The digestibility of high protein and high energy feedstuffs by yearling channel catfish

Yearling (1+) channel catfish (Ictalurus punctatus) were held in a regulated environment (28 C and 14 hour light period) and fed high protein and high energy feedstuffs in order to determine apparent digestible crude protein (ADCP) and apparent digestible energy (ADE). ADCP was determined by feeding a semi-purified diet containing 45% carbohydrate and substituting the test feedstuff at an isonitrogenous level. Feedstuffs tested for protein digestibility included corn gluten meal, peanut meal, poultry by-product meal, soybean meal, menhaden fish meal, blood meal, and meat and bone meal. ADE was determined by feeding a practical catfish diet and substituting the test feedstuff at a level of 10% for oil feedstuffs and 20% for meal feedstuffs. The same meal feedstuffs were used for ADE determinations as for ADCP determinations. Oil feedstuffs included safflower oil, corn oil, coconut oil, tallow, lard, margarine, and poultry oil. The fish were offered the experimental diets at a rate equal to 3% of their body weight once daily. Fecal samples were collected 12 hours after the fourth feeding by anal suction. Chromic oxide was used as an external indicator of digestibility. ADCP values ranged from 92% for corn gluten meal to 65% for poultry by-product meal. Mean ADCP from plant sources was higher than the mean ADCP from animal sources. ADE values for meal feedstuffs ranged from 80% for corn gluten meal to 28% for blood meal. Mean ADE values for plant and animal feedstuffs were similar.