Factors Affecting Puberty in Swine 1,2

Data on 211 crossbred gilts were utilized to investigate the effects of season of birth, presence or absence of boars and number of gilts per pen on age and weight at puberty. The gilts were allotted to treatments at an average age of 140 days. Gilts born in the fall reached puberty at a younger age and a lower weight (P<.01) than those born in the spring. There also was a higher incidence of "silent" estrus, (i.e., ovulation without psychic estrus) in fallborn gilts (P<.01). The presence of boars substantially reduced (P<.01) age and weight at puberty. Gilts exposed to boars had a higher incidence of "silent" estrus (P<.01) than those denied the presence of boars. Age and weight at puberty were substantially reduced (P<.01 and P<.05, respectively) in gilts grouped 30 to a pen vs those individually penned, but there was no effect of grouping on the incidence of "silent" estrus. Interactions of season of birth and boar presence and season of birth and grouping were significant. No reduction in age at puberty was achieved in fall-born gilts when exposed to boars or group penned, whereas the presence of boars and/or group size (30/pen) caused a substantial reduction in age at puberty in spring-born gilts. (