Effects of age and live weight on the sexual development of gilts and boars fed two planes of nutrition.

The aim of the present study was to determine the respective influences of age and live weight on the sexual development of boars and gilts. The Large White animals used were fed on a liberal plane of nutrition close to ad libitum (CTRL group) or restricted on a live weight basis (SA and SW groups). CTRL and SW pigs were slaughtered and their genital tracts examined at 125 kg of live weight; those in the SA group were slaughtered and examined at the same age as their CTRL littermates. Control and SA boars and gilts were about 180 and 200 days old, respectively, while SW boars and gilts were about 240 and 260 days old, respectively. The SA group pigs weighed about 90 kg. Testis weight was influenced by live weight but not by age, while epididymis and seminal vesicle weights and bulbourethral gland weight and length were dependent on both age and live weight. Age had a significant influence on puberty attainment in gilts while live weight had nearly no effect. Percentages of cyclic gilts in the CTRL, SW and SA groups were 32, 79 and 20, respectively. Ovarian weight was mainly dependent on live weight in cyclic as well as in prepuberal gilts. In the latter animals, the weight and length of uterine horns and cervix were influenced by both age and live weight, whereas in cyclic gilts the only obvious effect was that of age on uterine horn weight. Season of birth (autumn vs spring) had no effect on the puberty attainment of gilts.