Effect of embryo removal and intrauterine infusion of embryonic homogenates on the lifespan of the bovine corpus luteum.

Three experiments were conducted to determine the day at which the bovine embryo first affects luteal lifespan and if intrauterine infusion of homogenates of bovine embryos would extend luteal lifespan in nonpregnant heifers. Exp. I was a 2 x 2 factorial design and utilized 23 pregnant or nonbred Holstein heifers that were subjected to embryo removal procedures on day 15 or day 18 postestrus (estrus = day 0). Exp. II was a 4 x 2 factorial design and utilized 39 pregnant or nonbred Holstein or beef x Holstein heifers that were subjected to embryo removal procedures on day 13, 15, 17 or 19 postestrus. Removal of embryos at day 18 (Exp. I) and day 17 or 19 (Exp. II) prolonged (P<.01) luteal lffespan as compared to nonbred controls or when embryos were removed on days 13 or 15 of pregnancy. In Exp. III, seven heifers received twice daily intrauterine infusions of a homogenate of 17and 18-day-old embryos and seven received control infusions. As compared to the control group, intrauterine infusions of homogenized 17and 18-day-old embryos lengthened (P<.01) the interestrous interval by delaying regression of the CL. The results of these experiments indicate that between days 15 and 17 of pregnancy the bovine embryo produces a substance that prolongs the functional lifespan of the CL. (