Fermentation in the large intestine of single-stomached animals and its relationship to animal health

Abstract

The phasing out of antibiotic compounds as growth promoters from the animal industry means that alternative practices will need to be investigated and the promising ones implemented in the very near future. Fermentation in the gastrointestinal tract (GIT) is being recognized as having important implications for health of the gut and thus of the host animal. Fermentation in single-stomached animals occurs to the largest extent in the large intestine, mainly because of the longer transit time there. The present review examines the micro-ecology of the GIT, with most emphasis on the large intestine as the most important site of fermentative activity, and an attempt is made to clarify the importance of the microfloral activity (i.e. fermentation) in relation to the health of the host. The differences between carbohydrate and protein fermentation are described, particularly in relation to their endproducts. The roles of volatile fatty acids (VFA) and NH 3 in terms of their relationship to gut health are then examined. The large intestine has an important function in relation to the development of diarrhoea, particularly in terms of VFA production by fermentation and its role in water absorption. Suggestions are made as to feeds and additives (particularly those which are carbohydratebased) which could be, or are, added to diets and which could steer the natural microbial population of the GIT. Various methods are described which are used to investigate changes in microbial populations and reasons are given for the importance of measuring the kinetics of fermentation activity as an indicator of microbial activity.

Bacterial fermentation in the gastrointestinal tract of non-ruminants: Influence of fermented feeds and fermentable carbohydrates

“…The most important part of hydrolysis by enzymes takes place in the small intestines. However, a larger proportion of digestion, which takes place by microbial fermentation in non-ruminants, occurs in the large intestine (Ewing and Cole 1994;Williams et al 2001). Furthermore, fermentation in non-ruminant animals occurs to the largest extent in the large intestines (caecum and colon), mainly due to the longer transit time of the diet in this part of the GI tract (Williams et al 2001).…”

“…However, a larger proportion of digestion, which takes place by microbial fermentation in non-ruminants, occurs in the large intestine (Ewing and Cole 1994;Williams et al 2001). Furthermore, fermentation in non-ruminant animals occurs to the largest extent in the large intestines (caecum and colon), mainly due to the longer transit time of the diet in this part of the GI tract (Williams et al 2001). In chicken particularly, a major portion of microbial fermentation is concentrated in the caeca (Barnes et al 1980).…”

“…Therefore, energy availability to the host animal fed low energy diets containing potentially fermentable substrates could be increased by microbial fermentation. It is now realised that one of the principal functions of the GI tract includes the salvage of energy and nutrients through its symbiotic relationship with gut microflora (Williams et al 2001).…”

“…According to Williams et al (2001) about 68 % of the energy value of fermented carbohydrates can be metabolised into SCFA. All SCFA can contribute to the energy supply of the host (Lan et al 2005b).…”

“…Interest in the role of commensal gut microflora within the GI tract is presently growing, particularly due the advantage which the fermentative properties of beneficial gut microflora could confer on gut health (Williams et al 2001;Verstegen and Williams 2002;Gidenne and Licois 2005;Williams et al 2005).…”