Historically, many dairy cattle producers relied upon medicated milk replacer in their calf health management program. Although the use of medicated milk replacer is now more restricted as a result of the Veterinary Feed Directive, it is important for veterinary practitioners to understand the pros and cons of using medicated milk replacer in dairy calf management. This module describes the indications for medicated milk replacer, its role in the development of antimicrobial drug resistance, as well as management practices that help reduce the need for medicated milk replacer.
This submodule aims to describe factors to consider in the use of medicated milk replacer. By the end of the module, you will be able to:
- describe medicated milk replacer and how it is regulated under the Veterinary Feed Directive.
- identify antibiotics that historically were most commonly added to medicated milk replacer.
- list the disadvantages associated with using medicated milk replacer.
- describe proper management and preventive medicine that are critical to long-term calf health.
- describe a good colostrum management program for dairy calves.
It is a Tuesday morning at the Dairy Solutions Veterinary Clinic. When Dr. Karl arrives, his receptionist meets him at the door with a message from local dairyman Chuck Erby regarding a continuing struggle with scours (diarrhea) in his calves.
When Dr. Karl returns the call, Chuck explains, “For the past two weeks I’ve had several scouring calves and some calves with pneumonia too. One calf died this morning, and several more look like they may die soon.” Chuck is calling for help in treating the sick calves, but Doc knows that the long-term solution to Chuck’s problem requires improved management to help his calves stay healthy. Doc agrees to stop by later that morning.
Dr. Karl and a fourth-year veterinary student named Gretchen head out to visit Chuck and his calves. Dr. Karl explains that Chuck Erby is a long-time client who runs a small dairy operation with about 80 milking cows. [Note: Most dairy herds will have about as many calves and heifers as they have cows of milking age.] Over the past few years, Mr. Erby has had frequent problems with scours in his calves and usually treats these cases with antibiotics and supportive therapy such as fluids and electrolytes. Mr. Erby has almost no help in running his farm and has said he does not have time to make the management changes that Doc has recommended before.
When they arrive, Gretchen sees that few updates or changes have been made to the original farm structures. The milk house is small and cluttered with various items including tools, drugs, cleaning solutions, and clothing. The tie-stall barn houses the milking herd and has poor lighting and ventilation. Cows are tied facing the walls on each side of the barn, and a walkway traverses the middle of the barn. A few calves are housed at one end of the tie-stall barn. Twice a day the cows walk by the calves on their way to the milking parlor.
Several abandoned calf hutches are just a few yards from the milk house. Gretchen recently learned in school that calf hutches are a good way to isolate calves from each other and the older cattle to reduce their exposure to opportunistic enteric and respiratory pathogens. [Note: Opportunistic pathogens are agents that can cause disease in the presence of the proper combination of contributory causes that are present on most farms.] Gretchen wonders if maybe Dr. Karl will attempt to convince Chuck to try using the calf hutches again, even if they may be more work.
Dr. Karl and Gretchen start looking at the calves. The bedding seems to have been recently changed—perhaps in anticipation of their visit. However, because the calves are dirty, Dr. Karl suspects that the level of sanitation for the calves has not been very good. The calves are not isolated from each other and are exposed to the milking herd twice a day when the cows take the concrete walkway to get to the milking parlor. Dr. Karl tells Gretchen that on previous visits he has told Mr. Erby to isolate the calves from each other and from the cows to prevent transmission of pathogens, but this clearly has not been done.
Gretchen reviews the farm's medical history and noticed Mr. Erby was purchasing 50 lb bags of medicated milk replacer for his calves. He was using medicated milk replacer containing oxytetracycline and neomycin “to aid in the treatment of bacterial diarrhea (scours).” She remembers from lecture that neomycin, oxytetracycline, and chlortetracycline are the antibiotics most commonly added to medicated milk replacer. She asks, "Mr. Erby, do you always use a milk replacer that contains antibiotics?"
Medicated Milk Replacer
"I guess I didn’t realize my milk replacer had antibiotics,” replied Mr. Erby. Later, Gretchen learned that some dairy producers have been used to purchasing medicated milk replacer (milk replacer to which low levels of antibiotics have been added) without really understanding that the term “medicated” means that subtherapeutic levels (concentrations lower than what is needed for effective treatment of clinical disease) of antibiotics have been added. Other producers knew that medicated milk replacer contained antibiotics, but did not realize the concentrations were too low to treat clinical disease caused by bacteria such as E. coli and Salmonella. Gretchen mentioned that medicated feed can no longer be purchased over the counter according to the Veterinary Feed Directive (VFD) implemented on January 1, 2017. The usage of medically important antibiotics in animal feed (including milk replacers) requires veterinary oversight and bans the usage of antibiotics for the purpose of growth efficiency and disease prevention. Information on currently approved and no longer approved antibiotics for medicated milk replacer dispensed under the VFD may be found at the FDA.gov website.
Intrigued, Gretchen wonders about the difference in price between medicated milk replacer and nonmedicated milk replacer. When she gets back to the veterinary clinic, she thumbs through a couple of pages in some farm catalogs and finds that the price from one company for a 50 lb bag of medicated milk replacer is $45.99 and nonmedicated is $39.99. That’s a difference of about 10 percent: using the nonmedicated milk replacer could save Chuck about $600 a year.
Dr. Karl explains that medicated milk replacers used to have a label stating they are to be used for disease prevention and growth promotion, and on this basis were often thought to be an economically sound choice. Studies conducted under conditions of modern calf management in the 1990s, however, showed that medicated milk replacers were not highly useful for growth promotion (5, 6). In a 2006 study, Raymond (2) discussed several studies which had conflicting results regarding the benefits of medicated milk replacer, but pointed out that effective passive transfer in cattle is more effective in reducing calf morbidity and mortality compared with subtherapeutic feed additives. With respect to medicated milk replacer, Raymond (2) reports that more than two-thirds of farms in his Washington study were not using medicated milk replacer, illustrating that medicated milk replacer is not necessary to maintain calf health.
Dr. Karl tells Mr. Erby, “Preventing scours needs to start right at the birth of the calf. The calf should be isolated immediately from the dam and all other animals to prevent disease transmission. The calf should be given good quality colostrum within one to two hours of birth (4). The quality of colostrum can be assessed with a colostrometer to measure the immunoglobulin levels. Total immunoglobulin concentration of the colostrum should be greater than 60 mg/ml. A second feeding of colostrum should take place within 12 hours of birth. Maximum absorption occurs within the first 24 hours of life, so it is important to administer the good quality colostrum within the first 24 hours. After two feedings of good quality colostrum, you can then start feeding milk replacer or pasteurized milk.” Dr. Karl has been telling Mr. Erby that he should occasionally test his colostrum for immunoglobulin levels. The calf should receive the equivalent of about 10 percent of its body weight in colostrum each day. The amount of colostrum for each feeding should be two to four liters depending on the size of the calf. This quantity of colostrum will likely require the use of an esophageal feeder. Thereafter, calves should be fed milk or milk replacer at 10 percent of their body weight each day for six to eight weeks. The calves should also be supplied with free choice grain and water.
Now it's time to Check Your Understanding of Medicated Milk Replacer 1.
- Isolate the calf from the dam and other cattle at birth to prevent disease transmission. (Note that Chuck’s calves are constantly being exposed to manure from the adult cows and the other calves.)
- Give good quality colostrum, ideally from mature cows. Assess the quality of the colostrum by using a colostrometer to measure the immunoglobulin level. Good quality colostrum has a total immunoglobulin concentration greater than 60 mg/ml. (Note that Chuck does not check his colostrum but just assumes the colostrum he feeds is of adequate quality.)
- Ideally, the first feeding of colostrum should be given within one to two hours after birth. A second feeding of colostrum should be given within 12 hours after birth. All feedings of colostrum should be given within the first 24 hours of birth for maximum absorption. (Note that Chuck admits to not getting colostrum to his calves this quickly.)
- Each time that colostrum is fed, give two to four liters, depending on the size of the calf. Give an 80 lb calf four liters of colostrum, which is approximately 10 percent of the calf’s body weight. Give a 60 lb calf three liters of colostrum, which is approximately 10 percent of the calf’s body weight. (10 percent body weight of an 80 lb calf is 8 lbs. 8 lbs = 128 oz = 4 quarts or 3.79 liters.)
- Occasionally check the immunoglobulin level in the calf’s blood to assure that the colostrum has been properly absorbed. A reasonable goal for the immunoglobulin level in the blood is 10 g/l. (Note: Chuck does not do this.)
- After the first two feedings of colostrum, other milk (e.g., milk replacer or pasteurized milk from the bulk tank) can be fed.
- Continue to feed milk to the calves twice a day for six to eight weeks. Give an 80 lb calf four liters of milk, which is approximately 10 percent of the calf’s body weight. Give a 60 lb calf three liters of milk, which is approximately 10 percent of body weight. (10 percent body weight of an 80 lb calf is 8 lbs. 8 lbs = 128 oz = 4 quarts = 3.79 liters.) The amount of milk or milk replacer should be adjusted as the calf grows.
- Supply free-choice fresh grain and clean water.
Medicated Milk Replacer
Gretchen asks Dr. Karl, “Besides the additional cost and low dose of antibiotics being used, are there any other disadvantages to using medicated milk replacer instead of nonmedicated milk replacer?”
“Any use of antibiotics can contribute to the development and maintenance of antimicrobial resistant bacteria," Dr. Karl says. "Such resistant bacteria may eventually lead to treatment failures on farms if antibiotics are needed for treating sick animals. Also, antimicrobial resistance genes may be transferred to human pathogens and can eventually find their way to people via direct animal contact or through meat or milk products. Another problem is that the use of medicated milk replacer can result in residues in meat, such as neomycin drug residues in veal (7)."
He continues: “Antibiotic resistance may develop more quickly when subtherapeutic levels of an antimicrobial are used, such as the low levels used in medicated milk replacer (8). High doses of antibiotics tend to kill the entire target bacterial population and can also kill most of the commensal bacteria. In contrast, low doses of antibiotics are more likely to select for bacterial subpopulations with antibiotic resistance traits, thereby allowing these subpopulations to survive and reproduce (8). These commensal bacteria are ‘innocent bystanders,’ but they can still develop resistance traits that can eventually be shared with their more pathogenic bacterial relatives and neighbors.”
Now it's time to Check Your Understanding of Medicated Milk Replacer 3.
Sanitation and Hygiene
The next day while driving, Gretchen asks Dr. Karl, “How can over 40 percent of all dairy farms do just fine without ever using medicated milk replacer?”
Dr. Karl replies, “I like to encourage dairy producers to prevent scours and respiratory disease with the use of good sanitation and hygiene, proper nutrition, vaccination, appropriate ventilation, and a good colostrum program. Most dairy managers agree that it is more cost effective to prevent disease than to allow the calves to get sick and then try to treat them. Dairy producers that have good management practices with low rates of calf disease will usually not benefit from using a medicated milk replacer. The antibiotic resistance fostered by the unnecessary use of antibiotics makes it more difficult to treat future animal diseases and may contribute to the antibiotic resistance burden in animal agriculture and human medicine. Plus, medicated milk replacer costs more than nonmedicated milk replacer.”
Now it's time to Check Your Understanding of Medicated Milk Replacer 4.
- Many producers used to purchase medicated milk replacer without recognizing that it contained antibiotics and without understanding that the dose of antibiotics was too low to treat common bacterial causes of calf scours or respiratory disease.
- Use of medicated milk replacers can contribute to the dissemination of antimicrobial resistant bacteria, possibly causing treatment failures on farms or in human hospitals.
- Almost half of US dairy producers have found that sound animal husbandry practices eliminate the need for the routine use of medicated milk replacers. They have found that it is more effective to prevent scours and respiratory disease in calves through management procedures such as sanitation, isolation and an adequate amount of high quality colostrum given within 24 hours of birth.
- USDA. 2005. Part IV: Antimicrobial Use on U.S. Dairy Operations, 2002. USDA:APHIS:VS:CEAH, National Animal Health Monitoring System, Fort Collins, CO #N430.0905.
- Raymond MJ, Wohrle RD, and Call DR. 2006. Assessment and Promotion of Judicious Antibiotic Use on Dairy Farms in Washington State. Journal of Dairy Science. 89:3228-3240.
- Biosecurity Practices of U.S. Dairy Herds. Info Sheet. Veterinary Services. USDA:APHIS:VS. May 1996.
- Colostrum Feeding. APHIS Info Sheet. USDA:APHIS:VS:CEAH, December 2002.
- Morrill JL, Morrill JM, Feyerherm AM, and Laster JF. 1995. Plasma Proteins and a Probiotic as Ingredients in Milk Replacer. Journal of Dairy Science. 78:902-907.
- Quigley, JD III, Drewry JJ, Murray LM, and Ivey SJ. 1997. Body Weight Gain, Feed Efficiency, and Fecal Scores of Dairy Calves in Response to Galactosyl-Lactose or Antibiotics in Milk Replacers. Journal of Dairy Science. 80:1751-1754.
- Reminder - Medicated Milk Replacers Can Cause Antibiotic Residues in Bob Veal Calves. CVM Update. FDA:Center for Veterinary Medicine. July 29, 2004.
- Berge AC, Lindeque P, Moore DA, and Sischo WM. 2005. A Clinical Trial Evaluating Prophylactic and Therapeutic Antibiotic Use on Health and Performance of Preweaned Calves. Journal of Dairy Science. 88:2166-2177.
- Heinrichs AJ, Wells SJ, and Losinger WC. 1995. A Study of the Use of Milk Replacers for Dairy Calves in the United States. Journal of Dairy Science. 78:2831-2837.
- Braidwood JC and Henry NW. 1990. Clinical efficacy of chlortetracycline hydrochloride administered in milk replacer to calves. Veterinary Record.127:297-301.
- Schifferli D, Galeazzi RL, Nicolet J, and Wanner M. 1982. Pharmacokinetics of oxytetracycline and therapeutic implications in veal calves. Journal of Veterinary Pharmacology and Therapeutics. 5:247-57.
- Luthman J, Jacobsson SO, Bengtsson B, and Korpe C. 1989. Studies on the bioavailability of tetracycline chloride after oral administration to calves and pigs. Zentralblatt für Veterinärmedizin. Reihe A. 36:261-8.
- Palmer GH, Bywater RJ, and Stanton A. 1983. Absorption in calves of amoxicillin, ampicillin, and oxytetracycline given in milk replacer, water, or an oral rehydration formulation. American Journal of Veterinary Research. 44:68-71.
- NAHMS Dairy 2007. USDA:APHIS:VS Centers for Epidemiology and Animal Health, 2150 Centre Ave, Bldg B. Fort Collins, CO 80526.