Of the various feed processing operations, grinding and pelleting are the important ones influencing the gastrointestinal tract development and nutritional physiology in broilers. The primary aim of grinding is to reduce the particle size, which increases the surface area enhancing the access of digestive enzymes to substrates. Fine grinding, however, negatively affects the development of the gizzard that plays an important role in nutrient utilisation and intestinal health. Coarser particles, on the other hand, result in a rapid and conspicuous enlargement of the gizzard highlighting that the anatomical development and digestive physiology of the gastrointestinal tract can be manipulated by dietary means. The presence of coarse particles in the gizzard enhances digesta motility and backflow within the gastrointestinal tract. Normal refluxes do not occur when birds are fed finely ground pelleted diets. Feed particle size influences the gizzard mass, nutrient utilisation and bird performance to a greater extent when the broilers are fed mash than pelleted diets. The particle size-reducing property of the pelleting process decreases the grinding requirement of the gizzard and negatively influences gizzard mass so that its function is reduced to that of a transit organ. Published data on the effects of feed processing on intestinal segments other than the gizzard, however, are contradictory and inconclusive.
Presented at the International Fibre Summit 2019 (https://internationalfibre.com/). Reproduced with permission from the organizers.