Project Number: 3602-32000-008-01
Project Type: Reimbursable

Start Date: Dec 01, 2007
End Date: Dec 01, 2008

Objective:
To determine the sequence of display and aggressive behaviors performed when unacquainted sows are mixed. To determine the best method of pre-exposing sows to each other prior to mixing so that aggression is reduced.

Approach:
The largest single challenge of keeping sows in groups is that of inter-sow aggression. We know that sows will fight when mixed and when having to compete for access to resources. However, there is little information on the sequence of detailed behaviors that are performed by adult sows when mixed, that either result in a fight or a decision not to fight. We also do not know to what extent the sequence of aggressive behaviors can be changed, and hence fighting reduced, by pre-exposing groups of sows to each other prior to mixing. This project will be carried out in two parts ¿ the first part to increase our understanding of the aggressive process and the second part to apply our knowledge to reduce fighting at mixing. Firstly, we will investigate the social interactions of 32 previously unacquainted pairs of sows to gather detailed information about the sequence of behaviors performed by both parties during any fight or withdrawal without a fight. Also in this part of the study, we will investigate group effects by looking at the social interactions of pairs of sows when a group of 3 sows is mixed with another previously unacquainted group of 3 sows (9 possible unacquainted pair combinations). We will then carry out an applied study in which groups of 4 sows are mixed into unacquainted resident groups of 8 sows (32 possible unacquainted pair combinations), following different methods of pre-exposure. Pre-exposure involves gating off part of the residents¿ pen into which the 4 sows can be placed. Once the pre-exposure period has ended, the gating is removed and the sows are allowed to mix. We will investigate the length of time over which pre-exposure occurs (24h and 72h) compared with immediate mixing without pre-exposure. We will use 8 groups per treatment. Behavior will be recorded using DVR systems and analyzed to determine duration and intensity of aggressive interactions for 48h post-mixing and for 24h periods at 1 wk, 2 wks, 1 month and 2 months post-mixing. Sows will be lesion-scored prior to mixing and at 48h, 1 wk, 2 wks, 1 month and 2 months post-mixing and sow weights, litter size and number of piglets weaned will be recorded. Data will be analyzed using Markov analysis to determine patterns in sequences of behavior and ANOVA to determine differences between treatments.