ARS | Publication request: Relationships of birth weight traits with age at first estrus and number of ovulations in Landrace-Duroc-Yorkshire gilts

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 8, 2013
Publication Date: N/A

Technical Abstract: Selection for increased litter size has resulted in greater within-litter variation in piglet birth weight and a reduction in litter average birth weight; believed to be associated with intrauterine growth restriction as a result of limitations in uterine capacity. This leads to increased preweaning mortality, reduced growth performance, decreased muscle fiber number and reduced carcass quality. Low birth weight gilts have more primordial and fewer primary and secondary follicles suggesting that variation in average litter birth weight could negatively impact reproductive traits. The objective of this study was to examine the effects of birth weight traits with age at puberty and number of ovulations in gilts. Age at puberty, the first standing estrus in the presence of a mature boar, was determined for 2,187 gilts beginning at approximately 140 d of age. The number of ovulations for 2,173 gilts was determined during postmortem examination by counting the number of corpora lutea on the ovary after the first or second parity. Partial correlation coefficients for total born, total born alive, litter average birth weight, CV of litter average birth weight, individual birth weight, and deviation of individual birth weight from litter average birth weight with age at first estrus and number of ovulations were estimated using a model that fit season and line as fixed effects and sire as a random effect. Average age at first estrus and number of ovulations was 195.1 ± 0.4 d of age and 16.3 ± 0.1 ovulations, respectively. Litter average birth weight ranged from 0.79 to 2.45 kg with CV ranging from 23.5 to 44.7%. There were no significant correlations for age at first estrus with any of the birth weight traits examined. The number of ovulations was weakly correlated (r = 0.08, P < 0.001) with individual birth weight but not any of the other birth weight traits. These data do not support the concept that differences in average litter birth weight contributes to variation in pubertal age or ovulation rate in pigs. USDA is an equal opportunity provider and employer.