**1. Introduction**

Livestock farming is a vital component of agriculture with the potential to promote the economic growth of both developing and developed countries, more so in developing countries. Livestock sustains the world population by providing various services and goods such as meat, milk, eggs, skin, and by-products [1].

Intensive farming refers to a method of food production that relies on intensification techniques. This farming system involves management practices and operations such as concentrated animal feeding, a large number of livestock raised in confinement at high stocking density, and use of selectively bred animals that grow more quickly than naturally occurring breeds and get large enough for slaughter in a shorter period [2]. The intensive livestock farming industry provides employment opportunities for millions of rural households, thereby helping reduce poverty in rural areas, especially in developing countries [2, 3].

By 2050, global livestock production is expected to double-growing faster than any other agricultural subsector, with most of this increase taking place in developing countries [4]. The expansion of the livestock industry may help meet the increasing demand for livestock products, especially in developing countries, which is adding additional pressure on the worldwide livestock farming systems [3]. However, the overall viability of the industrial livestock farming systems depends largely on animal performance and production efficiency, which are negatively affected by the scarcity and fluctuation in the quality and quantity of the animal feed supply. At a certain period of the year, the quality of grazing and browse deteriorates due to seasonal influences, resulting in a decline in animal productivity, unless supplements are provided for the animals [5]. Nonetheless, the conventional feeds commonly used to supplement ruminants are either not available or are available at a high cost, which means that strategies to make livestock farming more efficient to respond to the increasing demand for beef, milk, eggs, and other products are needed. One way to reduce the feeding costs without compromising the nutritional quality would be to use nonconventional feed resources such as by-products from agro-industrial processing and vegetable wastes that are locally available [6]. Many by-products used as alternative feeds are rich in fatty acids such as lauric, myristic, and linoleic, which may enhance productive animal performance [7].

During the dry season in tropical countries, especially in Africa, when only mature senescent material is available, both intake and digestibility are low. As a result, available nutrients do not meet the requirements of the animal, which compromise the animal's ability to reach its genetic potential, unless the nutrient status is increased through supplementation using concentrates that supply primary nutrients such as protein, carbohydrate, and fat [8]. Thus, a better understanding of the quality of by-products and their use in animal feed may probably make livestock farming more efficient, especially in developing countries [9].

This chapter presents an overview of the intensive livestock farming systems in developed and developing countries and discusses the use of agro-industrial byproducts as alternative sources of nutrients to improve livestock productivity, as well as the key nutritional components that are likely involved to improve the reproductive efficiency of animals.
