This Is AuburnElectronic Theses and Dissertations

Comparison of crystalline lysine and intact lysine used as a supplement in practical diets of Channel catfish (Ictalurus Punctatus) and Nile tilapia (Oreochromis niloticus)




Nguyen, Lay Jr

Type of Degree

Master's Thesis


Fisheries and Allied Aquacultures


Lysine is an essential amino acid commonly deficient in practical diets especially those contain high levels of plant protein ingredient, resulting in reduced growth and feed efficiency of aquatic animals. Supplementation of lysine in the formulated diets is essential to improve the nutritional values of feed. In general, there are two popular ways to improve the levels of essential amino acid in the diets, by feeding mixtures of complementary proteins and by supplementing deficient proteins with crystalline amino acids. Historically, crystalline lysine has been used commercially to improve the amino acid balance and consequently the nutritional profile of the diets. However, the use of crystalline lysine has been observed to cause reduced growth and feed efficiency of fish in some studies related to palatability, pH change, leaching and rapid uptake. The introduction of intact lysine via high lysine corn protein concentrate, which contains high concentrations of lysine and other essential amino acids, is a potential alternative to crystalline lysine. The study was conducted using channel catfish and tilapia to evaluate the production performance of these fish to increasing levels of lysine from crystalline and intact lysine supplemented in practical diets. A practical lysine deficient basal diet was developed using corn protein concentrate (Empyreal® 75) as a primary protein source. To this diet either graded levels of crystalline lysine or similar levels from a high lysine corn protein concentrate (LystoTM) were used, thus allowing the comparison of both source. The results of this study indicated that channel catfish and tilapia have positive performance with increasing lysine supplementation up to the requirement. Fish fed with the higher levels of lysine had the highest weight gain and lowest feed conversion ratio. The regression analysis on the increased level of inclusion of crystalline lysine and intact lysine showed a general trend with parallel increases. Based on the growth data obtained from this study, it can be concluded that the effectiveness of using intact lysine via high lysine corn protein concentrate as a lysine supplement is not significantly different from crystalline lysine. Thus, the high lysine corn protein concentrate is a feasible ingredient for aquaculture feeds, which can be used to partially substitute soybean meal without addition of crystalline lysine.