Sexual maturity as risk for development of deviant behaviours in pig production systems with entire males

Male piglets are castrated primarily to avoid the unpleasant boar taint in

meat, and additionally for the predisposition of castrates to accumulate fat

and for their lower risk of developing unwanted behaviours. There are two

main strategies available for withdrawing from surgical castration: one is

immunocastration and the other is to raise entire male pigs or boars.

Additionally, raising intact boars is more profitable because of the

production of carcasses with lean meat and better feed conversion. Boars

(compared to castrates) exhibit more aggressive, sexual, damaging social

behaviour and reduced feeding behaviour with a lower prevalence of sickness

behaviour as a result of good health and low susceptibility to chronic

inflammation. In this review, the behaviours specific for boars as a result

of sexual maturity are reviewed, with an overview of differences in the

behaviour of surgically castrated barrows, immunocastrates and boars reared

in group-housed systems. The raising of boars allows for good welfare of

these animals in early life, but later, on reaching sexual maturity, the

welfare of boars can be diminished because of their propensity to

aggression and more mounting behaviour than castrates. Innovations in the

breeding and management of boars are needed to improve their performance and

to reduce welfare implications of these animals raised in social groups, and

in particular to minimize deviant behaviours towards pen mates.