The influence of different doses of oestradiol benzoate on the attainment of puberty in the gilt

Abstract

ABSTRACTForty Large White ♂ × (Large White (f × Landrace ♀) pre-pubertal gilts were used to study the influence of five different doses of parenteral oestradiol benzoate (OB) on the attainment of puberty. Five gilts from eight litters were treated at 140 days of age with either 5, 10, 15, 20 or 25 μg OB per kg body weight (BW). The doses were split equally into three bolus injections given on consecutive days. Daily boar contact commenced on the day that the first oestrogen injection was given and continued until the gilts were mated. All gilts were slaughtered at either 20 days post coitum or at 235 days of age for those gilts not exhibiting a second oestrus.The numbers of gilts which ovulated within 10 days after OB injection were: 5/8, 7/8, 8/8, 6/8 and 5/8 for treatments 5 ng/kg BW through to 25 fig/kg BW, respectively. These differences were not significant (P > 0·05). The duration of behavioural oestrus after OB injection was positively correlated to the dose of oestrogen administered (r = 0·98, P < 0·01). There were no significant differences in age at puberty between treatments, and no significant differences were found in the subsequent reproductive performance.