Just because calving season is finished and the cows have been put to grass, it's no time for producers to let their watchful guard down. Without frequent observation of the herd, a number of conditions can result in serious economic loss.
These disease conditions, which we've reviewed in previous columns, include pinkeye, foot rot and abomasal ulcers. There's also “summer pneumonia.”
Summer pneumonia is a term used to describe a respiratory condition that develops in suckling calves during summer months. The condition often goes unnoticed until several calves are found dead or in the disease's late stages.
It seems unusual to experience pneumonia under non-stressful conditions in this age of calf. The common risk factors usually discussed with pneumonia — commingling, transportation, exposure to infectious agents, stressful weather, confinement and dietary changes — don't apply here.
But, veterinarians generally believe that warm, summer, daytime temperatures coupled with cool, summer nights and declining maternal immunity to respiratory pathogens can result in a combination of stress and low immunity. When exposure to potential pathogens occurs, the result can be clinical disease.
Some of the organisms responsible for disease can be carried by healthy animals and yet not cause disease. Such organisms include Mannheimia (Pasteurella) hemolytica, Pasteurella multocida, Hemophilus somnus and the viruses Infectious Bovine Rhinotracheitis (IBR), Bovine Viral Diarrhea (BVD) and Bovine Respiratory Synscitial Virus (BRSV).
Summer Pneumonia Symptoms
In cases in which animals are found alive, summer pneumonia symptoms include calves laying off by themselves, looking gaunt and ears down. They also look depressed with their dams showing no evidence of being nursed. Rectal temperatures range from 104° to 106° F.
With early diagnosis, response to antibiotic therapy is normally very good. When viruses are part of the problem, however, response to therapy will be less successful.
When the first case is discovered, producers must diligently check for new cases. It's important to work with your veterinarian to determine the best therapy for the cases in your herd.
Severe outbreaks may require therapy of calves that have not yet displayed clinical signs of disease. This is not appropriate in every case, however.
Vaccination is another strategy, particularly if a virus is assumed to be part of the cause. Vaccination may slow the virus' spread and help stop the outbreak.
In instances in which summer pneumonia becomes an annual problem, then pasteurella and viral vaccines should be considered at spring turnout. Because the use of modified-live vaccines in suckling calves is not approved, remember to read all vaccine labels and plan your vaccination schedule with your veterinarian.
Performance, Quality Losses
The prevalence of summer pneumonia isn't known. A 1993 National Animal Health Monitoring Service study attributed 8% of all deaths in suckling calves to respiratory disease. The data, however, doesn't indicate how many calves were affected and recovered.
Feedlot data indicate that respiratory disease costs range from $58-90 for every sick animal treated. Iowa State University steer futurity tests further broke down that lost opportunity cost to a per-head basis of $28.90 due to chronics and deads, $18.10 because of treatments, $2.38 in quality grade loss and $6.10 in longer feeding times.
These data sets, of course, don't indicate the impact of respiratory disease during the suckling phase. It's reasonable to assume the impact on performance and carcass quality of affected animals is long term.
In addition, the use of intramuscular antibiotics during the suckling calf phase can potentially create a blemish or reduce tenderness in that muscle.
Gerald Stokka, DVM, MS, is an associate professor and Extension beef veterinarian at Kansas State University in Manhattan. Mike Apley, DVM, PhD, is an assistant professor of beef production medicine at Iowa State University in Ames. This column appears in alternate months.