Influence of age at nutritional restriction on growth and sexual development of gilts

Large White females were fed on a plane of nutrition close to ad libitum during the entire experimental period (CTRL group, n = 48) or restricted during a limited period of their growth (RP1 group: 28-62 kg, RP2 group: 64-96 kg, RP3 group: 97-131 kg, n = 48/group). Blood samples were taken before 200 and 230 days of age in order to detect cyclic gilts by assaying their progesterone levels. Animals were slaughtered at approximately 260 d of age and their genital tracts were examined. Overall feed intake, feed conversion ratio and daily gain were significantly lower in restricted than in CTRL gilts (average daily gain: 678, 680, 668 and 741 g/day respectively in RP1, RP2, RP3 and CTRL groups, P less than 0.05). At slaughter, animals from the 3 restricted groups has similar live weights but were lighter (152 vs 164 kg live weight, P less than 0.05) and leaner than CTRL (fat thickness: 29.5, 30.5, 28.0 and 34.1 mm respectively, in RP1, RP2, RP3 and CTRL groups). Respectively, 9, 43 and 76% of the gilts were puberal at 200, 230 and 260 days of age. The percentage of cyclic females was not influenced by treatment at 200 and 260 days of age while it was higher in CTRL (50%) and RP1 (56%) groups than in RP2 (35%) and RP3 (29%) groups at 230 days of age (P less than 0.05). At 260 days of age, ovarian and genital tract weights were not influenced by treatment either in prepuberal or in cyclic gilts.(ABSTRACT TRUNCATED AT 250 WORDS)