THE EFFECTS OF ALTERED SUCKLING INTENSITY, BOAR EXPOSURE IN LACTATIONAND GONADOTROPINS ON ENDOCRINE CHANGES, FERTILITY AND THE INCIDENCE OF LACTATIONAL ESTRUS IN MULTIPAROUS SOWS

One of the more promising techniques for the improvement of soul produ ctivity has been the use of partial weaning or the separation of the s ow and litter for periods of between 3 to 12 h/day towards the end of lactation. The purpose of the present study was to examine changes in steroid hormone concentrations, oestrus and fertility responses in lac tating sows subjected to altered sticking, boar exposure and gonadotro pins in mid lactation and at weaning. Thirty-two crossbred sows were a llocated at random to one of four experimental treatments. Treatment 1 sows (no. = 8) were separated from their respective litters for 3 h/d ay from 12 clays post partum through until weaning which was carried o ut at 21 days post partum. Treatment 1 sows were also given in-pen boa r exposure for 1 h/day between day 12 post partum and weaning. Treatme nt 2 sows (no. = 8) were given the same protocol of litter separation (LS) and boar exposure (BE) as in treatment I and they were also given a combination of gonadotropins (Gn) on day 17 of lactation. Treatment 3 sows (no. = 8) were given LS + BE as above and the sows were inject ed with Gn on the day of weaning. Treatment 4 sows were controls given no LS, BE or Gn (no. = 8). During lactation, treatment 1 sows exhibit ed significantly (P < 0.05) reduced progesterone concentrations compar ed with treatment 2 so ius. There were no other significant effects of treatment for any of the periods considered. The separation of sows f rom their piglets with or without gonadotropic treatment did not resul t in lactational oestrus in any treated sows. No significant treatment differences were found in the subsequent litter size (piglets born al ive or total number of piglets). In conclusion, the present results ha ve demonstrated no significant effects of LS, BE and Gn treatment duri ng lactation on sow and litter performance. This teas associated with law levels of peripheral plasma progesterone in all lactating sows.