AGE, WEIGHT, BACKFAT AND TIME OF MATING EFFECTS ON PERFORMANCE OF GILTS

Abstract

An experiment was conducted involving 429 gilts that were managed to stimulate estrus after 140 d of age, bred at first, second or third observed estrus and to study factors relating to estrus and reproductive performance to weaning of the first litter. The average at first estrus followed by the coefficient of variation (%) in parentheses were: age 167.2 d (11.8); weight 106.8 kg (15.5); backfat 19.1 mm (17.8); backfat/weight 0.18 (16.2) and weight/age 0.64 (11.5). Sixty-two and one-half percent of the gilts exhibiting estrus did so between 140 and 170 d of age. Fifty-eight percent of the gilts exhibited estrus prior to 180 d of age and were less than 110 kg liveweight. There were relatively low correlations between indices of growth rate and fatness with age at first estrus. Reproductive performance was not enhanced by delaying breeding to second or third estrus after puberty. Key words: Pigs, reproduction, sexual maturity, age, weight, backfat