Tuesday, July 12, 2005

Antibiotic Feed Ban?

I graduated from veterinary school in 1965 and one of the first seminars I attended was on antibiotic drug resistance with the idea of banning the use of antibiotics in livestock feed. Today (2005) forty years later, the U. S. Food and Drug Administration (FDA) faces regulatory petition to ban antibiotics in the feed. Why? Are the proposed regulations politically motivated and unnecessary? Science versus politics? 

The Preservation of Antibiotics for Medical Treatment Act of 2005 was reintroduced in the Senate with a House companion expected to follow. Sponsored by Senator’s  Olympia Snowe and Edward Kennedy, the bill would phase out non-therapeutic use of antibiotics in feed over two years unless manufactures adequately demonstrate that specific drug uses do not promote resistance in humans. The petition and legislation targets penicillins, tetracyclines, macrolides, lincosamides, streptomycins, aminoglycosides, and sulfonamides. Since 1965, this issue has been proposed and scientific data has been presented to no avail. Science versus politics?

The Animal Health Institute (AHI) state “ Scientific evidence, including government monitoring and surveillance data, demonstrates the careful use of antibiotics in food animals has public health benefits that far out weigh the very small risks.” “ We oppose these misguided efforts and will continue to work to ensure the proper and careful use of antibiotics to keep food animals healthy and contribute to public health through the provision of a safe supply of meat, milk and eggs.”

As recent as October 2003, FDA’s use of Guidance #152 establishes safety criteria for evaluating antimicrobial drugs with regard to microbiological effects on bacteria and human health concerns. This establishes if there is a valid risk assessment done that show’s a significant problem, FDA has the power to deal with it. American Association of Bovine Practitioner’s (AABP) Executive Director, Dr. Gatz Riddell states, “ advocacy groups are blatantly against antimicrobials in production animals and this political pressure is based on distorted facts.”

I stay confused on this issue.

 In the April 15 issue of the Morbidity and Mortality Weekly Report (MMWR), which is published by the National Centers for Disease Control and Prevention, reports that food borne infections caused by several bacterial pathogens are on the decline. The MMWR describes preliminary surveillance data for 2004 and compares them with baseline data gathered from 1996-1998.

The report states that the estimated incidence of infection with Campylobacter decreased 31 %, Crytosporidium and Listeria decreased 40 %, Shigatoxin producing Escherichia coli 0157 decreased 42 % and overall Salmonella infections decreased 8 %.

Although Salmonella incidence decreased overall, of the most common Salmonella serotypes, only the incidence of S. typhimurium decreased significantly, 41 %.

“Dramatic multiyear reductions in illnesses from E. coli 0157 mean the U. S. is now below Healthy People 2010 goal of 1.0 case per 100,000 persons. This is a remarkable national achievement, “ said Merle Pierson, PhD, USDA acting under secretary for food safety. “ We are also very close to meeting the Healthy People 2010 goal set for illness from Listeria monocytogenes and Camplobacter.”

The reductions in illnesses have occurred concurrently with several important food safety initiatives and educational efforts. (Not withdrawal of antibiotics) Multiple interventions that might have contributed to this decline include industry response to the FSIS 2002 notice to manufactures to reassess control strategies for STEC 0157 in the production of ground beef. Enhanced strategies for reducing pathogens in live cattle and during slaughter may have also played a role.

References:
DVM Magazine; May 2005; Exclusive News
JAVMA Vol 226, No 11, News/Public Health


Thursday, December 23, 2004

Electronic Identification of Cattle

This author is not trying to get into the debate of promoting an animal identification plan but to provide information or location where more information can be obtained about such a plan.
     U.S Agriculture Secretary Ann M. Veneman stated “All of these animal health issues point to the importance of the development of a National Animal Identification System, which is a key priority for USDA… Together, we must develop a system that works.”
     The United States Animal Health Association (USAHA) has endorsed a plan to implement a national system for animal identification as a work in progress.
     The U.S. animal Identification Plan (USAIP), as it is called, defines the standards and framework for implementing a phased-in national food animal and livestock identification program.
     The National Animal Identification Development Team that was comprised of a diverse group of livestock industry participants including producers, producer’s organizations, breed associations, marketers, processors, and state, federal animal health officials were given the task to develop a system to assist in rapid animal traceback in the event of an animal health emergency.
     To stay informed of the rapidly changing proposal and the implementation of a USAIP plan, producers and others with interests in the industry are encouraged to use http://www.usaip.info/. Many of the rules and details of the proposed plan will become more evident as it moves through the political process.
     Another source of information can be obtained from Electronic ID, A User’s Manual published by Beef, December 2003.
     This issue of Beef was solely dedicated to examining animal identification (ID) using radio-frequency identification (RFID) technology. It was designed to add to the industry awareness of animal traceback in general and RFID technology specifically. The RFID technology appears to have the inside track to become the foundation of such a traceback system.
     The December 2003 issue included articles detailing the technology, its providers, the specifications, and to help the livestock producers evaluate and understand electronic ID.
     Kansas State University in cooperation with Beef magazine did an extensive survey of the products and services offered by various companies in the animal identification business. These results may be found at http://www.beefstockerusa.org/.
     A Guide for Electronic Identification of Cattle produced by Kansas State University Agriculture Experiment Station and Cooperative Extension Service is an excellent publication providing an overview of radio frequency technology and its application in a national identification program for the beef industry.
     Establishing common data sharing standards is becoming critical to the future of the segmented beef industry. A collation of five leading agriculture data service companies have announced plans to create this industry’s first data exchange standards.
     The five participating companies:
  • AgInfoLink USA, Longmont, Colorado
  • APEIS Corporation, Norfolk, Nebraska
  • Emerge Interactive, Inc., Sebastian, Florida
  • IMI Global, Inc., Platte City, Missouri, and
  • Micro Beef Technologies, Ltd., Amarillo, Texas                  are establishing the Beef Information Exchange to address the need for a uniform set of data movement standards among the nation’s beef industry producers.
     Initially, the Beef Information Exchange will facilitate rapid and secure sharing of data required for a national identification system to address potential mandatory identification and traceback requirements. The system may be expanded to accommodate a greater variety of production data. Establishing common data-sharing standards creates a standard information platform, which will allow for greater operational efficiency, reduced supply uncertainties, and potentially lower costs.
     The time has come to learn more about an animal identification plan and make it work in our segmented industry.
     References:
 1. Cattle Health Report
 A National Institute for Animal Agriculture Publication
2. A Guide for Electronic Identification of Cattle.
    Kansas State University Agricultural Experiment Station and Cooperative Extension Service
3. Electronic ID: A User’s Manual
    Beef Magazine, December 2003
4. Beef Production Medicine 2004

Monday, September 20, 2004

Implants and thier Use in the Feedyard


Most procedures performed during the processing of feeder cattle are geared toward the prevention of problems and, therefore, economic savings. However, implanting gives a direct enhancement of performance and, therefore, economic gain.
When administered properly, implants make money for the cattle feeder. It is estimated that an implant provides a return on investment anywhere from 10:1 to 20:1. That variation is due to such factors as market price, size, weight and genetic potential of the feeder animal, and type of ration.
In any case, implanting feeder cattle is a sound economic practice that should be performed for financial gain.
Implants act to improve feed efficiency (pounds of feed required to produce a pound of gain in body weight) and rate of gain (pounds of body weight gained per day).
They are considered to be anabolic agents, enhancing protein metabolism and muscle production in the animal. Though the mechanism of action is not yet completely understood, it is felt that these agents regulate naturally produced compounds in the body to enhance growth and muscle production. In effect, they may stimulate a more consistent daily production level of these compounds, as they tend to be erratic by nature.
Our industry faces a continuing challenge to educate the consumer as to the wholesomeness and safety of our product. Public concern about implanted beef plus the concept and promotion of “natural” beef-have clouded the realistic picture.
These concerns are unjustified and the issue is one of public relations and education, rather than one of health.
Consider these facts: 168 pounds of implanted beef contains the same amount of estrogen as one egg. Four ounces of beef contain 1.59 nanograms (1 billionth of a gram) of estrogen. An adult man averages 130,000 nanograms of estrogen production daily, and an adult woman produces an average of 480,000 nanograms of estrogen daily. The point is, not that these relatively higher levels of estrogen in eggs or humans are harmful (this is not the case), but that the level of estrogen in implanted beef is minuscule.
A second or reimplant is often considered, especially in “longer day” cattle-those fed more than 100 to 150 days. Many variables have to be considered when deciding whether or not to reimplant, and there is no single answer.
Consideration must be given to the type of cattle being fed (sex, breed, weight, condition on arrival, genetic potential, etc). In addition, the layout and facilities of the feedyard may or may not be conducive to reworking the cattle for reimplanting.
Many reimplanted cattle weigh in excess of 800 pounds and the working facilities should be adequate to safely and effectively handle these larger cattle. Excessive stress or injuries could defeat the economic gain of the reimplant.
If reimplanting is performed, consider this trip through the chute an opportunity to perform other health-related procedures. These might include a respiratory virus revaccination to abate late day respiratory pulls; a seven-way clostridial revaccination for enterotoxemia and blackleg; or a pour-on or dip for lice.
Proper technique is vital to the efficacy and performance of the implant. An experienced, conscientious person “at the head” when processing cattle will make the feedyard money. Special attention to sanitation and proper placement is imperative.
Currently, available implants are required to be placed subcutaneous on the dorsal surface of the ear outside the annular cartilage ring. After implantation, the implant should be easily palpable and away from any potential trim sites. Avoid any blood vessels or previous implants and ear-tag first so as not to disrupt an implant site.
We encourage processing crews to use sharp implant needles, change them when dull, and lay the needle on a disinfectant-soaked sponge between usages. Do not dip the needle in a liquid disinfectant as this moistens the inner core, causing partial dissolution and “gumming” of implants.
It is helpful to run occasional checks to evaluate implant technique. This may be done either at initial processing, when doctoring cattle, at reimplantation, or on a post mortem check at an abattoir. Crushing or bunching implants may result in over-absorption and decreased duration of efficacy. Abscessed implants, walled-off implants, and implants placed in the cartilage of the ear may result in under-absorption and decreased efficacy.
The buller syndrome sometimes is tied to implants. Though there may be some relationship, this problem probably is more related to technique, rather than brand of implant used. In our experience, the buller syndrome is a multi-factorial problem—more tied to season of the year, weather patterns, type, age and breed of cattle, bunk management and pen space per head. 
     Growth Promotants



      Classification

Ingredients
           Product





     Category I


       Active Days = < 70


Low Estrogen Equivalent


           Ralgro

36 mg Zeranol
           Synovex C

10 mg Estradiol Benzoate, 100 mg Progesterone
           Component E-C

10 mg Estradiol Benzoate, 100 mg Progesterone
           Revalor G

8 mg Estradiol, 40 mg TBA
           Synovex T40

8mg Estradiol, 40 mg TBA
           Component TEG

8 mg Estradiol, 40 mg TBA



     Category II   


 Active Days = >70, <90


Strong Estrogen Equivalent


           Synovex S

20 mg Estradiol Benzoate, 200 mg Progesterone
           Synovex H

20 mg Estradiol Benzoate, 200 mg Testosterone Propionate
           Component E-S

20 mg Estradiol Benzoate, 200 mg Progesterone
           Component E-H

20 mg Estradiol Benzoate, 200 mg Testosterone Propionate
           Ralgro Magnum

72 mg Zernol
           Compudose

25.7 mg Estradiol 17-B
           Encore

43.9 mg Estradiol 17-B



     Category III


Active Days = > 90, < 110


       Low TBA Equivalent


           Revalor S

24 mg Estradiol, 120 mg TBA
           Synovex T120

24 mg Estradiol, 120 mg TBA

Thursday, July 1, 2004

What is Pre-conditioning?

The Bovine Respiratory Disease Complex (BRDC) results from a complex series of steps: (1.) stress, (2.) viral infection, and (3.) bacterial infection.

Stress can be caused by routine procedures such as castration, dehorning, nutrition, weather (change of environment), congregation (co-mingling) and transportation. Stress causes the entire body to be more prone to infection. This occurs by allowing disease causing organisms easier route of entry and by disarming some of the body’s important defense mechanisms against disease.

Viruses that commonly take advantage of the situation usually include IBR and BVD. Other viruses such as BRSV and PI3 sometimes can cause problems. Although viruses may cause death, the major role they play in the BRDC is to allow the third factor-bacteria-to gain a foothold and possibly lead to death.

Mannhemia haemolytica, Pasteurella multocida, and Haemophilus somnus account for
the majority of bacterial infections of the BRDC.

This complex series of steps causing the BRDC with large economic losses with high morbidity and mortality resulted in the development of pre-conditioning.

Pre-conditioning programs vary considerably, but generally include weaning, training to eat and drink from troughs, vaccination, and treatment for internal and external parasites, castration, and dehorning. Pre-conditioning is a general term used in the beef industry to basically describe the time period and management of calves which takes place at the farm/ranch before arrival into the feedyard. Therefore, pre-conditioning can be defined as the preparation of feeder calves for the marketing and shipment to the feedyard. Pre-conditioning is intended to give the calf time to return to normal behaviors, improve feed intake, and allow time for the immune system to rebound from weaning stress and immunization. (Bartle, Steve ADM Alliance Nutrition) Don’t confuse or compare the term pre-conditioning towards backgrounding. Backgrounding is a similar approach; however, the vaccinations and other management procedures take place at a separate facility-not at the farm/ranch.

American Association of Bovine Practitioners (AABP 1968) defined the following areas in pre-conditioning:
  • Weaned at least three weeks before sale.
  • Trained to eat from a feed bunk and to drink from a trough
  • Treated for parasites.
  • Vaccinated for blackleg, malignant edema, PI3, IBR, Pasteurella, and sometimes BVD and Haemophilus.
  • Castrated and dehorned.
  • Identified with an ear tag.
  • Sold through special auctions
Historically, most pre-conditioning programs supported a 21-30 day weaning period; however, more recent efforts have been directed toward increasing the number of days weaned before shipment and improving management procedures on the ranch. The Texas Ranch to Rail data shows it take at least 45 days for calves to develop independent behaviors, achieve consistent intake targets, and to develop immunity from vaccination. Therefore today, most programs require a 45-day weaning period. Several pre-conditioning programs have also been replaced by individual programs developed at the producer level and by commercial programs promoted by biological firms. (Radostits, Otto Third Edition)

The vaccination requirements also vary but most include modified live vaccines such as IBR, BVD, PI3, BRSV, Mannheimia haemolytica leukotoxoid, and clostridial bacterins. In any pre-conditioning program, it’s important to meet beef quality assurance standards and all label directions should be followed regarding injection location, dosage, needle size, and timing of vaccination including boosters.

Different alliances of which this author works with have different requirements but a general outline includes:
  • Ownership-cows or calves originate from pre-conditioned facility
  • Bulls must be castrated and healed before shipment
  • Calves dehorned or tipped and healed before shipment
  • Calves must be weaned for 45 days or longer
  • Treated for internal and external parasite
  •  Vaccination program:
    At branding or six weeks prior to weaning:
    A vaccine containing chemically altered modified-live IBR and PI3, modified-    live BRSV and inactivated BVD.
    Seven-way clostridial bacterin
    Mannheimia haemolytica leukotoxoid or Mannheimia haemolytica and Pasteruella multocidia combination
  • Radio frequency identification ear tag
  • At weaning:
    Revaccinate with modified-live IBR, PI3, BRSV and BVD
  • Heifers will need to be palpated and determined open or an abortion program   must be implemented at point of origin.
 The nutrition and management during the pre-conditioning period is dependent upon the producer’s objective. Oklahoma State University (extension publication F-3031) list several possible objectives:
·        Optimize condition and health for the pre-condition phase
·        Produce added weight at low cost
·        Market calves through a program requiring pre-conditioning for best market potential
·        Minimize the risk of digestive upsets and disease
·        Achieve a specific target weight.

Suggested Nutrient Recommendations for Stressed Calves

(Adapted from 1996 Nutrient Requirements for Beef Cattle)
     Dry Matter,%-------------------       80-85
     Concentrate,%------------------       50-75
     NEm, Mcal/lb-------------------      0.82-0.90
     NEg, Mcal/lb--------------------      0.46-0.56
     Crude Protein,%-----------------     12.5-14.5
     Calcium,%-----------------------      0.60-0.80
     Phosphorus,%-------------------      0.40-0.50
     Potassiun,%----------------------     0.80-1.40
     Magnesium,%--------------------    0.20-0.30
     Sodium,%-------------------------    0.20-0.30
     Copper,ppm------------------------- 10-15
     Iron,ppm----------------------------- 100-200
     Manganese,ppm--------------------  20-40    
     Zinc,ppm----------------------------  75-100
     Cobalt,ppm-------------------------- 0.10-0.20
     Selnium,ppm------------------------ 0.10-0.20
     Iodine,ppm--------------------------  0.30-0.60
     Vitamin A, IU/lb-------------------  2500
     Vitamin E, IU/lb-------------------  50-100

Management practices that minimize weaning and arrival stress will result in fewer calves requiring health treatments. The importance about prevention of disease, particularly the BRDC, does not only affects the morbidity (health treatments) and mortality (deathloss) but data also shows the impact on average daily gain, feed efficiency and carcass merit.

Health and Performance Effects of Preweaning Management

(Reprinted from Cattle Health Tech)
How does preweaning management influence disease resistance, average daily gain, feed efficiency, quality grade, and yield grade of carcasses? This question has been addressed in various research projects over the course of several years.
1. Compared to fresh, unweaned calves, calves that were preweaned and fed for 30-45 days at the ranch had:
  • 20 % less sickness and death loss
  • Similar average daily gain
  • 2%-to 7% poorer feed conversion
2. Compared to fresh, unweaned calves, calves that were limit creep fed (1-3 lb/head/day) for the last 60 days had:
  • 20 % less sickness
  • 25 % less death loss
  • 0%-3% better feed conversion
3. Compared to polled steers, calves that must be castrated and/or dehorned/tipped at the feedyard generally had:
  • 3 % poorer average daily gain
  • 3 % poorer feed conversion
  • Lower quality grade at slaughter (castration only)
4. Compared to nonvaccinated calves, calves that were vaccinated for IBR, BVD, PI3, BRSV and Pasteurella on the ranch had:
  • 20 % to 30 % less sickness
  • 40 % less death loss
  • Similar feedyard performance.
 The Texas A & M Ranch to Rail program has consistently shown an impact of health on the ability of steers to express their genetic potential and the costs associated with sick cattle beyond the cost of medicine. Healthy steers had an average of $93.20 more favorable return than sick steers in the 20003 program and an average net return over a five-year period has been $37.54 per head.


General Rules for Treatment in the Feedyard

 In the feedyard, questions arise daily concerning medication programs for respiratory disease. Its the single biggest disease problem.

When faced with a history of no response to medication, we spend very little time on the actual medications. The more important consideration is determining management procedures aimed at prevention and treatment of diseased cattle.

Following are some rules of treatment that need to be observed when evaluating a
feedyard health program. They also are good guidelines when training new personnel to pull and treat sick cattle.

Pull Sick Animals Early
The first and foremost rule of treatment is to pull sick animals early, pull appropriately and treat aggressively.

If sick animals are not pulled from the pen before respiratory disease becomes an advanced problem, medication response will generally be very poor.

Good pen riders are able to spot animals just as they are breaking with pneumonia. This corresponds to the latter stages of the incubation period of disease and is before the animal actually shows clinical signs. It takes a certain eye to be a good pen rider; some
cowboys seem to have it instinctively; others have developed it over the years.

Pull Animals Properly
Animals must be pulled for sickness appropriately. If sick animals are not pulled properly, they will not get the hospital care they need, hospital pens will become needlessly overcrowded, and the doctor crew will become overworked.

Heavy pulls do not always coincide with proper pulls. Sometimes, heavy pulls from a pen occur, leaving some sick animals and pulling some with no obvious signs of illness. If heavy pulls occur in a pen (greater than 25%), then steps should be taken toward
mass medication.

Treat Aggressively
What does treating aggressively mean? It means that when an animal is pulled initially for respiratory disease, it is treated with strong therapeutic agents (antibiotics) that will stop pneumonia at its earliest stages, and not allow further progression of the disease
process. This will effectively decrease total treatment days, decrease the number of retreatments and, of course, prevent high death losses.

With good therapeutic agents and supportive care, sick animals will not have to be rested between treatments, if additional treatment is deemed necessary. Antibiotics are stressful on the animals system, so supportive measures are used to stabilize the adverse changes that occur following treatment, as well as treat the disease.

Supportive Care
Supportive care includes such drugs as (1) B-complex vitamins, to stimulate the appetite and replenish body loss, (2) antihistamines to open swollen, narrowed airways, and
(3) electrolytes to replace body water loss as well as body electrolyte loss.

The primary objective of supportive care is to counteract the serious side effects of disease and subsequent changes referable to antibiotic usage. Supportive care also includes nutritional support in the form of fresh hay and high-energy rations, plus hospital
management aimed at prevention of overcrowding and further stress.

All drugs used in beef cattle, including antibiotics and supportive medications, have a specific purpose and use. Your consulting veterinarian is the best source of information on proper use of these drugs. The feedyard health crew must be well versed on the
proper use of drugs because a drug used improperly is sometimes worse than no medication at all.

Visual Inspection
Visual inspection of sick animals in the hospital is absolutely necessary. Occasionally feedyard personnel will look at the thermometer and forget to look at the animal.

To prevent this oversight, all animals should be given a severity code, such as severely sick, moderately sick or mildly sick. This simple system encourages the health crew to assign a uniform code to the sickness of all animals.

This coding system allows sequential assessment of sick pulls and progress through the hospital treatment program. Secondary benefits of this system allow various persons to treat the animal on subsequent days and assess response to treatment. Also, it allows assessment of sick animal pulling.

Three-Day Treatment
If you are using an antibiotic that requires daily administration, treatment of sick animals should be continued for at least three successive days. This can be accomplished with one shot or administration or with three successive days of treatment. In the end, this will decrease the treatments and the pen deaths following treatment.

Research and experience has shown that only one or two days of treatment has detrimental side effects. Antibiotics can be changed during these three-day periods, but not after only one day of treatment.

Alternate routes of administration or increased dosages can be used on the second day of treatment when added response is needed on this treatment day. If treatment response is inadequate after two days of therapy, then alternate treatments or increased dosages should be considered.

You never want to give up on the treatment of an animal, but you should realize the limitations of antibiotic therapy and strike a happy median between cost-benefit and continued treatment. It is very discouraging to treat an animal day after day, only to have it die after an extended treatment period.

As a general rule, treatment of a sick animal for six continuous days or three treatments will constitute adequate treatment. Continued treatment often will result in a chronically sick animal or a dead animal.

Accurate Records
The last rule of treatment is the keeping of clear, concise and accurate records. The feedyard runs on paperwork. Because of the large numbers of cattle that any feedyard handles and many sick animals that are treated, records are absolutely essential. These records will not only provide bookkeeping services, but will allow you to assess treatment response. Records must be (a) easy to fill out, (b) supply the appropriate information, and (c) be easily compiled for further evaluation.

These rules are formulated from sound medical practice and experience. Some of them vary depending on your particular antibiotic or medication program. But they will, in most cases, result in a successful medication program.

Friday, September 26, 2003

Mass Medication – The Practice and Problems

Mass medication programs are useful when used appropriately in food animal production. But your goal should be kept in focus when deciding the method, route of administration and product to be used.
   The treatment may be preventive or therapeutic, or a combination of the two, depending upon the stage of the disease in question in the individuals comprising the group treated. When utilized effectively, mass medication is a medically and economically sound procedure, combining veterinary science with practical production economics. On the other hand, when misused or misdirected, it can be an inefficient additional expense and a confounding factor to satisfactory therapy. Mass medication is defined as the administration of a pharmaceutical product to an entire group of food animals for disease control purposes.This treatment usually includes antibiotics directed at bacteria, mycoplasmas or rickettsia and compounds controlling
coccidial infections.

Goals of Mass Medication
   Two main goalsmorbidity and mortality controlare most often the focus of mass medication programs in food animals. Morbidity control is more easily and effectively achieved; mortality control is more difficult.

Morbidity
   Morbidity is defined as the cumulative sum or percentage of animals that must be removed from their pen or herdmates for individual treatment. Costs incurred on these animals include not only direct medical costs, but also the time and money spent in removing and holding them in a separate location for treatment and returning them back to the group.
   By controlling morbidity, at least one of the following  three objectives are realized:
   1. Health costs are minimized when treating the entire group with mass medication (plus the remaining sick individuals after mass treatment), resulting in less total dollars spent than treating all sick animals on an individual basis from the start.
   2. Facilities are inadequate to handle a large number of sick animals on an individual basis, thus making mass treatment more cost effective than facility construction or expansion.
   3. Personnel are lacking in time or capability to handle a large number of sick animals on an individual basis, thus making mass treatment more cost effective than hiring more or better capable personnel.
   On a strictly medical cost return example, lets assume that the mass medication of a group of 100 animals undergoing a disease outbreak costs $2 per head for a total of $200. And assume that the cost to treat an individual animal for the disease is $15. Using these figures, mass medication in order to  be cost effective, would have to prevent or stop the disease in at least 14 animals that otherwise would have required individual treatment. Remember, this solely assesses the return on a medical cost basis and does not include facility or personnel costs, or additional losses occurring when an animal must be separated  from the group.
Mortality
   Mortality, defined as the sum or percentage of dead cattle out of the subject group, is more difficult to alter directly with mass medication. Certainly when indirect factors such as inadequate facilities or poor ability to identify sick individuals early are a consideration, then mass medication may improve the final mortality rate.
   However, when all aspects of individual cattle identification and treatment are adequate and uncompromised, mass medication as a rule does not decrease overall mortality. Some sick individuals require more therapeutic care and supportive management than what can be provided in a mass medication program. Additionally, mass treatment can make sick animals harder to identify by temporarily abating the clinical signs but allowing a relapse back into clinical disease one to several days after the program.

   Any medical procedure, including mass medication, can be evaluated by four criteria:
     1. Cost. Is the expense of the mass treatment justified as compared to the results expected or observed with less expensive products or combinations?
     2. Stress. How stressful is the mass treatment on the cattle? Does clinical benefit compensate for the stress involved?
     3. Efficacy. How effective is the mass treatment (in vitro and in vivo)?
     4. Convenience. How easy is the mass treatment and does the convenience compensate for any shortcomings?

Route Of Administration
   Several types and forms of products are available utilizing various routes of administration. The route  chosen depends upon the disease being treated, the facilities and husbandry conditions and the economics of the delivery system or procedure. Here are four  alternative routes:
   1. Feed. Several feed ingredients are available and approved for mass medication in beef cattle. The key factor in successful group medication is consumption of adequate levels of the ingredient by all or most of the group. As simple as this sounds, it often is overlooked. Either uneven mixing practices, behavioral eating patterns or individual animal anorexia due to disease may  influence the outcome of mass medication.
   Sick animals often go off feed. So mass medication should be geared as a preventive approach early if respiratory disease control is the focus.
   Oxytetracycline and chlortetracycline are available as feed additives for disease control. Additionally, oxytetracycline is available in combination with neomycin, and chlortetracycline is available in combination with sulfamethazine. Indications for use and withdrawal times vary with the level or dose of the product included.
   Besides being included into mixed feed in a microingredient or premix form, these products are also available in a crumbles or pellet form to be top dressed over feed. The crumbles and pellets have shown to be especially palatable to cattle and may stimulate increased consumption as a secondary benefit.
   For control of coccidiosis, four feed ingredients have been approved: amprolium, decoquinate, lasalocid and monensin. In determining which product to use, its important to know (a) the life cycle of the coccidial organism, (b) the duration of time it must be fed, and (c) how to include it in a feeding program. Also, each product differs in approvals to be fed with other ingredients and this must be considered.
   Tylosin is also approved as a feed ingredient with a primary role of liver abscess control in feeder cattle.
   2. Water. Fewer products are available to medicate water than for feed. Sulfonamides are the antibacterial compounds available for medicating water. The same principle applies to water medications as with feedthe animals must drink the water in order to receive a benefit. Water medications can decrease the palatability of the water, and this may increase the uncertainty of adequate delivery of the medication to appropriate animals. In an attempt to overcome this, flavored gelatin powder has been added with the medication to alter the smell and taste of the water. Practitioners vary in their preference of flavor to be added. To achieve the effective dose required, the mechanics of water medication must be monitored closely to ensure that the proper amount is added initially and maintained through the medicating period. Continuous flow or automatic refill tank systems prove unmanageable, so all sources of water must be manually filled and medicated.
   3. Oral. Individual oral medications require that the animal be caught and restrained for administration of the product. Liquid and bolus forms are available. The liquids include neomycin sulfate and some sulfonamides. These are primarily for bacterial enteritis and absorption through the GI tract is limited. The liquid medications are administered through a drench wand or hook.
The boluses available consist of one or a combination of sulfonamides and neomycin sulfate. They are approved for the treatment of enteritis, respiratory disease and foot rot. Absorption across the GI tract must occur at significant levels in order to reach target tissues of lung and feet.
Long-acting, sustained release boluses containing a sulfonamide are available, giving 48 to 72 hours of therapeutic blood levels from a single administration. Boluses are time-consuming to administer and adequate head restraint must be obtained. Multi-dose balling guns are frequently used to administer boluses but have been shown to result in a higher incidence of pharyngeal trauma and abscessation than single dose equipment. This may be a consideration during mass medication of a large group when time becomes a factor.
   4. Injectable. Antimicrobials alone or in combination represent a high percentage of all the mass medication regimens performed on food animals. However, increasing concerns over injection site trauma and scarring in muscle tissue has led to the reevaluation of many habitually routine procedures, not the least of which is intramuscular mass medication.
   The intramuscular, subcutaneous and intravenous routes of administration have all been used for mass medication purposes. The intramuscular route has been the method of choice until recent concerns about carcass quality. The neck area is the site for both intramuscular and subcutaneous injections. A disadvantage of intramuscular injection of mass medications is the muscle soreness that can develop with some products or combinations. The propylene glycol-based products and 200 mg/ml products are especially noted for this. In extreme cases, the stress caused by muscle soreness precludes any therapeutic benefit achieved from the injection.
   The subcutaneous route of injection becomes increasingly more popular when compatible with the medication being administered. Though some scarring may occur, the muscle trims at carcass fabrication are minor compared to intramuscular injections. Large volumes of medication are more easily accommodated. Technique is critical to obtain a true subcutaneous injection, and it is preferable to manually tentthe skin prior to needle insertion to avoid abrasion of underlying muscle tissues.
   The intravenous route of administration is desirable for compatible products due to negligible impact on carcass quality. But like the oral boluses, this often proves too time-consuming and inconvenient  for mass medication purposes. If injectable sulfonamides are used, however, this route must be utilized as it is the only approved route of administration  for these products.
   Long-acting injectable antimicrobial formulations are currently available. Long-acting oxytetracycline is available in a 200 mg/ml and 300 mg/ml preparation. Long-acting
combinations of procaine penicillin G and benzathine penicillin are also being marketed commercially. Another parenteral administration is the use of Tilmicosin at the label dose of 10 mg/kg.
   Previously, bioavailability and convenience were the major concerns regarding mass medication routes of administration. However, recent pressures from the beef packing industry, and subsequent response and investigation by production-oriented veterinarians and producer organizations, have prompted new research and focus on injection site dynamics and tissue characteristics.
   Mass medication techniques are especially suspect when a majority, or all, of the food animals in a particular group are medicated. It is critical that all animals medicated are somehow identified so appropriate withdrawal times may be observed and potential carcass trims at slaughter may be traced back to the problem procedure.

Specific Program Applications
   In the feedyard. Mass medication programs are widely utilized in receiving programs on high risk stressed or sick cattle. Injectable antibiotics or combinations are the most common form of treatment.
   Respiratory disease is the main focus and these programs are geared toward morbidity control. Intramuscular and subcutaneous routes of administration are the norm and programs vary from one to three days in duration.
   Occasionally during prolonged wet or dry periods, foot rot reaches epidemic proportions in a feedyard. Individual therapy is effective; however, many of these cattle are in the finishing phase of the feeding period. So it is costly (in lost performance) to remove them from their home pen and inconvenient to a follow a withdrawal period.
   Mass medication with a feedgrade tetracycline has proven effective in stopping epidemic foot rot. Oxytetracycline fed at just less than two grams per head per day has no withdrawal requirement and is an effective prophylaxis against further cases; also, its therapeutic in mild to moderate cases already present.
   Tylosin is available in feed additive form for control of liver abscesses. Prior to the introduction of this practice, it was common to feed one of the tetracyclines at high levels (2-4 grams) three days a month for the same purpose.
   Decoquinate, lasalocid, or monensin are commonly fed as a coccidiostat in receiving and starting rations. Factors affecting the choice as to which is fed include (a) the degree of challenge, (b) concomitant approvals with other additives and (c) feeding program.
   Amprolium also has been approved and used as a treatment for clinical coccidiosis, as well as being apreventive compound.
   In stocker operations. Mass medication in stocker cattle is widely utilized, much as in high risk stressed or sick feeder cattle. But many stocker operations dont have holding and working facilities to handle sick cattle. Thus, individual animals must be roped and thrown or driven long distances to facilities in order to be treated. Either scenario is highly stressful and may not be conductive to a satisfactory treatment response.
   Therefore, it often is cost effective to aggressively mass medicate received cattle in order to minimize, if not prevent morbidity. Parenteral aminoglycosides, particularly neomycin, require extremely long and somewhat unpredictable withdrawal periods200 days or more in some casesand should not be used to avoid a violative residue.
   Surfactants, though not antimicrobials, are commonly placed in the water of stocker cattle for bloat prevention. This is especially useful in high moisture, rapidly growing legume pastures where bloat potential is high. Of course, enough surfactant must be ingested, within tolerable palatability limits, to prevent a frothy bloat in the rumen. When they quit drinking, you have added too much.
   In cow-calf operations. Antimicrobial mass medication in cow-calf herds usually is directed at calf disease. Antibiotics may be included in creep feed as prophylaxis against respiratory disease, although this is generally unsuccessful since sick calves usually back off the creep feed. Individual calves are often caught and handled one time during an outbreak and given long-lasting oxytetracycline injection and longacting sulfa boluses.
   Weaned calves also can be medicated through the water with sulfonamides. This proves too costly in sucking calves, however, because they share a common water source with the cow and most of the medication goes to the cow.
   Anaplasmosis control in cows has been achieved with mass medication in endemic or problem areas. For prophylactic purposes, constant feeding of a tetracycline at low to moderate levels has been utilized. During an acute outbreak, herds can be medicated with intramuscular long-lasting oxytetracycline at 9 mg/lb body weight.
   For prevention of grass tetany and milk fever, magnesium and calcium can be provided to cows on a mass medication basis. This is usually in the form of free choice mineral licks or blocks.          
   Additionally, prostaglandins have been injected on a mass basis for estrus synchronization in cow herds.

Mass Medication Criteria
   Since the decision to mass medicate a group of animals is quite subjective, here are several criteria to consider:
   1. Clinical appearance and past performance of similar cattle. This requires a key person to evaluate the animals upon arrival and daily thereafter in determining the need for mass medication. A knowledge of the morbidity/mortality patterns of previous animals from the same origin is helpful. A keen ability to observe and clinically evaluate the group also is helpful.
   2. Morbidity patterns. This criterion proves useful for deciding when to mass medicate for respiratory disease in the feedlot. When morbidity exceeds predetermined percentages, either on a daily or cumulative basis, mass medication is indicated. For example, a pull rate out of a pen of 10% any one day or a cumulative 25% over a three-to-five day period indicates mass medication.
   3. Feed consumption. When routinely measured, feed consumption can serve as an early indicator of an impending disease break, before observable clinical signs appear. A sudden drop in feed consumption suggests mass medication should be considered, particularly in high risk cattle.
   4. Body temperature. When cattle are being worked as a group, rectal temperature has been used as a judgment criterion to selectively medicate individuals. Individuals below the selected temperature point receive either no antibiotic or a less expensive, less efficacious one.
   However, it must be recognized that (a) temperature elevations occur for reasons other than infection and (b) animals harboring a bacterial infection do not always maintain a fever.
   The ambient environmental temperature, the animals disposition, and the order in which the animal is worked in the group can all elevate the body temperature. Conversely, extended disease progressing to a weak moribund animal or previous treatment with corticosteroids can lower the body temperature.

Choosing the Product
   Product choices are reasonably clear cut for the feed, water and oral routes of mass medication. The injectable route is not so clear.
   Here are some characteristics to consider when selecting an injectable mass medication program:
   1. FDA approved for use in beef cattle. Extralabel drug usage currently is left to the discretion of the veterinarian under some general guidelines. Abuse of this privilege may jeopardize the veterinarians position.
   2. Inexpensive. Return on the money spent is the key here. Will an expensive but highly efficacious drug afford results that justify its use over a less expensive and possibly less efficacious drug?
   3. Effective against respiratory and GI pathogens. These conditions are common and frequently found simultaneously in the same animal.
   4. Active in small volumes. Injection mechanics and tissue damage are more likely and of more concern with large volume formulations.
   5. Non-irritating upon injection. Injection site scarring and the stress of muscle soreness must be weighed against clinical benefit.
   6. Wide safety margin. Accurate dosing may prove difficult in a group with variable weights. Narrow safety margins increase the chance of overdosing and causing adverse reactions or toxicity.
   7. Easy to administer. The intramuscular and subcutaneous routes remain the easiest methods of delivery.
   8. No interference with subsequent antibiotic use. There are many theories and questions exist as to resistant bacterial strains after antibiotic administration. Most likely, resistance develops against antibiotics after previous treatment with a different one.
   9. Does not mask effects of disease condition. The alteration of an infection from clinical to subclinical adversely affects sick animal identification. Also, early or continued treatment can facilitate the development of a chronic disease.
   10. Short withdrawal time. Extended withdrawal times preclude the option to recognize and pull poorly performing animals. Also, it increases the risk of violative residues and, in extreme cases, may delay the marketing of a finished animal. 
   When choosing a specific injectable product or combination for mass medication, bacterial cultures and sensitivity determinations are of value, if time permits.
   Some antibiotics show 100% efficacy continuously over time, i.e. ceftiofur, sulfachlorpyridazine, and trimethoprim/sulfa on isolates of Pasteurella-Mannheimia/Hemophilas. Unfortunately, however, 100% cure rates are rarely experienced because effective antibiotic therapy is just one aspect of achieving a cure. The best results come from ongoing culture and sensitivity monitoring.
   In summary, mass medication is a health management tool that, when used appropriately, results in cost savings and sound economic return to the food animal producer. Careful planning and consideration should precede the implementation of a mass treatment program, clearly defining the goal to be achieved and a detailed plan of execution. For economic as well as professional reasons, indiscriminate administration of antibiotics to large groups of
food animals should be avoided.