Puberty Studies of Swedish Crossbreeding Gilts^*

Abstract

A number of factors such as breed, feeding and management are considered to influence the attainment of puberty in gilts. The season of birth also has been indicated as a source of the variation in age at puberty (e.g. Bane et al. 1976). The chronological age is considered to be of greater importance than live weight (Anderson & Melampy 1972), but severely restricted feeding delays puberty. The recommendation in Sweden is to breed the gilts during their second or third estrus. No information is, however, available concerning the age at puberty of Swedish crossbred gilts of today. The object of the present investigation was to investigate the age at puberty of Swedish crossbred gilts by the use of careful heat checking and analyses of peripheral blood plasma levels of progesterone.