Improving gut function in pigs to prevent pathogen colonization

Intestinal pathogens in livestock cause either clinical or subclinical infections which increase morbidity and (or) mortality, causing economic loss as well as increasing the negative health and environmental impact of animal food products. Optimal functioning of the gastrointestinal tract (GIT) provides a foundation to ensure optimal animal performance at all stages of its life. This is particularly true in pigs which, among domestic species, give birth to the most immature newborn. This is a legacy of life in the wild, where a single litter has minimal contact with others and the long suckling phase ensures the correct development of various gut functions: •• digestive function; • gastro-intestinal cell line barrier; • gut-associated lymphoid tissue (GALT); and • gut-associated microbiota. Increasing genetic progress in breeding animals has resulted in larger litter size. The need to breed numerous animals rapidly in intensive production systems has resulted in the early weaning of pigs, typically between 1 and 4 weeks post-farrowing, depending on individual countries. The intensification of animal production systems also limits the ability of reared animals to express their ancestral natural behavior. In addition, modern pig production chains, based on the multisite system, often involve several transfers between sites, resulting in acute and chronic stress and underestimated effects on the health of pigs. These conditions both inhibit gut development and impose greater pressures on gut function. Until recently the widespread use of antibiotics has guaranteed sanitary control in all phases of pig production, especially when acute stress events expose pigs to gut inflammation and/or gut dysbiosis, as in weaning or after a transfer to a different production site. However, this use of antibiotics is no longer acceptable in modern production systems. To minimize the problem of antibiotic resistance, the use of antibiotics is now restricted to those classes of antibiotics which are not needed to treat human diseases and limited as much as possible to the treatment of ill animals only. Some countries (e.g. those of the European Union [EU]) have banned additives such as zinc oxide designed to promote growth and prevent post-weaning diarrhoea (PWD) in order to limit the co-selection of antibiotic-resistant microorganisms and to reduce the environmental impact of intensive livestock production. The attention of experts, technicians and breeders is now to focus on intervention measures that, without compromising production efficiency, improve pig gut functionality from an early age to prevent intestinal colonization of pathogen microorganisms and food-borne pathogens. These measures need to take into account three areas: •porcine genetics; • management measures; and • dietary interventions.