Understanding and Reducing Aggression Using Pre-exposure Before Sows Are Mixed in a Grouped Gestation System26 February 2014
Allowing sows to get to know on another - by being neighbours - in the service area seemed to make them more aggressive when they were later mixed in group housing for their pregnancy, according to new research from Purdue University.
The largest single challenge of keeping sows in groups is that of inter-sow aggression, according to Jeremy Marchant-Forde of the USDA-ARS, Livestock Behavior Research Unit at Purdue University and co-workers there and at Iowa State University. It is well known that sows will fight when mixed and when having to compete for access to resources. However, there is little information on the effects of pre-exposure when sows are mixed together.
This project, funded by Pork Checkoff, aimed to investigate whether housing sows next to each other in the service house (pre-exposure) would influence the amount of aggression observed when they were subsequently moved into group gestation pens.
The first experiment compared lesion scores, production and behaviour of 20 groups of three sows from mixing to farrowing, having previously been housed in service crates for 35 days post-service.
In one treatment, groups of three pen-mates were housed in adjacent crates; in our other treatment, groups of three pen-mates were randomly formed from non-neighbours.
In the second experiment, the treatments were the same, except the post-service time period prior to grouping was only seven days.
Total body lesion scores were significantly higher for pre-exposed sows in the 35-day experiment and numerically higher in the seven-day experiment. In both experiments, significantly more lesions were seen around the head, neck and shoulders of the sows, indicative of pre-exposed sows engaging in more reciprocal fighting behaviour.
Detailed analysis of the behavioral data is ongoing but time-budgets indicated no effect of treatment during the early post-mixing period.
Closer examination of aggressive behaviour so far has shown no significant differences between treatments in aggression but many of the measures show numerically higher numbers for pre-exposed sows.
There is also no effect of treatment on production, with sows in both experiments having similar total litter sizes and numbers born alive and dead.
Overall, the study has shown that pre-exposing sows to each other in service crates prior to mixing appears to be disadvantageous at subsequent mixing.
Although neighbouring sows will acquire some information and familiarity about their neighbours, it seems possible that the inability to resolve aggressive interactions within the service crates actually promotes aggressive behaviour when the sows are placed into an environment in which aggression can be resolved, suggests Dr Marchant-Forde.
He and his colleagues recommend that when sows are selected from a group from the service crates, non-neighbours should be selected.
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