Reproduction in the gilt 3. The effect of exogenous oestrogen on the attainment of puberty and subsequent reproductive performance

Abstract

Ten Landrace × (Landrace × Large White) young female pigs were allocated to each of four treatments. The experiment was arranged as a 2 × 2 factorial design, the variables being oestradiol benzoate v. ethyl oleate and boar v. visual testing. The oestradiol benzoate (or ethyl oleate) was administered at 140 days of age, the treatment consisting of six injections, over a 3-day period, of 0·5 ml of either ethyl oleate or a solution of 0·4 mg/ml β-oestradiol-3-benzoate in ethyl oleate. Subsequently the gilts were either inspected visually each day or taken to a vasectomized boar for oestrus detection. All gilts were mated at the second oestrous period, and slaughtered on the 20th day of gestation. Those gilts receiving exogenous oestrogen attained puberty significantly earlier (P<0·01) than the control gilts. Of the 20 gilts treated with oestrogen, 12 (60%) attained puberty within 5 days of the start of treatment. No significant difference was found between boar testing and visual testing, although receptivity to mating appeared to be lower for visually tested gilts. There are no significant differences between treatments in ovulation rate, conception rate or embryo survival.