Looking Inside the Lungs
September 17, 2019
Dairy veterinarians are turning to ultrasound imaging of the lungs to spot-check protocols for pneumonia.
As the seasons change, the risk of illness increases for dairy calves. As temperatures drop, young animals divert energy from their immune system and growth to maintaining body temperature – creating an opening for disease to take hold.
There is a high incidence of respiratory disease among dairy calves, as shown in the USDA National Animal Health Monitoring System survey. The widespread occurrence is compounded by broad losses.
There are direct losses due to respiratory disease, such as death losses and treatment costs. In addition, some researchers suggest that bovine respiratory disease (BRD) in the first 60 days of a calf’s life will decrease survival to first calving, increase age of first calving, increase calving difficulty and lower milk production, according to the University of Kentucky Extension.
Early disease diagnosis and treatment has long been a cornerstone in effectively battling respiratory disease. Yet, there are problems with this method. Visual assessments of clinical signs can’t distinguish between viral or bacterial causes, and some sick cattle never even exhibit traditional signs like cough, fever or nasal discharge.
“Over the last 10 to 20 years, we’ve seen the development of newer, more targeted antibiotics that have better penetration in the lungs and last longer in the lungs so they can be given less frequently,” says Theresa Ollivett, DVM, Ph.D., assistant professor at the University of Wisconsin-Madison. “We’re feeding calves better, we’re recognizing how to get good quality, clean air into barns. Still, we haven’t cut down the number of animals dying from respiratory disease.”
Ollivett believes the next advancement may be improved diagnostics – allowing dairy producers to detect changes in calves’ lungs when clinical signs are not even present.
“Part of the problem is that the calves that are sick may not look sick, and the calves that don’t look sick may actually be sick,” she says. “Until we start looking at the lung level, we’re not going to be able to move away from the high incidence of disease we have now.”
Veterinarians could use the portable ultrasound equipment they currently use to diagnose pregnancy to examine the lungs.
“Not all calves get a fever. Not all calves look sick when they first get sick,” she says. “About one-third of calves won’t have clinical signs when they first develop lung disease. The pneumonia will be there, but it won’t have manifested yet. The animals won’t tell you they are sick. In general, for every clinical case of pneumonia producers see, there are two to four cases that you can’t see.”
Earlier detection gives a sick calf improved chances of making a full recovery with less of an impact on growth, and it also reduces the amount of viral or bacterial shedding, which gets other calves sick.
Ollivett envisions lung ultrasounds implemented as a periodic spot-check to ensure producers are effectively identifying and treating animals.
“You still have to be practical and periodically check on animals most at risk, with ultrasound assessments on the farm,” she says. “Often, in indoor housed calves, disease starts around 21 days of age. Every month, or every other month, veterinarians could ultrasound the lungs of a proportion of the calves. If the incidence is going up, then it’s time to ask ‘what’s broken in my system?’ It helps you stay ahead of major problems.”
This spot-checking system helps provide a baseline over time on a specific farm and identify how changes in treatments are working. Producers could work with their calf feeder to tweak programs or adjust their own protocols.
“The ultrasound could also help answer the questions we have right now: did my treatment work? Do I have the right class of antimicrobial for whatever is going on in my farm? Am I picking these calves up early enough? It helps you tweak the program to find those calves that are sick and treat them effectively,” Ollivett adds.
Early diagnosis of disease must be implemented in conjunction with other tried-and-true management practices, Ollivett advises. Producers must still focus on prevention of disease, which should include:
- • Ensuring adequate colostrum is received after birth and provide adequate volumes of high-quality milk or milk replacement
- • Providing clean and draft-free bedding areas
- • Properly ventilating within calf barns
- • Avoiding overcrowding
“Closed barns help keep the environment warmer, but they can also lead to more viruses and bacteria,” Ollivett says. “We have to ensure air circulation is good and designed properly. It’s one of the most common problems – not that producers don’t have the right fans or tubes, but that they aren’t designed properly.”
- • Losses from respiratory disease can include: death losses, treatment costs and future milk production.
- • Bovine respiratory disease (BRD) in the first 60 days of a calf’s life will decrease survival to first calving, increase age of first calving, increase calving difficulty and lower milk production.
- • Veterinarians could use the portable ultrasound equipment they currently use to diagnose pregnancy to examine the lungs.
- • Lung ultrasounds implemented as a periodic spot-check to ensure producers are effectively identifying and treating animals.
In: September Digital Edition 2019Topic: Livestock