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Title: Increasing the frequency of co-mingling piglets during the lactation period alters the development of social behavior before and after weaning

Author
item KANAAN, VANESSA - Universidade Federal De Santa Maria
item Lay Jr, Donald
item RICHERT, BRIAN - Purdue University
item PAJOR, EDMOND - University Of Calgary

Submitted to: Applied Animal Behaviour Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2011
Publication Date: 4/1/2012
Citation: Kanaan, V.T., Lay Jr, D.C., Richert, B.T., Pajor, E.A. 2012. Increasing the frequency of co-mingling piglets during the lactation period alters the development of social behavior before and after weaning. Applied Animal Behaviour Science. 15(2):163-180.

Interpretive Summary: In social species, such as pigs, the presence of conspecifics can be a significant aspect of the early environment. However, under normal farming practices, piglets from different litters rarely interact until weaning, which is often associated with a high incidence of fighting and minor injuries. One possible explanation is that social interactions with non-littermates during the lactation period are important for the development of piglets’ social skills. Accordingly, if litters were allowed, at an early age, to interact more frequently with unfamiliar animals, as occurs in natural settings, social behavior problems might be reduced at weaning and later in life. Thus, the purpose of the present study was to determine how the frequency of co-mingling unfamiliar litters during the lactation period affected the development of social behavior in piglets before and after weaning. Treatments were applied such that pigs were either co-mingled once with an unfamiliar litter (between days 10 to18 after birth), co-mingling twice (between days 10 to 14 and with another litter days 14 to18), or served as controls and were not co-mingled prior to weaning. Piglets were weighed and ear-injury scores were recorded throughout the experiment. No treatment differences were found in weight or ear-injuries. Following mixing at weaning, the twice co-mingled piglets spent less time engaged in aggressive interactions than did piglets co-mingled once. During the social challenge, piglets twice co-mingled spent more time in proximity to one another, had shorter latencies to first aggressive interaction, and spent less time fighting than did control piglets. During the social recognition test, twice co-mingled piglets recognized the stimulus piglet at a faster rate than did control piglets. These results suggest that social recognition is one of the factors that modulate improved social responses in co-mingled piglets. Co-mingling piglets resulted in improved social skills (decreased aggression, more rapid establishment of social hierarchies, increased time spent in non- aggressive contact, etc.,) compared to control piglets. Co-mingling treatments did not differ from one another. However, increasing the frequency of co-mingling from once to twice increased the difference from control significantly for some variables. Further development of our understanding on how a pig’s social skills are developed will help to decrease aggression and improve welfare.

Technical Abstract: The purpose of this study was to determine how increasing the frequency of co-mingling affected piglets' behavior development before and after weaning. Co-mingling once (CM1), piglets interacted with 1 unfamiliar litter Days 10-18 after birth, co-mingling twice (CM2), piglets interacted with 1 unfamiliar litter Days 10-14; and with another, Days 14-18. Control (CM0) piglets did not interact with unfamiliar litters before Day 18 (n = 16 liters per treatment). The study weighed piglets and recorded ear-injury scores throughout the experiment; however, there were no treatment differences. The DM2 piglets spent less time engaged in aggressive interactions (p < .05) than did the CM0 piglets following mixing at weaning. During the social challenge, CM2 piglets spent more time in proximity to one another, had shorter latencies to first aggressive interaction, and spent less time fighting than did CM0 piglets (p < .05). During the social recognition test, CM2 piglets recognized the stimulus piglet at a faster rate than did CM0 piglets (p < .05). Overall, CM2 resulted in changes to some social behaviors compared with CM0 but not with CM1.