Graduate Thesis Or Dissertation
 

The influence of heredity and some environmental components on occurrence of puberty in gilts in confinement

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  • In a swine production and breeding experiment, Yorkshire gilts were evaluated for the influences of heredity-and some environmental components on occurrence of puberty in gilts in confinement. In the first experiment, 186 Yorkshire gilts reared and maintained in total confinement were used in a study to assess effects of several environmental variables on occurrence of puberty and subsequent estrus periods. The four social combination groups were: reared-together and exposed-together (RT-ET), reared-together and exposed-separately (RT-ES), reared-separately and exposed-together (RS-ET), and reared-separately and exposed-separately (RS-ES). The percentage expressing puberty and days to puberty were not significantly different among the four social groups nor was regularity of estrus cycles. Based on these findings there appears to be no added benefit of allotting gilts in the various social groups used beyond the effects resulting from mixing to provide unfamiliar penmates and providing boar exposure. Secondly, it appears that gilts which achieved pubertal estrus promptly continued to have high cyclic adequacy. In the second experiment 438 Yorkshire gilts reared and housed in total confinement were used to determine hereditary in fluence on occurrence of puberty and days from commencing of experiment to puberty. Line-of-sire effect was significant (P = .10) for percentage occurrence of puberty. Difference among line-of-sire for days to puberty were not significant (P > .05). Maternal variance components were significantly larger than the sire's variance components for both traits (P < .05). Paternal half-sib estimate of heritability was .05 ± .11 for occurrence of puberty and was -.11 ± .10 for days to puberty. Maternal half-sib analysis gave 1.06 ± .22 and 1.18 ± .36 for percentage occur rence of puberty and days to puberty. Based on these findings there appears to be a basis for modest expectation of improvement in performance of the two traits through selection based on differences in performance among lines-of-sires and among litters effects. There is indication that the ability to achieve occurrence of puberty and the number of days to puberty within a given time period are relatively independent of each other.
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