The physiological role of the gastrointestinal microbiota has become an important subject of nutrition research in pigs in the past years, and the importance of intestinal microbial activity in the etiology of disease is doubtless. This review summarizes the recent knowledge related to the microbial ecology of protein fermentation and the appearance of protein-derived metabolites along the pig intestine. The amount of fermentable protein depends on factors such as dietary protein concentration, protein digestibility due to secondary or tertiary structure, the interaction with dietary compounds or anti-nutritional factors, and the secretion of endogenous proteins into the gut lumen. High protein diets increase the luminal concentrations and epithelial exposure to putatively toxic metabolites and increase the risk for post-weaning diarrhea, but the mechanisms are not yet clarified. Although the use of fermentable carbohydrates to reduce harmful protein-derived metabolites in pigs is well-established, recent studies suggest that the inclusion of fermentable carbohydrates into diets with low protein digestibility or high dietary protein level may not ameliorate all negative effects with regard to epithelial response. Based on the current knowledge, the use of diets with low levels of high-quality protein may help to reduce the risk for intestinal disease in young pigs.

During the prenatal, neonatal and post-weaning periods, the mammalian gastrointestinal tract undergoes various morphological and physiological changes alongside with an expansion of the immune system and microbial ecosystem. This review focuses on the time period before weaning and summarizes the current knowledge regarding i) structural and functional aspects ii) the development of the immune system, and iii) the establishment of the gut ecosystem of the porcine intestine. Structural and functional maturation of the gastrointestinal tract gradually progress with age. In the neonatal period colostrum induces gut closure, leads to an increase in intestinal weight, absorptive area and brush border enzyme activities. During the first weeks of life, an increased secretion of stomach and pancreatic enzymes and an increased uptake of monosaccharides and amino acids are observed. The development in digestive function coincides with development in both the adaptive and innate immune system. This secures a balanced immune response to the ingested milk-derived macromolecules, and colonizing bacteria. Husbandry and dietary interventions in early life appear to affect the development of multiple components of the mucosal immune system. Furthermore, the composition of the intestinal microbial communities seems to be affected by the early postnatal environment, which might also contribute to gut maturation, metabolic and immune development. Understanding the interplay between morphological, functional and immunological maturation, as influenced by early microbial colonization and ingestion of dietary factors, is of utmost importance to identify management and feeding strategies to optimize intestinal health. We discuss some possible implications related to intrauterine growth restriction, and preterm delivery as these both dramatically increase the risk of mortality and morbidity. In addition, some nutritional interventions during the perinatal period in both sows and piglets will be discussed in the light of possible health consequences early in life and later on.

Despite a well-documented effect of high dietary zinc oxide on the pig intestinal microbiota composition less is it yet known about changes in microbial functional properties or the effect of organic zinc sources. Forty weaning piglets in four groups were fed diets supplemented with 40 or 110 ppm zinc as zinc oxide, 110 ppm as Zn-Lysinate, or 2500 ppm as zinc oxide. Host zinc homeostasis, intestinal zinc fractions, and ileal nutrient digestibility were determined as main nutritional and physiological factors putatively driving colon microbial ecology. Metagenomic sequencing of colon microbiota revealed only clear differences at genus level for the group receiving 2500 ppm zinc oxide. However, a clear group differentiation according to dietary zinc concentration and source was observed at species level. Functional analysis revealed significant differences in genes related to stress response, mineral, and carbohydrate metabolism. Taxonomic and functional gene differences were accompanied with clear effects in microbial metabolite concentration. Finally, a selection of certain antibiotic resistance genes by dietary zinc was observed. This study sheds further light onto the consequences of concentration and chemical form of dietary zinc on microbial ecology measures and the resistome in the porcine colon.

The industrial hemp sector is growing and, in recent years, has launched many novel hemp-derived products, including animal feed. It is, however, unclear to what extent individual cannabinoids from industrial hemp transfer from the feed into products of animal origin and whether they pose a risk for the consumer. Here we present the results of a feeding experiment with industrial hemp silage in dairy cows. Hemp feeding included changes in feed intake, milk yield, respiratory and heart rates, and behaviour. We combined liquid chromatography–tandem mass spectrometry-based analyses and toxicokinetic computer modelling to estimate the transfer of several cannabinoids (Δ⁹-tetrahydrocannabinol (Δ⁹-THC), Δ⁸-THC, Δ⁹-tetrahydrocannabinolic acid, Δ⁹-tetrahydrocannabivarin, 11-OH-Δ⁹-THC, 11-nor-9-carboxy-Δ⁹-THC, cannabidiol, cannabinol and cannabidivarin) from animal feed to milk. For Δ⁹-THC, which has a feed-to-milk transfer rate of 0.20% ± 0.03%, the acute reference dose for humans was exceeded in several consumer groups in exposure scenarios for milk and dairy product consumption when using industrial hemp to feed dairy cows.

Zinc (Zn) supplementation has been shown to reduce the incidence of diarrhea and to protect animals from intestinal diseases, but the mechanisms of this protective effect against virus infection in vivo have not yet been elucidated. Transmissible gastroenteritis virus (TGEV) causes diarrhea in piglets with an age-dependent decrease of severity.