Body Criteria Targets Before 1st Breeding
Target body weight for gilts at breeding should be between 300 to 340 lb to optimize reproductive performance and longevity in the sow herd. This weight threshold is needed at breeding to ensure gilts will not lose excessive protein reserves during their first lactation. Gilts generally have lower lactation feed intake which results in increased mobilization of protein stores for milk production and can lead to decreased reproductive performance (Clowes, 2003). Furthermore, breeding gilts at lighter or heavier weights can decrease total born over their entire lifetime or potentially result in increased stillborn pigs and lameness issues, respectively (Williams et al., 2005). Finally, backfat is not a reliable predictor of subsequent reproductive performance. This is because greater amount of backfat accumulation in gilts shows no evidence for an improvement in reproductive performance (Filha et al., 2010). Accumulating protein reserves is more important as increases in fat accumulation are lost by weaning after the first litter and excess losses in protein reserves can lead to decreased reproductive performance (Gill, 2006).
Therefore, bodyweight should be used as the target criteria before first breeding to optimize reproductive performance. Also, avoiding deficiencies or oversupply of nutrients in the diet helps achieve long-term reproductive success of gilts.