Genetic and phenotypic relationships of farrowing and weaning survival to birth and placental weights in pigs1

Abstract

Data obtained during 4 generations of divergent selection for placental efficiency were used to determine factors influencing survival at farrowing and weaning in litters produced by first-parity females. Data were collected from 193 litters and included records on 2,053 individuals. Farrowing survival (FS) and weaning survival (WS) were considered traits of the piglet and were scored 1 if the individual was alive at a time point or 0 if dead. Estimates of (co)variance components for direct and maternal additive genetic effects for FS and WS were obtained using an animal model and computed with the MTDFREML program. Estimates of direct heritability were 0.16 for FS and 0.18 for WS. Estimates of maternal heritability were 0.14 for FS and 0.10 for WS. Genetic correlation estimates between direct and maternal effects were high and negative for both traits. The direct genetic correlation between FS and WS was 0.92. Variables associated with FS and WS were determined using logistic regression procedures. Birth weight (BRW), placental weight, their interaction, and total born can be used as predictors of survival at farrowing in the absence of estimates of genetic merit for survival. The same model, excluding total number born, was the best model for predicting WS. In the presence of BRW information, placental efficiency did not improve the prediction of survival. While it was clearly disadvantageous for a piglet to be below the litter mean in BRW, being above the mean did not provide a substantial advantage in survival. Results from this analysis suggest that it is possible to select for increased survival at farrowing and at weaning. Information on a piglet's BRW, placental weight, litter average BRW, and deviation from litter average BRW can be used to optimize those values at levels resulting in high survival probability.

Estimation of genetic trends from 1977 to 1998 for farrowing characteristics in the French Large White breed using frozen semen

“…Unlike most other studies, where piglets born alive which die shortly after birth are classified as stillborn piglets, the current study only included piglets born dead. Birth weight becomes a major factor for survival in early lactation (Mesa et al, 2006). Our result was in agreement with Leenhouwers et al (2001), who found independence between farrowing survival and birth weight in a study where farrowing was carefully supervised.…”

Genetic control of the environmental variance for birth weight in seven generations of a divergent selection experiment in mice

“…Moreover, in the successful divergent selection experiment for BW in rabbits by Bolet et al (2007), a favourable correlated response for litter size at weaning and for survival from birth to weaning was also observed, but differences between lines in litter size at birth were inappreciable. Other authors have also reported higher mortality on heterogenous litters than on homogenous ones in rabbits (Poigner et al 2000) and in pigs (Mesa et al 2006). Argente et al (2012) found that environmental variance of litter size appeared to be negatively correlated with litter size after three generations of divergent selection in rabbits, showing that the relationship between homogeneity and litter size must to be studied in each case.…”

“…Anyway, nature is probably much more complex than the pure additive model fitted to analyse the variability, and it seems that this particular model somehow fails in this type of trait. In fact, when thinking of the possible causes of the efficacy of the selection process, multiple causes are at play such as those related to the morphology of the uterus (Bolet et al 2007), litter size , survivability (Mesa et al 2006) and many more other causes.…”

Estimation of genetic parameters for birth weight, preweaning mortality, and hot carcass weight of crossbred pigs1

“…Comparison with literature estimates is difficult because of the different structures of data sets and different models. In many studies, mortality traits were modeled with linear models (van Arendonk et al, 1996;Knol et al, 2002;Mesa et al, 2006), which ignore the categorical nature of those traits. Also, animals in this study were crossbreds, and some traits in crossbred populations have lower heritabilities than in purebred populations (Lutaaya et al, 2001).…”