Age at Puberty of Gilts Produced by Different Systems of Mating

Abstract

Observations were made during 4 years on the age at puberty in gilts in the swine breeding experimental herd maintained by the Wisconsin Agricultural Experiment Station in cooperation with the Regional Swine Breeding Laboratory. The numbers of gilts used were, in 1950, 150; 1951, 106; 1952, 95; 1954, 162. The mean age at puberty of the inbred gilts in 1950 was 227.7 days. They were significantly older at puberty than the line-cross gilts (193.5 days). The mean ages at puberty for the gilts representing the 4 systems of mating in 1951 (inbred, 244.0; two-line cross, 214.5; three-line cross, 198.4; four-line cross, 208.2) differed only in respect to inbreeding and line crossing, with no significant difference between the different line crosses. Inbreeding of a gilt was shown to have a significant effect on the age at which she reached puberty. The effect of inbreeding of the dam did not have a significant effect on the age at puberty of her offspring. Significant differences were found between the inbred and linecross gilts when classified into 154-day weight classes to remove much of the effect of differences in growth rate. The 1952 studies indicated a significant difference between purebreds and crossbreds. Differences between different line crosses were non-significant, as they were in 1951. Differences in age at puberty in 1954 were found between mating types within the purebred and crossbred system of mating as well as between the two systems. Differences shown between the average was age at puberty of the reciprocal crosses between two breeds and the average age at puberty of their purebred suggest non-additive inheritance.