The response and effects of inducing parturition on Day 274 of gestation in dairy cows with synchronised conception dates was investigated in selected herds around Victoria. Cows (n=227) were injected with dexamethasone trimethylacetate (30 mg, i.m.) with 444 herdmates as controls. Randomisation was based on scored udder development. Blood samples taken on Days 272 and 274 had average plasma progesterone concentrations of 4.50 and 4.49 ng/ml respectively (P>0.05). Treated (T) cows calved an average of 2.61 ± 0.21 days before their due date, compared to 0.17 ± 0.20 days for control (C) cows (P<0.001). There were no differences in the proportion of cows displaying symptoms of milk fever, mastitis, paralysis or acute metritis. The incidence of retained foetal membranes at 12h postpartum differed between the two groups (3% vs. 16%; C vs. T; P<0.005). Control cows received more assistance at parturition (15% vs. 10%, P<0.05). There were no differences between groups for cow or calf mortality, or for any parameter of milk yield. The effect of treatment on subsequent fertility was minimal.

KL, Davis, and KL Macmillan

Proceedings of the New Zealand Society of Animal Production, Volume 61, Christchurch, 184-187, 2001
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