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A new look at respiratory disease control in heifers

Robert Lynch Published on 11 January 2011

Post-weaned dairy calves endure a considerable amount of stress during the move into group housing. Multiple stressors – a new environment, diet change, social adjustments, even transportation – all combine to weaken the calf’s natural defense system.

At the same time, commingling with other calves increases pathogen exposure and encourages disease-causing organisms to flourish. This combination of reduced immunity at a time of larger pathogen loads allows respiratory disease-causing bacteria to penetrate the calf’s natural defenses and causes clinical pneumonia. In fact, respiratory disease is the cause of almost half of all heifer deaths after weaning.

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Like post-weaned dairy heifers, incoming feedlot cattle share many of the same stressors and are at risk of acquiring respiratory disease. Dairy producers may have opportunity to learn from the beef industry when it comes to warding off respiratory disease in young heifers.

Lessons from the beef industry
Beef cattle producers strategically use antibiotics as a control for respiratory disease at times, such as when high-risk calves arrive at the feedyard.

This proactive strategy, administered when cattle are at highest risk for bovine respiratory disease, is proven to minimize impact on cattle health. Feedlots that control respiratory disease in this manner have seen marked improvements in performance measures, such as average daily gain and feed conversion efficiency.

Recent research has shown that using antibiotic control during this highly stressful time is beneficial for improving dairy heifer health and performance. Forthcoming research suggests there may be long-term production benefits as well.

Disease control for stressful times
Control of respiratory disease using antibiotics, particularly during stressful periods like the transition to group housing, is an opportunity to improve calf health and overall herd immunity.

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About 6 percent of weaned dairy heifers experience respiratory disease nationwide, according to a survey conducted by the USDA. Heifers diagnosed with respiratory disease experience reduced average daily gain and calve later than unaffected heifers.

Moreover, these heifers are more likely to die, or be culled, before reaching the milking herd. Those that do join the milking herd are likely to have reduced lifetime productivity.

Producers who see consistent respiratory disease in post-weaned heifers should identify causative agents and other risk factors. Management and facility changes may be warranted to eliminate the risk factors.

Diagnostic tools are available from many state veterinary labs, using nasal swabs or bronchoalveolar lavage fluids to identify disease-causing agents. Once the pathogen is identified, the herd veterinarian can select an effective course of treatment.

If producers find that bacteria are important in the respiratory disease situation, it can be beneficial to give a one-time administration of an antimicrobial that provides a full course of therapy and is labeled for control. The key is to get an antimicrobial on board before disease breaks.

If producers are consistently seeing clinical signs of respiratory disease, such as coughing, elevated temperatures or mucus discharge shortly after weaning, there might be an opportunity to head off the disease problem before it affects growth.

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Using an antibiotic for control can reduce the number of clinical cases of respiratory disease, minimize permanent lung damage in survivors and improve survival to calving.

Ken Leslie, DVM, professor at the Ontario Veterinary College at the University of Guelph, says this practice is a valid option when respiratory disease rates are unacceptably high – for example, 20 percent or 30 percent to as high as 40 percent.

“Respiratory disease is so costly,” Leslie says. “When dairy calves come from nursery pens, hutches or barns to a group pen, they are high-risk.

I do not think it’s out of bounds for the dairy industry to consider a one-time administration of an appropriate long-acting antibiotic. I think it’s a very rational approach, particularly if it goes with documentation of unacceptable rates of respiratory disease. I’m very supportive of it.”

Performance benefits
Leslie, Amy Stanton and the Calf Health research team at the University of Guelph studied the use of a long-acting injectable antimicrobial at the time of calf movement to group housing and found the practice significantly reduced morbidity rates in weaned dairy calves.

This research, conducted on a large New York commercial heifer-raising facility, also showed performance benefits in calves given antibiotics for disease control at the time of post-weaning movement. The study appeared in the February 2010 issue of the Journal of Dairy Science .

Researchers noted a significant improvement in heifer growth rates in the 60 days following post-weaning movement, even in heifers not previously treated for respiratory disease.

In the study, calves were administered with either tulathromycin or a low dose of oxytetracycline (control group) at the time of movement from individual to group housing.

At 60 days post-weaning, calves that received tulathromycin weighed an average of 10.7 pounds more and were taller than the control group, even though they had no disease history and showed no signs of respiratory disease. The improvement in growth continued “for quite some time,” Leslie says.

The dairy industry is starting to pay closer attention to average daily gain as a measure of heifer performance. Heifers not burdened by the lingering effects of respiratory disease grow to their potential, reach maturity and freshen at an ideal age.

Since heifers do not make any money for the dairy until they produce milk, improving their growth by controlling calfhood disease at critical times is a strategy worth considering.

Leslie said Stanton has continued to follow performance of the heifers, and a yet-to-be-published study will address how post-weaning respiratory disease affects long-term productivity of heifers.

“Bovine respiratory disease in the 60 days after weaning had several very negative effects on long-term productivity and welfare of dairy heifers,” Leslie says.

Heifers experienced decreased growth and lower survival to first calving compared to healthy herdmates. They also were, on average, two months older at first calving and had increased risk of difficulty at calving. Heifers with respiratory disease also produced less milk than heifers that did not have respiratory disease.

The post-weaned dairy calf is at great risk for respiratory disease following the move into group housing. Respiratory disease at this time can have a significant impact on heifer performance immediately post-weaning and long-term.

Along with proper vaccination, nutrition and housing, the use of an appropriate injectable antibiotic to control respiratory disease is another management tool to help you protect your heifers’ health and future performance. PD

References omitted due to space but are available upon request to

Robert Lynch

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