Multiple enrichment devices reduce pig aggression and injury
Take Home Message: provide multiple hanging chains in pig grower pens at weaning to reduce stress and injury
“The social stressors associated with the abrupt weaning process on commercial farms can result in significant welfare issues for pigs; including behavioural problems and aggression, decreased immunological responses, reduced live weight gain and efficiency of feed conversion,” Writtle College’s Emma Bleach told delegates at the 2009 British Society of Animal Science’s annual conference.
“Slats and slurry systems in commercial housing systems for grower pigs provide a barren environment that can exacerbate these problems. Enriched environments have been shown to reduce aggression in pigs, particularly where devices that have manipulative and destructive properties are used.
“However, studies often include a single device that does not permit all animals to interact with the enrichment at any one time. The aim of our study was to investigate the effects of multiple metal chain enrichment on levels of aggression in growing pigs.”
A total of 240 pigs from 24 litters were selected at 28 days old and split into 12 groups of 20 pigs (two litters per pen); six control groups (CG); and six enhanced enrichment groups (EEG).
Pigs were housed in pens with slatted floors. CG pigs were provided with a single chain – 0.6m long and 5mm thick – per pen suspended to a height 0.25m above the pen floor (one chain per 20 pigs).
In the EEG pens six similar chains were suspended across the pen at 0.5m intervals to avoid sleeping and feeding areas (one chain per 3.3 pigs).
All pigs were offered pelleted concentrate feed ad lib throughout the study. Injuries were scored using a seven point scale on days one, three, five, seven, 14, 21 and 28 as a measure of aggressive behaviour within the groups of pigs. Live weights were recorded on days zero, seven, 14, 21 and 28.
The interaction of the pigs with the enrichment device was recorded using intermittent scan-sampling, at five minute intervals for 60 minutes on days one, three, five, seven, 14, 21 and 28.
“And we found that injury scores were significantly lower in the EEG pigs throughout the study period,” said Dr Bleach. “During the first seven days post weaning, injury scores in the EEG were lower than among the CG pigs, falling to a mean score of less than 0.5 by day 14.”
Interactions with the chains were greater in the EEG throughout the 28 day study, although there was a decrease in interactions with time in both treatment groups.
“The fall in the frequency of interaction with the chains over the study period indicates that habituation occurs with time post weaning,” she added.
Presented to the British Society of Animal Science Annual Meeting, March 30 April, 2009, Southport, UK.
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