A closer look at lungs

Ultrasound is a useful tool in detecting pneumonia in calves

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WISCONSIN DELLS, Wis. – Calves are not always the easiest animals to detect sickness in. While many farmers are aware of the clinical signs of pneumonia – coughing, fever, nasal discharge, sunken eyes and loss of vigor – how can one better detect the subclinical signs in a calf?
“Calves are not always super easy to interpret,” Dr. Kendra Wells said. “With an ultrasound, I am detecting subclinical lesions.”
Wells presented the benefits of thoracic ultrasound at the Vita Plus Midwest Dairy Conference June 15 in Wisconsin Dells.
Subclinical signs of pneumonia are occurring before the calf shows any physical signs of sickness. Wells said a calf can go from acting normal, eating and being active to becoming severely sick without any obvious warning. Upon euthanasia, Wells has often found that those calves’ lungs had lesions on them.
“A subclinical lesion occurs when a calf seemed totally normal but was still internally sick,” Wells said. “With the ultrasound, we’re able to detect it, and in certain cases, we are doing some subclinical treatment.”
Wells said the reason calves may not display symptoms is because of their biological nature to not show weakness as a way of survival.
“Cattle, in general, are the prey so their habit is always to try to hide something,” Wells said. “In nature, you have those wolves waiting to see who is the weakest link, and they’re going to attack them. If I’m the weakest link, I’m not going to try to show that.”
To find subclinical illnesses, Wells uses ultrasound to determine if a calf’s lung has lesions or not. She then scores the calves from zero to five based on the findings, with zero meaning no lesions and five meaning severely sick with multiple lesions. When looking at a lung with an ultrasound, Wells said a healthy lung will present reverberation lines while a lesion shows up as dark spots.
Lobular lesions are at the beginning of a bacterial pneumonia and score a two on the scale. They indicate the first step of what may end up being viral pneumonia.
Wells said there are different reasons for these signs and can sometimes be the result of an error on the caregiver’s part. If a calf is tubed wrong and ends up aspirating while being fed, then a lesion can show up when a calf is as young as 2 days old.
“It could just be that we messed up,” Wells said. “Sometimes, I will see calves that are less than 7 days old with these lesions, and then we go straight back and look at how the colostrum was fed.”
In other cases, lesions are the result of environmental factors. Particularly in the Midwest, Wells has seen more evidence of lesions during February than in other times of the year. This is due to closed barns to keep cattle warm which can restrict air flow and cause pneumonia or subclinical symptoms.
Housing type also plays a role.
“All of the hutch calves that I have scanned have been very, very clean,” Wells said. “With auto feeders, it’s kind of like sending all your kids to kindergarten when they bring bugs home and they get sick. There’s nothing wrong with auto feeders or hutches or barns, but it’s just what I’ve seen.”
With treatment, the lesion will shrink, stop growing or disappear by the time that animal becomes 2 years old. Wells has seen cases where lesions shrink weekly with treatment.
“This is still pretty new, so we don’t know yet what the antibiotic efficacy is,” Wells said. “I can’t say if the bug responded to the antibiotic without taking bacteria from that calf, putting it on a plate and testing it against the antibiotics. What I can say is that the calf responded to treatment.”
Wells also uses the #WeanClean Philosophy by Dr. Theresa Ollivett with the University of Wisconsin School of Veterinary Medicine. This system looks for the percentage of calves that have lung scores at weaning. Wells usually looks for a score of three or greater.
“That means these calves have had some event before that and have not cleaned up from that yet,” Wells said. “Your goal should be less than 50% calves with lesions. If I’m being honest, I have few herds that actually hit that. If you’re doing this and you’re frustrated with it, don’t be.”
Wells said there are many factors to consider when looking at lungs in calves and why some develop lesions and some do not. When a young calf of 2 weeks or less presents lesions, it is likely management at birth. If a 9-week-old calf is presenting evidence of lesions, Wells said to review the weaning program.
“This is not the be all and end all,” said Wells of calf lung health. “But, it is usually leading us to the next step of the program that we can improve to change what we are seeing on the ultrasound.”

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