High replacement rates for P1 and P2 sows have skewed current parity structures on most sow farms towards younger, less productive females. As a result, herd productivity is being limited because females are culled before they reach their peak periodsof reproductive efficiency. Management early in a gilt's life (Knol et al., 2010) and after she enters production can have a significant impact on her longevity as a sow (Vargas et al., 2009; Hughes et al., 2010; Kaneko and Koketsu, 2012). In essence, whether or not a sow reaches her most productive parities depends on how well her reproductive machinery is built during her prepubertal developmental period and how well it performs as an adult (Figure 1).
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