Bioactive plants and plant products: Effects on animal function, health and welfare

Livestock production systems and welfare standards of farm animals are changing. The concept of 'clean, green and ethical' animal production has been promoted to address societal demands for agricultural products which are produced with fewer chemical inputs ('clean'), less impact on the environment ('green') and greater care of the animals ('ethical'). Livestock production in developed countries relies to varying degrees on synthetic chemicals to manage livestock health, promote production and regulate impacts on the environment. However, some negative effects and consequences of these practices are emerging and there is a search for alternative options and more 'natural' ways of managing animal production. Bioactive plants and plant compounds, when included as feed and food components, have a broad range of effects in animals, including health promoting benefits animal production, but they can also be toxic or even lethal. While medicinal plants have been exploited for centuries, and are still used in developing countries to treat animals and promote their productivity, these practices generally lack documentation, research and standardization. There is global interest in harnessing bioactive properties of plants and their secondary compounds as alternatives to chemical, drugs and growth promoters. However, we need to gather information about their sources, concentrations and structure, as well as obtain knowledge of their absorption, metabolism and biological effects on the animal in order to evaluate their future use in livestock production. In this context, we discuss bioactive plants and compounds and elaborate on some of their effects on select animal functions and health, outlining benefits and limitations of their use in livestock production, as well as, research gaps in this area and future directions.