Anovulatory anoestrus (AA) is a major form of infertility in pasture- fed dairy cows in New Zealand and is most frequently treated by injecting equine chorionic gonadotrophin (eCF) after pre-treatment with progesterone (P4). The effectiveness of this treatment varies between herds. Injecting oestradiol benzoate (ODB) from 24 h to 48 h following PA4 and ODB priming can also induce oestrus and ovulation in AA cows. Two field trials compared responses in 572 cows with AA treated with P4 alone, P4 + eCG and P4 + ODB. The P4 was administered per vaginum for 5 or 7 days using a CIDR device. An injection of 1 mg ODB at 48 h after device removal in Trial 1 increased the insemination submission rate during the following 4 days from 55% among cows treated with P4, or P4 + eCG to 75%, and reduced the incidence of non-responding cows from 21% to 3%. In Trial 2, the comparable results to ODB treatments were 86% inseminated and 3% not responding. The increased submission rates were not due to the ODB producing oestrus without ovulation. Consequently, 42% of anoestrous cows treated with ODB conceived during the first week of AB, 75% conceived after 6 weeks of AB and only 5.5% were finally not pregnant. Comparable figures for herdmates treated with P4 but not injected with ODB were 29%, 66% and 12% respectively. Injecting a low dose of ODB from 24 to 48 h after P4 pre-treatment can be used to successfully treat AA in dairy cows.
Proceedings of the New Zealand Society of Animal Production, Volume 55, , 239-241, 1995
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