Diet production and utilization of corn fermented protein (CFP) compared to traditional yeast in healthy adult cats.

The inclusion of yeast in pet food can provide health benefits and increase palatability. Corn fermented protein is a co-product from ethanol production which contains approximately 20-25% yeast. The objective of this study was to determine the effects of the yeast in CFP on diet production and utilization when fed to healthy adult cats. The four experimental diets included a control with 15% soybean meal (CON) and diets containing either 3.5% brewer's dried yeast (BDY), 2.5% brewer's dried yeast plus 17.5% distillers dried grains with solubles (BDY+DDGS), or 17.5% corn fermented protein (CFP). All treatments except CON were formulated to contain 3.5% yeast. Experimental diets were fed to adult cats (n = 11) in an incomplete 4 x 4 replicated Latin square design. Cats were adapted to diet for 9 days followed by a 5-d total fecal collection. Titanium dioxide (0.4%) was added to all diets as an external marker to estimate digestibility. Data were analyzed using a mixed model in SAS (version 9.4, SAS Institute, Inc., Cary, NC) with treatment as a fixed effect and cat and period as random effects. Preconditioner discharge temperature was greater (P < 0.05) for CON and BDY (average, 96°C) compared to BDY+DDGS and CFP (average, 91°C). Extruder screw speed, die temperature, kibble toughness, and kibble hardness were greatest (P < 0.05) for CFP. The bulk density of BDY+DDGS at 392 g/L was greater (P < 0.05) than BDY and CFP (average, 342 g/L). The sectional expansion index of kibble for CFP was greater (P < 0.05) than BDY+DDGS and smaller (P < 0.05) than CON but similar to BDY. Fecal output was greatest (P < 0.05) for cats fed BDY+DDGS. Nutrient digestibility was lowest (P < 0.05) for BDY+DDGS. The concentrations of short-chain and branched-chain fatty acids in fecal samples were not altered (P > 0.05) by dietary treatment. Cats had no preference (P > 0.05) when comparing CON to BDY or BDY+DDGS. However, cats consumed significantly less CFP compared to CON. The significant differences for bulk density, fecal output, and nutrient digestibility among dietary treatments are likely due to a greater fiber effect of DDGS compared to CFP. Therefore, the yeast component in CFP may provide greater kibble expansion and nutrient utilization compared to DDGS when fed to cats.