The effects of contact frequency and season on the efficacy of the boar effect

Abstract

One hundred and twenty eight Large White/Landrace crossbred gilts were used in this study. The study was conducted in four replicates (spring, summer, autumn and winter), eight gilts being allocated to each of four treatments in each replicate. The treatments compared the effects on puberty attainment of exposing gilts to boar contact either daily (D), twice daily (2D) or three times daily (3D). Puberty attainment by gilts in the boar exposure regimens was compared with puberty attainment in a non-boar exposed control group of gilts (C). Boar exposure began at a mean gilt age of 160 days and continued for 60 days. The duration of boar contact was for 60 min, 30 min and 20 min per exposure period respectively for treatments D, 2D and 3D (i.e. all boar-exposed gilts received a total of 60 min of boar contact per day). There was no significant effect of season on the timing of gilt puberty attainment. Boar exposure significantly increased the proportion of gilts attaining puberty within 60 days of the commencement of treatments ( P < 0.001) compared with control gilts. Boar exposure three times daily significantly reduced mean gilt age at puberty relative to once-daily boar exposure (183.2 vs. 196.0 days of age respectively, P < 0.01). Twice-daily boar contact resulted in an intermediate mean gilt age at puberty (190.3 days). There was also a trend towards a higher proportion of gilts reaching puberty earlier with increasing frequency of boar contact. However, this difference was only significant ( P < 0.05) between once- and three times-daily boar contact at day 20 of treatment. It is concluded that the pubertal response of the gilt to the boar effect is enhanced when boar contact occurs several times each day compared with a single boar contact period. While the efficacy of these treatments may vary with season this effect was not evident in the present results.