Summary/Findings

The management of lightweight pigs that have resulted from increases in sow prolificacy are a major challenge for modern pig systems. The overall aim of this thesis was to develop intervention strategies that improve the performance of light piglets without penalising heavy piglets, with the pre- and immediate post-weaning period being the most critical windows for intervention.

In the first experiment (Chapter 2) creation of litter uniformity pre-weaning optimized the performance of piglets born lightweight, with long term benefits up to slaughter; heavy piglets on the other hand were penalized by this strategy. Despite heavy piglet efforts to compensate for insufficient milk intake by increasing creep feed intake, this was insufficient for achieving similar growths to heavy piglets kept in mixed litters. That being said, piglets born heavy ate high amounts of creep feed whereas piglets born light hardly consumed any creep feed.

In Chapter 3, it shown that irrespective of birth weight mid parity sows were identified as best foster sows. Their piglets were weaned heavy, whilst having eaten high amounts of creep feed. Second parity sows also weaned heavy piglets, but due to piglet low creep feed intake they were unable to maintain this weight advantage post-weaning. Despite the high creep feed intake of primiparous sow reared piglets, these piglets were weaned light and remained light post-weaning.

Lightweight piglets did not seem to benefit from an amino acid enriched post-weaning starter regime (Chapter 4). Although birth weight is still commonly used as indicator for identifying runt piglets, not all light piglets are destined to remain light. In fact, piglet shape at birth such as, length and head circumferences in relation to birth weight, seemed better predictors of post-natal growth.

Chapter 5 evaluated the effect of weaning age, weaning weight and an increased allowance of nursery diets on the performance of piglets through 5 months of age. The results suggested that an enhanced allowance of the nursery diets was beneficial, but that delayed weaning may yield long term benefits for piglets weaned lightweight.

The data from this thesis provide novel information and implications for the management of lightweight piglets. Some lightweight piglets are able to improve their post-natal performance and creating the optimal environment such as litter uniformity, rearing them by mid parity sows and weaning later will be beneficial to them.

The aim of this research is to reduce variability within pig groups through sorting for live weight, and by doing so to improve the efficiency of production systems. Its overall objectives are (i) to investigate the consequences of sorting on life time performance of light, normal and heavy pigs, and (ii) to develop cost-effective feeding regimes for normal and heavyweight pigs.  Current evidence on the consequences of sorting appears contradictory.  Although it is generally accepted that sorting in general benefits lightweight pigs, it has been suggested that it actually penalises heavyweight or normal weight pigs.  In addition there is currently considerable variation in the manner sorting for live weight is practiced in UK pig farms.  This probably depends on the production system (i.e. indoor slats vs. straw yards), due to the available pen/ group size of pigs.  For this reason the project objectives will be addressed in these different production systems. The research would be carried out jointly with Primary Diets, the feed manufacturer that develops specialist feeds for nursery pigs.  The outcomes of the research would be cost effective and resource efficient management practices that can be applied in the different UK systems.  Through the combination of small and large, Industry-based experiments the research will have immediate applicability, whilst providing the student with rigorous training on various management techniques that offer solutions to the UK Industry.