Effect of treatment temperature on dietary quality of ammonia fiber explosion (AFEX) treated casein for rats

Dietary quality of casein treated by the ammonia fiber explosion (AFEX) process was evaluated in weanling Sprague-Dawley rats. Two 19 day trials were conducted, in which four animals received one of the four (first trial) or five (second trial) treatment diets. Animal performance, nitrogen digestion characteristics and biological value were determined for diets (protein content 18%) containing untreated casein or casein AFEX treated at 40, 60, 80, or 100°C. AFEX treatment at temperatures of 40–100°C did not detrimentally effect (P > 0.10) feed intake, weight gain, or nitrogen intake. AFEX treatment at 60°C increased (P < 0.05) feed efficiency by 7% over controls. Higher (P < 0.05) fecal (0.23 vs. 0.15 g per 5 days) and urinary nitrogen (1.26 g vs. 1.12 g per 5 days), as well as reduced (P < 0.05) apparent nitrogen digestibility (91.4% vs. 94.2%), nitrogen retention (43.6% vs. 49.4%), and biological value (47.8% vs. 52.4%) were observed for diets containing casein treated at 60°C and higher temperatures vs. controls. Results from this study suggest decreased casein digestion and absorption, and decreased utilization of absorbed nitrogen with AFEX treatments of 60°C and higher.