FACTORS INFLUENCING AGGRESSION BETWEEN SOWS AFTER MIXING AND THE CONSEQUENCES FOR WELFARE AND PRODUCTION

Hierarchy positions in groups of sows are settled relatively quickly, though long term stability can be affected by several factors includin g method of feeding. Fighting is less intense between pigs of unequal sizes, may be reduced by previous exposure but is less affected by the presence of a boar. Larger groups have more hierarchy positions to re serve and therefore more fighting. Greater space allowance appears to have little effect on fighting at mixing but can reduce aggression in the longer term. Barriers can limit aggression by allowing losers to e scape more easily. Provision of ad libitum feed has been shown to redu ce aggression over the short term. Straw bedding has no effect on figh ting. Chemical intervention techniques would appear to delay rather th an reduce fighting. Newly mixed sows should be supervised to reduce fi ghting. The fighting which occurs during mixing results in physiologic al stress responses which can have detrimental effects on reproductive parameters. However, the short-term. nature of this response means th at detrimental effects can be avoided by careful timing of regrouping. It is therefore possible to achieve equally good reproductive perform ance in group-housing systems as in systems with individual housing, p rovided that good management is practised. (C) 1998 Elsevier Science B .V.