Improvement of sow longevity through identification of early lifetime performance indicators, including the assessment of gonadotropin response as a suitable selection tool for replacement gilts

Abstract

High sow turn over or replacement rate is an ongoing issue in the Australian pig industry. High sow turnover within a herd leads to a reduction in sow lifetime performance (calculated as the number of pigs produced per female per day of herd life), especially if replacement rates for early parity sows are high. High sow turnover rates result in a higher proportion of younger sows in the herd, in particular gilts, leading to increases in HFC (feed consumed per unit carcass weight produced) due to a greater proportion of gilt progeny within the herd (Smits, 2011). Over the past decade there has been considerable research into this topic, however, little improvement has been made. <br/> In 2013 the sow replacement rate was 56.1%, with the average parity at which a sow was culled sitting at 4.1 (Australian Pork Limited). A sow needs to at least reach her third or even her fourth parity before she begins to recover her own cost (Rodriguez-Zas et al. 2003; Levis, 2005). Therefore, her removal from the herd prior to parities 3-4 results in financial loss for the producer. There are a number of key reasons for premature sow turnover, with poor reproductive performance during the early parities a major cause of removal. In a review of the major causes for sow removal within a large commercial Australian farm, Hughes et al. (2010) found the single largest cause for culling was poor fertility, particularly in early parity sows. Interestingly, gilt culls accounted for 42.5 % of the fertility culls, with the majority of these (42%) failing to exhibit signs of pubertal oestrus in the required timeframe.