**1. Introduction**

Livestock, the world's fastest-growing agricultural subsector is also a key sector that aids economic and social growth in developing countries. It has been a major livelihood strategy for more than 600 million smallholder farmers in these countries [1]. They consider livestock keeping as an important asset that not only contributes to income generation but also accounts as a major source of animal source food (ASF), agriculture input like manure, traction, and also a safety net during emergency situations or lean agricultural seasons. Along with livelihoods, livestock supports the food and nutrition security of around 1.3 billion smallholders and contributes about 40% of the global value of agricultural output in developing countries [2]. Nutritionsensitive agriculture interventions and studies have gained momentum in the past years though the impact evidence is scarce particularly in the livestock subsector. Various systematic literature reviews have acknowledged that livestock interventions have not yet effectively considered nutritional outcomes and that the number of studies assessing impact is even scarcer [3–5]. Considering its contribution to global gross domestic product (GDP), as well as being constituted by five of the 10 highest

value commodities, the livestock sector can be used as an efficient tool for poverty elimination and achieving food and nutrition security in developing countries [6, 7]. Moreover, half of the world's poor people rely on the sector for subsistence, as well as income, insurance, and food, hence increasing food security and nutrition without emphasising on livestock would be a missed opportunity [8, 9].

Around 1 billion people, which accounts for one seventh of humanity, in Africa and Asia depend on livestock production and marketing for livelihood [10]. Further, the potential of livestock production systems to achieve food and nutritional security is evident from the fact that 34% of protein and 18% of calories consumed globally is supplied from livestock production [11], and livestock production allows food production on 57% of the earth's land that cannot be used for crop production [12]. Livestock can act as a transformative tool in the lives of the poor. It is a potential solution to tackle food and nutritional insecurity as well as poverty. Income generated from livestock can provide education, health, and other serviced necessary for the enhanced livelihood of the poor. But the challenge is to balance the positive and negative aspects of livestock production systems so that the advantages are fully realised while the negative effects on health and the environment are mitigated. This chapter elaborates on the potential of livestock for achieving improved human nutrition outcomes and its linkages to nutritional and health status by doing a critical analysis of the available literature on the topic.

#### **2. Methodology**

Considering the relevance of the topic, a thorough analysis of previous studies and works was done to obtain a comprehensive summary on the topic. The literature review surveyed research articles, books, short communications, conference papers, and other internet sources on the topic.

#### **3. Animal source foods (ASF) and human nutrition**

The main direct link of livestock to nutrition is through animal source foods (ASF), which are the inimitable source of high-quality proteins as well as bioavailable critical vitamins and minerals. This can be imperative in the diets of people in developing countries, which typically is carbohydrate dense and nutrient deficient and as evidence, these countries have the highest prevalence of anaemia in women [13]. The deficiency of micronutrients of which the ASF are abundant, like vitamin A, iron, iodine, zinc, B12, and folic acid, are very scarce in the diets of children and pregnant women and this causes poorer growth, cognitive disability, perinatal problems, and an increased risk of incidence and death. [14, 15]. Consumption of even relatively small amounts of animal-sourced foods contributes substantially to ensuring dietary quality [16]. For example, a woman would only have to eat about one eighth and over one third time as much liver and beef respectively as spinach to meet her daily iron needs [17]. Studies also report that animal-sourced diets are indeed the finest sources of essential nutrient-rich diet for children aged 6 months to 1 year [18]. Compared to plant foods, ASF provides more bioavailable vitamin A, vitamin D3, iron, iodine, zinc, calcium, folic acid, and necessary fatty acids, as well as higher quality protein [19, 20].

#### **4. Evidence on the impact of ASF on human nutrition**

Studies conducted worldwide provide strong evidence of the potential of ASF in improving nutrition especially in low-income and developing countries. *Leveraging Livestock Production Systems for Human Nutrition in Developing Countries DOI: http://dx.doi.org/10.5772/intechopen.101399*

Stunting and underweight which are indicators of chronic and acute malnutrition were reduced by 47–74%, respectively, in a randomised controlled experiment in Ecuador [21]. A study on children aged 6 months to 1 year from 49 countries found strong links between stunting and a generic ASF consumption indicator and concluded that consuming ASF was strongly related to child stunting [22, 23]. Supplementation of basal diets of Kenyan schoolchildren with small amounts of meat or milk increased their cognitive skills, leadership behaviour, physical activity, and initiative [24]. Iron-containing complementary foods like meat are especially important among infants who have insufficient iron stores or inadequate intake, as concluded in a recent systematic review [25]. Deficiencies of nutrients like vitamin B12, vitamin A, iron, zinc, docosahexaenoic acid, and iodine, which are critical for neurological development are present in ASF, have been associated with brain-related disorders, including low-intelligence quotient, autism, depression, and dementia [26]. Dairy consumption improves bone health during childhood and adolescence and reduces the risk of osteoporosis and type 2 diabetes [27]. Though studies have clearly reported strong evidence on the positive impact of ASF on human nutrition, its consumption is not adequate in developing countries. Hence, more effort needs to be taken to promote its consumption.
