Nutritional significance of fibre in feed formulation and factors that influence fibre fermentation

Abstract

In current practice fibre is not properly accounted for when formulating poultry diets. This is primarily because inaccurate 'crude fibre' values are still used and often only the anti-nutritional effects of fibre on viscosity and as a nutrient diluent are considered. However, more recent research has highlighted the advantageous impacts of fibre, including its ability to stimulate gastrointestinal tract development and optimise feed digestion. Of particular interest is how fibre fractions, in particular oligosaccharides, can be selectively fermented and utilised by beneficial microbiota, leading to production of lactic acid and short chain fatty acids and reduced proliferation of pathogenic bacteria. These smaller chain sugars are produced in the gastrointestinal tract as a result of non-starch polysaccharide (NSP)-degrading enzyme supplementation, but there is also heightened attention towards manufacturing these oligosaccharides commercially, producing a prebiotic supplement for poultry diets. The nature of the enzymatic treatment or procedure used to produce oligosaccharides dictates the degree of physiochemical changes that occur in the gut, and resulting response and nature of intestinal microbiota. Thus, a deeper understanding of the chemical and physical structure of fibre components could allow for tailored use of different fibres and enzymes to achieve the desired outcome when producing specific prebiotics in the gastrointestinal tract. Solubility, viscosity and fermentation capability are the main properties of fibre that affect the diversity and density of the microbiota populations in the digestive tract. Consequently, although it is important to accurately determine and formulate the total fibre content of the fibre poultry diets, elucidating the physiochemical properties and ability of the fibre source to be fermented may be of greater significance.