Abstract

Many cows treated for anovulatory anoestrus in Victorian herds which fail to conceive to first insemination also fail to return-to-service 18 to 24 days later. A trial in 16 herds in the Maffra district determined whether treatments to re-synchronise returns-to-service could also increase submission rates for a second insemination in these cows. The 810 Holstein cows initially treated for anovulatory anoestrus provided 691 for inclusion in the study. A previously used CIDRTM device was re-inserted 12 to 14 days after first insemination with injected oestradiol benzoate (1mg ODB), and was removed 7 days later. Some cows received no further treatment (Group 1; n=357); the remainder were each injected with 0.5mg ODB 24h after device removal (Group 2; n=334). Conception rates were similar for the two Groups (1st insem: 29% vs. 32%; 2nd insem: 44.5% vs. 46.4%). The higher submission rate for synchronised second inseminations in Group 2 (40% vs. 65%; P<0.01) meant that the median interval from first insemination to conception was reduced from 42 days (Group 1) to 23 days (Group 2 ; P<0.01); pregnancy rates after 6 weeks of AI were increased from 51.5% to 59.6%, respectively (P<0.01). The injection of ODB given after device removal for resynchrony improved the efficacy of treating anoestrous cows in these Victorian herds.

VE, Eagles, J Malmo, and KL Macmillan

Proceedings of the New Zealand Society of Animal Production, Volume 61, Christchurch, 176-179, 2001