antibiotic powder.Animalswere presented on-farmatweekly routine fertility visits
if the farmer considered they were due to be inseminated but had not been seen in
estrus. These prior fertility treatments comprised either 1) a single 500 μg injection
of a prostaglandin F2α (PG) analogue (cloprostenol, 2 ml, Estrumate® Schering-
Plough Animal Health, Uxbridge, UK) or 2) an EAZI-Breed™ progesteroneimpregnated
CIDR®device (AnimalReproduction Technologies Ltd., Leominster,
UK) inserted intra-vaginally for 8 dayswith orwithout a single 500 μg cloprostenol
injection 7 days later. These treatments were administered as deemed clinically
appropriate by the attending vet who did not know the details of the study.
Additionally, the farmer was not aware of on-going results during the study.
Individual cows were monitored from Day 20 postpartum until the first observed
estrus after the commencement of postpartum ovarian cyclicity (based on milk
progesterone metabolite concentrations).