Genetic parameters of Vulva Traits and Impact of Vulva Scores on Gilts
Culling in Large White Pigs
Abstract
Vulva morphologies represent significant traits in pig production.
Recent studies suggest vulva size can be predictive of the reproductive
performance of gilts. We aimed to analyze the genetic parameters of
vulva traits, including vulva length (VL), vulva width (VW), and vulva
angle score (VAS), as well as litter traits, including total number born
(TNB), number born alive (NBA), number stillborn (NS), and piglet
survival rate (SR), across three Large White pig strains (PIC, Topigs,
and Canadian). We estimated the correlations between vulva and litter
traits, as well as the reasons for culling gilts. The heritabilities of
vulva traits ranged from 0.167 to 0.426, whereas the heritability of
litter traits ranged from 0.013 to 0.147. The VAS in Topigs Large White
pigs exhibited the highest heritability. The genetic correlation
coefficients between vulva length and width in PIC and Topigs Large
White pigs were significantly positively correlated, ranged from 0.585
to 0.767. No significant correlation was found between vulva and litter
traits. Subsequently, we scored the vulva traits according to previously
reported studies. The average vulva width score of the gilts that were
culled due to prolonged estrus was significantly lower (2.75) compared
to that of gilts with normal estrus (2.90). In the population of gilts
aged 220 to 230 days, the gilts with higher vulva angle scores had a
lower risk of culling due to vulva inflammation with purulent discharge.
The results suggest that selecting for vulva traits in replacement gilts
is an effective strategy to reduce gilts culling rates.