Beneficial effects of bioactves in animal nutrition includes stimulation of feed intake, improvement in endogenous enzyme secretion, potentiation of immune response and antibacterial, antiviral and antioxidant actions apart from stabilizing gut flora and better assimilation of nutrients by improving villi morphology.

Natural herbal growth promoters remain active throughout the gastrointestinal tract and help in overall growth performance of broilers.Phytobiotics are of interest due to their high content of pharmacologically active ingredients. Biologically active constituents of plants are mostly secondary metabolites, such as terpenoids, polyphenols, glycosides and alkaloids.

Phytochemicals' potentially have useful growth-promoting effects:

• Direct microbicide effect is due to short chain volatile fatty acids (SCVFAs) which inhibit pathogens.
• Plants rich in oligosaccharides stimulate the growth of favourable bacteria by prebiotic effects.
• Block the adhesion of pathogens onto the mucosal layer of the intestine, thus prevent the onset of infection.
• Most of the phytochemicals boost immunity and stimulate the gut associated lymphoid tissue (GALT).
• Stimulate the production of digestive enzymes of the pancreas and intestinal mucosa, leading to a better feed utilisation and increase in growth.

Polyphenols constitute one of the most extensive groups of chemicals in the plant kingdom and more than 8000 such compounds have been isolated and described. Generally, most of polyphenolic compounds are poorly absorbed in the gut and their concentration in the target tissues is comparatively low.

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Allicin

More than 2,500 scientific published papers have been reported on the beneficial effect of garlic. Research has proved antifungal, antiviral, anti-inflammatory, and antibacterial properties. The sulphur compounds present in garlic enhances the function of natural killer cells and overall immunity. Garlic contains at least 33 sulphur containing compounds, several enzymes and 17 amino acids and minerals including selenium and active ingredient is allicin. Organosulphurous supplements prepared from garlic have gained increased popularity in the recent days.

Allicin is the key ingredient responsible for the anti-bacterial activity. Research has shown that allicin is responsible for regulating lipid profile, antioxidant and broad-spectrum anti-microbial effects (antibacterial and antiviral) defense against attack by pests.

It has been reported that crude protein and crude fat digestibility was improved and increase in Omega 3 level in meat with supplementation of allicin.

Curcumin

Turmeric (Curcuma longa), a domestic spice has the various applications having a specific bioactive compound called curcumin, a polyphenolic phytochemical with anti-microbial, anti-inflammatory, and antioxidant properties. Among various herbal supplements, turmeric (Curcuma longa L.), which contains bioactive secondary metabolites as curcuminoids, has been successfully used as a suitable feed supplement for poultry. Curcumin enhances the growth rate and weight of broiler chickens and yolk weight in laying birds by stimulating the digestive system by promoting the intestinal lipase, maltase, and sucrose activities as well as the secretion of pancreatic amylase, lipase, chemotrypsisn and trypsisn.

Curcumin is involved in the repair of lymphocytes in the lymphoid organs. The world Health Organization (WHO) has declared turmeric as a safest dietary element in animal feed.

Beneficial effects as curcumin as feed supplement:
• improvement in haematological and biochemical parameters.
• Improved immunity and increase in antibody titers after vaccination.
• Ameliorate heat stress.
• Prevention of harmful effects of aflatoxins.
• Enhanced antioxidant activity.
• Decrease in some potentially pathogenic bacteria counts like. E. coli, in the ileal content of the laying hens.

Capsaicin

Capsaicin is a proven antioxidant and anti-inflammatory.

• Capsaicin is more effective than vitamin E in inhibiting lipid peroxidation.
• Capsaicin can potentiate the activities of pancreatic and intestinal enzymes.

Trivalerin

Trivalerin is the esterified form of valeric acid. Glycerol esters of valeric acid have the benefit of getting the acid into the intestinal tract intact.

Valeric acid (C5) is the short chain fatty acid. A study performed to determine the antibacterial capacity of valeric acid on Salmonella enteritidis in vitro and the protective effect invivo model, reduced the expression of the key regulatory gene involved in epithelial cell invasion.

Experiments proved the beneficial effect of Trivalerin on growth performance. It improved the villus height/crypt depth ratio of the small and on protection against necrotic enteritis.