Piglet mortality: causes and prevention

The evolutionary biology of the pig means that it is predisposed to produce more offspring than it is likely to rear, and this tendency has been exacerbated under farm conditions by genetic selection pressure for increased prolificacy. Piglet mortality from birth to weaning typically amounts to 16-20%, with the major causes attributed to stillbirth, crushing and starvation. However, these ultimate causes mask the true predisposing factors, with interactive risk factors arising from the biology of the sow and piglets and the challenges of the neonatal environment. Intra-uterine competition for nutrients can result in a stillborn piglet or a live-born piglet with reduced viability, low birth weight and compromised chances for postnatal survival. Prenatal insults can impact on vigour and thermoregulatory abilities, resulting in a piglet unable to survive the challenges of asphyxia during birth, hypothermia following delivery and intense competition for colostrum. Reduction in piglet mortality requires co-ordinated genetic, nutritional, management and stockperson interventions. The incorporation of survival traits in genetic selection goals, the optimisation of maternal nutrition during breeding and gestation, and the avoidance of prenatal maternal stress through appropriate environmental conditions will promote delivery of more vital piglets and stimulate good maternal behaviour. Supervision and assistance during farrowing, with stockperson intervention to facilitate early and adequate ingestion of colostrum by all piglets, provision of appropriate thermal microclimates to reduce hypothermia, and skilful cross-fostering to ensure early establishment of litters of appropriate size and uniformity, are all key components of success. With an increasing societal focus on the ethical and welfare issues in pig production, but no alleviation of the financial pressures on pig farmers to remain competitive, the requirement to achieve a high number of piglets weaned per sow per year in an environment allowing adequate expression of sow behavioural needs will continue to pose challenges.