Preface   Feed additives are non-nutritive substances, preparations and micro-organisms that are added to animal feed which may favourably influence characteristics of the animal feed, feed intake, gastro-intestinal flora, digestibility of the animal feeds, animal production, health, fertility, and characteristics of animal products. Modern intensive livestock and poultry production has achieved phenomenal gains in the efficient and economical production of high quality and safe animal products and by-products. Due to increasing awareness regarding environmental and food safety issues, animal nutritionists have been assigned with the responsibility to produce clean, green and wholesome animal products in a sustainable and eco-resilient manner. The use of feed additives can be an important tool of achieving the livestock production. Despite mounting and convincing evidence that feed additives are very useful for economic and eco-friendly livestock and poultry production, most of the additives are not very popular to use. A part of the reason for this relative paucity may be the lack of complete and easily available informations on feed additives. We experienced that informations about the recent concept on different feed additives have not been presented in a single book so that readers can understand their intricacy and practical applications. However, reviews on different feed additives are distributed in diverse journals that are sometimes physically and financially out of reach of most of the students. Therefore, the need for the hour is to compile all the necessary informations pertaining to animal feed additives in a single publication and update the students, researchers and feed manufacturing agencies with current knowledge on this topic. This book on Animal Feed Additives discusses the impacts of feed additives on animal metabolism, health and production in a systematic and comprehensive manner with all updated informations. In preparing this reference book, authors from major teaching and research establishments, who have an enviable tract record in their respective specialism, have been selected. The book contains chapters on antioxidants, enzymes, probiotics, prebiotics, synbiotics, antimicrobials, organic acids, coccidiostats, mycotoxin binders, immunomodulator, hen egg antibody, hormones, beta agonist, methane inhibitors, defaunating agents, essential oil and herbal feed additives. The informations presented in this book are based on the latest data available from research being conducted in the field of feed additives. The book contains good amount of the experimental evidence with references which will enable the students and research workers to obtain information quickly when necessary. The book is dedicated to all the contributors, who made this book possible and who found their valuable time to write their comprehensive and authoritative chapters. We acknowledge and express our thanks to our family members, friends and well wishers, who have been incredibly supportive to bring this book. We hope the book will provide a comprehensive and valuable guide on animal feed additives to the students, teachers and researchers of animal science discipline.

Introduction Modern intensive livestock and poultry production has achieved phenomenal gains in the efficient and economical production of high quality and safe animal products and by-products. Furthermore, the overall performance of livestock can be increased by improving nutrients utilization, health status, fertility and efficiency of production. The use of feed additives has been an important part of achieving efficient livestock production. Feed additives are non-nutritive substances, preparations and micro-organisms that are added to animal feed to improve productive, reproductive and health performances. Any substance is considered as a feed additive when, not having a direct utilization as nutrient, is included at an optimum concentration in diet to exert a positive action over the animal health status or the dietary nutrient utilization. Hutjens (1991) defined feed additives as a group of substances that can cause a desired animal response in a non-nutrient role, such as pH shift, growth, or metabolic modifier. Feed additives are added deliberately to animal feed which may favourably influences characteristics of the animal feed, feed intake, gastro-intestinal flora, digestibility of the animal feeds, animal production, health, fertility and characteristics of animal products. Because of their chemical nature as active principles, additives are generally included in very small proportions in diet.

Introduction The competition between human and livestock population for the existing animal and plant resources has been of great concern to the poultry nutritionists. Today the poultry industry has already challenged by the high price of the feed ingredients. Moreover in the next century there will be a shortage of conventional feed stuffs for use in poultry production. Efforts are on to look forward for the new feed resources and to evaluate them for their inclusion in the poultry ration. However many of the feed stuffs are characterized by the presence of certain incriminating factors. The incorporation of feed stuffs containing incriminating factors may adversely affect the performance of poultry. The nutritional strategy involving the use of feed enzymes offer immense potential to overcome the problems. The use of enzymes in feed mixtures of growing poultry particularly for young chicks has been the subject of much research activity in the recent decades. The interest in the feed enzymes is a reflection in changing the attitude of the society and the economic climate of the feed industry. It has been seen that approximately 187 million metric tons of cereal grains (FAO, 2011) and 26.02 million tons oil seeds as per the trade estimate for 2011-12 are produced in India which yield non starch polysaccharides (NSP) as a part of variety of products.

Introduction During the intensive system of poultry production birds are exposed to several types of stresses. The birds can tolerate mild stress but when the stress is severe, there is imbalance between oxidants and antioxidants which lead to oxidative stress and lipid peroxidative damage of tissues, ultimately results in poor performance. Nutrition has a strong impact on oxidative stress. Insufficient intake of antioxidants, a high intake of prooxidants, or both may lead to oxidative stress. The detrimental effects of oxidation process can be prevented by addition of antioxidant compounds in the feed. Vitamin E, carotenoids and selenium (Se) are among important antioxidant components of poultry diets. It is important to understand the role of antioxidants in poultry nutrition in general and in production and reproduction in particular. The chapter, here in will discuss the stressors in poultry production, oxidative stress and possible alleviation through dietary antioxidant supplementation.

Pankaj Kumar Singh and Chandramoni Introduction The term “probiotic” is derived from Greek and means pro: for and bios: life (for life) in contradiction to antibiotic which means: against life. The term probiotic was first introduced by Lilly and Stillwel (1965) to describe growth-promoting factors produced by microorganisms. Parker (1974) first specified designation “probiotic”. He defined probiotics as microorganisms or substances, which contribute to the balance of the intestinal micro flora. Crawford (1979) defined probiotics as a culture of specific living microorganisms, primarily Lactobacillus spp. that are implanted in the organism and ensure the rapid and effective establishment of a beneficial intestinal population. Fuller (1989) discussed the definition given by Parker (1974) and considered it too broad, as cultures, cells, and metabolites are also included in antibiotic preparations. He redefined “probiotic” as a live microbial feed additive, which beneficially affects the animal by improving its microbial balance. Havenaar et al. (1992) pointed out that the definition of “probiotic” made by Fuller (1989) was restricted to feed supplements, animals, and their intestinal tract. Therefore, they generalized Fuller’s definition of “probiotic” as a mono or mixed culture of living microorganisms, which beneficially affect the host by improving the properties of the indigenous micro-flora. Through 1989, United States Department of Agriculture (USDA) advised manufactures to use the term: “direct-fed microbial” (DFM) instead of “probiotic” (Miles and Bootwalla, 1991). The USFDA defined DFM as a source of live naturally occurring microorganisms, including bacteria, fungi, and yeast. Vanbelle et al. (1990) pointed out that most researchers considered “probiotic” for selected and concentrated viable counts of lactic acid bacteria. Koh et al. (1992) pointed out that as a biological product for newly hatched chicks a bacterial culture producing acetic acid could be used. Such a culture might be supplied to the chicks either through their drinking water or by the feed. For controlling the biological balance in the chicken’s intestinal tract different probiotics may be used. The US National Food Ingredient Association presented, probiotics (direct fed microbial) as a source of live naturally occurring microorganisms and this includes bacteria, fungi and yeast (Miles and Bootwalla, 1991). According to the currently adopted definition by FAO, probiotics are: “live microorganisms which when administered in adequate amounts confer a health benefit on the host” (FAO/WHO, 2001). More precisely, probiotics are live microorganisms of nonpathogenic and nontoxic in nature, which when administered through the digestive route, are favorable to the host’s health (Guillot, et al., 1998; Thomke and Elwinger, 1998,).

Introduction Prebiotics are non-digestible food ingredient which beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of health-promoting bacteria in the intestinal tract, thus improving the host‘s microbial balance (Gibson and Roberfroid, 1995). Normally, prebiotics contain some type of a non-digestible carbohydrate fraction (Rehman et al., 2009). Almost 90% of oligosaccharides escape digestion in the small intestine and reach the colon where they selectively stimulate the growth and/or activity of beneficial bacteria like Bifidobacteria, Lactobacillus and Streptococcus, providing prebiotic properties (Stanton et al., 2003). These bacteria populate the gut filling any niches were pathogenic bacteria may attempt to take hold. This concept is better known as competitive exclusion. Prebiotics function by lowering the gut pH through lactic acid production, inhibiting/preventing colonization of pathogens, modifying metabolic activity of normal intestinal flora, and stimulation of the immune system (Doyle and Erickson, 2006). Studies have demonstrated that these bacteria reduce pathogenic bacteria like Salmonella spp., Clostridium diffile and Campylobacter spp. (Hopkins and Macfarlane, 2003; Stern et al. 2000), by diverse mechanisms including competitive exclusion of nutrients or adhesion sites to intestinal mucosa (Stern et al. 2000) and fatty acid of short chain production, like propionic and butyric acids, which modifies the acidic conditions and inhibits the growth of microorganisms that cause infections (Collins and Gibson, 1999).

Introduction Synbiotics refer to nutritional supplements combining probiotics and prebiotics in form of a synergism. The synbiotic concept was first introduced as “mixtures of probiotics and prebiotics that beneficially affect the host by improving the survival and implantation of health-promoting bacteria. Probiotics are live bacteria which are intended to colonize the large intestine and confer physiological health benefits to the host. A prebiotic is a food or dietary supplement product that enhances the activity of probiotics. Synbiotics are not drugs and the effects are due to changes in bacteria population or enhancement of activity of the bacteria. A synbiotic may contain fiber, but all fiber is not necessarily a synbiotic. Using prebiotics and probiotics in combination is often described as synbiotic, but the United Nations Food & Agriculture Organization (FAO) recommends that the term “synbiotic” be used only if the net health benefit is synergistic. A synbiotic contains fiber such as fructose oligosaccharide, galactose oligosaccharide, etc. and is intended to stimulate the microflora in the large intestine. The combination of probiotics and prebiotics work separately in the small and large intestine, but synergistically increase the overall gut health. Prebiotic has shown to increase the population and/or function of the probiotic it is paired with, as the probiotic is an external species, whereas prebiotics stimulate the flora which is already present.

Introduction With the perception that antibiotics should no longer be used as animal growth promoters, there has been widespread interest in natural methods of inhibiting detrimental bacteria. Their removal from the poultry diets is therefore brings with it consequences. This has lead to somewhat of a renaissance in research activity on the discovery and application of non antibiotic chemical compounds capable of either killing microorganisms outright or at the very least retarding growth sufficiently to limit their dissemination. Organic acids have a long history of being utilized as food additives and preservatives for preventing food deterioration and extending the shelf life of perishable food ingredients. In recent past organic acids have been used to control microbial contamination and replace antibiotic growth promoters in poultry (Ricke, 2003; Hassan et al.,2010; Adil et al., 2011).

Introduction After the discovery that low concentrations of antibiotics included in livestock diets had a beneficial effect on production efficiency, the use of antibiotic growth promoters (AGPs) became a common practice, benefiting both the livestock industry and consumers. Antibiotic growth promotion in agricultural and animal production has been practiced for about 50 years (Dibner et al., 2007). Orally ingested antibiotics promote growth and efficiency of poultry and other animals. Early indications of a beneficial effect on production efficiency in poultry and swine were reported by Moore et al. (1946) and Jukes et al. (1950).

Introduction An ionophore is a lipid-soluble molecule usually synthesized by microorganisms, which transport ions across cell membranes of susceptible bacteria, dissipating ion gradients and uncoupling energy expenditures from growth to kill these bacteria. The term ionophore was first used in 1967 for their ability of organic molecules to bind metal cations and form lipid soluble complexes that facilitate their transport across cell membrane. The ionophore antibiotics show wide varieties of biological activity ranging from antibacterial, antifungal, antimycoplasma, antiparasitic, antimalarial, antiviral, anti-inflammatory and tumourcell cytotoxic activity (Augustine, et al., 1987; Gumila et al., 1996). Presently seven polyether antibiotics include monensin, lasalocid, salinomycin, narasin, maduramycin, laidomycin and senduramycin are used around the world in various segments of cattle and poultry industries. These ionophores are mainly used as anticoccidial drugs in poultry and growth promoters in the ruminants. Polyether antibiotics are not used in human but recently, it has been shown that some of these compounds are able to selectively kill human cancer stem cells and multidrug resistant cancer cells. Hence, they are recognized as new potential anticancer drugs.

Introduction To improve the growth and health status, addition of antibiotics in the poultry feed was a common practice in last decade. Currently, in developed countries it is banned due to fatal consequences like development of antimicrobial resistant organism pool in the gut, persistence of antibiotic residue in the food chain that can reduce the food safety level. Therefore, various alternatives are now a day thought to use as poultry feed additives. Immunomodulaors are presently receiving wide attention as feed additives. The term ‘immunomodulation’ is generally used to describe the manipulation of immune system which consists either increase (immunostimulation) or decrease (immunosuppression) in the magnitude of the immune system function. The chemicals or biological substances producing this phenomenon are known as ‘immunomodulators’. Specific immunomodulation involves the change in the immune response with a particular antigen (e.g. vaccination). Whereas, non-specific immunomodulation alters the immune response in such a way so that it become sensitive to a wide range of antigens. Generally this kind of non-specific immunomodulators are used as poultry feed additive to increase the resistance against the wide range of infections. The principal components of the immune system targeted for immunomodulation include T cells, B cells, monocytes, macrophages, granulocytes and natural killer cells (Dalloul and Lillehoj, 2005).

Introduction There is concern that antibiotic-resistance in bacteria may make commonly used antibiotics less effective. Oral immunotherapy (passive immunization) with specific antibodies is a strategy that has been actively pursued in laboratory and clinical studies for the last two decades. Feeding of egg yolk antibodies to neutralize specific pathogens, especially enteric microorganisms, is a potential alternative to antibiotics. Oral administration of these antibodies has met with some degree of success in prevention of viral and bacterial enteric infections in humans, piglets, calves, fish and rabbits. It is proposed that the egg yolk antibodies may act against enteric pathogens by binding, immobilising and consequently reducing or inhibiting the growth, replication, or colony forming abilities of these pathogens. Three immunoglobulin classes (IgA, IgM and IgY) have been shown to exist in chickens. Chicken immunoglobulin G (IgG) has been designated as immunoglobulin Y(IgY) because it varies in several aspects from mammalian IgG. IgY is the main serum immunoglobulin in chickens. It is transported from the hen to the embryo via the egg yolk. The egg yolk thus contains high concentrations of IgY. Other immunoglobulin (Ig) classes are present only in negligible amounts in the egg yolk. It has been shown that the presence of immunoglobulins in eggs is an example of passive immunity. This is because these antibodies originated from the hen and are used to protect the offspring from various infectious diseases after hatch.

Introduction Coccidiosis is the most economically harmful disease encountered in commercial poultry production. It is caused by single celled protozoan parasites of the genus Eimeria which are commonly referred to as coccidia. Williams (1998) reported that the annual worldwide loss is about $ 800 million. The total loss due to coccidiosis is found to be Rs. 1.14 billion in India. The important finding is that almost 70 percent of the estimated cost is due to subclinical coccidiosis, by impact on weight gain and feed conversion rate. One of the reasons for these remarkable finding is probably the difficult diagnosis of subclinical coccidiosis. Chickens are susceptible to at least seven species of Eimeria. The most common species are Eimeria tenella, which causes the caecal coccidiosis, E. necatrix &E. maxima, which causes mid intestinal coccidiosis, E. acervulina which causes anterior intestinal coccidiosis and E. brunetti which causes posterior intestinal or rectal coccidiosis. E. mitis and E. praecox are generally mildly pathogenic and commonly occurring as co-infection/mixed infection in with other species. Coccidiosis is particularly difficult to combat because several different species of Eimeria exist in the field. Poultry may become infected with different species because the immunity that develops after infection is specific only to one species. Eimeria has direct and complex life cycle that involves many developmental stages within the host cells. Each Eimeria species has characteristic intestinal lesions and type of diarrhoea (with or without blood).

Introduction For the past few decades, a number of chemical feed additives such as antibiotics, ionophores, methane inhibitors and defaunating agents have been introduced into ruminant nutrition in order to improve rumen fermentation, and increase growth and milk production by improving intake and feed conversion efficiency. However, most of these supplements are not used routinely because of toxicity problems to the host animals and microbial adaptation to these additives. Most importantly, growing awareness from public health aspects has centered on the safety of tissue residues of these chemicals and also bacterial resistance to antibiotics as a result of increased use in the food chain. These supplements have been criticized by the consumers’ organizations on the ground of product safety and quality. Antibiotic feed additives are banned in European Union. The consumers’ demands have drived the search for natural alternatives to chemical feed additives for eco-friendly animal production. Plants are part of herbivore diets, and these plants contain bioactive compounds with antimicrobial properties can be of interest in animal nutrition. Therefore, recent research has been greatly focused to exploit bioactive plant secondary compounds as natural feed additives to improve rumen fermentation such as enhancing protein metabolism, decreasing methane production, reducing nutritional stress like bloat, and improving animal health and productivity (Wallace et al., 2002; Patra and Saxena, 2009a, b; 2010; 2011), which may be useful in eco-friendly livestock farming (Patra, 2007). This review discusses the effects of different plant metabolites on rumen fermentation, rumen microbial ecosystems and ruminant performance.

Introduction There is growing worldwide interest in reducing methane emissions from domestic ruminants. Methane is a potent greenhouse gas and its release into the atmosphere is directly linked with animal agriculture, particularly ruminant production. Methane emitted from ruminant livestock is regarded as a loss of feed energy and also a contributor to global warming. Methane is synthesized in the rumen as one of the hydrogen sink products that are unavoidable for efficient succession of anaerobic microbial fermentation. Various attempts have been made to reduce methane emission, mainly through rumen microbial manipulation, by the use of agents including chemicals, antibiotics and natural products such as oils, fatty acids and plant extracts. A newer approach is the development of vaccines against methanogenic bacteria. While ionophore antibiotics have been widely used due to their efficacy and affordable prices, the use of alternative natural materials is becoming more attractive due to health concerns regarding antibiotics. An important feature of a natural material that constitutes a possible alternative methane inhibitor is that the material does not reduce feed intake or digestibility but does enhance propionate that is the major hydrogen sink alternative to methane. Since methane contains energy, its emission during rumen fermentation is considered to be a loss of feed energy that is equivalent to 2-12% of the gross energy of animal feed (Johnson and Johnson, 1995). Some implications of these approaches, as well as an introduction to antibiotic-alternative natural materials and novel approaches, are provided.

Introduction Ruminants are provided with a microbial ecosystem in the gastro-intestinal tract which helps in the bioconversion of lignocellulosic feeds into volatile fatty acids which are utilized by the animal as a source of energy. This microbial biomass is also helpful in synthesis of microbial protein and B-complex vitamins for the host animals. Any disturbance in the microbial balance may affect the performance of the animal adversely and any improvement in the microbial environment may lead to the improvement in productivity of the animal. A number of chemical feed additive like hormone, antibiotics have been used to improve the performance of the animals. But due to residual left over in the animal products and risk of creating disease, resistance against antibiotics, the use of these chemical feed additives have been discouraged and even banned in some countries. As an alternative microbial feed additive seems to be more natural; as it is not creating any new thing in GIT but it is merely restoring the normal and ideal flora in the digestive tract to its full capacity.

Introduction The original concept of feeding bacterial direct fed microbial (DFM) to livestock was based primarily on potential post–ruminal effects, including improved establishment of beneficial gut microflora (Fuller, 1999). Calves fed Lactobacillus acidophilus have been reported to have reduced incidence of diarrhoea (Beecham et al., 1977) and reduced intestinal coli form count (Bruce et al., 1979). But now it is known that certain bacterial DFM also have beneficial effects in the rumen and one of the important groups of this type of bacteria is propionic acid producing bacteria (Elsden, 1945; Johns, 1951a; Langa, 2010). This group of bacteria includes Propionibacterium spp., Veillonella spp., Megasphaera spp., Selenomonas spp. and Succiniclasticum spp. (Table 1). Propionic acid producing bacteria (PAPB) are secondary bacteria which enhance propionate production by utilizing the end products of primary fibrolytic or starch utilizing bacteria which produce succinic acid and lactic acid (Swenson and Reece, 1996). Inoculation of in vitro fermentation with the lactate utilizing ruminal bacterium Megasphaera elsdenii prevented lactate accumulation and produced propionic acid when a highly fermentable substrate was used (Kung and Hession, 1995). Propionibacteria are also rumen active bacteria which can produce propionic acid by utilizing glucose, lactic acid and succinic acid (Elsden, 1945; Grinstead and Barefoot, 1992; Hugenholtz et al., 2002). Ghorbani et al. (2002) also reported that Propionibacteria convert lactate and glucose to acetate, propionate and CO2. They also reduce nitrate to nitrite and reduce nitrite load by 40-60% and minimize changes in blood nitrite and met hemoglobin (Rehberger et al., 1993). Succinic acid is an important end–product, but in practice this is converted into propionic acid by other bacteria such as Selenomonas ruminantium (Swenson and Reece, 1996; McDonald et al., 2002; Langa, 2010); such interactions between microorganisms are an important feature of rumen fermentation. Veillonella gazogenes are also active in the rumen and produce propionic acid by fermenting succinic acid (Johns, 1951a). Moreover in low quality forage-based diet Fibrobacter succinogenes are predominant fibrolytic bacteria which digest fibre faster and produce sufficient amounts of succinic acid in the rumen (Cheng et al., 1984; Miron and Ben-Ghedalia., 1992) and synergistic increases in propionate production and fiber digestion was found in co-cultures of Fibrobacter succinogenes and Selenomonas ruminantium (Sawanon et al,2003), and of Ruminococcus flavefaciens and Selenomonas ruminantium (Sawanon et al., 2006). These findings suggest that positive interactions occur between bacteria, mostly via metabolite exchange.

Introduction The process of making the rumen of animals free of rumen protozoa is called defaunation and the animal is called defaunated animal. The role of rumen ciliate protozoa on the performance of host animals became debatable issue when Becker and Everett (1930) demonstrated that rumen protozoa were non-essential for growth in lambs. Nevertheless, the reports of recent years reflect that though protozoa may be non essential for ruminant, still they have significant role to play in the rumen metabolism specially to stabilize the rumen pH (Santra and Karim, 2002a). Rumen protozoa are the largest in size among rumen microbes and contribute 40-50% of the total microbial biomass and enzyme activities in the rumen (Agarwal et al., 1991).

Introduction Enzymes are globular proteins that act as biological catalysts. They are produced by living cells to bring about specific biochemical reactions. Digestive enzymes catalyze the degradative reactions by which substrates (i.e., feedstuffs) are digested into their chemical components (e.g., simple sugars, amino acids, fatty acids) which in turn, are used for different body functions. Different enzymes are utilized for the complete digestion of complex feed. The enzymes are being used in the feeding industry from last several decades. Various digestive enzymes have been studied for use as feed additives to enhance animal performance They are commonly used to improve the nutritive value of feeds for non-ruminants (especially, poultry and swine). They are not routinely used in adult ruminant diets because the fibrolytic activity within the rumen environment is normally very high, and it is assumed that exogenous enzymes cannot survive proteolysis in the rumen (Kopency et al., 1987). Forages are the main feed component that serve as the major source of energy available to the animal in ruminant production system. However, due to slow or incomplete digestion of fibrous substrates only 10 to 35% of energy intake is available as net energy that significantly limits livestock performance and profits in production systems. To improve the ruminal fibre degradability many strategies have been developed to stimulate the digestion of the fibrous components in ruminant feeds. That includes, use of various feed additives which stimulates fiber digestion, physical and chemical processing of feeds in order to enhance the rate and extent of fiber digestion. However, the use of “natural” product to enhance production efficiency is highly recommended that can potentially play some role in replacing performance benefits vacated by antibiotics and hormones. Enzymes are proteins that are ultimately digested or excreted by the animal, leaving no residues in products, which was a major drawback in the use of antibiotics and hormones.

Introduction While world population is expected to increase from 6 billion to about 8.3 billion, India is likely to be the most populous nation with 1.6 billion in the year 2030. Therefore, it is essential to be prepared to produce sufficient food for the increased population with the application of newer technologies. The consumption of animal food was 10 kg/yr in the 1960s increasing to 26 kg/yr in 2000 and is expected to be 37 kg/yr by 2030 (FAO, 2008; 2009). Large increases in per capita and total demand for meat, milk and eggs are forecast for most developing countries for the next few decades (Delgado et al., 1999). In developed countries, per capita intakes are forecast to change slightly, but the increases in developing countries, with their larger populations and more rapid population growth rates, will generate a very large increase in global demand. Moreover, an increasing number of consumers demanding healthy and quality foods have pushed researchers into development of technologies that can control the proportion of lean and fat muscle deposition in meat producing animals. A number of technologies have been developed that led to remarkable improvements in the efficiency of animal production and in carcass composition and meat quality. There are some dietary additives and vitamins that may increase protein and muscle deposition, while often simultaneously reducing fat deposition by modifying nutrient metabolism in individuals.

Introduction For raising animal and its products especially protein, food and nutrition plays an important role. Feed cost comprises about 60% of total recurring expenditure. Feed additives play an increasingly important role in animal nutrition by augmenting the performance by maintaining the needs of essential nutrients, improving feed conversion therefore optimize feed utilization (Wenk, 2000). Feed additives are a group of feed ingredients that can cause a desired animal response in a non-nutrient role, such as rumen modifier, growth or metabolic modifier (Hutjens, 1991). These are used in micro quantities and require careful handling and mixing. The development and introduction of various new feed additives is a major and practical solution to improve the efficiency of animal production, to alleviate environmental pollution, to maintain animal health, welfare and to ensure the safe and of good quality food production.

Introduction Growth enhancement technologies have been widely embraced in the livestock industry to improve growth, efficiency and carcass traits. For over 50 years, estrogenic and androgenic hormone implants were widely used in the cattle feeding industry, and it is estimated that approximately 97 percent of feedlot cattle in the U.S. receive one or more implants during the finishing phase (Barham et al., 2003; Tatum, 2006). There is a large body of literature that indicates the positive growth enhancement effects which implants impart on growing and finishing cattle and producers have extensively used implants to increase live body weight, improve average daily gain and feed efficiency, and reduce the number of days cattle are on feed (Apple et al., 1991; Duckett et al., 1997;Milton and Horton, 1996; Perry et al., 1991). Likewise, there is a growing body of literature that indicates the positive response on growth and carcass characteristics that finishing cattle have to beta-adrenergic agonists. The hog industry, and more recently, the cattle feeding industry have increased utilization of beta-adrenergic agonists to improve the efficiency of production. While the use of Ractopamine hydrochloride (Paylean®, Elanco Animal Health, Greenfield, Indiana) has been used extensively in hog production since its approval by the Food and Drug Administration (FDA) in 1999, similar pharmaceutical feed additives have only recently been implemented in commercial cattle feeding operations. Beta-adrenergic agonist use in fed cattle has substantially increased following the FDA approval of Ractopamine hydrochloride (Optaflexx®, Elanco Animal Health, Greenfield, Indiana) in 2003, and the approval of Zilpaterol hydrochloride (Zilmax®, Merck Animal Health, Summit, New Jersey) in 2006. The use of both Ractopamine hydrochloride (RH) and Zilpaterol hydrochloride (ZH) have shown to elicit similar improvements in live weight gain, average daily gain, and feed efficiency as those reported in hormone implants (Allen et al., 2009; Avendano-Reyes et al., 2006; Beckett et al., 2009; Elam et al., 2009; Gruber et al., 2007; Kellermeier et al., 2009; Scramlin et al., 2010). In addition, these compounds have been reported to have profound effects on hot carcass weight, Longissimus muscle area and carcass cutability (Gruber et al., 2007; Hilton et al., 2010; Rathmann et al., 2009; Scramlin et al., 2010; Shook et al., 2009; Vogel et al., 2009). It is because of this that cattle feeders have drastically increased use of beta-agonists since their FDA approval, and a growing portion of the fed cattle population receive a dietary beta-agonist supplement that is provided within the final 20 to 30 days of finishing.

Introduction Supplementary feeding is an essential practice in fish farming operation which accounts for over 60% in total input cost. The dependence of candidate species on balanced supplementary feed increases with increase in stocking population in ponds targeting per hectare higher production as the standing crop of cultured species exceeds the natural feeding capacity of ponds. Therefore, feeding of artificial feed balanced in all nutrients such as protein, lipid, carbohydrate, vitamins and minerals containing optimum protein and energy ratio has assumed foremost importance in aquaculture industry. The use of balanced feed however, is directed towards optimum realization of genetic potentials of farmed species for survival, immunity, growth and reproduction (Mohanty, 2009). Consequent to researches done in India and abroad, a strong data base has been developed about the nutritional behavior of great majority of these cultivable fish and shell fish species and several feed formulations have been successfully undertaken. With optimum pond management, feeding of formulated balanced feed, it has been possible to increase aquaculture production as high as 15- 17 t/ha/yr for carps and 8-12 t/ha/yr in semi intensive prawn and shrimp farming in India (Mohanty, 2009).

Introduction Public concern over use of antibiotics in livestock production has increased in recent years because of their possible contribution to emergence of antibiotic resistant bacteria, and their transmission from livestock to humans. Accordingly, ruminant microbiologists and nutritionists have been exploring alternative methods of favorably altering ruminal metabolism to improve feed efficiency and animal productivity. Plant extracts contain secondary metabolites, such as essential oils (EO) that have antimicrobial properties that make them potential alternatives to antibiotics to manipulate microbial activity in the rumen. Essential oils are naturally occurring volatile components responsible for giving plants and spices their characteristic essence and color. Over the last few years, a number of studies have examined effects of EO, and their active components, on rumen microbial fermentation. However, many of these studies are laboratory based (i.e., in vitro) and of a short-term nature. Nevertheless, results from in vitro batch culture studies provide evidence that EO and their components have the potential to improve N and/or energy utilization in ruminants. Effects of EO on ruminal N metabolism is more likely mediated by their impact on hyper-ammonia producing (HAP) bacteria resulting in reduced deamination of amino acids (AA) and production of ammonia N.

Introduction Plant products have been used for centuries by humans as food and to treat ailments. Natural medicinal products originating from herbs and spices have also been used as feed additives for farm animals in ancient cultures for the same length of time. Keeping farm animals healthy is necessary to obtain healthy animal products. The main scope in animal husbandry is to ensure good performance of farm animals and get quality animal products, which can be achieved only with the effort to keep the animals healthy. Only quality feed together with proper hygiene, potable water and management can ensure the production of nutritious animal products with desired organoleptic properties (Saxena, 2008). A ban of antibiotics as feed additives in animal nutrition is realized since 1986 in Sweden and later on to various countries. A general ban is foreseen in some years from now, because of the increased occurrence of pathogens resistant against therapeutical antibiotics used in animals and humans. With the restricted use or ban of dietary antimicrobial agents we must explore new ways to improve and protect the health status of farm animals, to guarantee animal performance and to increase nutrient availability (Wenk, 2003). In this aspect, herbs and spices are not just appetite and digestion stimulants, but can, with impact on other physiological functions, help to ensure good health and welfare of the animals, what can positively affect their performance.

Introduction Mycotoxins are substances produced by fungal infections which in some cases do protect plants or plant seeds against parasites (Schardl et al., 1996). However, upon ingestion, inhalation or dermal contact, these mold producing substances are poisonous to vertebrates. Even with more than 100,000 species of fungi known, only some of them are active mycotoxin producers. The fungi species which are known to produce the most hazardous mycotoxins in agriculture and in animal production are Fusarium, Aspergillus and Pencillium spp. Mycotoxins vary greatly regarding their toxicological effects as they do not belong to a single class of chemical compounds (Jewers, 1987). The environmental conditions in which they are preferably produced also differ. Fusarium toxins, such as trichothecenes, Zearalenone and fumonisins are commonly produced on the field, whereas aflatoxins and ochratoxins are produced by Aspergillus and Penicillium spp. mainly after harvest and during poor storage conditions.