IMPORTANCE OF HERBAL FEED ADDITIVES IN POULTRY NUTRITION
Stressing on the fact of minimizing the use of antibiotics, chemical substances, or any other inorgnaic substances in animal feed especially poultry is increasing with every passing day. Those substances that could be deposited in human bodies through animal products like milk, eggs, and meat and are liable to cause an after effect on our health are being added to the feed of chicken. With the increasing awareness and consciousness among the consumers, alternate additives which are healthy, economical, and environmnetal friendly, have come into light. A brief account on these alternatives and their effectiveness is so strongly supported by Dr. Harshini from ICAR-Central Avian Research Institute with the necessary links attached. So, let us start.
With the changing food habits and increasing health consciousness, the use of feed additives from plant origin is gaining greater attention. The use of antibiotics and antimicrobial feed supplements is restricted keeping in mind the resulting antimicrobial resistance in consumers. Feed additives like prebiotics, organic acids, plant extracts, essential oils are proved to have beneficial effects on animal health and production. These herbal extracts apart from improving the digestibility can also act as antioxidants, anti-inflammatory agents, antibiotics, anti-parasitic supplements, and also immuno-stimulants. They share a broad safety level to the animals fed and to the humans who consume these animals or animal products. Research on standardization for correct dosage of a particular herbal extract for a specific property is the most discussed subject in today’s animal nutrition platform.
A recent ban on the use of antibiotic growth promoters in poultry feeds has drawn the attention of researchers towards the presence of similar substances in medicinal herbs. These are a new class of additives to be added to animal and poultry feeds. Herbs that have received huge attention recently are aloe vera, fenugreek, ashwagandha, cinnamon, tulsi, garlic, pepper, turmeric, neem, amla, cumin, rosemary, and Moringa oleifera.
Herbal preparations are considered safe, cost-effective, and environmentally friendly with no side effects. Hence their inclusion is encouraged to enhance feed utilization, maintain bodily health, and alleviate the adverse effects of environmental stress, and finally the overall performance of the bird.
MODE OF ACTION
Plants secrete a wide range of low molecular weight secondary metabolites which can act as defense systems against physiological and environmental stress like pathogens. These plant metabolites are known to have beneficial effects on animal metabolism and food products.
Most of these secondary metabolites belong to the class of isoprene derivatives, flavonoids, and glucosinolates and a large number of these compounds have been suggested to act as antibiotics or as antioxidants (Rhodes, 1996 or Hirasa and Take mass, 1998). Herbs develop their initial activity in the feed as a flavor and can therefore influence the eating pattern, secretion of digestive fluids, and total feed intake. Also, influence selective microorganisms by antimicrobial activity or by favorable stimulation of the eubiosis of the microflora.
The mechanism by which the majority of herbal feed additives exert their antibacterial effect is by acting in the bacterial cell wall structure, denaturing, and coagulating proteins. The essential oils alter the permeability of the cytoplasmic membrane to H+ and K+ ions that lead to disruption of the essential cellular process such as electron transport, protein translocation, oxidative phosphorylation, and other enzyme-dependent reactions resulting in the loss of chemiosmotic control and consequently bacterial death (Dormant & Deans, 2000). Also aid in the inhibition of nutrient absorption, enzymatic inhibition, effect synthesis of DNA, RNA, and proteins by bacterial cells.
The antioxidant activity of essential oils is due to phenolic compounds, flavonoids, and terpenoids which protect foods, tissues, and cells against the deleterious effect of autoxidation reactions.
Influence of herbal feed additives on feed intake, digestibility of nutrients, and performance
Most of the herbs act as sialogogues by stimulating the secretion of saliva making swallowing easier. The extracts of Salvia officinalis, Thymus vulgaris, Rosemarie officials, and the blend of carvacrol, cinnamaldehyde, and capsaicin improved feed digestibility in broilers (Hernandez F, Madrid J, 2004).
Curcuma, pepper, ginger, mint, fenugreek, onions and cumin enhance the synthesis of bile acids in the liver, a beneficial effect on digestion and absorption of lipids. Most of the spices stimulate pancreatic enzymes while some increase the activity of digestive enzymes apart from accelerating the digestion and shortening the feed passage time (Frankic et al.,2009). Example of Black pepper improving the digestibility in broilers is given in Tazi et al., 2014. Another study with the hot red pepper powder containing capsaicin when fed to broiler chickens improved body weight gain, feed efficiency, bile acid secretion, and reduced heat stress (Nang Nancy Mulang, 2019).
Herbal feed additives as ANTIMICROBIAL supplements
Antimicrobial activity against gram-negative and gram-positive bacteria is proved by several studies. Active principles in herbal feed additives change the fatty acid composition thus affecting the survivability of microbes by increasing their hydrophobicity. Herbs and spices act as microbial agents by changing the permeability of cell membranes and causing ion leakage, making microbes less virulent.
Herbal feed additives as ANTI INFLAMMATORY
Extracts of Curcuma, red pepper, black pepper, cumin, cloves, cinnamon, mint, and ginger have an anti-inflammatory effect. The anti-inflammatory effect is through the suppression of inflammatory prostaglandins.
Herbal feed additives as ANTIOXIDANTS
The commonly used herb for the preservation of feed is rosemary (Rosemarius officinalis). It can be used alone or in combination with the tocopherols. The antioxidant potential of medicinal plants related to the concentration of phenolic substances and vitamins A, E, C are well known for ages. The antioxidant property of garlic and onion is ascribed to the sulfur-containing active principles which inhibit oxidation of low-density lipoproteins and lowering lipid levels.
Herbal feed additives as IMMUNOSTIMULANTS
Herbs and spices rich in flavonoids, vitamin C and carotenoids improves the immune response. The plants containing molecules with immunostimulatory effects are echinacea, liquorice, garlic, and cats claw. These improve the activity of lymphocytes, macrophages, and NK cells increasing phagocytosis (Frankic et al., 2009). The effect of β-glucan and cow urine distillate is known to have an immunomodulatory function in broiler chicken in recent studies (Ganguly,2013).
Herbal feed additives as COCCODIOSTATS
Betaine a byproduct of the sugar beet industry seems to have a positive impact in fighting coccidiosis. It protects against osmotic stress associated with dehydration and permits the normal metabolic activity of the cells. The active component curcumin, of Curcuma longa, exerts its anticoccidial effect through antioxidant action on the immune system (Allen et al., 1998).
Nutritionally enriched or designer eggs are the eggs with an enriched or increased amount of one or more nutrients like omega-3 fatty acid or vitamin E, carotenoid, selenium, or zinc than those of a standard egg.
The value addition of table eggs with the use of herbal feed supplements in poultry fed with garlic, fenugreek, and curry leaves resulted in decreased levels of cholesterol in the yolk.
Supplementation of feed with garlic resulted in the hypolipidemic activity in the yolk and the addition of fenugreek and curry leaves resulted in the production of higher levels of Vitamin E and Selenium (P. Michael Raj et al., 2013).
The inclusion of herbal supplements as feed additives in the livestock and poultry feed has many advantages, residue-free, naturally obtained, improve digestibility, environment friendly, and thereby increase performance. Consumption of animal or poultry products produced by feeding with these supplements have no chances of antimicrobial resistance.
On the other hand, their limitations as the research on levels of inclusion of a particular herb for a specific character or economic trait need to be studied and standardized.
Dr. Harshini Alapati
MVSc. Poultry Science
ICAR- Central Avian Research Institute
Bareilly, Uttar Pradesh
Dr. Hemalatha Talluri
Dr. Amit Kumar Tripathy