To achieve the objective, the treatments (control and provision of grass silage) were applied to two separated dynamic groups of 37 sows each, into which nine new sows were introduced at the beginning of each replicate (3 replicates in total). Behaviour of the sows was recorded continuously by video cameras during the first 2 days after the introduction of the mated sows, and for 2 non-consecutive days during the following week. From the recordings it was evaluated the aggressive behaviour on the first day after mixing, and the location, the state and the activity of the new introduced sows was assessed during the first two weeks after the introduction. Direct observations were also carried out during the experimental period, and the injury level of the newly introduced sows was evaluated after one week they were introduced.
Results showed that the average proportion of observations in which the newly introduced sows performed or received aggressive behaviour was not different after mixing in the two experimental groups, resulting in a not different level of injury on the animals after one week. At this point it must be stressed out that the levels of aggression present in the study were low probably due to the low density environment present in the housing system, what could have contributed to the lack of significant effect of the experimental treatment. The stereotypic behaviour, sham chewing, was decreased in the resident and newly introduced sows when the silage was offered (P < 0.05), and also, newly introduced sows in the silage treatment spent less time performing exploratory behaviour compared to sows in the control treatment.
Therefore, it seems that the provision of silage to gestating sows housed in large dynamic groups may help to reduce stereotypic behaviour.
O’Connell. N.E. (2007) applied Animal Behaviour Science, 107: 45-57