Abstract:
The pig industry is an important and growing economic sector in South Africa and improvement in efficiency is vital. Reproductive traits have become more important as it has been realised that these entail the main source of profit, with the production of many viable offspring. As the focus on increasing litter size has amplified, there has been a concurrent decrease in within-litter birth weight uniformity. A decrease in uniformity has been linked to a decrease in piglet health and welfare, performance, and an increase in management requirements and costs. The purpose of this study was to investigate the merit of including within-litter birth weight uniformity in the breeding objective. An on-farm trial was conducted, that included 40 Duroc, 39 Landrace, and 40 Large White dams. Data was recorded for their first three parities to measure piglet performance, taking into account various effects. Piglet performance was measured using litter traits including number born alive (NBA), individual birth weight (BiW), 21 day weight (21W), weaning weight (28W), and 70 day weight (70W), as well as within-litter birth weight variation (CVB) and survival to weaning (SURV). A general linear model (GLM) was conducted to test the significance of piglet sex, dam breed, sire breed, season and year of birth, farrowing room, weaning room, fostering status (NAT/UNNAT), and the interaction of dam breed with sire breed, as effects. Sire breed and season and year of birth was found to affect NBA in all parities (p < 0.05), CVB was consistently affected by dam breed (p < 0.05), and SURV was affected by sire breed in all parities (p < 0.05). Most traits were affected by the interaction between dam and sire breed (p < 0.05). Parity affected NBA, BiW, CVB, 28W, and SURV (p < 0.05), and all these, except 28W, were affected by parity’s interaction with parental breed (p < 0.05). CVB was highest in the Large White dams in the first two parities, and highest in the Duroc in the third (p < 0.05), and mostly increased with increasing parity. Moderate correlations were found between NBA and BiW, and between BiW and 28W, for all parities (p < 0.05), and correlations between CVB and other traits were low. Further investigation with a larger animal sample size, more parities, and in a more controlled farm environment, is recommended.
