Various stress reactions seriously affect the feeding and growth of aquatic animals, reduce the survival rate, and even cause death. The addition of betaine in feed can help to improve the decline of aquatic animals' food intake under disease or stress, maintain nutritional intake and reduce some disease conditions or stress reactions.

Betaine can help salmon resist cold stress below 10 ℃, and is an ideal feed additive for some fish in winter. The grass carp seedlings transported for a long distance were put into ponds A and B with the same conditions respectively. 0.3% betaine was added to the grass carp feed in pond a, and betaine was not added to the grass carp feed in pond B. The results showed that the grass carp seedlings in pond a were active in the water, ate quickly, and did not die; The fry in pond B ate slowly and the mortality was 4.5%, indicating that betaine has anti stress effect.

Betaine is a buffer substance for osmotic stress. It can be used as an osmotic protective agent for cells. It can improve the tolerance of biological cells to drought, high humidity, high salt and hypertonic environment, prevent cell water loss and salt entry, improve the function of Na-K pump of cell membrane, stabilize enzyme activity and biological macromolecular function, so as to regulate tissue and cell osmotic pressure and ion balance, Maintain nutrient absorption function, enhance the tolerance of fish and shrimp when osmotic pressure changes sharply, and improve the speech rate.

The concentration of inorganic salts in seawater is very high, which is not conducive to the growth and survival of fish. The experiment of carp shows that adding 1.5% betaine / amino acid to the bait can reduce the water in the muscle of freshwater fish and delay the aging of freshwater fish. When the concentration of inorganic salt in water increases (such as seawater), it is conducive to maintain the electrolyte and osmotic pressure balance of freshwater fish and make the transition from freshwater fish to seawater environment smoothly. Betaine helps marine organisms maintain a low salt concentration in their bodies, continuously replenish water, play a role in osmotic regulation, and enable freshwater fish to adapt to the transformation to seawater environment.