The Response of Low-Fertility Cows to Insemination with Semen from Bulls of Another Breed

Early embryonic mortality is a major cause of infertility in farm animals. Warniek etal. (5) reported that embryonic death in the first 25 days of gestation is a major cause for repeat-breeding in sows (67.4 per cent). Laing (3) estimates the incidence of embryonic mortality in commercial cattle at approximately 30 per cent. In a study on the nature of, the reproductive failure in cows of low fertility, Tanabe and Casida (4) found a fertilization rate of 66.1 per cent but by 34 days after breeding the percentage of cows with normal embryos had dropped to 23.1 for a death rate of 65.1 per cent of the embryos.