A Case Study of Gilt Pool Management-U of A

¹G. Foxcroft, ²J. Goller, ²J. Willis, ³M. Meninga, ¹J. Barrie, ¹J. Hesse, ¹J. Mao, ¹S. Novak and ¹F. Almeida

Alberta Pork Research Centre: ¹Department of Agricultural, Food & Nutritional Science, University of Alberta

²Swine Research Unit, Edmonton Research Station; ³Department of Biology, King's University

Continual improvements in gilt pool management will make an important contribution to improving breeding herd efficiency. Gilt non-productive days and failure to meet gilt pool breeding targets are two of the most important factors limiting breeding herd performance. Data on gilt pool performance have been analyzed over the last two years in order to identify research needs in this area and to demonstrate factors contributing to efficient gilt pool management.

Study 1; Camborough "cull" gilts (N = 850) from a commercial multiplier received daily contact with mature vasectomized boars from day of arrival and were group penned and fed a commercial finisher diet to appetite. Time of onset of first standing heat was recorded and gilts were mated with v boars at pubertal estrus as far as possible. Known cyclic gilts (593) were allocated to specific breeding weeks targeted to provide batch farrowing of gilts during the regular working week (Monday to Friday). Breeding groups comprised either 1), gilts at their natural second or third heat n = 466), or 2), gilts (n = 127) in which heat was synchronized using treatment with the oral progestagen (Regumate). All gilts were bred twice by AI, 12 and 24h after onset of standing heat. Where possible the true reproductive status of recorded "non-cyclic" gilts was determined before culling. Approximately 70% of gilts were "known cyclic" within 60 days of introduction to boars. Of these, 29% showed estrus within 7 days and 84% within 28 days of arrival. 100% of Regumate treated gilts were in estrus in the breeding week following drug withdrawal, confirming the efficacy of this treatment. Retrospective analysis shows important effects of age, bodyweight and growth rate on gilt performance.

Study 2; A total of 132 cross-bred Camborough x Canabrid gilts, selected as littermate groups were subjected to a nutritional conditioning targeted to produce gilts of 160 days of age at 90 kg body weight at the time that gilts were moved, mixed with other litter groups and introduced to daily boar contact. This strategy was aimed at producing trios of cyclic littermates with similar pre-pubertal growth performance for experimental work. 55% of gilts were recorded in estrus within 30 days of introduction to boars, with approximately equal numbers of gilts reaching first estrus in each week after first boar contact. 69 gilts, representing 23 littermate trios, were synchronized with Regumate and bred by AI, 82% of which were pregnant at slaughter on d 28 after breeding. The lower initial estrus response in this group of gilts probably reflects the lower age and weight at boar contact.

Implications: 1)Further work on effective gilt conditioning programs is needed to induce early onset of puberty, allowing selection of the most fertile gilts before market weight. 2) Regumate is an effective tool for estrus synchronization.