Hormonal Induction of Lactation in the Cow

Abstract

Twenty-three Polish ‘Black and White’ cows, which had failed to conceive for eight to 14 months, were induced to lactate using exogenous hormones. The animals were divided into four groups on the basis of age and previous year’s milk yield. Groups I and II were given 15 injections each containing 0·05 mg oestradiol-17 β /kg and 0·125 mg progesterone/kg on days 1 to 7. Cows in group II were also given a total dose per animal of 22·5 mg reserpine between days 9 and 16. Groups III and IV received the same daily dose as groups I and II in 11 and seven injections respectively on days 1 to 5·5 and 1 to 3·5 respectively, and reserpine to a total dose of 22·5 mg per animal between days 7 and 13 in group III, and 30 mg per animal between days 5 and 13 in group IV. Twenty out of 23 cows were successfully induced into a lactation of practical value. According to Duncan’s multiple-range test, there were no significant differences in the milk yield over 200 days between groups I, II and IV, while group III was significantly decreased. Although oestrus was observed, no positive results of mating were obtained for cows in groups I and II, in groups III and IV (with reduced hormonal therapy) seven out of 10 cows conceived. The results show that shortening the hormonal therapy did not significantly reduce milk yield, provided that it was followed by a suitable dose of reserpine, but it did improve the fertility index. This could be of practical value, mainly in commercial herds where cows of high breeding value would otherwise be culled because of long-lasting sub-fertility.