestrous by rectal examination. A subcutaneous ear implant containing 3 mg of norgestomet was inserted, accompanied by an intramuscular injection of 3 mg norgestomet and 5 mg of oestradiol valerate (Syncro-mate B, Intervet). After 9 days the implant was removed and 600 IU of PMSG (Intervet) were given intramuscularly. Irrespective of oestrous behaviour, the animals were inseminated with frozen semen at two fixed times: 48 and 72 h after removal of the implant. Thirty animals having calved in the same period as the experimental animals and not seen in oestrus since then served as controls. Milk samples for progesterone analysis were taken on the day of insertion of the implant, the day of removal and on days 10 and 22 after the second A.I. Progesterone determination by means of an enzyme immunoassay (EIA) revealed that 33 buffaloes out of 40 (82.5%) were in true anoestrus. Ovulation occurred in 21 buffaloes out of 30 (70%). Three buffaloes could not be followed up further. The overall conception rate was 53.3%. The parity-wise conception rate was 40%, 44.4% and 72.2% in first, second and third or higher parity, respectively. None of the control animals displayed oestrus during the course of the study.