Estimation of genetic parameters for agonistic behaviour of pigs at different ages

Abstract

SUMMARYThe mixing of pigs unacquainted with each other in commercial pig production is a standard procedure which leads to agonistic interactions with a wide range of individual pig behaviour. Hence, the aims of the present study were to assess the heritabilities of agonistic behaviour and to estimate correlations between three different age groups (weaned pigs n = 1111, growing pigs n = 446 and breeding gilts n = 279). The behavioural observation analysis included a period of 17 h directly after mixing as weaned pigs, growing pigs and breeding gilts (220 days of age) whereby the following agonistic traits were observed: number of fights (NF), duration of fights (DF), initiated fights (IF), received fights (RF), fights won (FW) and fights lost (FL). The behaviour of the weaned and growing pigs was significantly influenced by cross-fostering, their weight at mixing and litter attributes. Cross-fostered animals showed fewer agonistic interactions as weaned pigs and as growing pigs than non-cross-fostered animals. The influence of weight revealed that heavier pigs had a higher NF score at weaning and as growing pigs. The random litter effect explained up to 0·08 of the total variance in weaned and 0·04 in growing pigs, whereby this could partly be explained by litter size. Pigs from larger litters tended to have more agonistic interactions. The heritabilities of the recorded traits were at a low to medium level but similar between the age groups. There were high correlations between NF and all other traits in weaned pigs. The trait IF showed that the more fights a pig initiated, the more it won. This was also found for growing pigs and breeding gilts. The relationships between the age groups provided no uniform trend. The phenotypic correlations were low and the genetic correlations varied widely, partly due to the small sample size.