Milk Production and Reproductive Performance of Cows Hormonally Induced into Lactation

Eleven cows and five heifers were induced to lactate by the administration of 17 β-estradiol and progesterone for 7 days followed by dexamethasone on days 18 to 20. Subsequent milk production varied from two animals which produced over 30 kg/day (approximately equal to previous production) to two animals which failed to lactate (<1 kg/day). Of the animals, 69% produced over 9 kg milk/day at peak yield. Although peak milk production was not reached until an average of 8.8 wk following commencement of milking, both peak production and production for days 2 to 8 were related closely to 305-day production. Reproductive status was monitored in 11 of the more successful cows. Ovaries of all animals were regressed by treatment, with first estrus occurring an average of 43 days following the last estrogen-progesterone injection. Nine cows were bred, and five conceived with no complications during pregnancy. Since all animals were culled from the University herd for reproductive problems, this method to induce lactation offers promise as a procedure to return problem breeders of good genetic quality to production.