β-Carotene is the precursor of vitamin A, and its conversion efficiency to vitamin A varies greatly with animal species. Beta-carotene has independent, vitamin A-independent physiological effects, can enhance information transmission between cells, is a chain-cutting reaction of antioxidants, can eliminate toxic oxygen free radicals in animals, and can improve animal immunity, resist the invasion of bacteria and viruses, improve the survival rate of cultured animals; Beta-carotene is a natural yellow or orange color, and it is also an effective colorant.
With the development of feed industry, a variety of feed additives and processing aids are more and more used in the production of compound feed, beta-carotene is one of them. The purpose of adding colorants to feed is to increase the color of livestock, poultry and aquaculture animal products, such as butter color of milk, egg yolk and skin color, poultry feathers color, and so on, so as to improve the value of products. In addition, the color of feed can also be changed through colorants to stimulate the appetite of livestock and poultry. Moreover, beta carotene can play an antioxidant role, thereby enhancing the body's immune function. Animals in the normal metabolic process will produce some highly active oxygen-containing molecules, such as free radicals, hydrogen peroxide, etc. Beta-carotene can regulate the concentration of free radicals and hydrogen peroxide in cells, thereby improving the immunity of animals.
Researchers in the United States have shown that Rhodotorula spp. and Trispora spp. can ferment to produce beta-carotene, which is a good deepening agent for egg yellow color. It can be used in chickens, ducks and geese. Egg yolks are dark yellow, orange-red commonly known as "red heart eggs", with the improvement of people's living standards, "red heart eggs" more and more popular; and eggs export also requires a certain color level standards, that is, must meet the export standards of 8. Therefore, the production of "red heart egg" has become an important topic that layer breeders should not neglect. Chickens eat diets rich in beta-carotene and lay dark yolks because they can store up excess beta-carotene which is not hydrolyzed into VA and increase egg production. The combination of beta-carotene and other vitamins can also prevent some laying hens from changing feathers, thereby increasing the laying rate during the feathering season.
Adding a certain amount of beta carotene to bulls can increase the number of spermatogenesis and improve sperm motility. On the contrary, when the supply is insufficient, abnormal chromosomes will be higher than normal semen. Beta-carotene is also very important to cows, if lack, will lead to weak oestrus, ovulation retardation, follicular cysts frequent, low fertility rate, early pregnancy abortion, serious, can lead to reproductive disorders, placental development arrest.
Beta carotene also promoted the growth of soft shelled turtle. Yang Xinyu et al. fed 89 Chinese soft-shelled turtles with an average weight of 128G with 0.4% beta-carotene in the feed. The results showed that the survival rate of the experimental group with beta-carotene was 15.8% higher than that of the control group, and the daily gain was 105.6%. Beta-carotene feed additive can enhance the disease resistance of soft-shelled turtle, promote the growth of soft-shelled turtle, improve meat quality and reduce feed cost, improve feed efficiency, and have no residue, no drug resistance and many other functions. It can make the soft-shelled turtle produced with pollution-free, high nutritional value and good flavor, so it will be increasingly widely used.
