Abstract

The aim of this study was to compare the rate of resumption of oestrous cycles and fertility to first insemination between anoestrous cows grazed separately (Split) or grazed in the main herd (Control) for 28 days and untreated or treated with progesterone (CIDR) and ODB from 7 days before the planned start of mating. Oestrus was detected in 54.7%, 46.3%, 93.5% and 86.8% of cows (Control, Split, CIDR and Split+CIDR, respectively) by 28 days after start of treatment (P<0.05). Compared to controls conception to first insemination was no different in Split and CIDR groups, but was reduced in the Split+CIDR group (P<0.05). The percentage of cows pregnant by 28 days after examination was 26.4%, 18.9%, 42.1% and 31.4% for Control, Split, CIDR and Split+CIDR groups, respectively (P<0.05). There was no overall effect of separate grazing on milksolids production or cow liveweights, but milksolids did vary between herds (P<0.001). Separate grazing did not enhance the reproductive performance of anoestrous cows.

BA, Clark, FM Rhodes, and S McDougall

Proceedings of the New Zealand Society of Animal Production, Volume 59, , 55-57, 1999