Effects of thermal treatment of some dietary feed ingredients on their digestibility and growth of common carp, Cyprinus carpio fingerlings

The purpose of the current study was to determine the effects of thermal treatment (autoclaving) of several dietary feed ingredients, including fishmeal, soybean meal, wheat bran, yellow corn, and barley, on the apparent digestibility coefficients ADCs, as well as the growth and feed efficiency of common carp, Cyprinus carpio fingerlings. The feed ingredients were autoclaved for 10 min at 121ºC and 15 psi in a laboratory autoclave. Two experiments were conducted, the first consisted of 11 diets, reference, and 10 experimental diets (reference was mixed with each raw or autoclaved test ingredient in a ratio of 70:30) to determine the digestibility of feed ingredients. The second experiment consisted of 8 diets, a control diet of raw ingredients and seven experimental diets were formulated, five of them in which one of the raw feed ingredients was replaced with the autoclaved one, the sixth in which three raw ingredients (wheat bran, yellow corn, and barley) were replaced together with the autoclaved ones, and the seventh in which all the raw ingredients were replaced with the autoclaved ones. The results of the first experiment presented that autoclaving significantly enhanced ADCs of dry matter, protein, and energy, of all feed ingredients except fishmeal. The results of the second experiment similarly presented that the thermal treatment significantly enhanced ADCs in the diets containing autoclaved soybean meal or wheat bran, yellow corn, and barley or all ingredients compared control diet. The growth and feed efficiency were better significantly in autoclaved soybean meal or all ingredients diets compared control diet. It is advised that plant-based ingredients, especially soybean meal, be thermally-processed to improve their nutritional value and lessen their environmental impact.