Intended and unintended consequences of the ZnO ban from pig diets on antimicrobial resistance, post-weaning diarrhoea and the microbiome.

点击翻译按钮获取中文摘要

In most countries, farmed pigs are typically weaned at around four weeks of age. Young pigs are especially vulnerable to gut problems due to their immature digestive system and are particularly susceptible to a condition known as post-weaning diarrhoea. Post-weaning diarrhoea results in distress and discomfort in affected animals, and can lead to death. Recovered piglets often have poorer health and reduced growth, affecting welfare and farm productivity. Gastro-intestinal disease is currently the single most significant challenge to the sustainability of UK and global pig systems and affects more than half of pig farmers worldwide, at significant cost to the industry. Until recently, post-weaning diarrhoea was controlled by the addition of Zinc Oxide (ZnO) to feed after weaning, which reduced disease and improved piglet outcomes. However, due to concerns that ZnO contributes to the development of antibiotic resistance, prophylactic use of ZnO has recently been banned in both the EU and UK. At present, there is no direct replacement for ZnO, but rather a range of practices. These include a variety of nutritional and management changes, that may be variously applied according to the circumstances of each farm. This is prompting concern that by withdrawing ZnO, post-weaning diarrhoea may become more difficult to manage, with adverse consequences on piglet health and welfare. Despite the sector's best efforts, treatment will more likely need to rely on antibiotics to treat disease and manage diarrhoea. This, therefore, presents us with a conundrum: banning ZnO may possibly increase antibiotic resistance on farms, because farmers may need to use more antibiotics in practice, to treat sick piglets after weaning. These intended and unintended consequences of ZnO withdrawal are the focus of this proposal.In this study, we will work closely with producers over the withdrawal period to investigate the impact of ZnO withdrawal on piglet health and to identify measures that may help. In particular we are interested in the consequences of ZnO withdrawal on the levels of disease-causing bugs on farms and any changes in carriage of antibiotic resistance by pigs. We will do so by collecting dung samples from a small number of commercial herds across the UK and comparing samples from before and after the ZnO ban. We have already collected pre-ban samples from a number of UK commercial herds, in a precursor pilot project to this proposed study. Laboratory analysis of these dung samples will show which disease-causing bugs are present, and allow us to look for changes in the characteristics of these bugs and their association with disease, before and after the ZnO ban. Using genome sequencing technologies, we will look for antibiotic resistance markers, to see whether these all change after ZnO is withdrawn. Our findings will provide a 'barometer' of piglet health across UK farms during the transitional withdrawal period. We will also examine what differences are seen in the healthy gut microflora in pigs in the presence of ZnO and whether particular beneficial bacteria can be identified. We will investigate how we can exploit these differences to develop alternative feed supplements, such as "friendly bug" supplements that may help in the control of disease and improve piglet health.By providing evidence-based information, this project will help offset existing uncertainties and inform wider discussion as the sector adjusts to 'zero zinc.' This in turn would be expected to lead to the development of pig production systems that deal sustainably with the challenge of managing the post-weaned piglet.