Conclusions from PROHEALTH experimental studies
Piglet mortality within the first 28 days after birth is a major concern for pig producers. On European farms, one piglet in seven dies in the period between birth and weaning, with over 50% of these deaths occurring in the first 72 hours. The main causes of piglet death vary according to age. For example, during the first 48 hours after birth, the main causes of death are hypoxia (oxygen starvation in body tissues), under-feeding and the resulting hypothermia (too low a body temperature). If piglets receive insufficient colostrum from the sow during their first few hours, it may result in a lack of vitality and incapacity to suckle. After the first 48 hours, infections and starvation become the main causes of death until weaning. Medications may be administered in an attempt to combat infectious disease, but this is a costly and environmentally questionable solution.
Until now, the roles of sow welfare, housing and diet during pregnancy, and their subsequent impact on piglet survival and immunity have been poorly explored. But a preliminary study by members of the PROHEALTH project had pointed towards a positive impact of so-called ‘enriched’ housing systems on sow health at the end of gestation and, later on, on piglet survival. Prompted by these results, the PROHEALTH teams aimed to investigate further by comparing two different housing systems for pregnant sows. The conventional group housing system was on slatted floors, with only slightly more than the legally required space allowance per sow. In the enriched system, group-housed sows were bedded on straw and had more space. Ten days before farrowing, sows from both systems were transferred to maternity rooms with similar lactation pens and management practices.
Maternal characteristics and piglet survival were compared from the two different housing systems. Maternal characteristics studied included sow behaviour and health, and composition of blood, colostrum and milk. Piglet characteristics studied included body tissues development, physiology, presence of different families of bacteria in the gut, vitality at birth, and survival rate. Colostrum and milk composition were under particularly close investigation, as colostrum is very rich in energy and contains vital maternal antibodies for piglet immunity. Colostrum and milk also contain other important immunity agents such as white blood cells, and regulatory and anti-microbial factors that contribute to piglet gut maturation and immune protection.
We found that the housing system did not affect the sows’ colostrum composition, but did affect the milk composition. Four days after farrowing more white blood cells were transferred to the milk of sows kept in the enriched system. Since sows also displayed some immune response differences 10 days before farrowing, it might be that the differences in the cellular composition of milk resulted from differences in maternal immune activation resulting from the two housing systems. This observation supports findings from preliminary studies, and provides a physiological basis for the improved sow and piglet health in enriched housing compared to conventional housing. Through a better understanding of the immune factors that contribute to piglet survival, PROHEALTH will continue to investigate ways to improve sow health and piglet survival in intensive production systems.