Dairy calf respiratory disease accounted for 22.5% of unweaned heifer mortality and 46.5% of weaned heifer mortality in the USDA NAHMS Dairy 2007 study. It can devastate the replacement heifer crop, but proper management of young calves at birth and beyond can go a long way in reducing morbidity and mortality. A study on the incidence of BRD in Ontario dairy herds reported that 15% of heifer calves are treated for respiratory disease prior to weaning, with a case fatality rate of 5%, and a more recent Saskatchewan study reported 40% of calves were diagnosed with BRD by producers prior to 6 months of age.
Start with SOPs
Failure of passive transfer is the number one way in which calf immune systems are set up to fail. There are a variety of reasons that failure of passive transfer occurs on dairy farms from the quality/quantity of colostrum, timing, stress, poor technique and other labor issues. Bob Patrick, DVM, Shamrock Animal Health Services, Eatonton, Ga., says putting in place standard operating procedures (SOPs) can help. His set protocols start with colostrum collection from clean udders at first milking, testing it for quality with a colostrometer (before pasteurization), pasteurizing and then freezing it. He likes to perform standard plate counts and coliform counts on random samples to monitor quality. For the newborn, protocols mean administering 3–4 quarts of colostrum within the first four hours of birth (using an esophageal feeder if necessary).
Patrick likes using pasteurized colostrum for the reduced risk of disease transmission (i.e. Johne"s, Mycoplasma and viruses) and it also stops bacterial proliferation. "There should be no more than one hour of time between collection from the cow to the pasteurizer," he recommends. If batch pasteurizing, you can pasteurize colostrum in bags submerged in milk (140'F for 30 minutes, 60 minutes if Mycoplasma is a problem). Use more commercial bagged colostrum if pasteurized colostrum is not available.
Patrick also likes to monitor calves with serum proteins or globulin at 48 hours after birth. "Written records are tough to keep, so we need to establish the protocols and make sure it"s done through monitoring. SOPs have little impact if they can"t be monitored. Most employees want to do things right, but sometimes they forget. Ask questions, do the lab work (proteins, cultures, etc.), and most importantly, be there sometimes when the task is being performed."
Amy Stanton, PhD, Ontario Veterinary College, University of Guelph, adds that measuring total protein can help producers stay on top of their passive transfer success rate. "On my family farm we had struggled with this issue until we began recording total protein on a regular basis," Stanton suggests. "By regularly monitoring this number we were able to see that although we had what we thought were adequate standard operating procedures in place, these procedures needed to be refined and more closely monitored to get the results we wanted, which was
Stanton likes to measure total protein when calves are between 1–7 days of age. "There are currently digital refractometers that are easy to use and getting this quick feedback on the colostrum management system allows producers to quickly assess the changes they make to their colostrum management program."
Patrick adds to stick to things you can measure and should be standard (i.e. serum proteins, bacteria counts, growth, necropsies, deaths).
Calf respiratory disease risks
If any animal needs proper ventilation to help develop a healthy respiratory system, it"s calves. Hutch-raised calves generally have pretty good ventilation, but calves in barns or inadequately ventilated pens can be at a higher risk for respiratory-related problems. Barns need adequate air turns per hour to prevent pneumotoxic substances (i.e. ammonia, moldy feed, even viruses) from accumulating. Moldy feed inhibits intakes and fungal toxins have nasty effects on immune systems, Patrick says. "Calves seem to be pretty resilient to some environmental contamination such as mud, manure, urine and dirt if adequate liquids such as milk and/or water and solid (grain) nutrition is afforded them."
Stanton agrees that the biggest problems for calves in terms of respiratory disease are poor air quality and nutrition. "If a barn or hutch has poor ventilation producers will always be working to overcome this because poor air quality can irritate the lungs and compromise the calf"s natural defenses against viruses and bacteria. If the calf is also under nutritional stress then they will not have the energy reserves to mount an immune response and their recovery from respiratory disease will be delayed."
For the older, newly weaned calf, risks leading to respiratory infection are many as it is subjected to many different stressors that can leave it susceptible to respiratory disease including nutritional, environmental and social stressors. "Take into consideration that calves go from having a rich, nutrient-dense meal provided to them at least twice a day that they can easily digest in an individual and protected environment and then over the course of days or weeks this meal is no longer provided," Stanton says. "In addition, they have to adapt to a new diet, develop their rumen, learn to interact with other animals, and are exposed to all sorts of new pathogens; it is not surprising that disease outbreaks occur." By ensuring that calves are over the nutritional stress of weaning before adding the social and environmental stressors, the risk for respiratory disease can be decreased, she adds.
Patrick adds that stress can be caused by the environment (too cold, too hot, too wet), commingling and inadequate feed and water space. "These things are usually additive," he says. "Poor nutrition may be ‘agroceriosis" or a ration-balancing problem or both. Many folks underfeed calves, especially during stressful environmental conditions."
Patrick has also seen significant improvement in respiratory disease morbidity in herds that have instituted early vaccination programs. "Producers and veterinarians should work together to determine if vaccination in the neonatal period should be a part of a respiratory disease management plan," he says.
Identify at-risk calves
Early identification of at-risk animals is beneficial. Stanton recently completed a study examining some behavioral indicators of poor weight gain post-weaning. "From this study, we found that calves with low post-weaning weight gain were less active than their herd mates and were more likely to isolate themselves from other calves while resting," Stanton explains. "Calves with poor weight gain following weaning and movement to a new environment are the calves that are not adapting to the environmental, nutritional, and social changes that weaning entails. By identifying calves that are not gaining weight or failing to thrive in the new post-weaning environment, producers can intervene before infection or clinical disease occurs. In doing so, the long-term negative effects on both productivity and welfare can be avoided."
Calves moved into "hospital" or less competitive pens may do better. Stanton says, "During clinical disease animals become anorexic and if they have to struggle to get feed they are likely to eat even less."
Records in and of themselves may or may not be helpful for identifying risks or keeping track of respiratory disease. "Morbidity and treatment numbers are subjective, depending on who"s diagnosing, doing the treatments, and recording," Patrick notes. "It"s hard to compare these numbers from farm to farm at times."
However, Stanton adds, it is important to track where on a specific farm the problems are and what factors are contributing to it. Often an earlier disease can affect later treatment efficacies. A study by Stanton found that a strategic intervention program to prevent respiratory disease and its negative effects on growth can be effective, but diseases in the nursery period must also be addressed.
Diagnosing calf BRD
Some of the most common pathogens involved in calf respiratory disease include bovine respiratory syncytial virus,Pasteurella, Mycoplasma, infectious bovine rhinotracheitis as well as non-infectious causes such as atypical bovine pneumonia.
Calves can get sick fast so early diagnosis and treatment is critical for short- and long-term outcomes. Patrick says elevated temperatures usually occur first, but that the first visual sign in wet calves is probably anorexia and depression, followed by nasal discharge, dyspnea, tachypnea and coughing. In grouped calves, anorexia is hard to evaluate and what is most often seen is lethargy, coughing and dyspnea.
Though a veterinarian is not going to necropsy every calf, posting some of them during the year can give a better idea of the pathogens involved as well as serve as a teachable moment for the calf raisers. "It"s impossible to develop plans to reduce morbidity and mortality if etiology is unknown," Patrick states. "A necropsy is a good teaching tool to show how devastating and important respiratory disease is."
When to say when
Calves can do down in no time with respiratory disease and die. They can also linger along, but how do you address this issue with your clients of dealing with chronic respiratory calves, or euthanizing because of welfare reasons?
This is a really complicated issue, says Stanton, and there are several factors that need to be considered or weighed. First, consider the severe or acute chronics that may live for several weeks. "Have you had a response to treatment? If this calf has been treated multiple times and is not improving then it is time to consider euthanasia because the data and on-farm experience is showing this calf is not likely to become a functional herd member. In addition, it is an ongoing struggle for this animal to breathe and for this reason this animal should be euthanized to avoid further suffering."
Calves that don"t respond (chronic cough plus anorexia, recumbency, emaciation) should be humanely euthanized, Patrick adds.
Second are the unidentified or mild chronics. "Some calves will appear to come around, but as you follow up with weights and future disease events, you can see they are not keeping up with the herd mates," Stanton says. Intervention for these animals is also needed, but it is less clear what this intervention should be.
"They may need to be managed differently to allow for compensatory growth such as lowering their competition, or if a physical exam reveals continuing symptoms re-treatment may be necessary. Failing successful treatment, euthanasia will need to be considered."
The AABP Euthanasia guidelines provide some very useful criteria to evaluate when making euthanasia decisions. According to these guidelines, the following criteria to be considered in decision making:
Pain and distress of the animal keeping in mind that respiratory distress is likely a painful and highly aversive state
Likelihood of recovery
Ability to get to feed and water
Medications used on the animal
Drug withdrawal time
Stanton encourages veterinarians to talk to producers about this situation. Once a decision has been made to stop treatment and the calf is suffering, euthanasia is the most humane outcome. "If an animal has a prolonged and painful death we have failed to be true caretakers of this animal," Stanton says. "This reflects poorly on the farm and the dairy industry, not only to outsiders such as animal activists and the media that may get involved, and also on farm staff. If it is routine farm practice to withdraw care from sick animals until they die, workers that go through this experience will learn to ignore this animal since they cannot help it and in doing so they are trained to ignore severe respiratory disease. Alternatively, workers who are attached to the calves and want to care for them will become disillusioned by this attitude and find somewhere else to work. Improved job satisfaction, improved animal empathy and care are intangibles that are hard to measure but they do affect the bottom line of the dairy."
SOPs for respiratory disease
Veterinarians need to develop standard operating procedures for calf management and should monitor those SOPs on their farm visits to identify problems or procedural drift. Stanton definitely encourages veterinarians and producers to develop some SOPs for respiratory disease.
"There is a tendency to overlook respiratory disease or wait until the case is severe before treating," she says. "Training on recognizing and treating respiratory disease can be very beneficial."
Stanton recommends the University of Wisconsin-Madison"s calf respiratory scoring sheet for this purpose. "Due to the high variation seen in symptoms of respiratory disease it is very useful in standardizing disease definitions and helping managers recognize this disease early," she notes.
"Respiratory disease is a very preventable disease that carries life-long implications if not controlled," Patrick sums. "Control in wet and weaned calves will almost eliminate its occurrence in older animals if sound vaccination and bio-security programs are in place."
The high price of calf BRD
Bob Patrick, DVM, says replacement rearing costs have escalated to $1,600–$2,000 for springers, making preventive measure more cost-effective. A typical treatment regimen for a heifer will cost $5 to $10 per 100 lbs. depending on the pathogen and treatment duration, he says. "The damage done may be difficult to quantify. Possible consequences including no ill effects to subclinical losses (decreased feed efficiency, delayed conception, reduced milk production) to total loss (culling or death) of a genetically superior animal."
Amy Stanton, PhD, adds that in Canada, the cost of rearing replacement heifers is the second largest operating expense on Ontario farms, and that BRD can be a significant factor. "The direct costs of treatment and prevention of this disease has been estimated at $14.71 U.S. per calf per year for milk-fed calves, at $1.95 US per calf per year for replacement heifers, and at $9.08 US per cow per hear over the entire herd," she says.
However, the most significant and underestimated cost of this disease is the long-term effect on the health and growth of calves, such as decreased growth, delayed time to first calving and increased risk of dystocia.
Stanton, AL , Kelton, D., Leslie, K.E., LeBlanc, S.J. , Millman, S.T (2009) "Associations between lying time and weight gain in post-weaned dairy calves" International Society of Applied Ethology: North American Regional Meeting: Montreal, Quebec.
Stanton, Amy. 2009. "Impact of BRD from the perspective of the Canadian Dairy Producer: Challenges and Opportunities." Bovine Respiratory Disease Symposium, Colorado Springs, Colorado, August 2009.
L. Stanton, D.F. Kelton, S.J. LeBlanc, S.T. Millman, J. Wormuth, R.T. Dingwell, K.E. Leslie. "The effect of treatment with long-acting antibiotic at post-weaning movement on respiratory disease and on growth in commercial dairy heifers" Submitted to Journal of Dairy Science
- University of Wisconsin calf respiratory scoring sheet