Effect of sex grouping during growth on 5α-androstenone development in boars at three commercial slaughter weights

Groups of boars and gilts were grown in either single-sex or mixed groups to slaughter weights of 81, 93 or 110 kg liveweight to examine the effects of sex grouping on growth performance, animal behaviour and the development of androstenone-taint in the males. Results confirmed the well known growth advantages of entire males and showed that no husbandry problems of any significance were incurred with the boars and gilts raised together, particularly in those groups slaughtered before reaching 100 kg liveweight. In pigs taken to heavier weights, boars were successfully reared with gilts without incurring management problems, although growth performance was slightly poorer for the boar/gilt groups compared with mixed castrates and gilts, and some of the boars had high concentrations of androstenone in the fat. Thus, for pigs intended for slaughter at heavy commercial weight, the evidence suggests that split-sex rearing (and therefore feeding) should be practised. No useful correlations of androstenone concentration in fat were found with thickness of backfat, age, carcass weight or liveweight at slaughter.