The influence of rice, maize and sorghum raw material particle size in extruded dry dog food on the digestibility of nutrients and energy and the fecal concentration of fermentation products was investigated.

Three diets with similar nutrient compositions were formulated, each with one starch source. Before incorporation into diets, the cereals were ground into three different particle sizes; a total of nine diets were in a 3×3 factorial arrangement. Fifty-four beagle dogs were randomly assigned to the diets, with six dogs per diet. The digestibility was measured with the chromium oxide method. The data were evaluated with ANOVA considering the carbohydrate source, grinding effect and interactions. The means were compared with the Tukey test and polynomial contrasts.

For rice diets, the cereal mean geometric diameter (MGD) and starch gelatinization (SG) did not change nutrient digestibility; only GE digestibility was reduced at the largest MGD. For maize and sorghum diets, the total tract apparent nutrient digestibility was reduced for foods with greater MGD and less SG. A linear reduction in nutrient digestibility according to cereal particle size was observed for sorghum. Higher concentrations of fecal total short-chain fatty acids (SCFA) were observed for sorghum diets than for other diets. The rice diets led to the production of feces with less lactate. The increase in raw material MGD did not influence fecal SCFA for rice diets, but for the dogs fed maize and sorghum foods, an increase in propionate and butyrate concentrations were observed as MGD increased.

In conclusion, for dogs fed different particle sizes of the cereal starches in the extruded diets, the digestibility and fecal characteristics were affected, and this effect was ingredient dependent.

Source: R.S. Bazolli et al., 2015. Effect of the particle size of maize, rice and sorghum in extruded diets for dogs on starch gelatinization, digestibility and the fecal concentration of fermentation products. J Anim Sci online, May 2015. doi:10.2527/jas.2014-8409