Effect of Placental Gonadotropin on Pregnancy Rate in the Bovine

Abstract

In four experiments a total of 773 heifers were synchronized with 6-chloro△⁶-17 acetoxyprogesterone (CAP). During a 26- to 29-day period after CAP treatment the heifers were artificially inseminated and treated with pregnant mare serum (PMS), human chorionic gonadotropin (HCG) or a combination of both. These placental gonadotropins (PGT) were given subcutaneously at the time of insemination or 3 days after the onset of estrus. At the first synchronized estrus treatment with 1,000 to 2,000 IU of PGT at the time of insemination increased pregnancy rate 12.8 percentage points (P<.025). Similar treatment at the second synchronized estrus gave values 10.3 percentage points higher than controls (P<.20). PGT given 3 days after the first synchronized estrus reduced pregnancy rate 20.6 percentage points (P<.001), whereas, similar treatment at the second synchronized estrus resulted in values higher than those of the controls (14.0 percentage points, P<.20). Both HCG and PMS appear to give similar effects on pregnancy rate. Copyright © 1973. American Society of Animal Science . Copyright 1973 by American Society of Animal Science.