Thirty-six Large White × (Large White × Landrace) young female pigs (gilts) were allocated to one of nine treatments. These were 30 min daily boar contact from 125, 132, 139, 146, 153, 160, 167, 174 or 181 days of age. Gilts were fed so as to maintain them on a pre-determined growth curve, gaining 0·45 kg per day. Once puberty had been detected, gilts were mated at the next (second) oestrous period and subsequently slaughtered 20 days post coitum.
The interval from first boar contact to puberty was significantly longer (P<0·05) amongst gilts first exposed to a boar at ages below 139 days. Amongst gilts older than this the interval was similar. Though the 174- and 181-day groups were significantly older at puberty (P<0·05) no significant differences were observed amongst the younger age groups. Synchronization of pubertal oestrus appeared to be better for the 160- and 167-day groups, with three out of four gilts reaching puberty within an 8-day period. There was no indication that weight at puberty, ovulation rate, percentage embryo survivval, or number of viable embryos at 20 days post coitum were affected by treatment.
From the results it appears that the optimal gilt age at which to commence boar contact, in terms of age at puberty, interval from first boar contact to puberty and synchronization of the pubertal oestrus, is in the age range 160 to 170 days.