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An Investigation of Factors that Affect the Efficiency of Limiting Amino Acid Utilization by Rainbow Trout (Oncorhynchus mykiss)

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Title: An Investigation of Factors that Affect the Efficiency of Limiting Amino Acid Utilization by Rainbow Trout (Oncorhynchus mykiss)
Author: Gholami, Afshin; Gholami, Afshin
Department: Department of Animal Biosciences
Program: Animal and Poultry Science
Advisor: Bureau, DominiqueBureau, Dominique
Abstract: Corn gluten meal (CGM) is a high protein ingredient commonly used in fish feeds. However, studies suggest that diets containing high levels of CGM elicit lower voluntary feed intake, growth and lower efficiency of utilization of limiting amino acid (AA) compared to other protein sources. It has been hypothesized that the AA profile of CGM (low lysine, excess leucine) could be responsible for these effects or protein from CGM could be digested faster than other protein sources, resulting in faster absorption and less efficient utilization of its AAs. A series of studies were conducted to examine the effect of feeding CGM on growth, efficiency of lysine utilization and the dynamics of protein digestion in rainbow trout. Results of growth trial indicated that weight gain, FE and nitrogen retention efficiency were significantly lower in fish fed CGM-based diets compared to those fed WGM based diets. Digestibility trial results revealed lower apparent digestibility of crude protein in CGM-based diets compared to that of WGM-based diets. The efficiency of digestible lysine utilization did not differ between the CGM and WGM-based diets. Serial digesta sampling of the gastrointestinal (GI) tract of rainbow trout and blood sampling were carried out to estimate digesta transit time and plasma AA concentrations. Results indicate that CGM-based diets passed through the GI tract four times faster than WGM-based diets. The ratios of plasma leucine to branched-chain amino acids, and leucine to lysine, were generally higher, for fish fed CGM-based diets compared to those fed WGM-based diets. To examine the impact of the excess leucine on growth performance and efficiency of AA utilization, rainbow trout were pair-fed CGM or WGM-based diets formulated to be deficient in lysine and contain adequate and excess leucine levels. Results indicated that excess leucine did not affect growth and efficiency of lysine utilization. The results from this thesis suggest that the lower digestibility of protein and AAs of CGM may in part explain the lower performance of CGM-based diet compared to other protein sources in some studies. Differences in the dynamics of digestion and absorption of AAs and their appearance in the circulation are evident. Therefore, it should be examined further in future studies.
Date: 2015-12

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