Aquaculture America 2021

August 11 - 14, 2021

San Antonio, Texas


Blaine Suehs* , Fernando Y. Yamamoto, and Delbert M. Gatlin III
*Department of Wildlife and Fisheries Sciences, Texas A&M University
534 John Kimbrough Blvd. 2258, College Station, TX 77843-2258

Certain dispensable or nonessential amino acids synthesized by the body have been demonstrated to provide some enhanced physiological roles in animals when supplemented in the diet, and thus have been termed functional amino acids. Glutamate has been identified as a possible functional amino acid for fish. Therefore, an 8-week feeding trial was conducted to evaluate the effects of varying levels of dietary glutamate on growth performance, immune responses, and whole-body composition of juvenile hybrid striped bass. Three diets were formulated from practical ingredients to contain 43% crude protein and 12% lipid, to which L-glutamate was supplemented at either 0, 1.0 or 2.0% of dry weight. All diets were randomly assigned to quadruplicate groups of 15 juvenile hybrid striped bass (HSB) initially averaging 5.65 g/fish in 110-L aquaria connected as a recirculating aquaculture system and fed twice daily at a percent of body weight which approached apparent satiation. A preliminary in vitro study also was conducted to evaluate if immunological responses of head-kidney isolated leukocytes from HSB would be affected by incremental levels of glutamate, glutamine and their combination in the culture media. Leukocytes were incubated overnight in a complete cell culture medium containing physiological levels of plasma amino acids as a control, while experimental groups were incubated with the reference media coupled with separate glutamate (1.0, 2.0, and 5.0 mM) and glutamine (1.0, 2.0, and 5.0 mM) supplementation, as well as a combined glutamate and glutamine (1.0 mM) treatment.

HSB  fed diets containing incremental levels of glutamate did not present differences in terms of percent weight gain ( average of 649 %  of  initial weight), feed efficiency (FE) (average of 0.75), whole-body composition, hepatosomatic index (HSI) ,  or  plasma  amino acid composition. However, i ntraperitoneal fat (IPF) ratio  was significantly  (P < 0.05) higher in  fish fed  the basal diet  (5.75%)  when compared to those fed the diet supplemented with  glutamate  at 2.0% (5.01%). F illet yield was  also  significantly higher in  fish fed  the  basal  diet ( 31.7%)  when  compared to th ose fed the diet supplemented with  glutamate  at 1.0% (29.9%) .

 In vitro intra- and extracellular superoxide anion (O2- ) production were linearly correlated with the addition of increasing glutamate levels while t he coupled  treatment of glutamate and glutamine (1.0 mM ) produced the greatest respiratory burst response of head-kidney- derived leukocytes.  The current experiment suggested a negligible in vivo response of HSB  fed diets with elevated levels of glutamate while in vitro  immunological responses to glutamate addition were  more apparent.