The social environment and the sexual behaviour of the domestic boar

Abstract

Agricultural scientists in the past have paid little regard to the behavioural response of the pig to the modern piggery environment, and serious disruptions in the behaviour of the domestic pig are increasingly being encountered. In some cases, these disruptions in behaviour are markedly restricting production. This paper summarizes a series of studies that examined the influence of the social environment during rearing and after puberty on the sexual behaviour of the boar. Boars reared from three weeks of age in the absence of visual and physical contact with pigs had significantly reduced (P < 0.01) copulatory performance and courting behav iour activity compared to boars reared from three weeks in either an all-male or a mixedsex group. A subsequent study indicated that lack of physical contact with pigs during rearing was responsible for approximately 70% of this depression in copulatory performance. A similar but non-significant trend was observed in boars reared in the same manner from I2 weeks of age. Boars individually reared from three weeks of age in adjacent wire-mesh pens had similar copulatory performance to that of group-reared boars. However, an apparently important feature of courting behaviour, “nosing activity”, was significantly reduced (P < 0.05) for the former boars. These data are interpreted as evidence of the importance of social contact, particularly physical contact with pigs, during rearing on the sexual behaviour of the boar. In addition, the social environment after puberty was demonstrated to have a major influence on the sexual behaviour of the boar. Post-pubertal boars isolated from female pigs for 12 weeks had significantly reduced (P < 0.01) copulatory performance and courting behaviour activity compared to boars housed near sexually receptive female pigs. The sexual behaviour of the former boars was restored within four weeks of rehousing near sexually receptive females. It was subsequently shown that the stimuli received from sexually receptive or sexually non-receptive female pigs were equally capable of maintaining the sexual behaviour of the boar. Therefore, the social environment, both during rearing and after puberty, is an influential determinant of the sexual behaviour of the boar. Failure by producers to consider the social environment when designing boar management practices will probably result in poor reproductive performance.