7 March 1997

Give sows space to grow faster

Reducing sow stocking rates could yield benefits in performance and welfare. Jonathan Riley reports

OVERSTOCKING outdoor pigs increases competition and aggression causing poorer perfor-mance.

Researcher Zoe Davies says that a wide ranging and ongoing study on pig welfare in outdoor conditions at Cambac Research centre, Reading, Berks, has shown that stocking density has a major effect on sow welfare.

"Within the study, which is in its second year, one element was to compare different stocking densities in dry sow paddocks," she says.

Stocking rates of 25 sows a ha and 18/ha caused great differences in animal behaviour and performance. Large huts were provided at five sows a hut and all sows were fed 2.2kg of sow rolls spread onthe paddock using a shotgunfeeder.

"Most aggressive encounters occurred at feeding with 2.4 aggressive encounters an hour observed where sows were stocked at 25 sows a ha. This was because competition for feed was more intense and sows spent more time running from one part of the paddock to another to gain more feed," says Ms Davies.

"In the lower-stocked paddock, there was far more space for sows to feed and encounters were only 1.1 a sow an hour, less than half the level seen in the more densely-stocked paddock.

"As a result – possibly because sows were more nervous – individual sows joining the higher-stocked group took longer to integrate. In some cases, these sows slept outside huts to avoid further aggression," she says.

Sows were weighed regularly and again the effect of overstocking was apparent because in the lower-stocked paddocks sows grew at 0.44kg/day, over twice as fast as the more densely-stocked sows which grew at 0.21kg/day.

"Condition was, therefore, poorer in the high density stocking rate paddock. But as Cambac is a welfare study centre, thinner sows were pulled out of the group before their welfare was compromised. It is impossible to assess how the performance of these sows would have been affected. Nevertheless return rates in the sows were more than double in the higher-stocked animals," she adds.

Competition for feed and aggression in densely stocked sows reduced performance at Cambac welfare research centre, Berkshire.


OVERSTOCKING


&#8226 Increases competition.

&#8226 Hampers growth rates.

&#8226 Knocks body condition.