| 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 (leaves 35-40). Issued also on microfiche from Lange Micrographics. The red drum (Sciaenops ocellatus) has traditionally been an important commercial and recreational fish species in the Gulf of Mexico; therefore, its aquacultural production for food and for stock enhancement continues to develop. The minimum dietary lysine requirement of juvenile red drum was previously quantified to be 1.55% of a 35% crude protein (CP) diet (4.4% of dietary protein). However, red drum are usually fed diets containing 40 to 50% CP under commercial production. Therefore, the purpose of this study was to reevaluate the dietary lysine requirement of red drum as a function of dietary CP, and determine the effects of dietary manipulations on ammonia excretion. Control diets at 35 and 45% CP contained only the intact protein provided by a 50/50 mixture of red drum muscle and wheat gluten. Four experimental diets at each CP level contained the mixture (64% of CP) and crystalline amino acids (34% of CP) to provide lysine levels above and below the previously determined requirement. Each diet was fed to triplicate groups of 20 juvenile red drum initially averaging 3.4 g/fish in 110-l aquaria containing brackish (7ppt) water at 27±1 °C and operated in a recirculating mode. Diets were fed at a fixed rate approaching apparent satiation twice daily for 6 weeks after which total ammonia nitrogen (TAN) excretion at 4-h postprandial was determined. Diets supplemented with crystalline amino acids supported similar weight gain (94 - 98%) as that obtained by fish fed control diets with intact protein. Based on weight gain, protein efficiency ratio (PER), and protein conversion efficiency (PCE) data, the minimum dietary lysine requirement was not ...
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