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An Improved Programme for the Treatment of Anoestrous Dairy Cows in New Zealand
Lawrence L.
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Objectives:
Under seasonal breeding programmes used in New Zealand, it is common for cows not detected in oestrus (NVO) to undergo a treatment comprising of progesterone (P4) for 7 days, with Gonadotrophin Releasing Hormone (GnRH) at device insertion and 2 days after device removal, and prostaglandin (PG)F2 alpha at device removal (GPG). Recent studies in beef cows have suggested that inclusion of equine chorionic gonadotrophin (eCG) at the time of device removal may improve conception rate. Hence the objective of this study was to investigate whether eCG improves pregnancy outcomes in NZ dairy cows.
Methods:
Cows not detected in oestrus (n= 1,906) from 12 herds were randomly assigned to one of four treatments: GPG alone; GPG with a CIDR device (Zoetis NZ; CIDR); GPG with a DIB device (AgriHealth NZ, Syntex S.A.; DIB); and GPG, with a DIB and 400 IU eCG (DIB + eCG) at progesterone device removal. For each treatment a 7 day interval existed between GnRH and PG, with GnRH injected 2 days later. For those treatments which included P4, the device was in place between the first GnRH and PG. Fixed-time insemination occurred approximately 72 hours after PG treatment. Initial pregnancy testing occurred by 84 days after fixed time insemination. Those cows not detected pregnant at this stage were retested. Statistical analysis was undertaken using general estimating equations and included potential confounders such as breed, body condition score at initiation of treatment, age, calving date, and herd. Outcome variables examined included conception rate to first service and the proportion of cows pregnant by 28 days into the seasonal breeding programme. […]
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About
Affiliation of the authors at the time of publication
AgriHealth, Auckland, New Zealand
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