Nitrogen excretion, ammonia, and greenhouse gases emission in Italian heavy pigs: the role of feed in environmental impact mitigation

This review examined the environmental impact of fattening pigs, with particular focus on the Italian heavy fattening pig, affected by dietary interventions aimed at mitigating nitrogen excretion and gases emission into the atmosphere, maintaining product quality and complying with the regulation frameworks. In the Italian heavy pig supply chain, environmental regulations are often difficult to comply with due to the constraints imposed by PDO. The pig sector is increasingly committed to developing strategies that can effectively mitigate its environmental impacts. In intensive pig farming, emissions of ammonia (NH3) and greenhouse gases (GHGs) can occur in every production phase, from animal housing to manure treatment, management, storage, and up to in-field application. All these phases present key actions to limit emissions of NH3 and GHG, according to Best Available Techniques (BAT) for housing and Best Practices (BP) for manure treatments and management. Nitrogen excretion in manure is another important aspect to consider for its negative effects when applied in Vulnerable Zones with considerable additions of animal waste and synthetic fertilisers. Nutritional strategies can contribute a priori to mitigate nitrogen excretion, NH3 emissions, and overall GHG output in heavy pigs, particularly in Italian PDO ham systems. While these interventions effectively mitigate NH3 and influence manure-related emissions, their impact on total GHG varies depending on diet composition, fibre type, additive combination, and post-excretion treatment.