A Brazilian scientist conducted a study using two different techniques to measure digestibility and metabolizable energy of maize gluten feed as an ingredient in petfood for dogs.

MGF, a co-product of wet milling of maize, is composed of the structures left after most starch, gluten and germ has been extracted from the grain. Two different techniques were used to asses the digestibility and energy values of MGF, though both studies used extruded diets fed to Beagle dogs with six replicates per diet.

In the first study, a difference method was used to replace 300 g/kg of a reference diet with MGF. Based on the difference method, the coefficient of total tract apparent digestibility of MGF was 0.53 for dry matter, 0.69 for crude protein, 0.74 for fat, 0.99 for starch and 0.55 for gross energy. As fed in the study, the calculated metabolizable energy of MGF was 7.99 MJ/kg.

A regression method was used for the second study, which used a regular basal diet and a basal diet with 70, 140 and 210 g MGF/kg of diet as a substitute for maize starch. The inclusion of MGF in this diet resulted in a linear reduction of the coefficient of total tract apparent digestibility of 0.99 for dry matter, 0.95 for crude protein, 0.87 for fat, 0.81 for starch and 0.99 for gross energy. Faecal production increased linearly from 56 g to 107 g per dog per day, faecal dry matter showed a linear reduction and faecal lactic acid concentrations increased linearly. Both urine and faeces also showed a linear reduction in pH levels.

Results of the ingredient coefficient of total tract apparent digestibility obtained by each of the two different methods showed a 6% or less variance for crude protein, fat, starch and metabolizable energy content, but the two methods produced different results for the calculated coefficient of total tract apparent digestibility of dry matter and organic matter. The low digestibility of MGF may be explained by its high dietary fiber content, according to the study. The study concluded that MGF may be a useful ingredient in dog food formulations designed to have low energy or reduce urine pH levels of dogs.