A note on genetic parameters for estrus symptoms in sows

Showing clear estrus symptoms contributes to the reproductive effectiveness of a sow. The aim of the study was to estimate genetic parameters and breeding values for estrus symptoms, a trait which included swelling and reddening of the vulva, interest in the boar and strength of the standing reflex. Around 31,000 reproductive sow cycles from three lines were scored on farms, using an ordinal scale (five categories). Variance component estimation was done by applying a threshold model. The estimates for the additive genetic variance, permanent environmental variance, heritability and repeatability are (standard errors in parenthesis) 0.10 (0.02), 0.06 (0.02), 0.09 (0.02) and 0.14 (0.02), respectively. The genetic correlation between estrus symptoms and litter size at birth was very weak (−0.05 ± 0.04). It seems that a selection for the trait estrus symptoms is possible and is not accompanied by a change in the litter size.