Management of post-weaning diarrhoea and the implications for AMR in response to the upcoming ban on zinc supplementation in pigs.

Piglet weaning through separation from the sow is a critical and stressful period in the life of a pig. At this stage piglets are particularly vulnerable to gut problems and have a tendency to develop a condition called post-weaning diarrhoea. This disease is primarily caused by bacteria and viruses which challenge the piglet's immature gut, and is a welfare and economic concern to farmers, because piglets suffer weight loss, discomfort and sometimes death. Zinc oxide is currently added to pig feed as a dietary supplement to reduce post-weaning diarrhoea and boost growth. However, whilst Zinc oxide improves piglet gut health, there are environmental concerns due to the potential contamination of land with zinc through pig manure and waste. High zinc levels are also thought to promote the ability of bacteria to evade antibiotics, resulting in antimicrobial resistance. For these reasons, from June 2022 the supplementation of pig feed with high levels of Zinc oxide will be banned in the UK and Europe. Within the pig farming sector there are serious concerns that this ban will have a damaging impact on the health and welfare of piglets during weaning. Farmers and veterinarians anticipate post-weaning diarrhoea will become harder to manage and will require more medical treatment. As a consequence, antibiotic use to treat piglet gut infections may increase, exacerbating already high usage within the pig industry. This has implications for limiting levels of antimicrobial resistance in livestock and the food-chain.

Working directly with farmers during the transitional period to "zero zinc", in this study we aim to investigate the impact of the ban on piglet health and growth. Our goal is to identify practical measures that will make an on-farm difference to reducing disease, whilst improving animal welfare and productivity. We will examine a range of farm management, husbandry and biological measures, to see which factors influence post-weaning diarrhoea in piglets. We will do this by collecting pig faecal samples from farms both before and after the introduction of the June 2022 ban, and identifying any changes in the type and numbers of microbes found in piglet faeces. We will look at the composition of the "friendly" gut bacteria, as well as disease-causing bugs, and examine levels of resistance to antibiotics. At the same time we will analyse data from participating farms to measure piglet health status, and track any management changes farmers may have introduced to lessen the impact of the Zinc oxide ban. This, together with a questionnaire-based survey of pig farmers across the UK, will provide a picture of both the perceptions and reality of the Zinc oxide ban on piglet weaning. Crucially, by working directly with farmers, we hope to find acceptable solutions that may reduce disease in piglets, whilst providing information to help offset the uncertainty accompanying the journey to "zero zinc".

Piglet weaning is a critical life-stage, associated with high vulnerability to diarrhoeal disease and poor weight gain. Post-weaning diarrhoea (PWD) is a condition that causes considerable economic loss to the pig industry due to the impact on this most pivotal phase of a pig's production cycle. Zinc oxide (ZnO) is currently used as a feed additive at pharmacological levels of 2500 ppm to mitigate the challenges during weaning, reducing diarrhoeal incidence while improving production measures such as weight gain. However, there is an environmental impact of high ZnO usage, which is also associated with an increase in antimicrobial resistance within the pig gut microbiota.
From mid-2022, ZnO supplementation of weaner/post-weaning piglet diets will not be permitted above a maximum level of 150 ppm. It is anticipated that this will result in an increase in PWD, impacting pig productivity, animal health and welfare. This project will have two main objectives, the first the establishment of a bio-bank of pre- and post-ban faecal samples for microbial analysis to elucidate the impact of the ZnO ban on pathogen occurrence, antimicrobial resistance indicator genes and microflora composition in weaning and later aged pigs. The second, an epidemiological analysis of data from participating farms to identify potential risk factors affecting diarrhoeal disease, together with on-farm motivations and barriers towards management of health throughout the weaning period.
The immediate months prior to implementation of the June 2022 ban, together with the period of withdrawal, present a unique opportunity to objectively compare the pre- and post-ban experience of PWD within the UK pig sector. Directly working with stakeholders, this project aims to identify practical measures for on-farm implementation to reduce disease occurrence and improve productivity, whilst providing information to help offset the uncertainty accompanying the transition to "zero zinc".