Uniformity of body weight in growing pigs is persistent during growth but affected by sow- and litter-related factors

Abstract

Improvements in sow management and selective breeding have substantially increased litter sizes in the past decades. Larger litters are associated with lower average birth weights and lower within-litter BW uniformity. Lightweight piglets (< 1 kg) face many difficulties: they are more vulnerable to cold, have lower colostrum intake, often fail to catch up in growth and are less likely to survive. This observational study investigated (1) whether sow and litter-related factors are associated with within-litter BW uniformity over the pig's lifetime, (2) the associations between piglet, sow and litter-related factors and BW, weaning dip and growth performance and (3) the factors associated with the probability of piglets being classified as lightweight at birth and their survival. Detailed data from 54 litters of hybrid sows that birthed 924 piglets, 860 of which were liveborn, were analysed. Piglets were weighed at various stages to assess within-litter BW uniformity and BW evolution. Strong correlations (r = 0.29-0.80) were found for within-litter BW uniformity at several time points, from weaning (7.6 ± 1.7 kg) to 17 weeks of age (59.9 ± 9.2 kg). Parity, litter size and chest circumference of the sow were positively associated with within-litter BW variation, while the number of functional teats showed a negative association. Individual BW and growth performance were positively influenced by parity, cumulative birth interval, birth weight, percentage of male piglets and relative birth order, but negatively associated with litter size, condition loss of sow during lactation and female sex. Furthermore, higher birth weight (+0.39 per kg), female sex (+0.23 compared to males) and higher weaning age (+0.14 per day) were associated with more postweaning growth deviations. The odds of being lightweight were lowest for piglets from parity 2 sows (odds ratio = 0.14), decreased with longer birth interval (odds ratio = 0.97) and increased with litter size (odds ratio = 1.13) and female sex (odds ratio = 1.97). Survival odds improved with more functional teats (odds ratio = 1.56) and condition loss of the sow during lactation (odds ratio = 1.22), but were negatively influenced by litter size (odds ratio = 0.88) and birth interval (odds ratio = 0.96). These results underscore the complexity of sow-, litter- and piglet-related features influencing litter BW uniformity, BW, piglet survival and growth.

Keywords: Birth weight; Growth performance; Piglets; Survival; Variation in body weight.