Feed additives

(Feed additives include performance-enhancing antibiotic growth promoters, many coccidiostats, binding agents and enzymes.)

Feed additives include:

·         Technological additives – e.g. preservatives, antioxidants, emulsifiers, acidity. ...

·         Sensory additives – e.g. flavours, colourants.

·         Nutritional additives – e.g. vitamins, amino acids, trace elements.

·         Zootechnical additives – e.g. digestibility enhancers.

·         Coccidiostats and histomonostats.

Feed additives are products used in animal nutrition to achieve an effect on the feed itself, on the animals, on food products obtained from the animals consuming the feed additive, or on the environment. For instance, feed additives are used to enhance flavour of feed, to meet the need for certain nutrients or to increase the performance of animals in good health.

They are used in feed for food-producing animals and in pet food.

Feed additives include:

Technological additives – e.g. preservatives, antioxidants, emulsifiers, acidity. Regulators, silage additives.

Sensory additives – e.g. flavours, colourants.

Nutritional additives – e.g. vitamins, amino acids, trace elements.

Zootechnical additives – e.g. digestibility enhancers.

Coccidiostats and histomonostats.

Feed additives may not be put on the market unless they have been authorised following a scientific evaluation carried out by EFSA demonstrating that the additive has no harmful effects on human and animal health and on the environment.

Feed additives represent various classes of molecules, compounds, or organisms that promote ingestion, absorption, assimilation of nutrients, growth, and health. They affect physiological processes, such as immune function, stress resistance, and reproduction. Feed additives include feeding attractants, immunostimulants, prebiotics, probiotics, acidifiers, essential oils, or other inclusions. These additives are usually not required nutrients.

Feed attractants enhance the ingestion of feeds. Natural feed attractants have been characterized in many sea urchin species, and their efficacy in feeds has been reviewed by Lawrence et al. (Chapter 9). Sea urchins can show feeding preferences due to the presence of attractants, resulting in increased feed intake. This would be particularly important in formulated diets, where some ingredients (nutrients) are water-soluble or are expensive, and rapid ingestion is highly desirable. Immunostimulants have received minimal attention. Beta-glucans are presumed immunostimulants in most aquatic organisms (Soltanian et al., 2009). Laminarin increased embryo survival in S. intermedius, but the exposure was waterborne and not dietary (Kiseleva et al., 2008). Vitamins and minerals often promote an immune function, but these are not considered immunostimulants as they function primarily to assist normal immune reactions. Although an adaptive immune response is not seen in the Echinodermata (Silva, Chapter 13), stimulation of phagocytic activity by coelomocytes (innate immune response) may be improved by immunostimulants.

Prebiotics, such as acidifiers, essential oils, probiotics, and antibiotics are all feed additives that optimize the gut flora of fish and shrimp, enhance the immune response, increase stress resistance, promote animal and gut health, and increase digestion and nutrient availability (Anuta et al., 2011). Molecules and compounds stimulating a positive response of gut microflora and probiotics (gut microflora enhancing a biological response) have not been evaluated as feed additives in sea urchins.

·     1    Enzymes

·      2   Pro/Prebiotics

·    3     Antioxidants

·       4  Antibiotic growth promoters

 This chapter discusses the role, need, and use of different feed additives used in the diet of food-producing animals.

Feed additives are minor components of the animal ration and are used for improving the quality/digestibility of feed and the nutritive and aesthetic quality of food or improving animal performance and health.

Some of the most commonly used feed additives in animal rations include enzymes, pro- and prebiotics, antioxidants, antibiotic growth promoters, and coloring agents. Overall, these different ingredients are aimed at enhancing digestibility or availability of bound nutrients (e.g., enzymes), improving animal gut health (e.g., pro/prebiotics) and food product quality (e.g., antioxidants), reducing nutrient loss (e.g., phosphorus, nitrogen), and promoting environmental protection. Enzymes

Exogenous enzymes are commonly added to the diet of monogastric animals as a means to reduce the antinutritional effects of the feed. Cereal grains and plant-based byproducts are the major components of the ration. Several nutrients present in these products are in a “bound” form, meaning that monogastric animals do not have the enzymes to digest and release the nutrients to make them available to the animal. Phytate phosphorous and nonstarch polysaccharides (NSP) are the two major antinutrients present in feed.

Phosphorus (P) in cereal grains are present as phytic acid (myo-inositol hexakisphosphate), the primary phosphate storage compound in seeds. Typically, phytic acid contributes 50% to 80% of the total phosphate in plant seeds.

More than 50% to 80% of phosphorus (P) in the feed is present as phytic acid and is not available to the monogastric animals.

The salt form of phytic acid is called phytate, and almost all phytic acid (Figure 19.1) is present as a mixed salt (phytin). Phytate P is poorly available to monogastric animals due to the lack of endogenous enzymes and can reduce the digestibility of other nutrients, affecting growth and performance

Microbial phytase is the most commonly used exogenous enzyme in the feed for monogastric animals. Phytase (myo-inositol hexakisphosphate phosphohydrolase) catalyzes the stepwise removal of phosphate from phytic acid or its salt phytate. Phytase can reduce the antinutritional effect of phytate and improve the digestibility of phosphorous (P), calcium, amino acids, and energy, as well as reduce the negative impact of inorganic P excretion to the environment. Phytase efficacy varies among feedstuffs due to phytate solubility. Overall, the efficacy of exogenous phytase enzymes is affected by both feed (source of enzymes, solubility, particle size) and animal (gut pH, retention time) factors

NSPs are plant cell wall components and are the other major antinutrients present in cereal grains and oil seeds.

NSPs are a major part of fiber (fiber is the sum of NSP and lignin) and are regarded as feed components that are either poorly digested or have antinutritive properties. NSPs include water-soluble and insoluble components such as cellulose, lignin, arabinoxylan, glucan, and oligo- and polysaccharides containing different sugars such as arabinose, galactose, rhamnose, and mananose. The common NSP in rye and wheat are arabinoxylans, while barley and oats contain a high level of mixed-linked β-glucan (3%–4%; Figure 19.2).

Figure 19.2. Nonstarch polysaccharides in wheat S

Carbohydrate-degrading enzymes act on complex carbohydrates and degrade them to smaller polymers and are used in monogastric animal diets high in NSP (e.g., wheat, barley, rye).

Pro/prebiotics

The term pro/prebiotics is used to designate organisms and or substances that contribute to healthy microbial balance in the intestine and include both living organisms and nonliving substances. Promoting favorable gut microflora is important especially when antibiotic growth promoters (AGPs) are phased out from animal feeds. Probiotics help prevent and control gastrointestinal pathogens and/or improve the performance and productivity of production animals through various mechanisms. Healthy microbial populations in the gastrointestinal (GI) tract are often associated with enhanced animal performance, reflecting more efficient digestion and improved immunity.

Pro/prebiotics function through enhancing the healthy microbial population of the gut.

Probiotics are live microorganisms and are of bacterial and nonbacterial origin. With the exception of certain yeast and fungal probiotics, most of the microorganisms used are of bacterial origin. Examples of bacterial probiotics are several species of Lactobacillus, Bifidobacterium, Bacillus, and Enterococcus. Nonbacterial (yeast or fungal) probiotics include Aspergillus oryzae, Saccharomyces and Candida pintolopesii.

Supplementation of probiotics has been shown to increase the population of beneficial microorganisms, such as Lactobacilli and Bifidobacteria. These healthy bacterial colonies then inhibit the growth of harmful microorganisms by producing substances (e.g., bacteriocins and/or organic acids) and by competitive exclusion. Thus probiotics serve as an alternative to antibiotic feed additives to manage and reduce pathogen load by reducing intestinal colonization and spread of other enteric pathogens. Probiotics have been shown to be effective in reducing postweaning diarrhea in piglets and morbidity and mortality in pigs.

Prebiotics are nondigestible functional ingredients that selectively stimulate the growth of favorable bacteria in the gut of the host (food for the good microbes). Prebiotics are classified as disaccharides, oligosaccharides, and polysaccharides, and most commonly used prebiotics include lactulose, mannan-oligosaccharide (MOS), inulin, and fructooligosaccharides (FOS).

Prebiotics are nondigestible ingredients that serve as “food for the good microbes.”

Symbiotics may be defined as a mixture of probiotics and prebiotics that beneficially affects the host by improving the survival and implantation of health-promoting microbes in the gastrointestinal tract.

Antioxidants

With the advent of rations containing a high level of animal and vegetable fats, the requirement for antioxidant protection has become very apparent. Oxidation occurs in feeds and feedstuffs, resulting in the rancidity of fats and destruction of vitamins A, D, and E and amino acids, resulting in lowered energy values for the diet. Antioxidants are added in animal diets to improve the quality of feed and to increase shelf life. Antioxidants are of two types, natural and synthetic products. These products have the ability to prevent or terminate free radical production thereby providing protection against reactive oxygen species. Through these processes, antioxidants minimize rancidity of oils while enhancing shelf life along with feed quality.

Adding antioxidants to feed is an effective way of enhancing freshness and increasing shelf life.

Natural antioxidants include tocopherols, followed by other aromatic plant extracts (e.g., rosemary extract) and essential oils. The natural form of vitamin E is RRR-α-tocopherol. Synthetic vitamin E consists of a mixture of different stereoisomers and is called all-racemic-α-tocopherol or all-rac-tocopherol. One IU of vitamin E is equal to 1 mg of all-rac-α-tocopherol acetate. In the feed industry, vitamin E is available commercially as all-rac-α-tocopherol acetate and RRR-α-tocopherol acetate.

Other synthetic compounds with antioxidant properties include ethoxyquin (generic term for 1,2-dihydro-6-ethoxy-2,2,4-trimethylquinoline), butylhydroxytoluene (BHT), and butylhydroxyanisole (BHA). Ethoxyquin, however, has been demonstrated to be the most efficacious, followed by BHT and BHA.

Antibiotic Growth Promoters

Antibiotic growth promoters (AGPs) are substances administered at a low subtherapeutic dosage in the feed to destroy or inhibit bacterial growth and enhance performance.

Several other biological and chemical substances are used to improve animal production performance.

Antibiotics are not the only substance added to animal feeds. Anabolic steroids and β-agonists have been largely used in intensive meat production to improve nutrient availability and lean meat deposition in food animals. The recombinant bovine somatotropin (rBST) has been used to enhance milk production in the dairy industry. β-agonists (cimaterol) are a class of substances that act on adrenergic receptors with anabolic effects in animals. Anabolic steroids enhance lean meat deposition and muscle protein accretion and metabolize fat stores, resulting in increased lean growth rates and are used in animal production systems to increase growth rate, feed efficiency, and carcass leanness. Anabolic feed additives have been banned in the European Union; however, in the United States, two hormones are approved as feed additives: melengestrol acetate for feedlot heifers and ractopamine for swine.

Feeding AGP is prohibited in the European Union. Many countries regulate, but do not prohibit, their use for growth promotion in animals.

Others

In addition to the major additives listed previously, there are several other minor ingredients included in the feed depending on species, types of feed, and market. These include natural or synthetic pigmenters to enhance egg yolk and broiler skin color (e.g., carophyll, lutein, zeaxanthin), mold inhibitors to prevent mold growth (e.g., organic acids), mycotoxin binders that bind to the mycotoxins and prevent them from being absorbed, coccidiostats to prevent coccidiosis (protozoan infection in poultry), and pellet binders to reduce feed dust and help pellets adhere better.

Key Points

List of Feed additives:

Prevention of deterioration of feed quality

1 Antioxidants : Ethoxyquin, Dibutylhydroxytoluene, Butylhydroxyanisol

2 Mold Inhibitors: Propionic Acid, Calcium Propionate, Sodium Propionate

3 Thickeners: Sodium Alginate, Sodium Caseinate, Sodium Carboxylmethyl Cellulose, Propylene Glycol, Sodium Polyacrylate

4 Emulsifiers: Glycerin Fatty Acid Ester, Sucrose Fatty Acid Ester, Sorbitan Fatty Acid Ester, Polyoxyethylene Glycerol Fatty Acid Ester, Polyoxyethylene Sorbitan Fatty Acid Ester

5 Adjusters: Formic Acid

Supplementation of nutritional components and other active ingredients in feed:

Amino Acids: Aminoacetic Acid, DL-Alanine, L-Arginine, L-Lysine Monohydrochloride, L-Carnitine, Guanidinoacetic Acid, Monosodium L-glutamate, Taurine, 2-deamino-2-hydroxymethionine, DL-Tryptophan, L-Tryptophan, L-Threonine, L-Valine, DL-Methionine, L-Methionine, L-Lysine sulphate

Vitamins: L-Ascorbic Acid, Calcium L-Ascorbate, Sodium L-Ascorbate, Sodium-Carcium-L-Ascorbic acid-2-phosphate ester, L-Ascorbic acid-2-phosphoestermagnesium, Acetomenaphthone, Inositol, Dibenzoyl Thiamine Hydrochloride, Ergocalciferol, Choline Chloride, Thiamine Hydrochloride, Pyridoxine Hydrochloride, β-Carotene, Cholecalciferol, DL-α-Tocopherol Acetate, Cyanocobalamin, Thiamine Mononitrate, Nicotinic Acid, Nicotinamide, p-Aminobenzoic Acid, Calcium D-Pantothenate, Calcium DL-Pantothenate, d-Biotin, Vitamin A Powder, Vitamin A Oil, Vitamin D Powder, Vitamin D3 Oil, Vitamin E Powder, 25-Hydroxycholecalciferol, Menadione Dimethylpyrimidinol Bisulfite, Menadione Sodium Bisulfite, Folic Acid, Riboflavin, Riboflavin Tetrabutyrate

Minerals:

Potassium Chloride, Ferric Citrate, Calcium gluconate, Iron and Sodium Succinate Citrate, Magnesium oxide, Aluminum Hydroxide, Zinc Carbonate, Cobaltous Carbonate, Sodium Bicarbonate, Magnesium Carbonate, Manganese Carbonate, Zinc bis(2-hydroxy-4-metylthio butyrate), Copper bis (2-hydroxy-4-methylthio butyrate), Manganese bis (2-hydroxy-4-methylthio butyrate), Ferrous DL-Threonate, Calcium Lactate, Ferrous Fumarate, Zinc Peptide, Iron Peptide, Copper Peptide, Manganese Peptide, Potassium Iodide, Potassium Iodate, Calcium Iodate, Zinc Sulfate,Exsiccated, Zinc Sulfate, Zinc Methionine Sulfate, Cobaltous Sulfate,Exsiccated, Cobaltous Sulfate, Ferrous Sulfate,Exsiccated, Copper Sulfate,Exsiccated, Copper Sulfate, Sodium Sulfate,Exsiccated, Magnesium Sulfate,Exsiccated, Magnesium Sulfate, Manganese Sulfate, Dipotassium Hydrogen Phosphate,Exsiccated, Disodium Hydrogen Phosphate,Exsiccated, Potassium Dihydrogen Phosphate,Exsiccated, Sodium Dihydrogen Phosphate,Exsiccated, Sodium Dihydrogen Phosphate

Synthetic Antimicrobials ((annotation 1):

Amprolium plus Ethopabate, Amprolium plus Ethopabate and Sulfaquinoxaline, Morantel Citrate, Nicarbazin, Calcium Halofuginone Polystyrenesulfonate

Antibiotics(

Zinc Bacitracin, Avilamycin, Enramycin, Salinomycin Sodium, Semduramicin Sodium, Narasin, Nosiheptide, Bicozamycin, Flavophospholipol, Monensin Sodium, Lasalocid Sodium

Flavours(1): Flavour

Sweeteners: Saccharin Sodium

Enzymes:

Amylase, Alkaline Protease, Xylanase, Xylanase and Pectinase Complex, β-Glucanase, Acid Protease, Cellulase, Cellulase,Protease and Pectinase Complex, Neutral Protease, Phytase, Muramidase, Lactase, Lipase

Probiotics:

Enterococcus faecalis, Enterococcus faecium, Clostridium butyricum, Bacillus coagulans, Bacillus subtilis, Bacillus cereus, Bacillus badius, Bifidobacterium thermophilum, Bifidobacterium pseudolongum, Lactobacillus acidophilus, Lactobacillus salivarius

 Organic Acid: Fumaric Acid, Sodium gluconate, Calcium formate, Potassium diformate