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Divergent selection for age at puberty impacts sow reproduction
The objective of the study was to associate selection for age at puberty with first litter reproductive performance. Estrous data was collected from a cohort of PIC Landrace × Large White gilts (n=393) at the NCDA Tidewater Research Station. Gilts were placed in curtain-sided buildings on fully slotted floors in groups of 15 (0.84 m2per pig). Fans and timed misters were used for cooling once temperatures reached 27°C. Starting at 130 days of age, each group of gilts was penned with three mature boars for 7 minutes daily and estrous behavior recorded. Puberty was defined as the first observed standing reflex to the back-pressure test. Both a young and an old age at puberty group of gilts (average age at puberty 171 and 241 d, respectively) were kept for breeding. Both groups of gilts were mated to the same 12 boars and farrowed during the same month. Sow reproductive traits measured included; number born alive, average birth weight, litter birth weight, number weaned, average weaning weight, litter weaning weight and whether a sow exhibited estrus by 7 d after weaning (W2E_7). Analysis of variance was used to analyze continuous reproductive traits and a chi-squared analysis was utilized for the categorical trait, W2E_7. Table 1 shows the first litter reproductive performance of the young and old age at puberty groups. Of the first litter reproductive traits measured, only W2E_7 differed (P < 0.01) between puberty groups. The current study found a younger age at puberty did not impact litter traits but had a substantial impact on post-weaning expression of estrus. Results suggest that selection for a younger age at puberty would improve an important component trait of sow longevity, W2E_7.
| Table 1. First litter reproductive performance for gilts divergently selected for age at puberty | ||||
| Genetic | Line | |||
| Trait | Young age at puberty | Old age at puberty | SE | P-value |
| Number born alive | 11.2 | 11.6 | 0.90 | 0.64 |
| Average birth weight, kg. | 1.17 | 1.15 | 0.05 | 0.67 |
| Litter birth weight, kg. | 12.7 | 12.9 | 0.92 | 0.78 |
| Number weaned | 9.7 | 9.9 | 0.60 | 0.71 |
| Average weaning weight, kg. | 5.2 | 5.1 | 0.15 | 0.43 |
| Litter weaning weight, kg. | 51.2 | 49.6 | 2.89 | 0.57 |
| Exhibited estrous by 7 days after weaning, % | 88 | 58 | - | 0.01 |
Keywords: gilt, puberty, reproduction