No abstract

The term gut health is currently becoming more important for domestic animals including poultry. Gut health refers to the fundamental organ system which covers multiple positive functions like effective digestion, stabilizing intestinal microbiota, gut pH and modulation of effective immune response. Gut health depends on proper balance of microbial population. A wide range of feed and pathogen associated factors influence this balance, and adversely affect the animal health status and production performance. Antibiotic stimulators have been used in farm animals to achieve maximum production. But drug resistance and residual effects of antibiotics in animal products (milk, meat and egg etc.) have raised serious issues in human life. Therefore, The European Union (EU) has strictly banned the application of antibiotic stimulators in livestock nutrition in several others countries including China. As a result, an alternative to antibiotic growth promoters are required to support the profitable and sustainable animal production system. Probiotics as nutraceuticals has been categorized as an alternative natural feed supplement for commercial utilization. Such products have been recognized as safe feed additives in animal industry. Very few studies have comparatively described the effect of probiotics on gut health of domestic animals. Therefore, the aim of this review is not only to explore the beneficial effects of probiotics in improving gut health of domestic animals as an alternative to antibiotic growth promoters, but also to evaluate the probiotics associated health and risk factors, and to provide comprehensive scientific information for researchers, scientists and commercial producers.

Antibiotic growth promoters in livestock nutrition cause microbial resistance which produces threats to human health. Therefore, tannins have been considered as natural alternative antibiotic feed additives which possess various biological properties including antimicrobial, anti-inflammatory, antioxidant and immunomodulatory. Additionally, these plants also have antiparasitic and anti-bloat characteristics which contribute to inhibit the enteric methane emission in order to improve nutrient digestibility, milk and meat quality, fatty acids composition and ruminant production. Antibiotic growth promoters have been practiced in animals feeding to increase feed intake, growth rate, weight gain as well as reduce metabolic disorders and energy losses in the rumen. In 2006, the European Union banned the usage of antibiotic growth promoters in the feeding of livestock. This antibiotic resistance issue has increased demand to explore the natural feed additives that might be useful for animal production system. Consequently, natural forages have been categorized as potential feed additives in animal production since it improves nutritive value, protein digestibility, increase amino acid absorption and growth rate. But, some plant materials are usually rich in tannins known as anti-nutritional factors. Therefore, the application of tannin-rich plants in ruminant nutrition needs great precaution due to its possible injurious effects (dose dependent) on animal health such as metabolic disorders. Hence, there is need to give attention to the usage of tannins in ruminant nutrition as an alternative to antibiotics feed additives to investigate its effects on enteric methane emissions and ruminants production. In addition, safety and risk associated with tannins feeding have also been briefly discussed.

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