The current study was conducted to investigate the influence of short-term feeding of test diets during metabolizable energy assays on growth performance, nutrient utilization, jejunal histomorphology, cecal short-chain fatty acids, and nutrient transporters in broilers. One hundred twenty-six broiler chickens were assigned to six treatments, each with seven replicates. Experimental diets were fed between days 14 and 21. Treatments included a corn−soybean meal reference diet and five test diets with low-protein soybean meal (LPSBM), wheat bran, soy hull, corn gluten feed, or rice bran. Birds were weighed on days 14 and 21; excreta, cecal content, and jejunal tissues were collected on day 21. Seven-day weight gain was highest (p < 0.01) for birds receiving the reference diet or LPSBM, whereas FCR was lowest (p < 0.05) for birds receiving the soy hull diet. Cecal acetate and total short-chain fatty acids were higher (p < 0.05) for wheat bran compared with the soy hull test diet. Jejunal villi were longer (p < 0.05) for chickens receiving the reference diet or LPSBM test diet. Glucose transporter (GLUT1) mRNA was greater (p < 0.05) in broilers receiving rice bran compared with soy hull test diets. Therefore, when reporting energy assays, it is important that indicators of animal growth or gut health be included to help contextualize energy utilization.
Keywords: broiler chickens; digestive physiology; fiber; metabolizable energy assay.