Enhancing innate immunity is the frontline of disease prevention and control. Nutrition is a key factor in immunity, disease control, and prevention. Passive and active immunity and building antibodies are affected by nutrition, quantitative and qualitative feed constituents, and hygiene. Fatty acids, protein/amino acids, minerals, and vitamins are vitally important for enhancing immunity and health. In general, under stress conditions, low hygiene, disease outbreaks, and the absence of effective treatment and vaccines, enhancing protection, prevention, and control programs it is essential to improve health to ensure sustained animal performance and economic success. The deficiency of nutrients may increase the threat of emerging diseases and thus assuring adequate supplementation with vitamins C, E and D is essential under such condition. However, nutritional intervention programs may enhance immunity and health status but have a limited impact.
Protein and Amino Acid Nutrition
The relationship between nutrition and immunity for chickens is of vital importance from a quality and quantity point of view. An important issue that might affect poultry immunity, health, and performance is dietary constituents. Crude protein is the most expensive item in poultry nutrition, at both the protein level as well as the protein source; essential amino acids are crucial. Due to the nature of the poultry digestive tract, concentrated feeds are required, and essential amino acids rather than crude protein are vital. Immune function is a complex system that requires higher concentrations of nutrients (amino acids, fatty acids, vitamins, and minerals) than those for productive traits. Besides, immunity is given first priority with regard to nutrient distribution among body functions. Protein and essential amino acids are vitally important for growth and antibody formation and a well-functioning immune system.
Nowadays, poultry diets are formulated based on digestible amino acids rather than crude protein. This goal is achieved by supplementation with industrial amino acids such as methionine, lysine, arginine, tryptophan, and threonine to ensure adequate intake of limiting essential amino acids. Recent evidence has highlighted that a decrease in dietary crude protein diets could be compensated with limited amino acid supplementation at minimum crude protein level while enhancing the broilers’ capacity to cope with infection. A low protein diet supplemented with essential amino acids was found to be useful tool to maintain performance and immunity of chickens when other nutrients were met.
Fats and Fatty Acids
Essential fatty acids, principally n-3 polyunsaturated fatty acids, are essential for human and animal health and immunity. The use of n-3-fatty acids to yield functional foods impacts the nutritive value of animal products (and modulates animal and human immune function. The dietary n-6 : n-3 ratio is essential for a proper immune system function. Increasing the n-6: n-3 ratio augments inflammation due to elevated pro-inflammatory mediators (cytokines), such as tumor necrosis factor α (TNF), interleukin-1 (IL-1) and IL-6. Increased cytokine levels adversely influence animal appetite. The effects could be attributed to T lymphocyte signaling pathways, as well as cytokine and eicosanoid synthesis (i.e., mediators of inflammatory response), and by varying the molecular configuration of lipid portfolios. Thus, it seems that an optimum n-6: n-3 ratio between 2–4:1 is essential to avoid an excessive inflammatory response and their resultant health hazards. This correction can be made by using n-3-rich feeds/foods. In addition, the n-6:n-3 ratio impacts egg, meat, and milk quality and animal immunity. However, the nutritional requirements of essential fatty acids need further exploration.
However, IgG was increased due to feeding a fish-oil-enriched diet, and fish oil and canola raised γ-globulin and α2-globulin. In addition, avian influenza and Newcastle disease antibody titers were sustainably increased due to enriching a broiler diet with 1.5% coconut fat. Fish oil supplementation increased follicle length and width of the bursa of Fabricius and depth of the thymus cortex, but the fish oil decreased the follicle length-to-width ratio. The improved immunity of broilers supplemented with canola oil concurred with an increased villus height-to-depth ratio. There was also an augmented antioxidant balance in broilers supplemented with coconut and canola oil. The n-3 fatty acids addition enhances antibody production against the Newcastle disease virus. Dietary fish oil markedly increases antibody titers and the relative spleen and bursa weights compared to the control group. Coconut fat ameliorates broiler digestion of lipid and raised productive performance during the course of coccidiosis infection.
Nutritional immunomodulation is defined as the impact of additives on certain functions of the immune system and/or decrease hazards of infection by bacterial, viral, protozoa, and fungus. Some feed additives, such as photogenic plants, plant extract, prebiotic, probiotics, synbiotics, bee pollen and propolis, yeast, and enzymes, have reported immunomodulatory effects. Hence, there is a great interest in using them to decrease the environmental hazards and carry-over effects of antibiotics on human health. Their effects include improving metabolic status, decreasing physiological stress, inhibiting the excursion of cytokines by the macrophages, and antimicrobial activity, thus enhance immunity.
It is widely recognized that beneficial microbiota—probiotics, lactic acid bacteria, and Saccharomyces cerevisiae, with its cell wall constituents glucan and MOS—and organic acids are necessary for immunity and gut health. These additives substantially contribute to several mechanisms for disease prevention and control of pathogen growth. They improve antioxidants status, vitamin synthesis, and nutrients digestion. Beneficial microbiota can also help maintain animal health. In this respect, the progress in the probiotic as immunomodulatory interventions shows the prospect to improve animals’ tolerance to bacterial diseases such as salmonella, help detoxify aflatoxin, and decrease the hazards of nitrate. The advantageous impact of immunobiotics on immunity and subsequent health of an animal is directly regulated by indirect a direct interrelationship. The proliferation and differentiation of cells, production of cytokines, secretion of IgA, synthesis of antimicrobial peptides, and increased intestinal cell tight junctions may be affected by the interaction activity between microorganisms and the response of both non-immune and immune cells.
The immunological effects of minerals and their essential role in immunity and health are well-known. Microelements such as calcium (Ca), phosphorus (P), and vitamin D3 are essential for bone health and preventing bone disease (rickets, osteomalacia, and lameness). These benefits are critical for broilers and laying hens to prevent cage layer fatigue and poor eggshell quality. Essential micro-minerals such as zinc (Zn), iron (Fe), chromium (Cr), copper (Cu), selenium (Se) and iodine (I), are important as antioxidants and immune and health enhancers, and they are required for red blood cell and thyroid hormone functions. In general, the recommended doses of trace minerals to boost immunity are ~50–100% higher than the levels needed for productive performance. This requirement depends on the type of and form of the mineral, animal age and strain, environmental stress, and hygienic conditions. However, some elements—particularly heavy metals—can have a negative effect on the environment, causing pollution due to increasing mineral excretion in animal manure.
A recent trend in mineral nutrition has focused on replacing inorganic minerals with organic sources and nanoparticles, particularly green nanoparticles obtained from plant tissues, on improving mineral utilization, animal immunity, and decrease environmental pollution. Furthermore, these green nanoparticles are highly biodegradable and, therefore, do not exert negative consequences on the environment.
The use of nano-minerals in trace mineral nutrition increases their bioavailability, decreases antagonism between minerals at intestinal sites, and reduces excretion and, hence, trace-minerals related pollution. The nutritive nanoparticles enhance performance in livestock and poultry and immunity due to increased digestive effectiveness.. Nano-forms of Cu and Zn can have a cumulative influence and may become a substitute for chelated organic and inorganic forms and can improve animal performance and immunity.
Zn is the second most abundant microelement after iron. It has many functions, including nucleic acid synthesis and repair, metabolism, immune response, redox homeostasis, and apoptosis, and it plays a vital role in the host-pathogen relationship. Zn homeostasis is closely connected with the normal operating of both eukaryotic and prokaryotic cells, and thus many pathogens are indirectly or directly influenced by perturbations in Zn homeostasis. Zn inhibits the activity of RNA polymerase in a number of viruses, including coronavirus, hepatitis C virus, arterivirus, and rhinovirus. Immunity of poultry were improved due to Zn supplementation (112). In addition, zinc is a cofactor for the thymus hormone thymulin and modulates cytokine release and proliferation. Zinc plays important role as a nonpharmacologic immune booster in broiler chicks.
The trace mineral Selenium is essential for human and animal nutrition. It is used to sustain physiological function, immunity, health, and product quality. Selenium is an essential constituent of the 24 selenoproteins in the avian genome. In addition, Se is a constituent of the antioxidant enzyme glutathione peroxidase (GPX). This enzyme guards cells against oxidative stress. Selenium is also part of the deiodinase enzyme essential for the activation of the thyroid hormone. The main functions of selenoproteins are control of redox of biochemical function, antioxidant balance systems, thyroid hormone anabolism and catabolism, anticancer protection, and immune function booster. Hence, Se-enhanced animal products can improve animal immunity, prevent diseases caused by Se deficiency, and enrich general health. Se fortification can enhance the antioxidant balance of animals and improve product quality and animal performance.
Vitamins boost animal immunity. Recent recommendations have been made to boost animal immunity and health under normal and heat stress conditions using vitamins: 200 mg/kg diet vitamin C, 100–200 mg/kg diet vitamin E, and 2500–4000 mg/kg diet vitamin D3. Water-soluble vitamin C improves the antioxidant balance, provides antiviral function, relieves oxidative stress, enhances immunity, and spares vitamin E. α-Tocopherol, known as vitamin E, is the most common natural fat-soluble vitamin; it acts as an antioxidant that guards cell membranes against oxidative impairment due to lipid peroxidation. It also enriches the function and proliferation of lymphocytes and macrophages and increases phagocytic activity and decreases oxidative damage under normal and heat stress conditions. Vitamins E and C have a great effect on productive performance and immune response of animals exposed to heat stress.
Vitamin D3 reportedly has immunological effects that considerably influence the progress of skeletal health, muscle, and Ca and P homeostasis. Eggshell formation and bone health in laying hens is essential and involves the integration between the metabolism of Ca, P, and vitamin D3. Vitamin D3 or its active form 25-(OH)D, both have strong immunomodulatory properties with the ultimate help of T cells (Th2).
Vitamin B groups are also essential for boosting immunity due to their crucial role in the metabolism of protein, fat, and carbohydrates, and adequate vitamin B intake is essential because water-soluble vitamins are not stored in the body, and daily supply must be ensured.
The health status of the present day poultry is facing new challenges day by day which can be conquered by the right scientific and advanced nutritional approaches and thus, making the poultry farming more profitable and presentable in the global market. There is a stiff competition and restrictions in the global market of poultry products which can be conveyed with proper management of emerging diseases with economic productions and quality poultry products free of elements detrimental to human health. Researchers have made efforts to prevent such damage to poultry and poultry products through dietary manipulations. Different disease conditions are responsible for high morbidity and mortality of poultry. Nutritional strategy and proper feed formulation with specific dietary regimen can combat this up to a certain extent by minimizing the incidence of various infectious diseases, nervous disorders and metabolic disorders.
1Manoj Kumar Singh, 2Jinu Manoj and 3R.K.Sharma1Assistant Professor, COVAS, SVPUAT, Meerut, Uttar Pradesh
2ADIO, Central Laboratory, LUVAS, Hisar, Haryana
3Professor & Head, Department of Livestock Production Management, GBPUAT, Pantnagar, Uttarakhand