Betaine is a trimethyl derivative of glycine. As a feed additive, betaine can promote animal growth, improve carcass quality, relieve heat stress and regulate animal reproductive performance. Betaine provides methylation for most of the body's methylation reactions by participating in methionine metabolism. In recent years, more and more studies have revealed that betaine plays an indispensable role in relieving stress.

The study showed that cherry Valley ducks were randomly assigned to the control group and the experimental groups supplemented with 0.12% betaine but with different feeding methods. 42D feeding experiment was conducted. In the latter half of the experiment, heat stress environment was created by heating and humidification. The growth performance, hematocrit, platelet count and cecal short-chain fatty acid level of ducks in experimental group were significantly higher than those in control group under heat stress condition. Studies on broiler chickens showed that diets supplemented with 0.1% betaine can alleviate the decline of growth performance and meat quality caused by heat stress, and improve the oxidative stress state. Under heat stress condition, diet supplemented with 0.1% betaine can significantly improve the survival rate, laying rate and egg production of hens. Betaine can also improve feed efficiency and reduce rectal temperature of finishing pigs under heat stress.

Forty-eight sows were randomly assigned to the control group and the betaine group (supplemental level of 1.92 g/kg) from 5 days before the expected date of delivery until the end of lactation. Reproductive indicators were recorded for two consecutive parities. The results showed that the litter weaning weight of betaine group was significantly higher than that of control group, and the interval between weaning and estrus was significantly lower than that of control group .At the second trimester, the number of live piglets and weaned piglets in betaine group were significantly higher than those in control group. A study on Bama minipig showed that dietary supplementation of 0.35% betaine in sows significantly reduced the mortality rate of piglets, tended to increase the number of weaned piglets, and significantly increased milk protein and urea nitrogen contents in colostrum of sows. Other studies have found that dietary betaine supplementation (0.3% to 0.4%) can increase the probability of sow litter size greater than 15.Dietary betaine supplementation (0.63% and 1.26%) can increase the content of betaine in spermatoplasm, and has a tendency to increase the total sperm number of boars. A total of 120 Rugao Yellow chickens aged 38 weeks were randomly assigned to the basal diet group and betaine group (0.5%) for a 4-week feeding experiment. The results showed that the laying rate of the hens in betaine group was significantly higher than that in the control group.