Veterinary Quarterly. Extension Veterinary Medicine College of Veterinary Medicine & Biomedical Sciences

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1 REVIEW Extension Veterinary Medicine College of Veterinary Medicine & Biomedical Sciences Volume 22, Number 4 Winter Department of Large Animal Clinical Sciences, CVM, TAMU, College Station, Texas This is number eighty-seven of a continuing series of multi-species quarterly reviews and practice tips for veterinarians in Texas. Information in the Review is intended to be timely, concise and of practical value. Ideas and input from practicing veterinarians are encouraged. Sources of abstracts, articles or practice tips will be credited. Bruce Lawhorn Visiting Professor, Swine Practice F.C. Faries, Jr. Extension Program Leader for Veterinary Medicine Steve Wikse Associate Professor and Extension Veterinarian Beef Cattle BEEF CATTLE PRACTICE Update on Diagnosis of Trichomoniasis Trichomoniasis is one of the most devastating diseases of cattle. Although it no doubt has been present in Texas beef herds for many decades, it has been diagnosed with increased frequency in recent years throughout the state. Steps to diagnose trichomoniasis are critical to investigation of reproductive problems in beef herds. The following material covers important points about current guidelines for diagnosis of the disease. Reproductive Impact of Trichomoniasis The two most common ways Tritrichomonas foetus is introduced into Texas beef herds are by bulls or cows from a herd infected with T foetus slipping through poor fences to infect a clean neighboring herd; and by placing a newly purchased non-virgin bull that is infected with T foetus into a clean herd. Bulls that have had breeding experience must be tested for trichomoniasis prior to mixing with a clean herd! In this issue Following infection of cows with T foetus, conception occurs at a moderately reduced rate accompanied by embryonic deaths and abortions. The most common outcome of T foetus infections is early embryonic death, which results in repeat breeders. Traditionally, abortions due to tricho- 1. Update on Diagnosis of Trichomoniasis 2. Ethanol Boom Causing Multifaceted Paradigm Shift throughout Food Production Systems 3. Resources for Current DDGS Recommendations for Livestock and Poultry Feed 4. A Producer s Guide to Managing Porcine Circovirus-Associated Disease Available 5. Nuflor Oral 2.3% Concentrate Solution Available as Swine Drinking Water Medication 6. New Guidelines for Maximum Residue Limits (MRLs) for Pork Exported to Japan Changing How U.S. Swine Veterinarians and Producers Manage Drug Withdrawal Times 7. Placenta Submission Becoming More Important for Equine Abortion Diagnosis 8. Small Scale Composting as Practical Way To Dispose of Horse Manure 9. Sheep Management Classes Available Online 10. Marijuana Toxicosis in Dogs: 213 Cases 11. Veterinary Continuing Education Seminars 2007, Texas A&M University Educational programs of Texas Cooperative Extension are open to all people without regard to race, color, sex, disability, religion, age or national origin. The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Court of Texas Cooperating

2 moniasis were felt to occur mainly in early pregnancy. It is now well proven that they can occur throughout gestation right up to the time of calving. It s a new idea to consider T foetus infection as an important potential cause of mid- or late-gestation abortions. However, one study showed that a third of T foetus abortions occurred in the last trimester. Pregnancy rates in the high 70 percentiles occurred in recent clinical trials where replacement heifers were bred by infected bulls and where pregnancy was examined early. Abortions then occurred in the weeks following pregnancy diagnosis. Under natural conditions, pregnancy rates can be dismally low (in the 50 to 65 percent range) during the first year of infection in a naive herd. In an outbreak I encountered, a breeding group of 161 cows dropped from a pregnancy rate of 92 percent one fall to 65 percent the next fall. (There were 10 neighbor cows in the corral with my client s cows that fall.) Beef herds that have been infected for years may have pregnancy rates in the high 70 percentiles due to development of transitory immunity in infected cows. In outbreaks of trichomoniasis, palpation may reveal that there is a lower than normal percentage of cows in the last trimester of pregnancy and a higher number of cows pregnant in earlier trimesters. This is especially true in herds with long breeding seasons (6 to 8 months). Cows become infected in the first couple of months of the breeding season, but clear infection in 1 to 4 months and become pregnant. This leads to huge increases (3 months) in calving intervals and lower weaning weights. Diagnosis of Trichomoniasis Diagnosis of trichomoniasis is a challenge because other reproductive tract infectious agents can paint similar clinical pictures in beef herds. Reproductive losses due to Campylobacter foetus, Leptospira hardjo-bovis and bovine viral diarrhea virus infection can be indistinguishable from those of T foetus. The occurrence of pyometra in a small percentage of cases is an important unique manifestation of trichomoniasis. Diagnosis of trichomoniasis is accomplished by visualizing the motile organisms in cultures or by identifying DNA of organisms in samples or tissues. Diagnosis can be made by sampling bulls, cows, fetuses or placentas. Bulls. The traditional way to diagnose T foetus infection in a herd has been to culture organisms from smegma collected from the prepuce of bulls. There are several ways to collect the smegma sample, including prepuce washings of saline, dabbing with cotton swabs and scraping combined with aspiration into a pipette. The pipette, or dry method, is preferred in the United States. The prepuce is trimmed, and a 21-inch sterile insemination pipette is inserted into the fornix of the prepuce. The pipette is then repeatedly scraped back and forth about 2 or 3 inches in the same spot with gentle pressure while applying suction with a 12 or 20 cc syringe. I do that about 40 times, gradually trying to dig deeper into the epithelial crypts of the mucosa where the organisms are most abundant. A portion of samples collected that way will consist of grey mucus. Some will have just enough blood to turn pink. Diagnosticians feel that samples with no blood are positive just as much as those with a little blood, but many other practitioners and I think samples that are a little pink are the best. It is not good to collect a sample that looks like pure blood or a sample with a lot of dirt. Bloody samples can t be helped in bulls that have an inflamed prepuce mucosa that yields blood with the slightest scraping. Diagnosticians hate samples that contain dirt. Dirty samples are difficult to avoid under muddy conditions. I have been able to collect fairly clean samples under muddy conditions by placing a sheathed pipette into the fornix of the prepuce, pulling the sheath back a few inches, scraping with aspiration, then pulling the pipette back into the sheath and removing it from the prepuce covered by the sheath. An alternative method of obtaining a clean sample is to wash the sheath prior to sampling. Since it s natural to hold portions of the pipette that are contaminated when collecting samples, I like to wear a fresh pair of exam gloves for each sampling to prevent cross contamination of samples The mucus collected in the pipette is then deposited into an In Pouch TF packet (Biomed Diagnostics, San Jose, California). Survival of organisms from collection at the ranch to incubation at the diagnostic laboratory is much higher in In Pouch TF packets than Diamond s media. Be sure the In Pouch TF packet expiration date has not passed. Veterinarians who have bacterial incubators can incubate and read the In Pouch TF packets in their clinics. They should be read every 24 hours for 5 days. Organisms are most commonly observed (at 40X, 100X, 400X) in positive samples at 48 hours of incubation, but can be found anytime between 24 hours and 5 days. Samples generally should be incubated at 37 C. However, some laboratories favor 36 C. Studies have demonstrated the same isolation rate of T foetus when samples were incubated at 22 C as 37 C. I know that T foetus is sensitive to excessive heat but might have overheated some samples in my incubator that was accidentally set at 42 C. Consequently, I now set the incubator at 36 C when I read my own samples. Organisms are easy to see under a good light microscope and look like little bumper cars running around hitting into each other. The Texas Veterinary Medical Diagnostic Laboratory has developed a polymerase chain reaction (PCR) test for positively identifying the DNA of organisms present in positive tests of T foetus. Since 1999, when intestinal trichomonads (Tetratrichomonas spp, Pentatrichomonas hominis and others) were cultured from preputial smegma of truly virgin bulls, it has become prudent to perform PCR tests on all

3 positive cultures. It would be a tragic mistake to send an excellent bull to slaughter because of a positive culture that was actually a nonpathogenic intestinal trichomonad. The PCR test is much more sensitive than culture in identifying T foetus in samples. For example, in an outbreak of trichomoniasis which I discovered at a pregnancy examination, 3 of 6 cultures of samples collected from open cows were culture positive. In addition, 5 of the 6 samples were PCR positive. (PCR detected 2 more positives). I often request both culture and PCR testing of samples I collect because the combination might increase the odds of diagnosing T foetus infection if it is present in the herd. PCR tests are performed following incubation of the In Pouch TF for 5 days. Cows or heifers. Although culture of smegma samples collected from the prepuce of bulls is the standard way to diagnose trichomoniasis in beef herds, culture of uterine discharges from females found open at pregnancy diagnosis can be just as effective. Enlarged uterine horns with thickened walls can be detected in some of the open cows at palpation. Examination of the anterior vagina of these cows via a vaginal speculum often reveals a grey to yellow purulent discharge. A disposable mare vaginal speculum works well. It s easy to collect a sample of exudate to culture by sweeping the fornix of the vagina with a gloved hand. It can also be done by aspiration of exudate into an insemination pipette inserted to the fornix of the vagina. The same procedure can be used to obtain a sample of exudate from the occasional cow that develops pyometra. It s important to collect samples from at least 6 open cows because the immune system of some cows that were infected with T foetus early in the breeding season will have cleared the infection by the time of pregnancy examinations. Culture of samples collected from cows at pregnancy examination in herds with impaired fertility offers a quick way to determine if trichomoniasis is the culprit. Fetuses. Diagnosis of trichomoniasis can be made by examining aborted fetuses by culture of the organisms from abomasal fluid. It can also be done by visualization of the organisms in the placenta or fetal tissues. There are consistent patterns of lesions in the placenta and fetus of abortions caused by T foetus. In over half the cases, bronchopneumonia with organisms in airways is clearly discernable in standard hematoxylin and eosin (HE)-stained sections. Organisms sometimes can be seen by pathologists in sections of the eosophagus, abomasum and intestine. They can also be seen in the placenta if it is not severely autolyzed. Bottomline Trichomoniasis is a common cause of severe reproductive losses in Texas beef cow/calf operations. Several other infectious agents can cause reproductive problems similar to those seen in outbreaks of trichomoniasis. However, pyometra is a unique manifestation of T foetus infection. Lower pregnancy rates and delayed pregnancies that result in lower weaning weights make trichomoniasis one of the most economically devastating diseases of beef cattle herds. New diagnostic aids, such as the In Pouch TF packet and the PCR test, have made efforts to diagnose trichomoniasis more successful. Diagnoses can be made from samples collected from bulls, cows or heifers and from aborted fetuses or their placentas. Attempts to diagnose trichomoniasis must be a critical part of all investigations of impaired fertility in Texas beef herds. Remember the old saying, If you don t look for it, you won t find it! From Steven E. Wikse, DVM, DACVP, Associate Professor and Extension Beef Cattle Veterinarian, Food Animal Section, Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences and Texas Cooperative Extension, The Texas A&M University System, College Station, Texas FOOD ANIMAL PRACTICE Ethanol Boom Causing Multifaceted Paradigm Shift throughout Food Production Systems A recent Iowa State University Center for Agriculture and Rural Development (CARD) paper provides various preliminary scenarios about the longterm impact of corn-based ethanol on the grain, oilseed and livestock sectors of U.S. agriculture. The executive summary of the paper states: Estimates of the longrun potential for ethanol production can be made by calculating the corn price at which the incentive to expand ethanol production disappears. Under current U.S. ethanol tax policy, if the prices of crude oil, natural gas, and dried distillers grains with solubles (DDGS) stay at current levels, then the break-even corn price is $4.05 per bushel. A multi-commodity, multi-country system of integrated commodity models is used to estimate the impacts if we ever get to $4.05 per bushel corn. At this price, corn-based ethanol production would reach 31.5 billion gallons per year, or about 20 percent of the projected U.S. fuel consumption in Supporting this level of production would require 95.6 million acres of corn to be planted. Total corn production would be approximately 15.6 billion bushels of corn, compared to 11.0 billion bushels today. Most of the additional corn acres come from reduced soybean acreage. Wheat markets would adjust to fulfill increased demand for wheat. U.S. corn exports and production of pork and poultry would all be reduced in response to higher corn prices and increased utilization of corn by ethanol plants. These results should not be viewed as a prediction of what will eventually materialize. Rather, they indicate a logical end point to the current incentives to invest in corn-based ethanol plants.

4 The paper focuses on the winners and losers by concluding, Much of the debate surrounding the current incentives to the ethanol sector suggests that these incentives are driven in large part by a desire to reduce U.S. dependence on imported oil. By stimulating the production of ethanol to as much as 20 percent of total fuel use, these incentive structures appear to be well on their way to meeting this goal. Other beneficiaries include landowners, who will benefit from a dramatic increase in corn prices and associated increases in land rents. U.S. crop growers will benefit until the higher profits are captured by higher land values and land rents. Dairy and beef producers who are near ethanol plants will benefit from having access to DDGS. Owners of ethanol plants will benefit until corn prices rise to eliminate the current arbitrage in ethanol production. Specialized pork and poultry producers who do not own shares in ethanol plants will lose as higher corn prices (and eventually reduced international competitiveness) cause production levels to decline. The transition to these lower production levels will be painful for most of these producers. Ethanol construction and the flow of profits from ethanol facilities will stimulate rural economies. However, there will be less livestock in these same areas which will eventually work to offset this advantage. A standard argument in international trade is that, while most trade arrangements have winners and losers, the successful agreements are so beneficial to the winners that they create enough surplus to help the losers adjust and adapt. An interesting policy question that we are in the process of addressing is whether the long list of positives associated with the expansion of corn-ethanol production is sufficient to offset the shorter list of negatives. The discussions from the entire paper can be accessed at Adapted from Amani Elobeid, Simia Tokgoz, Dermot J. Hayes, Bruce A. Babcock and Chad Hart, CARD Briefing Paper 06-BP 49, The Long-Run Impact of Corn-Based Ethanol on the Grain, Oilseed, and Livestock Sectors: A Preliminary Assessment, November 2006, Center for Agriculture and Rural Development, Iowa State University, Ames, Iowa, , For information about this paper, contact Bruce Babcock at 578 Heady Hall, Iowa State University, Ames, Iowa ; (phone) 515/ ; (fax) 515/ ; or ( ) Babcock@iastate.edu. Resources for Current DDGS Recommendations for Livestock and Poultry Feed The University of Minnesota offers an excellent resource on the most current information on use of distillers dried grain and solubles (DDGS) in dairy, beef, swine and poultry rations. You can find it at Another excellent resource by the National Corn Growers Association (NCGA) is a 16-page pamphlet that outlines the basic DDGS feeding recommendations for beef and dairy cattle, swine, sheep and poultry. It breaks down the maximum dietary inclusion levels for rations and explains how best to utilize DDGS. Contact information for questions is also included. You can order this pamphlet from Mel Gibson at 636/ It is a condensed version of the October 2005 NCGA s Distillers Grain Feeding Recommendations, which is available from NCGA at From Pork Magazine, November 2006, pp. 8 and 10. SWINE PRACTICE A Producer s Guide to Managing Porcine Circovirus- Associated Disease Available The American Association of Swine Veterinarians and the National Pork Board have teamed up to create an excellent information source, A Producer s Guide to Managing Circovirus-Associated Disease. It provides guidelines for swine producers who are dealing with porcine circovirusassociated disease (PCVAD). Its various topics include disease signs of PCVAD, importance of a veterinaryassisted diagnosis and measures helpful to minimize the effect of PCVAD in each stage of production. This 18-page, color guide can be viewed at PCVADBrochure.pdf. Print copies are free for producers and industry educators from The Pork Store at www. porkstore.pork.org. Click on Resources and then Swine Health. From the American Association of Swine Veterinarians, 902 1st Avenue, Perry, Iowa, ; (phone) 515/ ; (fax) 515/ ; ( ) aasv@aasv.org; (website) Also from the National Pork Board, 1776 Northwest 114 Street, Des Moines, Iowa 50325; (phone) 515/ ; (fax) 515/ ; ( ) pork@pork.org; (website) Nuflor Oral 2.3% Concentrate Solution Available as Swine Drinking Water Medication Florfenicol Solution (Nuflor Oral 2.3% Concentrate Solution) was approved in July 2006 as drinking water medication for swine to treat swine respiratory disease associated with Actinobacillus pleuropneumoniae, Pasteurella multocida, Salmonella choleraesuis and Strep suis Type 2 infections. The recommended dosage of Nuflor Oral 2.3% Concentrate Solution is 10 mg/kg per day. This results from producing a stock solution that will medicate 128 gallons with each gallon containing 400 mg florfenicol (100 ppm). It is only available as 2.2 liters in a 1-gallon plastic bottle. Each bottle medicates 128 gallons of drinking water. The medicated water should be the pigs only source of drinking water for five consecutive days. The preslaughter withdrawal period is 16 days. From Schering- Plough Animal Health Corporation, 556 Morris Avenue Bldg S 4, Summit, New Jersey Questions should be addressed to Schering- Plough technical service veterinarian at 877/ or at

5 New Guidelines for Maximum Residue Limits (MRLs) for Pork Exported to Japan Changing How U.S. Swine Veterinarians and Producers Manage Drug Withdrawal Times Maximum Residue Limits for Pork Exported to Japan the Facts Recently the Japanese have adopted new food safety standards and residue standards that will apply to all food products including pork, fresh and frozen, offal and processed meats. These new standards are based on the Codex Alimentarius, a series of international standards established by the Food and Agricultural Organization of the United Nations and the World Health Organization to ensure food safety. U.S. standards were developed by the Food and Drug Administration to ensure food safety. Codex and U.S. residue standards may differ for certain products and residue testing. Compliance with U.S. product withdrawals will satisfy most, but not all, of the new maximum residue levels (MRLs) set by Japan. Japan represents a market for over $1 billion of U.S. pork or 45 percent of the value of U.S. exports. In fact, it is the largest market for U.S. pork in volume and value. Japan purchases approximately 753 million pounds of U.S. pork muscle. One animal in violation of Japanese product specifications can sever this market for U.S. pork. Testing Protocols for Pork Products Exported to Japan Specific testing protocols for veterinary drugs in pork and pork products will be clarified as information becomes available. Japanese testing protocols for pork muscle require testing be done at or near identifiable injection sites. Therefore, the use of injectable products represents more of a risk than the use of other animal health products used in the finishing stage. Producers are encouraged to evaluate the use of animal health products, including injectables, in their finishers and review injection techniques. What the Pork Checkoff Is Doing The Pork Checkoff has been working with pharmaceutical companies to determine what animal health products may require changes in their withdrawal periods to meet Japan MRLs. The Pork Checkoff will continue to update its site at Producers/JapanMRL.aspx with the latest information from pharmaceutical companies. (Information from the individual pharmaceutical companies can be found through the More Info link at the bottom of the website page.) What This Means to the Swine Producer Certain veterinary products will require longer withdrawal periods if swine are being sent to a packing plant that channels pork into a Japanese export market. Following veterinary drug manufacturers directions for correct use of animal health products is essential. What Producers Need To Do Swine producers are advised to take the following steps to find out if they are affected by these new regulations: Contact your packer and find out if your product is being channeled into the Japanese export market and is affected by new MRLs. Search the list of animal health products in the database of the website Producers/JapanMRL.aspx. View those that are currently used in the finisher phase of your operation to see if their withdrawal periods are needed if you are in the Japanese export market. Contact your herd veterinarian if you have questions about whether the animal health products listed in this website are used in your operation and are affected and require a change in usage. With the help of your herd veterinarian, develop protocols for the use of animal health products. These protocols should include (1) a procedure to determine if animal treatment is necessary and when is the most effective time to treat an animal, and (2) a tool to determine the most appropriate products to use and the correct technique for treatment of pigs in the finisher stage of production. Japan MRLs Position Statement Adopted by the American Association of Swine Veterinarians (AASV) Go to position-japanmrl.html for the AASV position statement on Japanese MRLs. Adapted from Maximum Residue Limits (MRLs) for Pork Exported to Japan, Producers/JapanMRL.aspx; and from AASV Recommendations to Meet Japanese MRL Requirements of U.S, American Association of Swine Veterinarians, 902 1st Avenue, Perry, Iowa 50200, EQUINE PRACTICE Placenta Submission Becoming More Important for Equine Abortion Diagnosis Due to continuing progress in the knowledge and identification of equine placental abnormalities, as many as 80 percent of equine abortion cases may be associated with placental changes. The placenta, amnion and umbilicus (fetal membranes) are critical specimens for submission in all equine abortion cases. Also, the fetus, dam s sera and sera from 10 percent of normal pregnant mares at the same location should still be sent if possible. From the Oklahoma State University (OSU) Animal Health Update, the newsletter of the OSU Center for Veterinary Health Services, Winter Small Scale Composting as Practical Way To Dispose of Horse Manure The Texas Cooperative Extension (TCE) publication, Composting Horse Manure (B-6084), is a complete guide for small scale composting of

6 horse manure generated at veterinary clinics and stables. It briefly describes composting, compost maturity, optimal conditions for composting, making compost from horse manure, measuring compost temperatures, monitoring compost maturity, laboratory analysis of compost, tips for the small scale composter and a composting demonstration carried out on a veterinary large animal hospital. It also addresses modest income generation from finished compost. This and other TCE publications may be downloaded or can be purchased from the TCE Bookstore at From Texas Cooperative Extension s B-6084, Composting Horse Manure (6-99), Bert W. Averman, Associate Professor and Extension Agricultural Engineer; Larry McDonald, Extension Associate/Water Quality; Robert Devin, Randall County Extension Agent-Agriculture; and John Sweeten, Professor and Director, Texas Agriculture Experiment Station, Amarillo, The Texas A&M University System. SHEEP AND GOAT PRACTICE Sheep Management Classes Available Online Introduction to Sheep Management, Introduction to Sheep Health and Ewe Ration Formulation are online courses offered to sheep enthusiasts (adult and youth) by the Pipestone Lamb and Wool Program. This is a sheep management education/consulting program offered by Minnesota West Community College in Pipestone, Minnesota. Introduction to Sheep Management is a 14-lesson, self-paced course with continuous enrollment and provides an overview of year-long sheep management. Introduction to Sheep Health is more structured, is designed for more interaction and requires the text, Gate s Practical Guide to Sheep Disease Management (3rd edition). Ewe Ration Formulation is structured, is designed for interaction like the Sheep Health course and requires the text, The Sheep Production Handbook (2002 edition). To register for one of the online courses, contact Sue Lovell at sue. lovell@mnwest.edu or at 507/ You can also register at www. mnwest.edu/formmail/formdl.htm. For more information, visit Pipestone Wool and Lamb at or contact Philip Berg. He is at Philip.berg@mnwest.edu and at 507/ From Sheep Industry News, November 2006, p 6. CANINE PRACTICE Marijuana Toxicosis in Dogs: 213 Cases Marijuana (Cannabis sativa) is commonly used as a recreational drug among humans. Animals may be exposed following ingestion or accidental inhalation of smoke. From January 1998 to January 2002, 213 incidences were recorded of dogs that developed clinical signs following oral exposure to marijuana. Among them, 99 percent had neurological signs and 30 percent exhibited gastrointestinal signs. The marijuana ingested ranged from 0.5 to 90 grams. The lowest dose at which signs occurred was 84.7 mg/kg, and the highest dose was 26.8 g/kg. Time for onset of signs ranged from 5 minutes to 96 hours. Management consisted of decontamination, sedation (with diazepam as the drug of choice), fluid therapy, thermoregulation and general supportive care. All affected animals with follow-up information made full recoveries. Adapted from Jancyzk P, Donaldson CW and Gwaltney S, Two Hundred and Thirteen Cases of Marijuana Toxicosis in Dogs, Veterinary and Human Toxicology, 46:1, pp , 2004 as reported in Animal Health Spectrum, Mississippi State University Extension Service, Volume 15, Number 3, Fall 2004, p. 4. Veterinary Continuing Education Seminars 2007 College of Veterinary Medicine and Biomedical Sciences Texas A&M University *April Annual Feline Symposium (Dr. John August) *June Annual Food Animal Conference (Dr. Steven Wikse) *July Small Animal Dentistry (Dr. Jonathan Bert Dodd) *August Dermatology Conference (Dr. Christine Rees) *September Annual Exotic Pets Conference (Dr. Sharman Hoppes) *October Clinical Neurology Conference (Dr. Jonathan Levine) *November Annual Equine Conference (Dr. Jeffrey Watkins) *November Small Animal Emergency Medicine and Critical Care (Dr. Maureen McMichaels) *November 30-December 2... Annual Equine Reproduction Symposium (Dr. Dickson Varner) *Confirmed Calendar is subject to revision. For more information on these programs of self-study and personalized continuing education, please call (979) , fax (979) , or ceoffice@cvm.tamu.edu. Visit our web site at From the Office of Veterinary Continuing Education, Texas Veterinary Medical Center, College Station, Texas.