The Role of Organic Acid-Preserved Grains in Sustainable Pig Production: Impacts on Growth Performance, Digestive Health and Environmental Impact

The principal objective of this thesis was to investigate the nutritional and environmental implications of preserving cereal grains and faba beans using an organic acid mould inhibitor. Specifically, this research aimed to evaluate the use of these preserved feed ingredients in pig diets across all production stages, with the overarching goal of optimising gastrointestinal health, nutrient digestibility, and growth performance while reducing the environmental impact of pig production systems. Chapter 2 investigated the effects of replacing conventional drying of wheat and barley with organic acid preservation on post-weaning pig performance, intestinal health, nutrient digestibility, and microbial profiles, with or without zinc oxide supplementation. Preserved cereals showed lower mould counts and mycotoxin levels after storage compared to dried grains, and pigs offered the preserved grain diet exhibited enhanced growth, reduced diarrhoea incidence, improved ileal nutrient digestibility, and beneficial microbial shifts compared to those offered dried grain diets. Chapter 3 extended this investigation to maternal nutrition, evaluating the inclusion of preserved cereals in sow diets during late gestation and lactation. While sow reproductive performance remained similar, preserved grain improved maternal total tract digestibility and digestible energy intake, reduced faecal Proteobacteria in sows and their piglets, improved piglet faecal scores, and increased offspring faecal Lactobacillus at weaning. Pigs weaned from preserved grain-fed sows exhibited enhanced growth and feed efficiency from weaning until slaughter. Chapter 4 assessed whether combining maternal and direct feeding of preserved grain could provide additive benefits from birth to slaughter. While no synergistic effects were detected, both maternal and direct feeding independently enhanced pig growth performance, nutrient digestibility, and microbial profiles throughout production. Notably the combination of maternal and direct feeding of preserved grain achieved the greatest overall performance, yielding the highest final body weight and most favourable shifts in microbial diversity and composition throughout production. Chapter 5 built on these biological findings and applied life cycle assessment (LCA) to quantify the environmental implications of incorporating preserved grains in a commercial pig setting. Organic acid preservation of wheat and barley reduced the global warming potential of grain preservation by up to 18% and cut fossil resource depletion by over 70% compared to conventional drying. Incorporating preserved grains into sow and progeny diets further reduced the cradle-to-farm-gate environmental footprint of pig production, lowering global warming potential, acidification potential and eutrophication potential by up to 12%, with cumulative benefits amplified by improved animal performance. Chapter 6 explored the combined nutritional and environmental effects of incorporating organic acid-preserved cereals with faba beans into finisher pig diets, focusing on their potential to replace imported soya bean meal. While preserved cereals alone did not affect growth performance or carcass characteristics in soya-based diets, their inclusion improved nutrient digestibility in faba bean-based diets. Replacing soya bean meal with local faba beans reduced the global warming potential of pig production by 36%, although they increased acidification and eutrophication impacts by 7% each, due to higher dietary inclusion rates. Notably, combining preserved cereals with preserved faba beans impaired growth, suggesting the need to manage dietary acid load carefully. Together, these studies demonstrate that organic acid preservation offers a multifunctional strategy to improve grain quality, optimise pig health and performance, and reduce the environmental footprint of pig production.