A study on the reproductive development in gilts
1. Some aspects of the sexual maturation in the female pig have been reviewed. 2. The significance of age at puberty in pig production and the factors affecting reproductive development as assessed by puberty attainment have been discussed. 3. The validity of a new method for assessing the relative reproductive maturity of prepubertal gilts by administration of 20 microg/kg LBW of oestradiol benzoate has been evaluated. This appeared to give similar results relative to boar stimulation. 4. No significant effect on reproductive development in gilts of plane of feeding (60, 80 and 100 percent of appetite) during the late prepubertal stage (140 to 190 days of age) and the body tfeight differences induced by such treatments was evident. 5. Reproductive maturity of crossbred gilts evaluated between 148 and 184 days of age appeared to be least around the age of 160 days and increased thereafter, but chronological age, body weight and fatness appeared to be poor indicators of the relative reproductive maturity within the age range studied. 6. Crossbred gilts attained puberty in a shorter interval follow boar stimulation (around 90 kg live body weight) than Large White (21 days longer them crossbreds) or Landrace (6 days longer than crossbreds) gilts and the above interval appeared to be more live body weight than age dependent, 7. The dam had a significant effect on establishing the reproductive potential of the gilt piglet, On a 13 day weaning system the effect of litter size at birth on reproductive development of the gilt appeared to be stronger compared to litter size at weaning. The strong dam effect observed is likely to be the result of genetic and environmental effects prevailing in the perinatal period and/or on the interaction between these two sets of factors. 8. The pituitary response to administered GriKH assessed two ages (55 and 140 days of age) appeared to be a good indicator of the developmental potential in gilts.