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Effect of progesterone on length of estrous cycle in cattle.

1970; National Institutes of Health; Volume: 31; Issue: 3 Linguagem: Inglês

Ginther Oj,

Reproductive Physiology in Livestock

The effect of progesterone on the length of the estrous cycle and the effect of human chorionic gonadotropin (HCG) as a cycle-shortening e ffect on progesterone was studied in cattle. Progesterone was injected sc at a dose of 100 mg/cow/day. HCG was injected im at a dose of 2500 IU/cow/day. Exogenous progesterone shortened the estrous cycle when given on Days 0-3 (16.2 days p less than .05) 1-4 (17.6 days p less than .09) and 2-5 (16.7 days p less than .05) compared with controls (20.6 days). Injections of progesterone on Days 3-6 4-7 or 5-8 did not change the cycle markedly. The cycle was lengthened (p less than .05) by progesterone on Days 8-11 (22.4 days) 12-15 (22.9 days) and 16-19 (25 days) compared with controls (20.4 days). Simultaneous administration of progesterone and HCG on Days 1-4 prevented the cycle-shortening effect of progesterone.