Variation between Boars in Semen Characteristics and Fertility

The most important factor influencing the income from a livestock breeding herd is the number of offspring produced per female per year. This number varies between herds and species and is influenced by such factors as disease, nutrition, genetics, management, climate, and endocrine balance. It has been estimated that over 30% of the potential offspring from the sow are lost between ovulation and the thirtieth day of pregnancy. It would be of great economic value to reduce this loss both in terms of increased number of offspring per pregnancy and increased number of offspring per year. The sow has long been considered to be solely responsible for litter size; therefore, much of the research effort in this area has been directed toward the female. Recent studies have indicated that the incidence of fertilization failure and early embryonic mortality are due in part to some inherent abnormalities of the male germ cell. Although actual fertility tests remain the only absolute test of male fertility level, it would be of value to find some reliable, rapid and inexpensive laboratory measure of fertility in order to eliminate males of low fertility from the herd prior to the breeding season. This research was designed to study: 1. The variation of certain semen characteristics between boars and between ejaculates within boars. 2. The relationship between these semen characteristics and fecundity in the gilt