Animal welfare in the newborn piglet: a review

The objective of this review is to integrate clinical findings and laboratory analyses in such a way to improve the welfare of newborn piglets and achieve better prognoses of neonatal viability. Deaths during the intrapartum period account for a significant proportion of pre-weaning mortality in farms worldwide. Piglets which die during parturition generally have normal size and typically lack gross lesions at post-mortem examination. However, circulatory abnormalities in the umbilical cord help in assessing piglet viability. Cord lesions can be classified as normal (adhered), oedematous, congested or haemorrhagic and should always be evaluated in perinatal deaths. The likelihood of neonatal survival decreases rapidly as the severity of umbilical cord lesions increase. The physiometabolic blood profile which includes acid-base balance, degree of dehydration, mineral balance, metabolic expenditure and gas exchange are also useful clinical elements for properly assessing neonatal viability. Neonatal survival is notably reduced when the blood pH falls below 7.0, lactate rises above 90 mg/dl, bicarbonate drops below 10 mmol/l, or the pCO(2) increases above 110 mm/Hg. Blood calcium is also an excellent indicator of neonatal stress when used in combination with the other parameters mentioned above. Trembling due to an imbalance in the movement of calcium in muscle is also a factor involved in neonatal mortality. Neurological function in the newborn piglet could also be evaluated by adapting the Apgar score widely used in human perinatology. Neonates with scores lower than 6 in a 10 point scale have generally lower survival rates. The two most important indicators for this vitality score are breathing latency and bradycardia. If the neonate has apnoea for more than 5 min and the cardiac frequency does not increase to more than 110 beats per minute the prognosis for survival is rather poor.