Induced calving: a comparison of treatment regimes

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Abstract
Calving was induced in 374 cows with either dexamethasone trimethyl acetate (O) or dexamethasone isonicotinate (V) as an initial injection. Cows that had not calved were injected 7–12 days later with betamethasone (B) or cloprostenol (E). The time from injection to calving was O, 7.7; V, 6.9; O + B, 12.9; O + E, 11.2; V + B, 11.4 and V + E, 11.4 days respectively. Calf mortality was O, 3; V, 8; 0 + B,27;0 + E, 23; V + B,34 and V + E, 29% respectively. Mortality was positively related to prematurity and negatively to birthweight. The overall incidence of retained foetal membranes was 25% and was not significantly different between treatments. There were no significant differences between induced cows and untreated herdmates calving at similar times in: days from calving to first oestrus (38 v. 39 days); percent of cows with premating oestrus (52 v. 51%); days from calving to conception (66 v. 69 days); and conception rate at first mating (57 v. 53%). Ten percent of induced cows and 3% of the controls did not become pregnant again(P <0.01). Milkfat production was 127 kg in 187 days for the controls and 121 kg in 181 days (P < 0.05) for the induced cows. Therefore O and V have similar actions as initial injections for induced calving; kB and E were effective as second injections with E causing a more concentrated calving. Milk production and fertility were slightly reduced in the induced cows compared with herdmate controls, but these effects were probably outweighed by the benefits of induced calving.

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