**1. Introduction**

Agricultural sector plays an inevitable role for the economy of most Asian and African countries and is the greatest source of domestic income. In addition, it manipulates 70–90% of the gross working population. Sustainably feeding the world is the crucial challenge in the forthcoming years. Surprisingly, the agricultural sector meets the food needs of 50% families besides income [1]. Livestock animals are important source of food to billions of the world's population. It is also agricultural backbone in developing countries because it adds about half of the value to agricultural output [2]. Livestock contribution to agriculture is 56% among which 11% is imparted to GDP. This escalation is due to increasing demand for livestock product which in turn is driven by growing population size, income, lifestyle change and industrialization in economically developing nations. The need for livestock products is estimated to get doubled by 2030 in unindustrialized countries. However, in technologically advanced countries, the need for such products is comparatively lower and is expected to grow slowly over a specified period of time [3]. Despite the demand variability, livestock dichotomy exists between industrializing and industrialized countries in terms of meat and milk production which are the major commodities obtained from dairy animals globally. Meat is an important source of proteins (myosin, myoglobin and collagen), vitamins (thiamine, niacin riboflavin), iron and zinc etc. Annually, 340 million tonnes meat is produced and the quantity is three times more from the past 50 years. The United States of America (USA) is the world's largest cattle and buffalo meat producing country accounting for 12 million tonnes of meat [2]. Milk, on the other hand is produced by 150 million householders in rural, urban and peri-urban areas and contributes to food security, income and nutrition. The world annual milk production has risen from 530 million tonnes in 1988 to 843 million tonnes in 2018. India is the world's largest milk producing country followed by USA, China, Pakistan and Brazil [4].

Everyone is aware with the importance of agricultural subsector (dairy and livestock industry) in the country's economy; still this sector is prone to variety of emerging and re-emerging threats. The threats associated with ungoverned livestock farming in the form of nutritional deficiencies, metabolic disorders, changing environmental conditions, diseases (either infectious or non-infectious) and antimicrobial resistance has led to the importance of understanding bovine

science. Therefore, in this chapter we will learn about the impact of different kinds of re-emerging and emerging threats on bovine community.
