Dietary fiber and protein fermentation in the intestine of swine and their interactive effects on gut health and on the environment: A review

Fermentation of both dietary fiber (DF) and protein in the pig intestine is a matter of interest because of their potential beneficial or harmful effects on gut health and on the environment. This paper reviews some of the relevant information available on DF and protein fermentation and their interactive effects on the gut environment of pigs and its contribution to emission of nitrogenous gases and odor from pig manure and piggeries. The fermentation of protein and the associated production of metabolic compounds are discussed in relation to DF fermentation, their impact on gut health, bacterial protein synthesis and nitrogen (N) excretion. Some nutritional strategies to reduce protein fermentation in the gut such as the reduction of the amount of crude protein (CP) in the diet and/or the inclusion of fermentable DF are also presented. Also, to cope with the negative impact of intensive pig production on the environment, different nutritional approaches such as reducing N excretion by lowering CP intake, shifting the N excretion pathway from urine to feces and lowering the pH of manure by lowering the pH of urine and feces have been reviewed. Overall, inclusion of DF and reduction of CP in pig diets seems to be an effective nutritional strategy that may counteract the negative effects of protein fermentation in the pig gut by reducing ammonia concentration, shifting N excretion pathways in the gut and minimizing the negative impact of intensive pig production on the environment.