Some factors affecting the age of puberty in swine

The attainment of sexual maturity in the female is generally stated to be a gradual process. The rate of growth and function of the female reproductive tract is controlled by the hormones secreted by the anterior pituitary gland. The factors affecting the release of the pituitary anterior pituitary gonadotriphins are incompletely understood. Work, particularly, with birds and certain laboratory animals has shown that light is one important factor influencing the release of the gonadotropic hormones. Also, there is evidence suggesting that light and temperature or a combination of these environmental factors may affect the time of beginning of the breeding season in ewes. Likewise, there is some evidence that the presence of the ram with ewes near the beginning of the breeding season increases the number of ewes coming in heat.

This experiment was initiated to study some of the factors influencing the age of puberty in swine. Vocational Agriculture teachers throughout the state have made complaints that students with swine projects were reporting difficulties in getting gilts bred at the proper age. Normally, gilts should be bred when they are approximately eight months of age. It was in reaction to these inquiries that a preliminary experiment was initiated to test the effect of the level of protein in the growing ration of gilts on the age at first estrus. In this trial, similar breeding difficulties were experienced until the boars were turned with the gilts; shortly thereafter, breeding activity began. On the basis of this preliminary data, an experiment was designed to further test the effect of presence of the boars in stimulating first estrus.