164 Livestock’s vital role in nourishing the world.

Abstract This objective of this paper is to summarize the critical role that livestock play in nourishing the world. Approximately 13 and 20% of the energy and 28% and 48% of the protein consumed globally and in developing countries, respectively are derived from livestock products (animal-source foods, ASF). Livestock manure supplies approximately 18 and 28% of the total N and P inputs to global cropland, respectively and global livestock manure N and P production has exceeded global fertilizer use. Further, 250 million ha of cropping in developing countries is dependent on animal traction. Livestock play a vital often undervalued role in recycling and upgrading crop residues and crude nitrogen sources in diets that are largely (86%) inedible by humans into highly nutritious ASF. Certain livestock also play pivotal role in providing vital ecosystem services such as carbon sequestration, bioremediation of polluted fields, increasing soil fertility, health and microbial growth, aquifer recharge, etc. Livestock contribute to proper nutrition in the Global South through the income derived from sales of ASF and livestock, through empowerment of women who own livestock, and by nourishing the family. In fact, in countries like Niger, over 80% of the population participates in livestock production, underscoring the vital role of livestock in supporting livelihoods. Furthermore, ASF have been described as “brain foods” or “vital nutrient clusters” because relative to plant-source foods, they have higher quality protein due to their full complement of highly digestible amino acids, greater supply of important polyunsaturated fatty acids, greater bioavailability of essential minerals, especially iron and zinc, and they are the only natural source of highly absorbable forms of vitamin B12, vitamin A, vitamin D3, choline etc. Consequently, including ASF in diets is critical to augment the nutritional quality of breastmilk, to reduce the risk of infant stunting and wasting and instead ensure their proper neurocognitive and physical development, to prevent rickets and other mineral deficiency maladies in adolescents, and to prevent sarcopenia, bone fractures and loss of muscle mass in adults. In addition, ASF have various bioactive compounds that play key roles in regulating blood pressure, modulating the gut brain axis, and supporting various physiological functions. In conclusion, livestock play a fundamental role in feeding and nourishing the world and they are vital for life and livelihoods in developing countries.