Biology of Reproduction, Vol 3, 243-251, Copyright © 1970 by Society for the Study of Reproduction

Embryonic Mortality in the Alpaca

¹ Department of Animal Science, Cornell University, Ithaca, New York, 14850, and Faculty of Veterinary Medicine, San Marcos University, Lima, Peru

Four groups of 20 females each were sacrificed on days 3, 28-31, 40-55, or 87-95 following mating, to determine the fertility rates and the extent and time of embryonic losses. In a second experiment each of 21 adult and 20 yearling virgin females were mated to intact males, with or without single intramuscular doses of 300 IU of HCG given 2 hr before mating. Ovulation and fertilization rates on day 3 were determined in a representative half of the animals at sacrifice, or laparotomy, and in the other half maintenance of pregnancy was tested at monthly intervals. Fertility rates declined from 70% on day 3 to 35% on days 28-31 and showed little change thereafter. Although both ovaries were equally active, significantly more pregnancies were found in the left horns by days 87-95. Migrations of embryos from right to left uterine horns were found in three cases suggesting that the right uterine horn provides a less suitable environment for the embryo. Maintenance of pregnancies through day 90 in the second experiment was significantly higher (p < 0.05) in females treated with HCG before mating. No pregnancies were maintained in control animals up to this stage. Plasma progesterone levels at day 30 were higher and 20-ol levels lower than in the natural service animals, suggesting a decreased conversion of progesterone to 20-ol in the HCG-treated animals. Ovulation and fertilization rates in yearlings were similar to adults, but pregnancy rate on day 30 was significantly higher (p < 0.05) in yearlings.