The effect of limiting the number of days of contact with boars, season and herd of origin on the attainment of puberty in gilts

Abstract

The effect of limiting the number of days of boar exposure on the attainment of puberty in gilts was examined in two herds (Medina and Muresk) and in two seasons (winter and summer). The treatments used were full boar contact for 20–30 min per day from 165 days of age for (a) 1 day, (b) 10 consecutive days or (c) daily until puberty or slaughter and (d) an isolated control. Those not detected in oestrus were slaughtered 80 days (Medina) or 135 days (Muresk) after first boar exposure. In the winter neither treatment nor herd had any significant effect on the proportion of gilts which reached puberty (0.93 in both herds). In the summer a lower proportion of control gilts reached puberty at Medina than in the winter (0.33 vs. 1.0, P<0.01) but the proportion of each group exposed to boars which reached puberty was not affected by season. At Muresk the proportion of gilts reaching puberty in the summer was lower than in the winter for control (0 vs. 0.86, P<0.01), 1-day (0 vs. 1.0, P<0.01) and 10-day (0.38 vs. 1.0, P<0.05) gilts but the proportion of daily gilts was 0.86 in both seasons. In both herds 10-day and daily gilts reached puberty earlier than control gilts ( P<0.01). At each treatment level the Medina gilts reached puberty significantly earlier ( P<0.001) than the Muresk gilts. When boar exposure was limited to 1 day or 10 consecutive days a degree of stimulation took place but daily exposure continuing until puberty was necessary for the maximum stimulation of puberty.