Evidence for litter differences in play behaviour in pre-weaned pigs

Sarah Mills Brown,Michael Klaffenböck,Ian Macleod Nevison,Alistair Burnett Lawrence

doi:10.1016/j.applanim.2015.09.007

Abstract

The aim of this study was to analyse spontaneous play behaviour in litters of domestic pigs (Sus scrofa) for sources of variation at individual and litter levels and to relate variation in play to measures of pre and postnatal development. Seven litters of commercially bred piglets (n=70) were born (farrowed) within a penning system (PigSAFE) that provided opportunities for the performance of spontaneous play behaviours. Individual behaviour was scored based on an established play ethogram for 2 days per week over the 3 week study period. We found strong evidence of litter differences in play behaviour (F(6,63)=27.30, p<0.001). Of the variance in total play, 50% was attributable to differences between litters with a lesser proportion (11%) to between piglets within litters. We found similar evidence of litter differences when we analysed the separate play categories (e.g. for locomotor play: F(6,63)=27.50, p<0.001). For social and locomotor play the variance was partitioned in a broadly similar way to total play; however for object play the variance was distributed with a more even balance across and within litters. In terms of explanatory factors we found little evidence that at the litter level differences in play were associated with differences in general activity. Of the prenatal factors measured, we found that birth weight was positively associated with total play and the play categories (e.g. with total play: F(1,64)=12.8, p<0.001). We also found that postnatal piglet growth up to weaning (as a percentage of birth weight) had a significant positive association with total play and the play categories (e.g. with object play: F(1,66)=20.55, p<0.001). As found in other studies, on average males engaged in more social play (e.g. non-injurious play fighting: F(1,63)=39.8, p<0.001). Males also initiated more play bouts on average than females (F(1,62)=4.41, p=0.040). We conclude that the study of differences between litters and individuals provides a robust approach to understanding factors potentially influencing play behaviour in the pig. This work also provides support for the use of play as a welfare indicator in pre-weaned piglets as the litter differences in play we observed were associated positively with physical development.

Highlights

Play is a commonly observed and characteristic behaviour of young mammals (e.g. Bekoff and Byers, 1998)
Of the variance in total play, 50% was attributable to differences between litters 26 with a lesser proportion (11%) to between piglets within litters
We found that postnatal piglet growth up to weaning had a significant positive association with total play and the play categories (e.g. with object play: F(1,66) =20.55, p

Summary

Introduction

Play is a commonly observed and characteristic behaviour of young mammals (e.g. Bekoff and Byers, 1998). Despite difficulties posed by the scientific study of play behaviour (e.g. Burghardt, 2005) it has been and remains a topic of considerable interest in the behavioural sciences (see Graham and Burghardt, 2010; Held and Spinka, 2011 for recent reviews). Pig play behaviour has been described in wild and domesticated species (e.g. Frädich, 1974; Dobao et al, 1985), and generally has similarities to play found in other species of young mammal. In a study of play in domesticated pigs (Sus scrofa) living in a semi-natural environment (Newberry et al, 1988), play increased in the first 6 weeks of life but thereafter declined to low levels by week 14 of 61 life. The behaviours that are recognised as play in pigs have some resemblance to adult behaviours (e.g. running; play fighting) but at the same time are recognisably different, being performed in an exaggerated, energetic and repetitive manner (e.g. Newberry et al, 1988)

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