8. Consequences of the lactational environment on behavioural problems of pigs after weaning

An important part of pig brain development takes place after birth and depends upon internal and environmental inputs. Therefore, the environment of the piglets during the lactational period may influence their cognitive and behavioural development, hence their predisposition to fight and to perform other forms of deleterious behaviours such as sustained belly nosing or tail biting. Such behaviours are of great concern to the pig industry for animal welfare and economic reasons. This chapter focusses specifically on predisposing factors during the postnatal period until weaning for the expression of fighting and other deleterious behaviours later in life. During that suckling period, the piglet acquires essential elements to develop a good immune status, proper gut microbiota, and high disease resilience for its future life. Health problems are a major risk factor for the occurrence of tail biting so that ensuring good colostrum intake and proper hygiene in the farrowing room might reduce deleterious behaviours in the long-term. Fighting behaviour is reduced by cross-fostering and socialisation before weaning whereas early-life competition for limited resources appears to increase subsequent aggressiveness. Therefore, any means allowing piglets from different litters to interact from the second week of age onward should be encouraged. Social stress, due to competition and cross-fostering, also stimulates the occurrence of other deleterious behaviours later in life and is highly dependent on litter size at birth. Therefore, the full consequences of large litters at birth should be evaluated in terms of health, welfare and performance over the whole life of pigs. Enriching the environment during lactation has diverse effects on fighting behaviour with no effect in most situations and a reduction, or even an increase, in some others. Similarly, it has diverse effects on tail biting and on manipulatory behaviours suggesting that the nature of the enrichment, the age, and the timing at which it is presented might greatly influence its impact on such deleterious behaviours. This chapter emphasizes that even though the environment in which post-weaned pigs are raised is of major importance for the expression of nefarious behaviours, the pre-weaning environment should also be optimized to reduce their likelihood.