Variation in Puberty Phenomena in Inbred Boars

Abstract

Ages at puberty (ability and willingness to mate within 15 minutes after being exposed to an estrual gilt) were obtained on 136 inbred boars of Chester White and Yorkshire ancestry in a 2 year period. Average ages at puberty were 196 days for 41 boars selected at weaning for breeding purposes in 1948 and 205 days for 95 unselected boars in 1949. Corresponding average weights at puberty were 166 and 141 pounds. Weights at 56 and 154 days in 1948 were not significantly associated with age at puberty in any line. In 1949 weights at all ages from 56 to 168 days were significantly correlated with age at puberty in 4 of the 5 lines. There was also a significant negative correlation between rates of gain during successive 14 day periods from 98 to 168 days and age at puberty in these same 4 lines. The correlations between stage of season when farrowed and age at puberty were insignificant in all lines in both years with only one exception. Fertility tests were made (artificial insemination) on 15 boars in 1948. Eleven boars were found to be fertile on the first test (50% or more cleaved eggs in their mates 1 to 2 days after heat) at an average age of 211 days (not tested at an earlier age). Three more were fertile on second test at an average age of 236 days. The remaining boar was tested 7 times before he was found to be fertile at 333 days of age. Sperm were found in the semen of 30 of 38 boars on the day of first mating in 1949 and in 7 others within 2 more weeks. Sperm were not found in the semen of the remaining boar for 5 weeks after puberty. Copyright © . .