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Induction of Lactation in Nonpregnant Cows by Estradiol-17ß and Progesterone from an Intravaginal Sponge

Ministry of Agriculture and Fisheries, Ruakura Agricultural Research Centre, Private Bag Hamilton, New Zealand

ABSTRACT

An intravaginal sponge impregnated with 500 mg estradiol-17ß and 1000 mg progesterone to induce lactation in nonpregnant dairy cattle was investigated. Sponge retention (>95%) was achieved by its attachment to a nylon collar. Treatment with the sponge for 10 days resulted in lactogenesis in 25% of treated cows compared with an 89% succes rate when an adjunct injection of dexamethasone esters (20 mg intramuscular) was given on day 6 or a 96% success rate when reserpine injections (2.5 mg intramuscular) were given on days 6, 8, and 10 after sponge insertion.

Milking was begun 12 days after sponge insertion (2 days after removal). Peak milk yield was unaffected by adjunct treatments but was greater in spring (mean 11.5 kg/day) than in autumn treated cows (mean 3 and 6 kg/day) in 2 yr of trials.

Concentration of estradiol-17ß in plasma rose rapidly after sponge insertion to a peak similar to that in cows in late pregnancy. Measurement of estradiol-17ß concentration in milk indicated less, even at first milking than in commercially distributed pasteurized milk. Milk fat and protein content were higher in milk from induced lactations compared with that from normally calving cows on the same day.