PhD, PAS Hooge Consulting Service, Inc.
Eagle Mountain, UT
U.S.A.
Antibiotic use declining
Dr Paula Fedorka-Cray with NARMS, USDA, stated at the 2001 Maryland Nutrition Conference that about 64% of antimicrobials used in the U.S. in 2000 went to humans and 36% to animals. Of animal antimicrobials, 73% were subtherapeutic and 27% were therapeutic. The figures are debatable but the best estimates at present (Hooge, 2001). The Animal Health Institute (2003) reported that sales of animal feed additives to prevent disease, enhance growth, and improve feed efficiency (not including vitamins, minerals, or nutritional supplements) in the U.S. dropped 10% in 2002, with projected sales of $557 million in 2002 compared to $618 million in 2001. This was the result of competition from generic drugs, financial difficulties in the poultry sector, and poultry companies voluntarily eliminating or reducing antibiotics in feeds due to pressure from fast food chains with animal welfare guidelines, the media representing the modern health-conscious consumer, and precedent-setting events in other countries.
Descriptive terminology
Dr Gordon D. Rosen (2003), speaking at the Carolina Poultry Nutrition Conference on replacements for antibiotics, observed that there are many different categories and literally hundreds of products available world-wide on offer for use alone or in admixture. Thousands of publications are relevant for appraisal and the literature is expanding rapidly.
However, terminology used in this field leaves much to be desired. For example, the terms "prebiotic" and "probiotic" have fallen out of favor with regulatory authorities and have been replaced by "oligosaccharide" and "direct-fed microbial". The word "synergistic" is sometimes misused when the response it not greater than the sum of those individual responses from the two components (indicating simple additivity). Also, researchers should routinely specify responses in absolute units in place of or together with percentages in scientific and commercial documentation so that improvements can be taken in their proper context.
Survey results
An opinion survey of 50 poultry industry personnel, ten in each of five categories (alternative product suppliers, users, consultants, educators/communicators, and academic researchers), by Rosen (2003), in addition to generating other information, allowed development of a list of important concerns and topics raised on the selection, dosage, and efficacy of alternative growth promoters. The following consolidated list has been adapted from that original list of 74 topics.
- Product - disparate types; large numbers of products; ill-defined admixtures; uniformity and quality control; uniqueness; activity definition; storage stability; application technology; processing thermostability; and in-feed analysis.
- Supplier - supplier caliber; promotional bias; selected test data; and all-inclusive bibliographies.
- Poultry Response - diverse response criteria; feed consumption; feed conversion ratio; mortality; carcass quality; palatability; water intake; litter quality; response frequencies or variations in responses; nutrient equivalence(s); genotype (strain) influence; nutrition and environment interaction; lighting pattern; dose-responses (animal and economic); recommended single dose and 0.5x, 1x, and 2x; insufficient test results; efficacy test designs; own tests; high test costs; small animal test numbers; inadequate replication; statistical methods; inappropriate test conditions; no negative controls; too-small-scale tests; no feed or nutrient composition; within- test comparison; few independent assessments; nutritional response models; annual economics; unaccounted variability; research versus reality; extreme deficiency conditions; invalid field trial designs; product admixture interactions; nutrition and environment interactions; heat stress; mode of action and response relationship; international differences; and regional adjustments.
- Regulatory, User, and Consumer - retailer and consumer influences; regulatory status; user opinions; environment improvements; safety data; and tissue residues.
- Veterinary - nutrition and/or prophylaxis; challenge definition; disease status; Clostridia; necrotic enteritis and Coccidiosis; diarrhea; enteric and systemic activities; gut microfloral activities; and in vitro support data.
- Categories of alternative Growth Promoters
For purposes of this paper, the different categories that will be discussed are: bacteriophages, betaine, botanicals and herbs, copper sources, direct-fed microbials (lactic acid producing bacteria, live yeast, mixed bacterial cultures, and spores), essential oils and spice extracts, enzymes, mannan oligosaccharides, organic acids, and specific antibodies. There are other supplements such as 25-OH-vitamin D3 that consistently improve poultry performance that are not discussed.
Bacteriophages
A future approach, now under development by USDA scientists at the University of Arkansas, Fayetteville, may be the use of tiny natural predatory viruses called bacteriophages against pathogenic bacteria, including superbugs resistant to conventional antibiotic treatment. Tiny phages (from Greek word meaning "eating" or "devouring") are among the simplest organisms on the planet, only about a millionth of an inch in size (a fraction of the size of most bacteria), and visible only under an electron microscope. Specific bacteriophages can destroy specific bacteria. Bacteriophages are widely distributed in nature: for example, in river water. They were first discovered in 1915 when their mysterious bactericidal activity produced clear areas in agar plates otherwise thriving with bacteria. The invisible microbe was a virus parasitic to bacteria (bacterial virus). This World War I era weapon to heal human diseases never fell out of favor at the Eliava Institute in Tbilisi, Georgia (former Soviet republic) where bacteriophages have been in human use there for 70 years with claims of miraculous results. Today, U.S. companies like Intralytix, Baltimore, MD, and Phage Therapeutics International, Bothell, WA, are developing phage catalogs to sequence the genetic code of a select 100 or so of the inestimably large number of bacteria-killing viruses found in nature (Hooge, 2001). Huff (2002) reported that a number of bacteriophages isolated from municipal sewer treatment facilities and poultry processing plants, when mixed with E. coli challenge culture or administered as an aerosol spray, completely protected birds from E. coli respiratory infection in the thoracic air sac.
Professor Mike Gasson, Institute of Food Research in Norwich, England has developed a method using enzymes called lysins produced by bacteriophages to attack specific pathogenic bacteria. Listeria and Clostridia have been two of the pathogens targeted. This technology is in the process of being commercialized (Anonymous, 2004).
Betaine
Choline is converted (oxidized) to betaine, and betaine provides labile methyl (-CH3) groups for methylation processes (for example, recycles homocysteine into methionine), and to some extent can spare methionine that also serves this minor purpose as a methyl donor in addition to its major structural function in proteins. Betaine is also recognized as an osmolyte, which influences the movement of water and can protect plant or animal cells (for example, intestine) against external stresses that cause moisture loss. Pre-formed betaine can be used as a dry or liquid (aqueous) supplement in poultry feeds. It has been concluded from poultry betaine research that improvements, in one or more of the following areas, usually result from betaine use: intestinal integrity, effectiveness of coccidiostats, body weight gain, feed conversion ratio, benefits in heat stress, live shrink loss, processing contamination, and breast meat yield (Davenport, ca. 1998; Noll et al., 2002). McDonald (1989) reported that the methionine requirement of caged laying hens was 10% lower when choline was added to the diet, indicating that choline or betaine may spare methionine for the methyl donor purpose. Some similar effects to betaine have been observed with sodium bicarbonate or sesquicarbonate (0.3% of diet) in combination with ionophore coccidiostats (Hooge, 1995).
Botanicals and Herbs
Nature's green pharmacy is abundantly stocked with remedies for various ailments of poultry and man, as well as substances that promote growth, immunity, disease resistance, and egg production. The bark, roots, flowers, fruit, or aerial portion of flowering, nonwoody stemmed plants (herbals) or any plants (botanicals), as crude preparations or purified extracts, have been used for centuries in animal production in China and India. For example, effective products such as Growell growth promoter, Coxynil anticoccidial immunity enhancer, and Respowell broad-spectrum anti- microbial from India and Avi-Med liquid solution for drinking water from England use blends of natural ingredients. However, except for a few products such as Yucca schdigera extract which reduces ammonia in manure (worldwide) and exerts some beneficial effect against Eimeria tenella in the ceca (some foreign countries), companies in the U.S. have found it prohibitively expensive and time consuming to obtain FDA approval for "safety" for each ingredient in a blend ("food additive petition"). For a performance claim(s), FDA requires that each component in the blend must be proven "safe" as well as the blend being proven "effective" for the stated purpose(s). In addition, AAFCO (state feed control officials) must adopt a feed ingredient definition for the product, to go in the ingredient section on feed labels, in order to be legal. One other possibility is that a product may be classed as "veterinary medical food" for veterinary use.
Therefore, the vast majority of botanical and herbal ingredients utilized in animal feeds in other countries today cannot legally be added to livestock or poultry feeds, or drinking water, in the U.S. because they constitute a potential threat to the human food supply. Interestingly though, deregulation of the herbal industry in the U.S. by the Dietary Supplement and Health Education Act (DSHEA) of 1994, allows people to buy a wide variety of natural products as "dietary supplements" (but not food ingredients) in health food stores for their personal consumption (in some cases, buying them for their pets; for example, condroitin sulfate and glucosamine for arthritis). Many of these products have disclaimers on the label indicating that they do not cure or treat disease, and that FDA has not reviewed their label statement. When any such product becomes known to FDA to be a health threat, based on consumer complaints or scientific information, FDA may act to remove it from the marketplace (as is happening with Ephedra in weight loss products). Not very often but occasionally, herbal and botanical products will be found to contain unacceptable levels of pesticides, heavy metals, or other contaminants. The Code of Federal Regulations does list a number of permitted animal feed ingredients, natural seasonings and flavorings, essential oils, oleoresins, and natural extractives that are acceptable (for example, anise, ginger, vanilla, chicory, etc.).
Copper Sources
Copper sulfate pentahydrate or tribasic copper chloride (TBCC®, Micronutrients, Indianapolis, IN) are often used at higher than minimum requirement levels for growth promotion in broiler chickens and turkeys. Like TBCC, organic copper sources usually have equal or higher copper bioavailability than copper sulfate, and thus lower the excreted copper levels, but are more expensive than either of the inorganic sources. Increased copper supplementation generally results in increased liver copper concentrations. Smith (1969) reviewed copper supplementation for chicks and indicated that levels of 76 to 225 mg copper/kg of diet (190 to 560 mg/kg as copper sulfate) promoted growth whereas levels in excess of 300 mg copper/kg diet inhibited growth. Fisher et al. (1970) and Fisher (1973) analyzed all data available on the use of copper as a growth promoting for broiler chickens. The regression lines obtained in the analysis indicated a maximum improvement of live weight at 169 mg copper/kg and for feed conversion ratio at 140 mg copper/kg of diet. Similarly, Wang et al. (1987) found that 188 mg copper/kg of diet gave maximum broiler weight gain when optimal levels of methionine were present. Celik et al. (2003) found that 200 mg added copper/kg of diet from tribasic copper chloride restored 125 of 197 g body weight loss and 15 points of 19 points worse feed conversion ratio due to 1 mg aflatoxin/kg of diet in broiler chickens grown to 42 days of age. Karimi et al. (2000) added 0, 100, or 200 mg copper/kg and 0, 400, or 800 mg vitamin C/kg of broiler diet, and observed that extra copper improved body weight and feed conversion.
Aldinger (1966) reported that in turkeys, 8 to 18 weeks of age, 240 mg added copper/ kg of diet from copper sulfate improved body weight gain and feed conversion ratio. Guenthner and Carlson (1976) added 120 mg copper/kg of turkey diet and obtained significantly improved growth rate of toms at 24 weeks of age. Copper levels in the liver were not significantly increased by adding copper to the diets in this case.
Liu et al. (2004) fed incremental levels of copper from copper sulfate or tribasic copper chloride to 21-week old laying hens for 16 weeks and calculated copper bioavailability to be 134% for tribasic copper chloride relative to copper sulfate. Common intercept multiple linear regression analysis of egg weight (parameter most sensitive to copper level in this study) on four copper levels (65, 130, 195, and 260 mg/kg) revealed the optimal supplemental copper level was 195 mg/kg for tribasic copper chloride and 260 mg/kg for copper sulfate because calculated optimum 390 mg/kg was unrealistic due to egg weight depression at 325 mg/kg level but not 260 mg/kg. Copper sulfate began depressing performance after 12 weeks whereas tribasic copper chloride did not. In a second trial, phytase retention in feed samples stored at 40o C for 21 days and sampled weekly was improved (P < 0.10) with tribasic copper chloride compared to copper sulfate (using 195 or 390 mg added copper/kg) or to the basal diet with no added copper.
Direct-Fed Microbials
The intestinal microflora of poultry is a complex ecosystem, largely still a "wild frontier" of scientific exploration. Apajalahti (2003) stated that only about 10% of the total microflora populations, and probably only about 10% of the intestinal pathogens, have been characterized. At Danisco in Finland, he has been using % G+C profiling and 16S rRNA sequencing to create a database describing all 640 or so bacterial species and about 140 genus level bacterial clusters in the chicken gastrointestinal tract. The intestinal bacterial community is extremely diverse, and its ability to adapt to almost any imaginable set of conditions is remarkable. The living microbes have nutrient and spatial requirements, and the amount of substrates they need is probably in the range of 10 to 20% of the dietary carbohydrates and proteins. The FDA has published a list of acceptable microorganisms that can be used in direct-fed microbial products (see AAFCO Official Publication as well). These products are sources of live (viable) naturally occurring, nonpathogenic microorganisms, including bacteria (vegetative or spore forms), fungi, and yeasts. There are certain optimal doses for each product.
Lactic Acid Producing Bacteria
The strains used in commercial products have gotten progressively better over the years, and technology for coating the dried bacteria now allows excellent survivability through steam pelleting. One product will be discussed here as an example -- Avi-Lution® (Agri-King, Inc., Fulton, IL; Prince Agri Products, Inc., Quincy, IL) -- which comes in dry, thermostable powder or water-soluble product. It contains a selected strain of lactic acid producing bacteria (based on in-house studies with mice inoculated with Salmonella typhimurium) and boulardii yeast. The feed-grade product has about 97% survivability through pelleting. The lactic acid bacteria are added to feed at a recommended level of 150 million cfu/lb or 330 million cfu/kg. Four broiler chicken pen trials, 42 to 56 days in duration on built-up litter and in some cases at moderately high stocking densities, have been conducted with this direct-fed microbial. Using the feed supplement, broiler body weights and feed conversion ratios have consistently been equivalent to or better than bacitracin-md or virginiamycin, without any significant effect on mortality. Average improvements (48.75 days) in the pen trials for treated compared to control diets have been: body weight, +0.104 kg or +4.00% (2.702 vs 2.598 kg); and feed conversion ratio, -0.118 or +5.59% (1.993 vs 2.111). Microbial analyses of contents of the total intestinal lumen or ceca have shown significantly fewer total coliforms, Salmonella, and Campylobacter, but more lactic acid producing bacteria through dietary supplementation (Hooge, 2001). The water-soluble product has been field tested successfully in young commercial broiler chicken and turkey flocks, often moving the contract grower up in relation to other growers and improving bonus potential. Some growers have used it through the water to successfully treat necrotic enteritis (no performance claims).
In a commercial caged laying hen field trial with two houses of 50,000 birds each on control feeds or Avi-Lution® supplemented feeds from 24 to 40 weeks of age, mortalities were similar (0.0429 vs 0.0435% weekly) whereas improvements with the supplement were found in hen-day egg production (90.38 vs 91.95%), feed/dozen eggs (2.753 vs 2.672 lb) and daily egg mass (51.42 vs 51.83 g/h/day), but egg weight declined slightly (56.89 vs 56.37 g).
Therefore, the feed cost per dozen eggs improved from 21.16 to 20.59 cents and feed cost/kg of eggs decreased from 32.08 to 31.82 cents due to adding the direct-fed microbial to the layer feeds.
Live Yeast (Saccharomyces cerevisiae boulardii)
About 200 E. coli bacteria can adhere to each boulardii yeast cell, and other pathogens with Type 1 fimbriae (mannose sensitive lectins) such as strains of Salmonella can similarly attach, making these bacteria unavailable to colonize and produce toxins on the intestinal wall. Nicholas turkey poults in battery cages were fed diets with 0, 0.1, 0.02, or 0.06% boulardii yeast from 0 to 21 days of age and 0 or 0.02% from 21 to 35 days (Bradley et al., 1994). Body weights were significantly increased at 7, 14, 21, and 35 days of age by yeast supplementation without affecting feed parameters. Line et al. (1997) added a level of 10% boulardii yeast to the feed of broilers for 60 hours prior to transport and found the Salmonella colonization rate of controls was 67.5% compared to 40% in treated birds. The chicks had been inoculated at an early age with the pathogen. The frequency of Campylobacter from the ceca was not affected. Line et al. (1998) added boulardii yeast at 1% or 10% levels to chick diets and found that the frequency of Salmonella typhimurium colonization in ceca was reduced whereas Campylobacter jejuni colonization was unaffected. Preston et al. (1999) reported that supplementation of wheat-soy-fish meal broiler diets with boulardii yeast resulted in a reduction in 21-day viscosity of ileal contents from 10.7 cps in controls to 4.2 cps in treated birds without affecting weight, feed conversion, apparent metabolizable energy, or caloric conversion. Because boulardii yeast can produce a protease which destroys Clostridium difficile toxin A experimentally (Castagliuolo et al., 1996), one future approach for broiler breeders could be to use live boulardii yeast along with mannan oligosaccharide (yeast outer cell wall) for best intestinal health.
Mixed Bacterial Cultures
A product called Broilact has been reported from Europe. Pre-Empt® (29 species of bacteria) has FDA approval in the U.S. as a competitive exclusion culture to protect young poultry from Salmonella colonization. It has apparently not received widespread use because of the price (about $0.01 to $0.02/chick or poult in the past) and sensitivity to antibiotics, including those in eggs carried over to hatchlings from breeders receiving antibiotics. Donohue et al. (2002) at the University of Arkansas have been screening large numbers of nonpathogenic microbes in vitro for efficacy against, or ability to out-compete, specific pathogens when cultured in combination with them. Young poultry are inoculated with these protective microbes and challenged with either Campylobacter or Salmonella to determine extent of colonization. Some of these isolates not only reduce pathogen colonization but also enhance gut development and function, such as villi height and surface area and mucin production by goblet cells. It is hoped that in the not-too-distant future an inexpensive, mixed culture highly effective against Campylobacter and Salmonella can be created for use in the commercial poultry industry.
Bacillus subtilis C-3102 Spores
In Japan, a select strain of Bacillus subtilis spores designated as C-3102 has been used for about a decade in broiler chicken and laying hen feeds at a level of 0.003% spores (Calsporin®, Calpis Ltd and Quality Technology International, Inc.; premix 0.05% level). It was introduced into the U.S. in 1998. Bacillus subtilis is normally found in decaying organic matter such as compost piles, but when viable spores are added to feed in sufficient numbers they can alter the digesta in the intestinal tract toward a more anaerobic condition favoring the proliferation of lactic acid producing bacteria and decreasing pathogen counts. In laying hens, this leads to an increase in eggshell thickness by an average of about +5.2% (0.018 mm, from 0.345 to 0.363 mm), based on patent information (U.S. Pat. Application No. 269725, approved Dec. 2003). In a field trial described in the patent application, involving 1.74 million control hens and 2.42 million treated hens, the number of defective eggs decreased from 1.46 to 1.35% (P < 0.01), egg production increased from 85.64 to 86.68% (P < 0.01), and egg weight increased from 64.59 to 64.76 g. Results of several broiler trials and one turkey trial in the U.S. have generally indicated that dietary Bacillus subtilis spores improve body weight and feed conversion ratio without affecting mortality, decrease litter nitrogen content and air ammonia concentrations, decrease pathogen counts on carcasses at processing, and improve breast meat yield (Fritts et al., 2000; Hooge et al., 2004; Blair et al., 2004).
Essential Oils and Spice Extracts
These products have been used in Europe for about a decade and have now been introduced into the U.S. An example of this type of product is CRINA® POULTRY blend (CRINA S.A., Gland, Switzerland; subsidiary of Akzo Nobel which also owns Intervet) specifically developed and patented for it effectiveness against Clostridia perfringens to prevent necrotic enteritis. Scientists developed specific blends for poultry, dairy, young pigs, and growing pigs years ago in anticipation of the antibiotic resistance issue today. Essential oils and spice extracts are active ingredients made synthetically (called "nature equivalent" in Europe) or produced directly from natural sources (full organic certified product available). CRINA (essential oils and spice extracts on uniform corn cob grit or other carrier) is used at low dose levels of 50 ppm for growth promotion and 100 ppm for prevention of necrotic enteritis (no performance claims). This product has substantial market shares in the broiler and turkey feed industries in various countries of Europe and the Far East. When antibiotics are removed from broiler feeds, necrotic enteritis may occur in 0 to 20% of the flocks but it often does so at random. Therefore, some type of supplement is needed to assure disease prevention in these flocks, which can suffer extra mortality, morbidity, and poor growth.
Enzymes
A large body of research literature exists on benefits of enzymes for poultry. They tend to alter intestinal microflora, especially in wheat- or barley-based diets, which predominate in Europe and Canada, and in this way work in tandem with antibiotics or to some extent replace them when they are taken out. Enzymes for corn soy based diets are becoming more effective (for example, Versazyme® by BioResource International, Inc., Raleigh, NC is an aggressive new proteinase).
Mannan Oligosaccharide (MOS)
Boulardii yeast outer cell wall component (mannoprotein) strongly binds pathogens such as E. coli and Salmonella spp. with mannose sensitive lectins, by what is referred to as a "receptor analog" mechanism, and decoys them away from the "sugar coated" intestinal lining. The MOS typically improves intestinal function or "gut health"; for example, increasing villi height, uniformity, and integrity. It also acts as a general immune stimulant (adjuvant type effect). The product was developed and first sold commercially in 1993 (Bio-Mos®, Alltech, Inc.). Extensive testing has been done worldwide with broilers, turkeys, and more recently laying hens. Reviews have been published on MOS for pigs (Pettigrew, 2000), broilers (Hooge, 2003), turkeys (Hooge, 2003), and broilers, turkeys, and pigs (Rosen, 2003). This product has an excellent track record for improving broiler and turkey body weight, feed conversion ratio, and livability (this benefit even greater than with antibiotics, on average). Based on these results, in the U.S. benefit:cost ratios for MOS have been estimated at 3.9:1 for broilers and 5.6:1 for turkeys. Rosen (2003b) stated that the beneficial effects of MOS were observed at an "improvement frequency rate" of 71% overall in broilers and turkeys. Shashidhara and Devegowda (2003) reported benefits for broiler breeders including increased egg production, hatchability, fertility (higher sperm count, millions per mL), and IBDV antibody titers, and lower "dead in shell" during incubation. Recent unpublished caged layer trials have shown increased egg production. The MOS should be given careful consideration when an alternative to antibiotics is needed for drug-free or organic poultry products. It has also been found to be compatible with antibiotics, especially bacitracin-md, showing an additive effect in broilers and turkeys.
Fructo-oligosaccharide (for example, FOS 50, Coors Biotech, Inc.), a substrate for beneficial bacteria but not available to some pathogens in the intestinal tract, was well researched in broilers in the 1980s and early 1990s for improving live and processed performance, and reducing carcass Salmonella. However, it was not widely accepted.
Organic Acids
Except as mold inhibitors, these have not received much attention by the U.S. poultry industry although organic acids or acidifiers are well known and used in Europe (and to some extent in baby pig diets in North America). Among them are acetic, butyric, formic, fumaric, lactic, propionic, and sorbic acids. Many are available as calcium, potassium, or sodium salts. Acid blends represent an array of pKa (pH at which 50% is dissociated), and in some cases, have better bacteria-inhibiting capabilities (broader spectrum of activity) than single acids. Products with higher pKa values are generally more effective. Acidifiers added to feed or water are included in some comprehensive farm-to-plate food safety programs (for example, Kemin Industries, Inc.).
Antibodies for Specific Purposes
Feeding antibodies to cholecystokinen (CCK; developed by injecting the antigen into hens and spray-drying eggs) can improve broiler body weight and feed conversion. Injecting hatching eggs with monoclonal antibodies to adipocytes can reduce fat deposits in market age broilers (Cartwright et al., 2000). The monoclonal antibodies could be injected into fertile hatching eggs by an automated egg injection system. There may be future potential for multi-purpose antibodies contained in spray-dried eggs from hens injected with multiple antigens to accomplish specific purposes (for example, perhaps anti-E. coli, Salmonella, and Campylobacter antibodies). In a related development, a new vaccine against Salmonella (PoulVac ST, Ft. Dodge Animal Health) has shown consistent live performance improvements in broiler chickens in pen trials using Salmonella positive chicks from the hatchery.
References are available on request
From Proceedings of the "Midwest Poultry Federation Convention", St. Paul, Minnesota, U.S.A.
