Apparent digestibility of selected feedstuffs in diets for hybrid striped bass (Morone saxatilis female X Morone chrysops male)

Hybrid striped bass were fed a reference diet or one of nine test diets containing selected protein and energy supplements: menhaden fish meal, meat and bone meal, blood meal, soybean meal, cottonseed meal, corn grain, wheat flour, wheat middlings, and rice bran. Test diets contained 70% reference diet mixture and 30% test ingredient. All diets contained 1% chromic oxide indicator. Fecal samples were manually stripped from anaesthetized fish to prevent contact with water. Apparent digestibility coefficients for dry matter, crude protein, and energy in the reference and test diets were determined, and digestibility coefficients for the test ingredients were calculated based on differences in the digestibility of test diets relative to the reference diet, Apparent crude protein digestibility was high (71-93%) for all ingredients tested. Apparent energy digestibility (AED) was significantly higher for ingredients of animal origin (fish meal and meat and bone meal; 80-95%) than for those of plant origin (soybean meal, corn, wheat flour, wheat middlings, and rice bran; 41-73%) with one exception-AED of meat and bone meal and cottonseed meal did not differ. Apparent dry matter digestibility (27-84%) varied significantly among ingredients of both plant and animal origin and appeared to be negatively related to fiber and starch content of the ingredient. Results indicated that hybrid striped bass utilized high-protein and high-lipid feedstuffs better than high-carbohydrate or high-fiber feedstuffs.