Management of replacement breeding animals.

In conclusion, replacement gilts should be finally selected before 110 kg body weight and should have been stimulated to reach puberty by this time. Currently, the best method for achieving this is ad libitum feeding and the correct use of boar exposure. However, whether ad libitum feeding will always be the best feeding strategy remains to be seen. The impressive success of selection programs and the potential for the use of growth promoters and repartitioning agents in the feeder barn may require that future replacements be identified at an early stage and raised under a separate feeding regimen. To produce a large first litter, gilts should be bred at their second estrus. There is unlikely to be any further increase in litter size by delaying mating to third estrus. A major consideration when choosing when to breed replacements is the length of their productive life. For many farms, this may be maximized by delaying breeding until the sow is 120 to 130 kg body weight with a minimum backfat depth of 18 mm. For the producer who is able to exert control over lactation condition loss, however, breeding replacements at about 110 kg body weight with backfat depths of 14 to 16 mm should not adversely affect long-term performance. Although it is true that, under some conditions, the lean gilt may become a problem, it is equally true that her potential is as great as her fatter contemporaries. Whether this potential is realized is largely under the producer's control. Regarding the boar, nutritional management need not vary from that provided for gilts. However, if replacement boars are raised on-farm, it is of great importance that they be allowed to socially interact with other pigs. Failure to provide this opportunity will result in a boar with reduced libido.