Additives Used in Feed

Feed Additives With significant potential in animal production, our country utilizes feed additives to improve the quantity of animal products and their compliance with hygiene and quality standards. Feed additives are substances used to increase feed utilization, improve the quantity and quality of animal products obtained, reduce costs, and protect animal health. It is essential that feed additives used in animal nutrition be measurable both in feeds and in the products obtained, so that their effects on human health can be monitored. In recent years, there have been fundamental changes in animal production; particularly the European Union has raised certain modifications regarding feed additives used in the feed industry, taking into account animals, humans, and the environment. The trend toward natural production in animal farming and the shift toward healthy nutrition have sparked discussions about feed additives. In parallel, issues arising from intensive antibiotic use have brought alternative feed additives to the forefront. This article provides information about additives used in feeds.

Introduction

Animal production uses feed additives to improve the quantity, hygienic quality, and compliance with standards of products. Today, consumers show greater sensitivity to potential hazards related to human health, food safety, and environmental protection. Within this framework, issues such as fertilizer use, biotechnological additives and agricultural products, pesticide residues, veterinary medicines, chemical additives, genetically modified products, and processing, preservation, transportation, and storage are being given careful attention. In animal production, the use of additives, which began with the use of antibiotics in the 1940s, has continued to increase to the present day, and many new additives have been produced. In recent years, there have been fundamental changes in animal production; particularly the European Union (EU) has raised certain modifications regarding feed additives used in the feed industry, taking into account the interaction between animals, humans, and the environment.

Despite advances in animal genetics, feed resources are diminishing.

The trend worldwide of removing animal protein sources from rations, the prohibition of using antibiotics as growth-promoting feed additives, and increasing health regulations on meat products are necessitating a new perspective on animal production. The healthiness of animal food products presented to human consumption is closely related to the feed consumed by animals. In the EU, strict attention is paid to food and feed safety in order to protect human and animal health. For reliable feed production, work continues in the European Feed Manufacturers Federation (FEFAC) and the EU Commission to establish international standards for animal feeds (Codex Alimentarius), implement and promote Hazard Analysis and Critical Control Points (HACCP) principles and Good Manufacturing Practice, and implement these standards. In our country, HACCP application has been made mandatory in food-producing companies according to EU harmonization requirements. HACCP is a preventive and protective system established to identify and control hazards that may arise at any stage in a facility, enabling food to be controlled and monitored from raw materials through processed product to the point of consumption. In animal production facilities, feed and premix plants, this system monitors all links from feed producers and farms to consumers, providing the possibility of clearly tracking food throughout the production phase. As of 2017 in our country, in the compound feed sector, within the approval scope there are 322 facilities producing compound feed for food animals, 108 producing their own feed, 15 producing feed additives, and 100 producing premixes; within the registration scope there are 193 facilities producing compound feed for food animals, 443 producing their own feed, 23 producing block mineral feed (lick blocks), and 28 producing feed additives and premixes. In the compound feed sector, as of 2016, a total of 20,401,852 tonnes of compound feed were produced, with 4,566,237 tonnes as broiler feed, 2,958,232 tonnes as layer feed, 3,827,073 tonnes as beef cattle feed, 5,840,262 tonnes as dairy cattle feed, and 3,210,048 tonnes as other compound feeds (Agricultural Statistics 2017). In the compound feed industry, feed additives are used alongside basic raw materials. Feed additives are generally obtained from abroad in pure, concentrated, or premix form by factories producing compound feed or by companies trading in feed additives.

Feed additives imported as pure or concentrated forms are diluted to specified ratios with suitable carriers in premix production facilities before use.

Feed additives can be added to compound feeds as single-additive premixes with a carrier substance, as mixtures containing multiple active substances, as special premixes such as vitamin concentrates, as compound premixes consisting of mixtures of vitamin-trace mineral or amino acids, or as mineral or complementary feed containing macro and trace elements. Feed additives used at significant levels and for various purposes in poultry compound feeds are used at lower levels in cattle and small ruminant compound feeds, mainly as vitamin-trace element premixes. In recent years, the increasing trend toward natural production and consumption has sparked discussions about feed additives. Additionally, due to problems arising from intensive antibiotic use, the use of alternative feed additives has come to the forefront. Within these alternative searches, natural products that could effectively and economically replace growth-promoting substances have gained importance. This article provides information about feed additives used in animal feeds.

Definition, Classification, and Properties of Feed Additives

A feed additive is an organic or inorganic substance added to feeds to ensure optimal nutrient consumption in safety, increase animal product quantity, improve feed utilization by aiding digestion and metabolism, protect animal health, positively affect the quality of animal products, facilitate feed preparation and storage, or provide economic benefit in another way. Although used at very low levels in compound feeds, their effectiveness and importance are considerably higher. For additives to be used, they must comply with the following conditions: 1. Must be completely safe for human and animal health and have no toxic or carcinogenic effects, 2. Must not adversely affect the composition and technological properties of animal products, 3. Their quantities in feed and products obtained from animals consuming this feed must be analytically determinable, 4. Must effectively and economically improve performance, 5. Must be safe for the environment, biodegradable, and must not pollute the environment, 6. Their effectiveness and stability must be established, 7. Must not cause cross-resistance with other additives, 8. Must not corrode equipment or cause corrosion, 9. Must be readily available. In our country, the Notification on Production, Import, Export, Sale, and Use of Feed Additives and Premixes (Notification No: 2005/1) defines feed additive as "substances that, when added to feeds or water, provide the effects specified below" and lists the relevant effects as follows: 1. Have a positive effect on feed characteristics. 2. Have positive effects on the properties of animal products. 3. Positively affect the color of ornamental fish and birds. 4. Meet the nutrient requirements of animals. 5. Make positive contributions to the environmental consequences of animal production. 6. Improve animal production performance and animal welfare, particularly through effects supporting the digestive system or digestion. 7. Have anticoccidial or histomonostatic effects. Today, numerous additives are used in animal nutrition. Table 1 provides a list of feed additives approved by the Ministry of Food, Agriculture and Livestock.  

1. Technological Additives Preservatives

These are substances that enable feeds to be stored for long periods without spoilage. To protect feeds from the effects of microorganisms, organic acids such as fumaric acid, lactic acid, acetic acid, propionic acid, sorbic acid, formic acid, benzoic acid, citric acid, acetic acid, malic acid and gluconic acid and their salts are commonly used. These substances have growth-promoting and feed utilization-improving effects by controlling microorganism populations in the intestinal tract, protection against microbiological spoilage, increased digestibility of feed in the intestines, and animal health-protective effects. Organic acids also regulate rumen fermentation and reduce methane formation. They are used by adding to feed or water (Van Dam, 2006). Sodium bisulfate, sodium sorbate, potassium sorbate, calcium sorbate, sodium bisulfite, sodium propionate, calcium propionate, potassium propionate, ammonium propionate, sodium citrate, potassium citrate, calcium citrate, L-tartaric acid, sodium L-tartrate, potassium L-tartrate, potassium sodium L-tartrate, orthophosphoric acid, hydrochloric acid, and sulfuric acid are among the substances used as preservatives in feeds.

Antioxidants

They are added to prevent oxidation and deterioration of fats and feed spoilage. Some antioxidants are synthetic, others are natural products. In recent years, the use of natural products is increasing. Some substances used for this purpose include tocopherols (vitamin E), ascorbic acid (vitamin C), propyl gallate (PG), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), butylated hydroxyl quinone (BHQ), citric acid, some amino acids, ethylenediaminetetraacetic acid (EDTA), phospholipids, phenols, and quinones. In recent years, the use of certain aromatic plants (sage, rosemary, bay leaf, clove, thyme, cumin, mint, cinnamon, etc.) as antioxidants has come under consideration. The antioxidant activity of aromatic plants is related to phenolic compounds such as flavonoids, phenolic acids, and phenolic terpenes in their structure (Javanmardi et al. 2003).

Emulsifiers

These are substances that form or maintain a homogeneous mixture of two or more immiscible phases contained in feed composition. They are used to ensure homogeneous distribution of fat added to feed to increase energy. The most commonly used substance for this purpose is lecithin.

Stabilizers

These are substances that maintain the physico-chemical properties of feed materials. They are used to increase the durability of vitamins, essential amino acids, and certain medicines added to feed at very low levels. Antioxidants and substances such as gelatin can be used for this purpose.

Gelling Agents

These are substances that increase the viscosity of feed materials and impart consistency to feeds for gel formation. Some of the emulsifiers, stabilizers, consistency increasers, and gelling agents include lecithin, glycerin, calcium alginate, agar, carrageenan, locust bean gum, tamarind seed, guar gum, tree gum, acacia gum (gum arabic), xanthan gum, gellan gum, sorbitol, mannitol, polyoxyethylene (20)-sorbitan monolaureate, polyoxyethylene (20)-sorbitan monooleate, polyoxyethylene (20)-sorbitan tristearate, microcrystalline cellulose, cellulose powder, methylcellulose, ethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, ethylmethylcellulose, stearyl 2-lactic acid, sodium stearyl 2-lactilate, calcium stearyl 2-lactilate, stearyl tartrate, glyceryl polyethylene glycol ricinoleate, dextrans, polyethylene glycol esters of fatty acids from soybean oil, sorbitan monostearate, and Chinese cinnamon gum.

Binders

These are substances that increase the binding tendency of feed particles.

Anti-caking Agents

They reduce the tendency of feed particles to bind to each other.

Coagulants

They cause liquid raw materials to thicken into a semi-solid clotted state. Binders, anti-caking agents, and coagulants include sodium ferrocyanide, citric acid, synthetic calcium aluminates, potassium ferrocyanide, colloidal silica, kieselguhr (diatomaceous earth, pure), calcium silicate, sodium aluminosilicate, bentonite-montmorillonite, asbestos-free kaolinitic clay, asbestos-free natural chlorite and steatite mixtures, vermiculite, sepiolite, sepiolitic clay, asbestos-free hydrated magnesium silicate, lignosulfonates, natrolite-phonolite, volcanically-derived clinoptilolite, and perlite.

Radionuclide Contamination Protectants

These are substances that suppress the absorption or increase the excretion of radionuclides. Ferric (III) ammonium hexacyanoferrate (II) and bentonite are used for this purpose.

Acidity Regulators

These are substances that regulate the pH value of feeds. For this purpose, sodium bisulfate, dL and L-malic acid, benzoic acid, potassium dihydrogen orthophosphate, dipotassium hydrogen orthophosphate, tripotassium orthophosphate, ammonium dihydrogen orthophosphate, diammonium hydrogen orthophosphate, sodium dihydrogen diphosphate, sodium sesquicarbonate, potassium hydrogen carbonate, ammonium carbonate, ammonium hydrogen carbonate, hydrochloric acid, ammonium chloride, sulfuric acid, sodium hydroxide, and potassium hydroxide are used.

Silage Additives

Enzymes, microorganisms, and organic acids added during the preparation of silage feeds to improve silage formation are additives in this group. Amylase (from Aspergillus oryzae), alpha-amylase (from Bacillus subtilis), betaglucanase (from Aspergillus niger), cellulase (Trichoderma longibrachiatum), and xylanase (Trichoderma longibrachiatum) are enzymes used. Microorganisms used in silage production include Bacillus subtilis, Enterococcus faecium, Lactobacillus brevis, Lactobacillus buchneri, Lactobacillus casei, Lactobacillus cellobiosus, and Lactobacillus paracasei. In silage feeds, organic acids and chemicals such as potassium sorbate, formic acid, sodium formate, propionic acid, sodium propionate, ammonium propionate, sodium benzoate, formaldehyde, hexamethylene tetramine, sodium nitrite, and sodium bisulfate are also used.

2. Sensory AdditivesColorants

When used in animal nutrition, they are substances that impart color to animal food products. They are commonly used in the poultry sector to improve the color of chicken meat and eggs. For this purpose, plant sources containing color substances at various levels such as yellow corn, alfalfa, corn gluten, marigold, and red pepper, carotenoids such as lutein, zeaxanthin, capsanthin, and lycopene extracted from natural sources, and various synthetic sources such as β-apo-8'-carotenal, β-apo-8'-carotenoic acid ethyl ester, and canthaxanthin are used. Substances such as acid brilliant green, allura red, bixin, brilliant black, caramel colours, carmine, chlorophyllin copper complex, erythrosine, indigotin, iron oxide red, black, yellow, patent blue, titanium dioxide, tartrazine, and sunset yellow that impart or regulate color in ornamental fish and bird feed materials are also used.

Flavor Enhancers and Appetite Stimulants

These are substances added to feeds to increase palatability and consumption. In addition to natural sources such as anise seed, ginger, and fenugreek, flavors such as saccharin, monosodium glutamate, and vanillin can be added to feeds for this purpose.

3. Nutritional AdditivesVitamins, Provitamins, Chemically Equivalent Substances, Trace Elements, Amino Acids

Amino acid salts and analogs are added to feeds to meet animal nutrient requirements. For this purpose, vitamins and minerals such as vitamin A, vitamin D3, vitamin E, vitamin K3, vitamin B1, vitamin B2, vitamin B6, B12, niacin, Ca-D pantothenate, folic acid, D-biotin, choline chloride, manganese, iron, zinc, copper, cobalt, iodine, and selenium, as well as amino acids such as L-Lysine and DL-Methionine are added.

Urea and Derivatives

They are generally added to ruminant rations as a protein source. The most commonly used compounds include urea, biuret, urea-phosphate, and diureido isobutane.

4. Zootechnical AdditivesDigestion Regulators

When used in animal nutrition, they are substances that improve feed digestion by affecting target feed materials.

Intestinal Flora Stabilizers

Microorganisms with positive effects on intestinal microflora or other substances with defined chemical properties are included in this group of additives. Enzymes, probiotics, prebiotics (oligosaccharides), essential oils, and plant extracts are used to regulate digestion and intestinal microflora. These additives show multifunctional effects.

Enzymes

These are additives used to increase utilization of difficult-to-digest feeds. For this purpose, proteases, lipases, phytases, pectinase, amylase, cellulase and other polysaccharidases produced from various fungi such as Trichoderma reesei, Trichoderma viride, and Aspergillus niger, or from Bacillus subtilis—particularly for the breakdown in the intestinal environment of polysaccharides not digested by poultry, thereby improving the energy value of feeds—has become a common practice. Some enzymes in the cellulase group (cellulase, xylanase, endoglucanase, exoglucanase), amylase, and proteases are also used to contribute to rumen digestion and improve performance.

Probiotics

These are feed additives that, when administered to animals, show antagonistic effects against pathogenic microorganisms in the intestines, create beneficial effects on intestinal microflora, and include non-pathogenic gram-positive and facultative anaerobic, lactic acid-producing live natural intestinal bacteria, yeast cultures and cells, fungi, enzymes, and industrial fermentation by-products (Pal, 1999). The microorganisms most commonly used in probiotic production are lactic acid-producing bacteria of the Lactobacillus and Streptococcus genera. Additionally, yeasts such as Saccharomyces cerevisiae and fungi such as Aspergillus niger and Aspergillus oryzae are also commonly used in commercial probiotic production.

Prebiotics (Oligosaccharides)

These are indigestible, non-living feed additives that increase the number and activity of beneficial bacteria living in the intestines and positively affect animal health. The most commonly used prebiotics are mannanoligosaccharides, fructooligosaccharides, chitosan oligosaccharides, and beta-glucans.

Plant Extracts

Plant extracts or essential oils, which have come to the forefront in recent years due to their natural origin, have antimicrobial activity and properties that promote growth and improve feed utilization. The positive effects of plant extracts are particularly evident in their ability to suppress pathogenic microorganisms in the digestive organs, prevent toxin development in feeds, increase the activity of digestive enzymes, strengthen the immune system, and improve performance. Aromatic plants such as thyme, rosemary, sage, clove, bay leaf, cinnamon, cumin, coriander, ginger, mustard, garlic, and mint, along with their extracts and oils, are used as additives.

Additives with Positive Environmental Effects

Substances used to reduce methane gas formation in ruminants and the phytase enzyme, which shows effects that increase utilization of phytate phosphorus in poultry, can be counted. Abundant methane production by microorganisms in the rumen results both in loss of feed energy as methane gas and in pollution due to methane released into the atmosphere. To prevent methane production, liquid oils, chloral, hemiacetal products of starch, and halogenated compounds (methylene tetrachloride, bromochloromethane), as well as antibiotics such as lasolosid and monensin, are used. Another additive effective in this regard is phytase, particularly used to increase utilization of phytate phosphorus in poultry. In addition to increasing utilization of plant-derived phosphorus, phytase helps reduce phosphorus pollution of groundwater and soils by reducing the phosphorus excreted with manure.

Other Zootechnical Additives: Toxin Binders

They are used to prevent mold growth in feeds. For this purpose, organic acids (propionic, sorbic, benzoic, and acetic acids), organic acid salts (such as calcium propionate and potassium sorbate), organic dyes, copper sulfate, and compounds such as ammonia are used. Adsorbent substances such as polyvinylpolypyrrolidone polymers, aluminum silicate compounds, activated charcoal, hydrated sodium calcium aluminosilicate, bentonite, perlite, diatomaceous earth, and zeolite are used as toxin binders in feeds (Pasha et al., 2008). Mannanoligosaccharides and glucomannan also function as toxin binders.

Buffer Substances

These substances are generally used to prevent rumen pH declines resulting from high-level concentrated feed use in ruminants. In recent years, sodium bicarbonate has become commonly used for this purpose. In addition, buffer substances such as various salts of volatile fatty acids, phosphate salts, ammonium chloride, and sodium sulfate are also used.

Chitosan

Chitosan, a product obtained by deacetylation of chitin, a biopolymer found in arthropods (crabs and shrimp) that resembles cellulose, is non-toxic, and is biologically available, is thought to have effects on digestibility, growth performance, energy and protein utilization, and rumen fermentation (Goiri et al., 2009).

Beta-glucans

They strengthen the immune system and show antitumor and antimicrobial effects (Leung et al., 2006). Lignin, a high molecular weight phenolic compound, when purified and used as an additive in poultry feeds, shows effects similar to prebiotics and has positive effects on animal health (Baurhoo et al., 2008).

5. Coccidiostats and Histomonostats

These are substances used to protect poultry from coccidiosis (bloody diarrhea) caused by Eimeria species protozoa that colonize the intestines of poultry. Among the preparations used to prevent coccidiosis are lasolasid, monensin, salinomycin, robenidin, naracin, maduramisin, and halofuginone. Feed containing coccidiostats and histomonostats must discontinue use 3 to 7 days before slaughter of animals, depending on the preparation. In other words, feed should not contain coccidiostats before slaughter.

Conclusion and Recommendations:

The following recommendations can be made regarding matters that should be given attention to the proper use of feed additives in our country (Kırkpınar, 2011): 1. In addition to informing producers about the effective use of additives, HACCP implementation should be established in feed factories to ensure traceability of the mixture in production stages; after production of premixes or feeds containing risky additives, production equipment should be checked and cleaned; production should guarantee avoidance of cross-contamination with different products being produced in the correct order; appropriate and approved production equipment should be used, and employees should be trained. Feed factories should inform producers about the special conditions of the feed, which additives are present in the feed, and how it should be stored. 2. Feed additives must be tested in official research institutions in terms of active ingredient content or activity before being marketed in our country. 3. Antibiotics, hormones, and similar stilbene group compounds imported under different names or illegally should be subject to stricter controls and illegal use should be prevented. 4. Careful attention should be paid to the use of feed containing no additives before slaughter. 5. In our country, feed additives approved by the EU are freely imported, produced, and offered for sale. However, the results of research to be conducted under our country's conditions should be taken into account regarding the usage levels and maximum residue limits of these additives. 6. As a dynamic and continuously developing sector, new technologies should be monitored in the feed and feed additive industries and transferred to applications. 7. Storage and transport of feed additives and feeds should be carried out properly. 8. Our food consumption profile should be determined, and maximum residue levels of additives and chemical contaminants should be established through epidemiological, toxicological, and allergenic studies, and screening studies should be conducted to monitor the proportions to which people are affected by these hazards. 9. Good agricultural practices should be promoted in our country, and databases should be created for effective risk management in risk situations. 10. Companies importing additives should be encouraged in research and development matters, should be supported in establishing their own research laboratories, and should be enabled to collaborate with universities and research institutions. 11. Research and development work should be rapidly promoted to produce feed additives from domestic sources in our country and reduce foreign dependence; using domestic sources, biotechnological feed additives should be encouraged to be produced, particularly by evaluating food industry waste, and the country should quickly transition from an importer position to a producer position. In conclusion, it should be borne in mind that in our country, there is still insufficient infrastructure and laboratory network capable of conducting research and inspection on the long-term effects of additives on animals, people consuming animal products, and the environment. The risks that additives used without establishing safe limits and without remedying inspection deficiencies will create in the future should not be ignored.   Prof. Dr. Figen Kırkpınar Ege University Faculty of Agriculture Department of Animal Science

References: 1. Baurhoo, B., Ruiz-Feria, C.A., Zhao, X. 2008. Purified lignin: nutritional and health impacts on farm animals. Anim. Feed Sci. and Tech. 144:175-184. 2. Goiri, I., Garcia-Rodriguez, A., Oregui, L.M. 2009. Effects of chitosans on in vitro Rumen digestion and fermentation of maize silages. Anim. Feed Sci. and Tech., 148:276-287. 3. Hayvan Beslemede Kullanılan Yem Katkı Maddeleri Hakkında Yönetmelik,T.C. Gıda, Tarım ve Hayvancılık Bakanlığı, Resmî Gazete:18.7.2013 Sayı: 28711. 4. Hayvan Beslemede Kullanılan Kullanımına İzin Verilen Yem Katkı Maddeleri Kayıt Listesi, T.C. Gıda, Tarım ve Hayvancılık Bakanlığı, Güncellenme Tarihi: 08.02.2017. 5. Javanmardi, J., Stushnoff, C., Lcke, E., Vivanco, J.M. 2003. Antioxidant activity and total phenolic content of Iranian Acimum Accessions, Food Chemistry, 83:547-550. 6. Kırkpınar, F. 2011. Hayvan Beslemede Yem Katkı Maddeleri Kullanımı, Gelişmeler, Sorunlar Ve Çözüm Önerileri. Uluslararası KatılımlıI. Ali Numan Kıraç Tarım Kongresi ve Fuarı, 27-30 Nisan, 2011, Eskişehir, 1527-1541 (Tam metin-sözlü bildiri). 7. Leung, M.Y.K., Liu, C., Koon, J.C.M., Fung, K.P. 2006. Polysaccharide biological response modifiers. Immunology Letters, 105:101- 114. 8. Pal, P.U.C. 1999. Probiotics benefits. Poultry International, 38,12:40-42. 9. Pasha, T.N., Mahmood, A., Khattak, F.M., Jabbar, M.A. Khan, A.D. 2008. The effect of feed supplemented with different sodium bentonite treatments on broiler performance. Turk. J. Vet. Anim. Sci. 32 (4):245-248. 10. Tarım İstatistikleri 2017. T.C. Gıda, Tarım ve Hayvancılık Bakanlığı Koruma ve Kontrol Genel Müdürlüğü. 11. van Dam, H. 2006. Organic acids and their salts. Feed Mix. 14 (4):28-31. 12. Yem Katkı ve Premikslerin Üretimi, İthalatı, İhracatı, Satışı ve Kullanımı Hakkında Tebliğ, (Tebliğ No:2002/66) Resmî Gazete:18.12.2002 Sayı:24967.