Plants extract and bioactive compounds on rumen methanogenesis

Feed additives are used in animal diets various beneficial reasons including animal growth, remedy for nutrient deficiency, adsorption of toxins, breakdown of anti-nutritional factors and reduced methane production in the rumen. In past 2 decades, many investigations have focused on studying effects of antibiotics on ruminal fermentation, however, European Union has banned the use antibiotics in animal feeds due to human food safety. Therefore, using plant extracts containing a high level of plant secondary metabolites (PSM) can be an alternative for improving animal performance without compromising food security issues. Most of the plant extracts contains PSM that can be serve as natural resource for animal production systems, nevertheless it is largely unexploited as it is considered as anti-nutritional factors. However, in recent years, various studies emphasized that a group of PSM (e.g. tannins, essential oil and saponins) has ability to manipulate rumen fermentation in a favorable way, thus can be used as natural alternatives for improving ruminant production systems. However, the role of PSM still remains unclear due to limited data and need to be more fully exploited to better understand their properties as bioactive compounds. The present review will discuss the use of plant secondary metabolites in rumen metabolism in terms of biochemical and physiological performance on ruminant production systems, covering topics on proven effectiveness, consumer acceptance, environment, animal safety and welfare.