Early indicators of a gill's reproductive potential

Abstract

The reproductive output of the sow breeding herd determines the productivity and subsequent profitability of any piggery. The average replacement rate for Australian sow herds is currently 55-58% (Australian Pig Industry Benchmarking Report 2019-2021), which is much higher than the acceptable level of 38% (Hughes and Varley, 2003). To reduce this replacement rate, the aim of this thesis was to determine if the reproductive potential of a replacement gilt could be identified prior to weaning, by determining a suite of markers that are indicative of in utero developmental programming of the reproductive axis. The markers of developmental programming and reproductive potential assessed in this thesis included birth weight, maternal parity, anti-mϋllerian hormone (AMH) concentration and gestated sex ratio of the litter. The overarching hypothesis was that low birth weight, gilt progeny would be reproductively inferior and less able to cope with suboptimal management, as proven by an imposed lactational feed restriction. The results of the three studies conducted suggest that selection of replacements from gilt litters is acceptable, providing they are not classified as low birth weight. While some significant differences were found in the ovarian development of offspring of male or female biased litters, the main commercial implication of the current study is that until further research is conducted selection from biased litters should be avoided. The results of this thesis conclude that the developmental programming of a gilt plays a significant role in her reproductive potential. To reduce replacement rates of the Australian sow herd the developmental programming needs to be considered when selecting potential replacement gilts.