BIOACTIVE AMINO ACIDS AS GROWTH STIMULATING NUTRACEUTICA IN SALMON

Background of the invention

Smoltification, transfer from freshwater to sea water, and the first period in seawater is physiologically and metabolically a very stressful period for salmonid fishes. The physiology of the fish is switched from freshwater to saltwater adaptation, but sub-optimal osmoregulation often result in depressed appetite, stunted growth, and increased susceptibility to disease. Other stress situations may also have a negative impact on the growth rate of fish species.

Arginine is one of the most versatile amino acids in addition to its function as a protein component (Walsh & Mommsen, 2001). Among several roles, arginine is an oxidative energy substrate, it is necessary for nitric oxide synthesis, elevates growth hormone, IGF 1, and insulin levels, and is a substrate for polyamine synthesis, which are vital for growth (Mommsen, 2001). Arginine is currently termed an indispensable amino acid necessary for optimal growth for young fish (Wilson, 2002), unlike in mammals, where this amino acid has a conditionally indispensable status (Flynn, et al., 2002).

Glutamate is a dispensable amino acid of the same structural group (glutamate family) as arginine. Glutamine, which is glutamate plus one ammonia molecule, is an important energy substrate for intestinal tissues in mammals, and is the precursor for proline and arginine synthesis in mammals (Young & Ajami, 2001). Whether the same biochemical pathways for intestinal glutamate/glutamine handling exist in fishes is unknown, although the final step in proline biosynthesis was recently described for rainbow trout (Dabrowski, et al., 2005; Terjesen and Dabrowski, unpublished). Interestingly, dietary glutamate supplementation has been shown to reduce arginine requirements in channel catfish, suggesting the pathway between glutamate and arginine exists in fish (Buentello & Gatlin, 2000). Further, dietary glutamine supplementation to juvenile carp was recently demonstrated to improve growth, feed conversion, and intestinal parameters such as total gut weight, fold height and enzyme activities (Yan & Qiu-Zhou, 2006).

Brief description of the drawings

Figure 1 shows the feed intake in 1+ smolts given diet A (control) and diet F (fortified). Figure 2 shows the estimated body weight of 1+ smolts given diet A (control) and diet F (fortified).

Description of the Invention

According to one aspect of the invention, arginine supplementation in a rapidly absorbed molecular from (e.g. free or dipeptide, (Tesser, et al., 2005)) is used to prime the anabolic machinery of the salmon prior to absorption and assimilation of the main feed components.

According to another aspect of the invention, glutamate supplementation is used to provide the intestinal tissues in salmon with an easily available energy substrate during periods of rapid growth.

According to another aspect of the invention, purified bioactive amino acids are added to the diets of Atlantic salmon smolts following transfer to seawater in the early summer. The amino acids are preferably arginine and/or glutamine.

According to another aspect of the invention is a fish feed product comprising purified bioactive amino acids. The amino acids are preferably arginine and/or glutamine.

According to another aspect, the present invention comprises a method for the use of purified bioactive amino acids as nutraceutica to boost the capacity for nutrient absorption and conversion of absorbed nutrients to muscle growth in Atlantic salmon during stressful periods. According to the invention, purified amino acids are added to the diet of fish, preferably salmonid fish such as Atlantic Salmon. The purified amino acids are believed to be absorbed in advance of amino acids and other nutrients resulting from digestion, priming the anabolic machinery prior to absorption and assimilation of the main feed components.

Examples

The invention will be further described by the following examples: Objective

To evaluate the endocrine, biochemical, molecular, and growth stimulatory effects of arginine and glutamate as dietary nutraceutical supplements for Atlantic salmon smolts after seawater transfer.

Preliminary results

Two diets were produced by high-pressure moist extrusion: A standard salmon diet (diet A), and a diet fortified with 5 g arginine (Arg HCl) and 7.5 g glutamate per kg (diet F). The total content of arginine was 27 g and 32 g per kg diet, respectively.

Each diet is fed to triplicate groups of Atlantic salmon for a period of 100 g following transfer to seawater in May 2007. These Atlantic salmon 1+ smolts are raised in 125 m ³ pens with 400 fish/pen at AKVAFORSK's model sea farm at Averøy (Norway). The feeding is appetite driven, and feed intake is recorded daily. The experiment will be terminated in the last week of September 2007.

As shown in Figure 1, diet F has stimulated a higher feed intake than diet A. This has resulted in faster estimated growth and higher body weight, as shown in Figure 2. Thus, the experiment verifies that a combination of arginine and glutamate may be used as nutraceutica to boost growth in Atlantic salmon 1+ smolts following transfer to seawater.

References

Buentello, J.A., Gatlin, D.M., 2000. The dietary arginine requirement of channel catfish {Ictalurus punctatus) is influenced by endogenous synthesis of arginine from glutamic acid. Aquaculture

188, 311-321. Dabrowski, K., Terjesen, B.F., Zhang, Y., Phang, J., Lee, K. -J., 2005. A concept of dietary dipeptides: a step to resolve the problem of amino acid availability in early life of vertebrates. J. Exp.

Biol. 208, 2885-2894. Flynn, N.E., Meininger, CJ., Haynes, T.E., Wu, G., 2002. The metabolic basis of arginine nutrition and pharmacotherapy. Biomed Pharmacother 56, 427-238.

Mommsen, T.P., 2001. Paradigms of growth in fish. Comp. Biochem. Physiol. [8] 129, 207-219. Tesser, M., Terjesen, B., Zhang, Y., Portella, M., Dabrowski, K., 2005. Free- and peptide-based dietary arginine supplementation for the South American fish pacu {Piaractus mesopotamicus). Aquacult. Nutr. 11, 443-453. Walsh, P.J., Mommsen, T.P., 2001. Evolutionary considerations of nitrogen metabolism and excretion.

In: Wright, P.A., Anderson, P.M. (Eds.), Fish Physiology. Academic Press, San Diego, CA, pp. 1-30. Wilson, R.P., 2002. Amino acids and proteins. In: Halver, J.E., Hardy, R. W. (Eds.), Fish Nutrition.

Academic Press, San Diego, CA, pp. 143-179. Yan, L., Qiu-Zhou, X., 2006. Dietary glutamine supplementation improves structure and function of intestine of juvenile Jian carp (Cyprinus carpio var. Jian). Aquaculture 256, 389-394. Young, V.R., Ajami, A.M., 2001. Glutamine: The Emperor or His Clothes? J. Nutr. 131, 2449S-2459.