The Controlled Induction of Puberty

Puberty, defined as the time at which ovulation and oestrus first occur in association with normal luteal function, usually takes place at about 200 days of age in the gilt (Duncan and Lodge, 1960). As the replacement gilt is reared solely for reproductive purposes, a delay in the attainment of puberty means a delay in the commencement of productive life. With the recent trend towards intensive confinement systems of pig production it has become increasingly desirable to be able to control the onset of puberty in the gilt. As discussed in Chapter 6, age at puberty can be affected by many factors including nutrition, genotype and the environment. Although there are numerous reports in the literature concerning environmental or physiological conditions which may either hasten or retard puberty in the gilt, few include studies of the associated hormonal changes. Therefore in reviewing those methods used in an attempt to control the onset of puberty in the gilt, particular emphasis is given to the endocrinology and mode of action of the technique involved.