Pneumonia can affect calves of any age. Most of the pathogens that cause lung infections are always present in the calf’s respiratory tract and become a problem only when his immune defenses are compromised by stress. Stress may be due to bad weather, extreme changes in temperature, a long truck haul, overcrowding in a dirty environment, or nutritional stress due to deficiencies of an important mineral like copper or selenium. A newborn calf in a drafty or humid barn (with saturated bedding, ammonia fumes that irritate lungs and airways) may get pneumonia.
A primary viral pneumonia may be mild, but secondary bacterial invaders may move in after tissues are damaged by a virus. For instance, a viral infection often destroys the tiny cilia on the lining of the windpipe and bronchi, so foreign material (including bacteria) can no longer be moved up out of the airways.
Bacterial pneumonia is generally more apt to kill the calf than is viral infection. Viral pneumonia may be insignificant and run its course without treatment — unless a secondary bacterial infection (such as Pasteurella) turns it into an outbreak of pneumonia that may go through a group of calves.
Young calves are most susceptible to pneumonia after their temporary immunity (antibodies from the dam’s colostrum) begins to wane. Calves that do not get colostrum or not enough (or not soon enough) have less defense against pathogens. Calves stressed by a hard birth or calves that become chilled immediately after birth may not get up and nurse soon enough, or can’t absorb enough maternal antibodies due to stress (which hastens thickening of the gut lining).
Calves of any age may develop pneumonia when weather conditions are stressful. Particularly dangerous are extremes of temperature in fall or spring with hot days and cold nights. Robert Cope, DVM (Salmon, Idaho) says these cases are often due to Pasteurella. “Those don’t need a virus to get started. When you get temperature extremes, we see a lot of Pasteurella pneumonias. What seems to be the key is a temperature differential of five to 10C or more (such as 15C afternoons, dropping to six degrees at night). With these conditions you may get primary Pasteurella infections and don’t need a virus to set them off. A virus vaccine (IBR, BVD etc.) won’t protect calves in this instance, but a Pasteurella vaccine will,” he explains.
SIGNS OF ILLNESS
A calf with pneumonia usually goes off feed, is dull and depressed, and may spend a lot of time lying down. He may stand humped up. Ears may droop, he may have a snotty or crusty nose, and respiration may be fast or laboured. He moves slowly because he is in pain. He may have a cough or noisy breathing. In severe cases the calf may have difficulty breathing and might breathe with his mouth open or with a grunting sound as the air is forced out of impaired lungs.
There are a number of pathogens that can cause respiratory disease. What we used to call “shipping fever” is now called BRD (bovine respiratory disease). There are more than 20 bacteria and viruses that can be involved in lung infections, according to Cope.
EARLY TREATMENT CRUCIAL
There are several good drugs available now for treating pneumonia, including Baytril, Nuflor, Micotil, Excede, Draxxin, and others that are all more effective for bacterial infections than the standard penicillins or oxytetracyclines and sulfas, says Cope, but the key to successful treatment is catching them quickly, and that’s not always easy. “Often by the time a calf is obviously sick, there’s permanent lung damage,” he says.
“The main thing with Pasteurella pneumonias, especially, is treating the calf before lung damage can become permanent. There have been studies that indicate the damage can become permanent within less than eight hours. At that point there will be scarring, even if you clear up the infection,” says Cope.
Whether the calf can make it to adulthood depends on how much scarring there is. “Once permanent damage exceeds 20 to 25 per cent of lung tissue, the calf won’t do well even if he survives. Those are the ‘chronics’ that never grow, don’t do well, and die about a week before you were going to haul your calves to market,” he says. The calf, even if he seems to be doing ok, will eventually outgrow his lung supply. He may not grow well, or outgrows his lung supply and then he suddenly dies, Cope explains.
Supportive care is important. Make sure the calf is warm and dry, protected from bad weather. If he’s not eating or drinking, you may need to force feed fluids, or give fluids with nutrients (milk to a pre-weaning age calf). Anything you can do to help a calf will help him fight the battle more successfully. If he has a high fever and does not feel like eating or drinking, anti-inflammatory drugs (like Banamine) can lower the fever and make him feel better — often enough that he’ll start eating and drinking again. Do not give Banamine to a dehydrated calf or there is risk for kidney damage. Using it in conjunction with fluid therapy, however, can be helpful.
Antibiotics are usually given, even if pneumonia may be viral, since secondary bacterial infection may occur. Be diligent with treatment and don’t quit too soon. Even if the calf is feeling better and breathing better, eating and drinking again and his fever is down, keep antibiotic levels high for at least two full days after all symptoms are gone, or he may relapse and be much harder to save the second time around.
There are some good vaccines available for helping prevent respiratory disease in calves. The best prevention in early calf-hood is to make sure each calf gets adequate colostrum, soon enough. If the cow’s vaccinations are up to date, she will pass some of that protection to her calf via her colostrum. “There is no substitute for good colostrum. If a calf doesn’t get it, he is vulnerable to everything,” says Cope.
“This protection is probably waning by the time most calves are three weeks old, however, and many cows’ immunity to Pasteurella isn’t that great. If you have cases of spring and summer pneumonia in calves, it may pay to vaccinate calves at around a month or so of age. It’s also important to see if there are any underlying problems on herd health. The cows may need a higher nutrition level. Energy, protein and trace minerals are things you should check, if calves are getting pneumonia. A cow that’s not in good shape herself will not have good colostrum,” he says.
If the cow does not have a properly functioning immune system — due to being low on selenium, energy, protein, etc. or has BVD — the calf will not get good colostrum. If you’re having a problem in calves, look at the cows. If you’re getting pneumonia in calves less than three weeks old, it’s generally less the calf’s fault than the cows’, says Cope.
Most calves that have good colostrum and nutrition can handle weather stress without becoming sick, especially if they have shelter. We have better treatments (more effective drugs) for treating pneumonia than we used to have, but prevention is still preferable. A total herd health program will go a long way toward preventing pneumonia, and involves more than just vaccinations.
Bruce Anderson, DVM, at the Caine Veterinary Teaching Center, Caldwell, Idaho says antibiotics may not always pull a calf through, because you may not realize how sick the calf is until it’s too late.
“Studies at the University of Nebraska’s Great Plains Veterinary Education Center, where groups of calves were followed from birth through feedlot and slaughter showed the calves that did not get good passive transfer (from colostrum) 18 months later performed less well in the feedlot. These calves had less functional lung tissue than normal calves, probably because they had respiratory infections and pneumonia early in life. It is really the sub-clinical pneumonias that hurt you, because you never know these calves were really sick,” he explains.
These are calves that may have been a little dull or off feed but they never get treated because they don’t appear sick — or you can’t catch them to treat them. They end up with compromised lungs, however, and do not perform as well as the rest of the herd. “At slaughter we find that some of these cattle have 10 to 15 per cent dead lung, or some old adhesions, and we know that they had a respiratory problem as a calf,” says Anderson.
Heather Smith Thomas ranches with her husband Lynn near Salmon, Idaho. Contact her at 208-756-2841