APPARENT DIGESTIBILITY OF SELECTED INGREDIENTS IN RED DRUM (SCIAENOPS-OCELLATUS) DIETS

Production of cultured red drum requires use of formulated diets for g row-out to marketable size. However, insufficient information is avail able regarding the nutrition of this species to make least-cost feed f ormulation practical. Knowledge of the digestibility of ingredients us ed in red drum diets could facilitate least-cost formulation and reduc e feed costs. The objective of this study was to determine apparent di gestibility of dry matter, crude protein, and energy in blood meal, co rn grain, cottonseed meal, grain sorghum, meat and bone meal, menhaden fish meal, rice bran, soybean meal, and wheat middlings in formulated red drum diets. Digestibility coefficients were determined using a re ference diet and test diets that contained 70% of the reference diet m ixture and 30% test ingredient. All diets contained 1% chromic oxide a s a digestibility indicator. Fecal samples were manually stripped from anesthetized fish to prevent contact with water. Apparent digestibili ty coefficients for dry matter, crude protein, and energy in the refer ence and test diets were determined, and digestibility coefficients fo r the test ingredients were calculated based on differences in the dig estibility of test diets relative to the reference diet. Apparent crud e protein digestibility coefficients ranged from 74 to 100% for all fe edstuffs tested, indicating that red drum utilized dietary protein eff iciently regardless of source. Protein digestibility was highest in fe edstuffs with high protein content (> 60%) and low fiber content (< 2% ). Apparent energy digestibility was relatively low for animal product s (54-60%) and lower for plant products (12-52%). Dry matter digestibi lity varied more among ingredients of plant origin (18-68%) than among those of animal origin (65-77%). Apparent digestibility of dry matter and energy was positively influenced by protein and lipid content of the ingredient and negatively influenced by crude fiber content. Diges tibility of starch appeared to vary widely among plant products.