Abstract

A major cause of delayed pregnancy and reproductive wastage in Australian dairy cattle is the failure of cows to be re-inseminated within 24 days of an unsuccessful insemination. Four commercial herds were observed to determine the incidence of this syndrome. Those cows inseminated in the first three weeks of the mating season (n=721 cows) were observed for a subsequent return to service, and non-return cows were diagnosed for pregnancy. Overall, 45% of cows were confirmed pregnant to first service, 37% returned to service within 24 days, and 19% were diagnosed as non-return, non-pregnant cows (Phantom cows). The majority of cases of Phantom cows (89%) were explained as having: a) a CL but not returning for service; b) having an abnormally long return to service (25 to 39 days); or, c) reverting to an anoestrous state. Other cases (<5% incidence) included ovarian cysts, pyometra and uterine adhesions. Repeated diagnoses of pregnancy identified few cases in which a pregnancy appeared to have failed (3.3%). The incidence of Phantom cows was higher for CIDR-treated anoestrous cows than cows synchronised with prostaglandin, and lowest for those cows not treated. These observations form the basis for further study of this syndrome in Australian herds.

DP, Nation, J Morton, J Cavalieri, and KL Macmillan

Proceedings of the New Zealand Society of Animal Production, Volume 61, Christchurch, 180-183, 2001