KN Understanding the impact of gut health

A healthy intestinal system in animals is important for a fit immune system leading to a better handling of infections, reduction of the use of antibiotics, and improvement of general health. A clear definition of gut health is difficult, however, compromised nutrient utilization, impairment of host metabolism and energy retention; are often related to microbial dysbiosis, a disturbed mucus layer and an impaired barrier function. The gastrointestinal tract harbours a dense and complex microbiota that confers health benefits to the host, such as: supporting nutrient digestion and absorption contributing to the maintenance of epithelial barrier training and maintenance of the host immune system competing with pathogenic microbes The intestinal microbiome is easily influenced by diet, oral antibiotics, pathogens and toxins, and other endogenous and exogenous stressors. In turn, all these events can have a negative effect on intestinal barrier function and the immune fitness of the animal. In the past, subtherapeutic concentrations of antibiotics were used to stabilize the intestinal microbiota. In the light of the emerging concerns regarding antimicrobial resistance, antibiotics have been phased out for use as feed additives. This has initiated research into non-antibiotic substances that influence the intestinal microbiome and gut health in general. There are several ways to improve compromised gut health in production animals by in-feed supplements. The microbiota com-position can be targeted through probiotics and non-digestible carbohydrates (prebiotics or carbobiotics). Probiotics such as Lactobacillus, Bifidobacterium and Bacillus spp., are suggested as alternatives for antibiotics and as growth promoters in animal nutrition [1,2]. A unique class of compounds are carbobiotics, exerting beneficial effects on gut health through the stimulation of beneficial bacteria, direct effects on epithelial integrity and immunomodulat-ing effects [3,4]. These beneficial effects were demonstrated in different model simulation stress situations in the daily life of animals. For example, low exposure of piglets or chickens to feed contaminated with the mycotoxin deoxynivalenol (DON), results in enhanced permeability of the intestinal barrier and subsequently the expression of pro-inflammatory mucosal mediators [3,7]. Besides local adverse effects of mycotoxins, through intestinal effects these feed contaminants might also affect the systemic immune system leading to increased susceptibility for bacterial and viral infections [8]. Another example of an external gut health compromising trigger is heat stress. Specifically, in chickens small intestinal integrity and nutrient transporters are compromised by heat stress leading to systemic inflammation. Again, carbohydrates, as well as polyun-saturated fatty acids, have proven to exert anti-inflammatory and radical-scavenging effects thereby protecting intestinal barrier integrity [4,5,6]. Taken together, recent research has identified diverse opportunities to protect gut health. Fundamental in vivo and in vitro research has demonstrated that improving gut health results also in an improvement of other important mucosal barriers, such as the alveolar barrier, thereby also contributing to the resilience of animals against infectious diseases and external stressors (the so-called gut-lung axis) [9]. Modulation of mediators of inflammation and (gut-associated) neurotransmitters is likely to have a beneficial effect even on animal behaviour and welfare, considering the recent understanding of the gut-brain axis [10].