The effects of contact frequency and transport on the efficacy of the boar effect.

Ninety six Large White/Landrace cross-bred gilts were used in this study, sixteen gilts being allocated to each of six treatments. The treatments compared the effects on puberty attainment of exposing gilts to boar contact either 0, 1 or 3 times daily (C, D and 3D), with or without the addition of transport "stress" (T). Treatments began at a mean gilt age of 160 days and continued for 40 days. The duration of each period of boar contact was 20 min. Those gilts receiving transport "stress" were placed on a trailer daily for the first ten days of the study and driven at a constant speed for 20 min. There was no significant effect of transport alone on the timing of gilt puberty attainment. Boar exposure significantly increased the proportion of gilts attaining puberty within 40 days of the commencement of treatments (P < 0.05) compared with gilts not receiving boar contact. Boar exposure three times daily significantly reduced mean gilt age at puberty relative to no boar exposure (190.2 vs. 202.3 days of age respectively, P < 0.01) while once-daily boar exposure gave an intermediate value (196.7 days). In addition, a significant (P < 0.01) interaction occurred between boar contact frequency and transport in this study. It is concluded that (a) transport alone does not provide a significant stimulus for early puberty attainment in the gilt, (b) 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, and (c) a combination of frequent boar contact and transport may result in a greater degree of gilt puberty stimulation than frequent boar contact alone.