| Summary: | Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item. Includes bibliographical references. Issued also on microfiche from Lange Micrographics. The availability of nutrients and energy in feedstuffs for fish may vary considerably, depending on a variety of factors including fish species, ingredient quality and processing conditions. The red drum is an emerging aquaculture species for which information concerning nutrient and energy availability is needed to more precisely formulate diets to meet their requirements and to enable effective substitution of ingredients. This study was conducted with red drum to determine apparent organic matter, protein, lipid, and gross energy digestibility coefficients and apparent phosphorus availability of the following ingredients: select menhaden fishmeal, regular-quality menhaden fishmeal, poultry by-product meal, meat and bone meal, dehulled soybean meal, cottonseed meal, and wheat. Test diets consisting of a 70:30 mixture of reference diet to test ingredient were utilized for the digestibility trial, with chromic oxide as the non-digestible marker. Organic matter digestibility of ingredients generally decreased as the nitrogen-free extract fraction increased, ranging between 94% for select menhaden fishmeal to 47% for wheat. Crude protein digestibility was high for most ingredients, ranging from 77% for regular menhaden fishmeal to 97% for wheat, with the exception of poultry by-product meal which was 49%. Lipid digestibility coefficients ranged from 59% for poultry by-product meal to 88% for wheat. Digestible energy coefficients were high for the animal meals, ranging from 72% for poultry by-product meal to 95% for select menhaden fishmeal; however, digestible energy coefficients for plant feedstuffs were considerably lower, from 62% for wheat to 70% for cottonseed meal. Phosphorus availability from animal products was variable, with a low of 27% for poultry by-product meal and a high of 66% for meat and bone meal. Phosphorus availability from soybean meal and cottonseed meal was 47 and 40%, respectively. Wheat had the highest phosphorus availability at 79%. Data from this study indicate red drum can digest and absorb the nutrients in animal products more completely than those from plant products. This difference presumably reflects their inability to effectively digest the nitrogen-free extract portion of plant products. These data provide more precise information concerning nutrient and energy utilization of red drum and will allow ingredient substitutions in practical diet formulations based on levels of available nutrients.
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