Data were collected from 249 cows over 2 years at Whatawhata Research Centre on pelvic area, weight and breed of embryo transfer mated cow, calf birth weight, breed and a defined calving difficulty score. Cow liveweight and pelvic area were significantly correlated (R2 = 0.56, P< 0.05), but cow liveweight and calf birth weight were not (R2 = 0.07, NS). Cow pelvic area and calf birth weight were also not related (R2 = 0.04, NS). In July of each year, the Jersey cows were 119 kg lighter (P<0.001), had a smaller pelvic area (264 vs. 322 cm2, P<0.001) and more calving difficulties (26 vs. 5%, P<0.001) than Hereford x Friesian (HxF) cows. Across breeds, pelvic area (P<0.01) and cow liveweight (P<0.001), when fitted individually, were negatively associated with the probability of a cow having an assisted calving. On its own, the impact of calf birth weight was NS, although it explained additional variation (P<0.05) if cow liveweight was in the model. Within the range of calf breeds (NS) we used, we predict that any of recipient breed, cow liveweight or pelvic area (in decreasing order of reliability) could be used to reject cows at ET that might cause problems at calving although errors of estimation will result in wasteful rejection of cows and will not eliminate calving problems.

DC, Smeaton, ML Scott, RW Webby, C Cameron, L McGowan, and A Brooky

Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 252-256, 2004
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