Identifying and investigating factors which affect sow productivity in UK and Irish pig herds

Increasing litter size in sows is accompanied by a rise in the number of unviable piglets at birth which limits the potential output of modern sows. Understanding sow and dietary characteristics that influence reproductive performance and developing nutritional strategies to improve piglet survival and growth to weaning will abate the negative impacts of high litter sizes. Therefore, this study took two approaches: 1. Use of historical data from two research sites to quantify the association between sow or dietary characteristics during gestation and resulting reproductive performance and 2. Two separate feeding trials to determine the effect of salmon oil, vitamin D3 inclusion level in gestation diets and salmon oil and dietary energy regimen in lactation on piglet viability and growth to weaning. Sow live-weight and back-fat depth in late gestation were found to be important for subsequent reproductive performance. Current recommended digestible energy intakes during gestation were found to be appropriate for the modern genotype, however, current amino acid requirements should be increased for gestating sows. Salmon oil inclusion in gestation and lactation diets increased the proportion of omega-3 (n-3) fatty acids in samples while increased dietary vitamin D3 level during gestation improved sow and piglet vitamin D3 status, but the growth performance of piglets was not improved as a result. From this thesis it can be concluded that the transfer of n-3 fatty acids and vitamin D3 from sow feed to the offspring is effective via placental transfer and milk secretions, but this did not improve performance. This conflicts with other work and further research is needed to clarify the associated biological pathways and mechanisms to explain these inconsistencies.