Looking to the future: Antibiotic use in poultry production

Health & Disease

July 30, 2019

While antibiotic usage is often acceptable to poultry producers, they should consider alternatives practices in order to stay competitive in today’s market. It’s becoming clear that the preference for antibiotic-free feeds and products is not merely a market trend; rather, it is an inevitable change that promises to become increasingly more present in our daily lives.

Reducing — or even preventing — the use of antibiotics in poultry operations has become a very important issue in recent years. Consumers are continuing to drive the demand, and opinions on antibiotic use in meat production have taken a top spot on the list of food concerns. While antibiotic usage is often acceptable to poultry producers, they should consider alternatives practices in order to stay competitive in today’s market.

Bacterial Resistance

Increased bacterial resistance to antibiotics has caused regulatory boards to become stricter about antibiotics in animal feed. The biggest concern is that antibiotic residue could be found in the meat and could possibly, then, be transferred to humans through food consumption.

The Food and Agriculture Organization (FAO) of the United Nations estimates that antimicrobial resistance is a cause of death for 700,000 people a year worldwide. The large-scale use of antibiotics could significantly increase that number, leading to the death of up to 10 million people by 2050. This issue is also of concern for the World Health Organization (WHO), which states that, if measures are not taken to contain this situation, superbugs will be more lethal than cancer by 2050.

Marketability

In markets like Europe, where large multinational supermarkets and fast food chains are now demanding antibiotic-free products, it’s more important than ever for producers to be aware of the concerns about antibiotic residues in meat in order to continue successfully exporting their meat.

The use of performance-enhancing antibiotics in animal nutrition has been banned in European Union (EU) countries since 2006, putting them ahead of the curve. Additionally, since the EU has a relationship with other important markets, they are also restricting the consumption of food products from animals whose diets include antibiotics. Clearly, if other countries want to export their products to the EU, adapting to these new standards of production will be necessary.

Antibiotic-free Solutions

At first, it may be difficult for producers to adapt their operations to a new diet. To help make this a smooth transition, take inventory of your operation and determine where you might be able to integrate new high-tech equipment. Also, implement an efficient and high-quality vaccination program that will keep your birds healthy and reduce the need for antibiotics.

Before making this change to the birds’ diet, it is important to consult with a technical nutritionist to evaluate environmental factors, such as water and air quality, as well as the ration and vaccination program, and to avoid any sanitation issues on the operation.

Natural alternatives to antibiotics are also available. Researchers have worked diligently to find solutions that are not harmful to human health while maintaining the quality and productivity of poultry operations. Companies and universities around the world are partnering to study and explore various natural solutions as alternatives to antibiotic use.

Three natural alternatives to potentially include in your birds’ diets are probiotics, prebiotics and organic minerals. Probiotics are beneficial microorganisms that keep the intestine healthy and support the birds’ development. Prebiotics prevent the growth of harmful bacteria in the animal’s gut, and organic minerals are essential for the general development of all animals.

A recent study by Alltech analyzed two groups of birds: one group with antibiotics in their diet and the other group fed an antibiotic-free diet that included natural, yeast-based solutions. The results showed that the flock’s health in each group was comparable. In addition, the antimicrobial-free birds showed a significant increase in weight, improved intestinal function and a lower mortality rate.

It’s becoming clear that the preference for antibiotic-free feeds and products is not merely a market trend; rather, it is an inevitable change that promises to become increasingly more present in our daily lives. Producers must adapt to this new reality in order to remain competitive in the protein industry. It is possible to reduce the use of antibiotics while still maintaining the quality, health, productivity and profitability of the operation by using natural alternatives.

Micro-Aid® Benefits Gastrointestinal Tract Health to Improve Animal Performance

Research

Jim

July 29, 2019

Download the complete Article

The environmental and performance benefits of Micro-Aid® Feed Grade Concentrate start within the broiler by promotion of a healthier gastrointestinal tract environment, better animal performance, and better nutrient utilization. Recent research shows 3.0% improvement in the Pectoralis major muscle increasing the value of these broilers.

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Preparation and characterization of high quality gelatin from different poultry sources

Research

Jim

July 29, 2019

Preparation and characterization of high quality gelatin from different poultry sources

How to Save Money on Poultry Feed

Feed & Nutrition

Jim

July 29, 2019

Those formulating poultry feeds continually walk a tightrope between trying to save money on the formula while avoiding a decrease in the production of eggs or meat. While the cost offeed/ton can be calculated to the nearest cent, the consequences of a marginal nutrient deficiency are usually invisible. A slight decrease in case weight or shell quality, or a several tenths of a pound increase in feed intake per hundred hens per day, will likely pass unnoticed.Perhaps the best way to minimize feed costs is to fully appreciate the nutritive contribution of under-utilized feed ingredients in a given region. In the southeastern United States, special attention should be given to both peanut meal and pearl millet.

Peanut meal has traditionally been severely undervalued in the ingredient market. As of this writing, the quoted price for peanut meal is $140/ton, versus $225/ton for soybean meal (including basis). Most peanut meals have about the same protein content as dehulled soy, although lysine and thre onine content is lower. Metabolizable energy, on the other hand, is about 100 kcal/lb higher for peanut meal than soy. One source of concern regarding peanut meal is its possible contamination with aflatoxin. This concern is valid, but of limited practical significance. Even at 200 ppb aflatoxin,if 5% peanut meal is used in the diet, the level of aflatoxin in the mixed feed is much too low to be of practical concern.

Research at the University of Georgia has demonstrated that peanut meal is a perfectly acceptable feed ingredient for laying hens (1). The nutrient value of currently available peanut mealshas now been well documented (2). For those interested in using peanut meal in their feeds, a confirmatory protein analysis is recommended, along with the use of the higher metabolizable energy values documented for modern peanut meals. If ME values from older tables of nutrient composition are used, excess body fat may result.

Pearl millet is being actively considered by farmers in the southeast as an alternative to other row crops. Work by Dr. Wayne Hanna and colleagues in Tifton, GA has led to the development of strains of millet suitable for cultivation in the southeastern U.S. Pearl millet is of particular interest because its metabolizable energy approximates that of corn, while its protein content is much higher. A typical protein value for pearl millet in Georgia is about 11%, with 0.38% lysine.

This compares very favorably with corn which typically contains 7-8% protein and 0.24% lysine.While the amount of pearl millet available to the feed industry is currently very limited,encouragement of its cultivation could lead to a significant feed savings for commercial egg producers. Based on current ingredient prices, the value of pearl millet based on its nutrient content was found to be 18% higher than corn. While it is recognized that shadow prices do not take into account issues such as bin storage, a need to grind pearl millet is not a concern. Research at the University of Georgia has found that whole pearl millet is satisfactorily digested by both broilers(3) and laying hens (4). The use of large particle calcium in laying hen diets clearly facilitates this process. This aspect of millet usage is clearly of importance as few feed mills have more than one post-grinding ingredient bin.

References

1. Pesti, G.M., R.I. Bakalli, J.P. Driver, K.G. Sterling, L.E. Hall, and E.M. Bell, 2003. Comparison of peanut meal and soybean meal as protein supplements for laying hens. Poultry Sci. 82:1274-1280.2. Batal, A., N. Dale, and M. Café, 2005. Nutrient composition of peanut meal. J. Appl. Poultry Res. 14:254-257.3. Hidalgo, M.A., A.J. Davis, N.M. Dale, and W.A. Dozier, III, 2004. Use of whole pearl millet in broiler diets. J. Appl.Poultry Res. 13:229-234.4. Dale, N. Unpublished data.

A Balancing Act – The Science Behind an Artfully Created Feed Formula

Feed & Nutrition

Jim

July 25, 2019

Dr. Amy Batal is the mastermind behind Sanderson Farms’ innovative feed formulas. By day, Batal is a nutritionist entrusted to care for the diets and overall health of millions of chickens at a time. By night, she is the loving wife and mother of five children who is passionate about nutrition, whether her customers are her family or the millions of animals entrusted to her care.

For Sanderson Farms’ Nutritionist, Dr. Amy Batal, the task of formulating a nutritious, cost-effective and sustainable food source for the more than 510 million chickens processed annually at Sanderson Farms is both a science and an art. According to Batal, the science portion of the equation is in using her 15 years of experience within the animal nutrition field to develop, down to the last kernel of corn, the exact feed profile necessary to grow healthy chickens while minimizing the company’s carbon footprint and impact on the environment. The artistic portion, on the other hand, is added into the feed equation when Batal artfully balances the implementation and distribution of her scientific feed formulas across Sanderson Farms’ eight feed mills and more than 900 independently-owned family farms.

For Batal, the science and art of balancing nutrition, cost-effectiveness and sustainability in Sanderson Farms’ feed does not make for an easy or even average work day. In a given day, she may spend time running research trials with Sanderson Farms’ veterinary staff to ensure proper nutrition of our birds, negotiate with suppliers for ingredient prices, or review agricultural statistics to determine the company’s standing within the industry.

Batal’s position is by no means just simply a desk job. On an average day, she can be found traveling anywhere from farms to feed mills to conduct audits and observe feed quality. Batal also strives to use her expertise in the field to spread her knowledge of feed formulation and nutrition throughout the industry.

Last year, Batal traveled to Nashville, Tennessee to present at USPOULTRY’s 2016 Feed Mill Management Seminar. During her presentation titled “Ingredient Changes…Why Are They Important and Why Should the Mill Manager Speak Up?,” Batal discussed the cost-effectiveness of formulating a premier poultry feed that is both sustainable and beneficial to birds, while also considering the logistics necessary to create and maintain the feed in mills.

With over 3.5 million tons of feed produced in our mills each year, feed is certainly a costly endeavor for Sanderson Farms considering approximately 75 percent of the company’s production costs are dedicated to feeding our birds. With this cost in mind, Batal frequently adjusts feed formulas in an effort to keep feed costs down without compromising the nutritional value for our chickens.

In order to combat the rising costs of ingredients, Batal devotes a considerable amount of time to negotiating ingredient prices with suppliers. Alongside Feed Ingredient Buyer, Steve Weathersby, she determines which ingredients are the most cost effective, the most readily available and the least variable. Because prices change weekly, Batal constantly adjusts which ingredients and how much of those ingredients she utilizes in a given feed formula depending on what ingredients are available for the right price.

For Batal, part of the art of creating a scientific feed formula includes experimenting with alternate ingredients to find just the right feed profile. Despite its significant impact on the company’s operating costs, cost effectiveness is not the sole concern when formulating a premier feed profile. Sanderson Farms’ feed must also be effective for the sustainable production of 100% Natural Chicken considering the company’s consciousness of its use of vital resources.

Since launching our Corporate Responsibility Program in 2010, Sanderson Farms has deliberately focused efforts to reduce our company’s impact on the environment. Sustainability is an increasingly important factor in the creation of our feed, yet most people don’t understand what sustainability truly means in regards to feed formulation. “Sustainable means utilizing every resource we have,” said Batal. “We feed as adequately or as optimal to the animal’s requirement as we can without wasting anything.”

While the company is certainly mindful of its utilization of resources, Batal gives credit to the birds themselves for being sustainable. “Think about it,” said Batal. “Chickens are great converters of something that’s really not of value to humans as a great protein source.”

Unlike beef and pork products, poultry is the most efficient converter of feed ingredients like corn and soybeans to pounds of meat. For every 2.3 acres of harvested soybeans and 1.6 acres of harvested corn, Sanderson Farms yields more than 10,000 pounds of salable chicken products.

At this point, you’re probably wondering what ingredients are used to compose a premier feed formula such as the formulas Batal works so tirelessly to create. In scientific terms, it’s a complex formula of energy sources, proteins, fats, amino acids, vitamins and minerals. When broken down, Sanderson Farms’ complex feed formula is quite easy to understand because it is developed from natural, wholesome ingredients.

When creating a feed formula, Batal begins with an energy source, which, for poultry, is primarily corn and soybean meal. Protein is then added to the formula through the use of alternative ingredients. One alternative ingredient source such as “meat and bone meal” may evoke discussion regarding the use of animal by-products in our feed, but Batal assures that the practice is science-based and serves as a critical source of protein in the bird’s diet. After all, chickens are omnivores that need a protein rich diet.

After corn, soybean meal and protein sources are included in the formula, fats are added along with vitamin premixes, mineral premixes and various other supplements. All of these ingredients are combined at Sanderson Farms’ eight feed mills where they are mixed and formed into pellets, which is the most efficient way to feed chickens.

Though Sanderson Farms’ feed formula sounds simple enough, Batal’s job is not as simple as creating one feed profile for all birds. Throughout their lifespan, chickens grow and develop through a multitude of stages, and each of those stages has a completely different nutritional need than the other.

According to Batal, protein requirements are highest when a bird is young. As chickens grow, their energy requirements increase. As a poultry nutritionist, Batal takes great care to consider the dietary needs of our birds throughout each stage of their growth and development. Therein lies the delicate balance between art and science that goes hand-in-hand with being the nutritionist for the third largest poultry producer in the nation.

For Batal, all of the hard work is validated by simply seeing the fruits of her labor. When questioned about her favorite part of developing an industry competitive feed formula, Batal simply replied, “all of it.”

“Amy has made us a stronger company since she came aboard,” said Randy Pettus, Director of Production for Sanderson Farms. “Our birds are receiving exactly what they need without excessive additives or costs.”

Such an unwavering dedication to the field of animal nutrition shines through Batal’s work and her uncompromised passion for the well-balanced diets of the company’s flocks. “The biggest thing is seeing what you do have an impact,” said Batal. Day in and day out, she works tirelessly to ensure Sanderson Farms’ chickens receive the best possible nutrition at all times in order to truly be 100% natural, 100% of the time.

USDA Releases “Feed Outlook: July 2019” Report

Feed & Nutrition

Jim

July 25, 2019

Source: USDA news release

To view the complete report, click here.

The July 2019 Feed Outlook report contains estimates for 2018/19 and projections for 2019/20 U.S. and global feed markets based on the most current World Agricultural Supply and Demand Estimate.

On July 16, 2019, Table 5 in the July 2019 Feed Outlook report was corrected to fix a computational error causing values for 2018/19 quarterly HFCS, glucose and dextrose, starch, alcohol for fuel, alcohol for beverage and manufacturing, and cereals and other products to be off by a factor of 2. All values are now correct.

House of Raeford Farms Announces $40 Million Feed Mill for Louisiana Complex

Feed & Nutrition

Jim

July 24, 2019

Arcadia processing plant and hatchery will also receive upgrades

House of Raeford Farms announced that construction would begin this summer on a new feed mill for the Arcadia, Louisiana complex. The facility, to be located in Simsboro,
Louisiana and Lincoln Parish, will be built at a cost of $40 million and be capable of producing 12,500 tons of feed weekly, double the capacity of the current mill.

The company will also make building modifications and add new equipment totaling over $7 million to the hatchery in Gibsland, Louisiana and the processing plant in Arcadia, Louisiana. As a result, the complex will add more than 100 new jobs, and live production will contract for 86 new poultry houses over the next two years with a new construction impact to the northwest Louisiana community of $28 million.

“House of Raeford is committed to our operations in Louisiana as evidenced by these major capital expenditures and planned employment increases,” said Bob Johnson, CEO of the family-owned and operated company. “In keeping with the growth objectives of our company, our Louisiana complex is also the first of our locations to offer No Antibiotics Ever chicken products to our customers.”

Construction of the feed mill will take 18 months to two years to complete, but improvements to the hatchery and processing plant will be finished earlier. In addition to these capital upgrades, House of Raeford’s totally rebuilt Wallace, North Carolina processing facility re-opened last year while the Greenville and Hemingway, South Carolina locations have recently undergone major equipment and facility improvements.

About House of Raeford Farms
House of Raeford Farms, Inc. is one of the nation’s top ten largest chicken producers, providing ready- to-cook and further processed chicken products to the foodservice, retail, and export markets. The company is family-owned and operated, and based out of Rose Hill, North Carolina with additional facilities in Georgia, Louisiana, North Carolina, and South Carolina.

Tosca Launches First RPC Custom Built for Poultry

Poultry Equipment

Jim

July 24, 2019

Engineered for durability, RPC withstands weight and water, eliminating box failures

Tosca (www.toscaltd.com), an innovator in reusable packaging and supply chain solutions, announced today the introduction of a breakthrough reusable plastic container (RPC) designed specifically for poultry. The Tosca poultry RPC was built to withstand weight and water, delivering greater product protection, reducing damage, as well as eliminating packaging waste.

Poultry is the fastest growing protein in the US, and it is also one of the most difficult products to ship. Poultry is heavy and ships with an ice crust which can be challenging especially in a corrugated box that breaks down when exposed to moisture or water. To address the challenges of shipping poultry, Tosca sought feedback from poultry industry professionals to understand the daily problems they face. These discussions combined with Tosca’s robust packaging experience working with 2 of the top 5 largest retailers, resulted in a heavy-duty container that will work over-time to get chicken to its destination looking its best. The new features include:

Highest quality food-grade polypropylene that is engineered for durability and easily withstands weight and water
A fluid retention channel to keep liquid away from the packaged poultry to help maintain cleaner product and avoid the typical ‘sticky’ packaging often found with poultry
A unique design that allows the RPCs to slide into place and interlock with other RPCs. This creates improved pallet load stability during transport.
Scalloped walls that maximize internal volume and ensures product lays flat and uniform and doesn’t move during transit

“Tosca has been creating innovative supply chain solutions for more than fifty years, and our new poultry container is evidence that we continue to develop smarter packaging that drives customer value,” said Eric Frank, president & CEO, Tosca. “We are excited about the market’s positive response to the new container and we anticipate it will drive significant efficiencies for our customers.”

Retailers are facing more challenges than ever before. Intense competition and evolving consumer demands mean retailers can’t afford a weak link in their increasingly complex supply chains. Tosca’s new poultry RPC is going to be a major disruptor in a supply chain that is long overdue for a packaging upgrade.

For more information about Tosca’s poultry supply chain game changer, click here.

About Tosca

Tosca (www.toscaltd.com) is a leading provider of reusable packaging and supply chain solutions across a diverse range of markets including eggs, case-ready meat, poultry, produce, and cheese. Tosca collaborates with retailers, growers, and suppliers to deliver the best flow of perishables through the supply chain, eliminating waste at every turn. Operating 14 state-of-the-art wash sites around the country, Tosca efficiently supports regional and national programs, providing unmatched service and lower supply chain costs. Our reusable plastic containers – the most comprehensive portfolio in the industry – improve product protection, reduce costs and are more sustainable than single-use packaging.

Chicken Embryo Malpositions and Deformities1

Production & Management
Eggs - Breeders
Eggs - Layers

Jim

July 23, 2019

Gary D. Butcher and Amir H. Nilipour²

Detailed information describing the categorization and incidence of embryo malpositions and deformities in commercial poultry is not readily available. Additionally, there is often little consistency in these data among hatcheries. Any decrease in the number of usable chicks may result in substantial economic loss to poultry integrations. In a typical hatch, it is common to lose about 1%–2% of the chicks due to deformities and malpositions. Deformities manifest during the process of embryo development, while malpositions occur in the last week of incubation before hatch. At a commercial hatchery over a 5 year period, more than one-half million eggs had been broken out for quality control purposes and many thousands of unhatched embryos had been examined to determine the frequency of the various deformities and malpositions. The objective of this study was to determine the relative incidences of malpositions and deformities, and their economic impacts. Major factors affecting their occurrence will be explained. Obviously, in any population it is anticipated to encounter malpositions and deformities during embryonic development. However, the incidence must be within accepted limits and changes must be made when excessive losses occur.

Malpositions

Investigation has demonstrated that the incidence of embryos unable to hatch due to malpostions varies from 1.2% to 1.8%, with an average of 1.5%. Malpositioned embryos are unable to pip the eggshell and escape due to improper positioning within the egg in the hatcher. It is interesting to note that numerous malpositions have been described, with some embryos exhibiting only one form of malposition and others experiencing combinations of malpositions. The majority of eggs with malpositioned embryos, as found in hatch residue, included embryos dead in shell, probably resulting from exhaustion and/or lack of oxygen. A smaller number of eggs contained live embryos trying to pip. Loss of embryos due to malpositions may be costly; therefore, it is important to routinely monitor the percent of the embryos not hatching. If the incidence due to malpositions exceeds the standard, corrective measures must be taken. Table 1 summarizes the most common malpositions present in routine egg breakouts from the common broiler breeder crosses currently used in the industry. The incidences vary for the light and medium breeder cross lines.

Table 1.Incidence of the common malpositions

Malposition #	Description of the malposition	%
1	Head between thighs	12.5
2	Head in the small end of egg	7.5
3	Head under left wing	7.5
4	Head not directed toward air cell	4.5
5	Feet over head	20.0
6	Beak above right wing	48.0

An embryo provided an optimum environment for development will position itself around 17–18 days of incubation for hatch. The proper position is with the head under the right wing with the head directed toward the aircell in the large end of the egg. The results of this study demonstrate that malposition #6, which is beak above the right wing, constitutes almost 50% of the malpositions, followed by position #5, feet over head with a frequency of 20%.

There are numerous reasons that malpositions occur. In a normal population, the incidence should not exceed 2.0%. If the incidence is elevated, breeder and egg management practices must be investigated and appropriate changes made to resolve the problem. Common reasons for increased incidences of malpositions are:

Eggs are set with small end up. As part of a monitoring program, check eggs in the egg room or in the setters to ensure that eggs have been set correctly.
Advancing breeder hen age and shell quality problems.
Egg turning frequency and angle are not adequate. Proper frequency of turning through a 45 degree angle assists the embryo to position for hatch. The standard turning rate in the setter is 1 per hour.
Inadequate percent humidity loss of eggs in the setter. Acceptable weight loss of eggs from setting to transfer is 11%–14%.
Inadequate air cell development, improper temperature and humidity regulation, and insufficient ventilation in the incubator or hatcher.
Imbalanced feeds, elevated levels of mycotoxins, and vitamin and mineral deficiencies.
Exposure to lower than recommended temperatures in the last stage of incubation.

Deformities

In any animal population during embryonic development, there is a predictable incidence of embryos that die or are not able to hatch due to deformities. Based on this comprehensive investigation, data demonstrated that the percent of deformed embryos ranged from 0.22 to 0.30% of the total hatch. These findings suggest that hatchability declines on the average of 0.25% due to malformed chicks. A combination of deformities and malpositions can be manifested simultaneously. Table 2 shows the incidence of common deformities observed from embryos at 15 to 21 days of incubation. The most common deformities are those of exposed brain (29%), without eye(s) (25%) and with beak abnormalities (+/-35%).

Table 2.Incidence of common deformities

Deformity	Description	%
1	Exposed Brain	29
2	Without eye(s)	25
3	4 legs	10
4	Deformed beak	27
5	No upper beak	8
6	Deformed twisted leg	1

Conclusion

The objective is to produce the maximum number of healthy chicks from eggs set. The percent hatchability in the commercial poultry industry ranges from 78%–88%. Many variables affect the level of success, including environmental temperature and humidity, lighting, body weight management, strain of breeder, etc. Normally, loss of about 1.8% of total hatch due to malpositions and deformities can be anticipated. However, if this is elevated, necessary corrective measures must be taken. The importance of a routine embryo diagnosis program can not be overstated. Without such a program and access to data generated, it is difficult to detect when increases in incidences of 0.5%–1.0% deformities and malpositions occur. Thus, it is not possible to “know where to look” for the problem and make the necessary changes. The competent hatchery manager will consistently be able to obtain superior hatches by being able to identify even small problems and promptly resolve them. In most cases in the hatchery, problems with hatchabiltity are due to a combination of several unresolved smaller problems.

Footnotes

This document is VM129, one of a series of the Veterinary Medicine-Large Animal Clinical Sciences Department, UF/IFAS Extension. Original publication date May 2002. Reviewed December 2018. Visit the EDIS website at https://edis.ifas.ufl.edu for the currently supported version of this publication.

Gary D. Butcher, DVM, Ph.D., professor, College of Veterinary Medicine; and Amir H. Nilipour, Ph.D., director of investigation and quality assurance, Grupo Melo, Panama, Rep. of Panama; UF/IFAS Extension, Gainesville, FL 32611.

Research Provides New Understanding of ILT Vaccines

Research

Jim

July 22, 2019

Institution: University of Delaware

Principal Investigator:
Dr. Calvin L. Keeler, Jr.
Department of Animal and Food Sciences
531 S. College Ave.
University of Delaware
Newark, DE 19716-2150

Infectious laryngotracheitis (ILT) is a disease of great concern to the poultry industry. This acute respiratory disease is caused by an avian alpha herpesvirus, infectious laryngotracheitis virus (ILTV). The poultry industry does not universally embrace the use of live-attenuated chicken-embryo-origin (CEO) vaccines to control this disease, because CEO ILT vaccines can exhibit significant pathogenicity in young birds, with an associated economic cost. The observed pathogenicity of CEO ILT vaccines is inconsistent in the field, leading to a widely held belief that the illness seen in chickens following the use of CEO ILT vaccine results from improper administration and subsequent vaccine spread and back-passage. Vaccine back-passage is the enhancement of vaccine virulence as it spreads bird-to-bird. Therefore, better understanding of the cause of severe vaccine reactions following the use of CEO ILT vaccines is an important industry need.

CEO ILT vaccines have been shown to be a mixture of viruses with differing biological properties. In this study, two of these subpopulations of virus from a commercial CEO ILT vaccine, designated UDCEOD2 and UDCEOD3, were found to be nonpathogenic in broiler chickens. The specific objective of this research was to characterize these ILTV strains exhibiting reduced pathogenicity.

The viruses were found to lose viability upon passage in birds, embryonated eggs and in primary liver cell cultures. Two attempts were made to evaluate the dose and route of inoculation for vaccine studies. In both cases the titer of the virus was found to be too low to provide protection. Without the ability to establish immunity, experiments to evaluate the onset and duration of immunity were not possible. These highly attenuated strains of ILTV were passaged 20 times in birds. They did not increase in pathogenicity and demonstrated a decreased ability to replicate. It was not possible to passage these viruses multiple times in either embryonated eggs or in liver cell tissue culture.

The results support the hypothesis that ILTV CEO vaccines do not revert to virulence upon passage in birds. Highly attenuated strains of ILTV appear to have a limited ability to propagate in birds. Therefore, since vaccine stocks have been shown to be composed of a mixture of genetically related viruses exhibiting differences in pathogenicity, “reversion to virulence” may represent a competitive situation where more infectious (virulent) subpopulations in the CEO ILT vaccine outcompete those that are nonpathogenic and less able to replicate when improper vaccine administration allows vaccine spread and back-passage in the field.