The effects of dexamethasone TMA when used to synchronize parturition in monozygous twin dairy cows

Abstract

Parturition was induced in one member from each of eight sets of monozygous twin dairy cows by intramuscular injection of 20 mg Dexamethasone trimethylacetate. The resulting gestation lengths were less (P < 0.01) than those of the untreated twin counterparts. The actual 'within' twin calving spread was reduced to nil to 32 days (mean ± S.D. 9 ± 12 days) from an expected range of 22 to 53 days (mean ± S.D. 38 ± 12 days). The drug had a variable latent period (time from injection to parturition) and had no apparent effect upon the ensuing lactation yield (P > 0.05) or the subsequent return to postpartum oestrus (P > 0.05). The induced calves had lighter birth weights (P <: 0.01) and a higher mortality (6/8) than calves-from untreated cows (no deaths). There was a significant (P < 0.01) positive correlation (r = 0.846) between gestation length and birth weight of the calf.