Antibiotics are widely used in pig and chicken industry to promote growth, reduce feed coefficient and reduce morbidity and mortality. However, many countries have begun to restrict or prohibit the use of antibiotics. Restrictions on antibiotics urgently require nutritionists to seek new antibiotic substitutes, such as organic acids, feeding enzymes, probiotics/probiotics, etc. Relatively speaking, plant extracts, especially plant essential oils, are a new type of feed additives, and their effects have not been fully explained.
In recent years, plant essential oils have been increasing in * pig raising and chicken industry. However, plant essential oils are not simple mixtures, but concentrated hydrophobic liquids containing volatile aromatic agents. In terms of biological activity and function, each chemical substance has its unique properties. This means that plant essential oils are complex substances with multiple effects. Other factors, such as plant species, ecological factors, climatic conditions, harvesting time, site of use and separation methods are all the factors affecting the chemical structure of plant essential oils.
1. Growth effect of essential oils
Many studies have reported the growth benefits of plant essential oils on pigs and chickens. Vanilla plants and essential oils usually improve the taste and palatability of feeds. The yield of botanical essential oil increased 2%, 0.9% and 3% for pig weight gain, feeding rate and feed conversion rate, respectively. For chickens, they were 0.5%, 1.6% and 2.6% respectively.
2. Regulate intestinal microbes.
As we all know, in vitro experiments, plant essential oils can play the role of anti bacteria, fungi and viruses. It is generally accepted that plant essential oils are more effective against Gram-positive bacteria than gram-negative bacteria. The inhibitory target of essential oils on Gram-positive bacteria is to destroy cell integrity, and the activity is dose-dependent, but the inhibitory effect on Gram-negative bacteria does not need to destroy cell integrity. In vivo experiments showed that plant essential oils could inhibit the growth of common pathogenic bacteria. Essential oils can improve intestinal microbial structure, thereby affecting microbial metabolism, improving intestinal integrity and protecting the intestine from disease damage.
3, affecting nutrient absorption and intestinal morphology
Plant essential oils can increase the secretion of saliva and bile * and enhance the activity of digestive enzymes, thereby improving digestibility and absorption rate of pigs and chickens. The absorption function of plant essential oils can be improved in feed formulation. Some studies confirmed that adding plant essential oil to low energy pig feed * was similar to that of the control group fed standard feed. The decrease in the number of pathogenic bacteria in the intestinal tract can enhance the ability of epithelial cells to regenerate villi, thereby improving the digestive capacity of the intestine. Therefore, it is worth looking forward to improving the intestinal morphology by adding essential oils to feed. Research reports showed that * the length of villi and crypt depth of jejunum and colon increased after pigs and chickens fed essential oils.
4. Immunomodulation
Usually, the digestive tract immune system is intestinal lymphoid tissue. Intestinal lymphoid tissue plays an important role in antigen defense. Kroismayer and so on, using real-time PCR and intestinal histomorphology, proved that plant essential oil could significantly reduce the expression of NF-kB * and TNF-a in intestinal transcription factors and the size of Pyle's aggregated lymph nodes in the intestine. In chickens, essential oils can reduce the size of mesenteric lymph nodes and spleens, and the number of epithelial lymphocytes and B lymphocytes. In addition, plant essential oils can also alleviate intestinal immune stress.
5. Antioxidant function
Meat product processing, storage and cooking stability are very important. In order to extend food safety during shelf life, synthetic antioxidants are usually used in production. However, the use of synthetic antioxidants such as butyl benzyl alcohol and butyl hydroxyanether has caused food safety problems. Therefore, more and more studies focus on natural additives as antioxidants. Labial herbs such as rosemary and Salvia can play an antioxidant role. In the study of Broilers and turkeys, plant essential oils can improve the oxidative stability of meat. Oregano essential oil can improve the lipid oxidation state of pork. In addition, plant essential oils can also improve redox balance and attenuate oxidative damage in different organs.