Considering the high price of fish meal and the shortage of natural resources, it has become a general trend to use other protein ingredients to reduce the use of fish meal in aquafeed.

The alternative sources of fish meal are mainly plant protein, animal protein and single-cell protein, but most of the substitutes cannot replace the fish meal at a high level in diet, which may be related to the existence of anti-nutritional factors, the decrease of feed palatability, the unbalanced amino acid profile and the absence of unknown functional factors.

It is worth noting that taurine is one of the important nutrient which may affect the palatability, growth and stress tolerance of aquatic animals fed with low-fishmeal diets.

Taurine can be synthesized endogenously from sulfur amino acids such as methionine and cysteine in the animal. The synthesis of taurine in fish varies from species to species, depending on fish species, developmental stage, feeding habits and aquaculture environment. However, de novo synthesis of taurine is low in most of fish species, it is necessary to supply taurine by dietary intake.

The primary source of taurine in farmed fish is from fish meal, while plant proteins are absent in taurine. The inclusion of plant ingredients results in a low content of taurine compared with fish meal based diet, which makes the insufficient level of taurine to meet the requirements of fish. Therefore, the application effect of taurine in aquafeed especially in low-fishmeal feed is worthy of attention.

Benefits of supplementing taurine

Improve feed palatability

Taurine can stimulate the sense of smell and taste, thereby increasing the feeding rate. Studies have reported that taurine is more attractive to shrimp than allicin and betaine, two of the most commonly used attractants at present. This positive effect of taurine has also been verified in tilapia, oblique grouper, turbot and other fish species.

Increase growth performance

Taurine can improve the growth performance of aquatic animals, especially those fed plant protein diets. The supplementation of taurine in the low-fishmeal diet with highplant protein content can significantly increase the growth rate and feed utilization of Nile tilapia (Table 1).

Improve feed utilization capacity

Taurine can improve the utilization of plant protein in fish. It was found that taurine supplementation could improve the feed conversion rate, protein deposition rate and energy deposition rate of rainbow trout in the diet with plant protein source as the main source. Taurine has been proved to have positive effect on feed utilization in tilapia, yellowtail fish and sea bream.

Improve antioxidant capacity

Taurine and its derivatives can remove reactive oxygen species and other oxidative harmful substances, so as to protect animals from oxidative damage. Taurine can enhance the antioxidant capacity of aquatic animals by optimizing antioxidant parameters in species such as rainbow trout, grass carp and sea bass.

Improve hypoxia tolerance

Taurine can improve the ability of fish to withstand hypoxia by improving the osmotic fragility of red blood cells. It has been proved that the survival time of grass carp under acute hypoxia increased as dietary levels of taurine increased, which means a better acute hypoxia-tolerance for the fish fed supplemented taurine.

Summary

Supplementing taurine in low-fishmeal diets can improve feed palatability, increase growth performance, feed utilization capacity, antioxidant capacity and acute hypoxia tolerance of aquatic animals.

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Article made possible through the contribution of Ying Chen, Yangyang Gong, Lei Zhang and Jiandong Li, Zhejiang NHU Co., Ltd.

Taurine plays an important role in aquatic feed