Study finds hidden pneumonia in nearly three quarters of calves

A study reported by ERR found that nearly three quarters of calves developed hidden pneumonia during their first month of life, and that the condition often worsened without treatment.

Researchers from the Estonian University of Life Sciences and Ghent University examined the health of 126 newborn Estonian dairy calves. They visited two South Estonian dairy farms twice a week and used portable ultrasound equipment to examine the calves’ lungs from birth until the end of their first month.

Ultrasound showed that every calf developed some degree of lung damage during the month. More serious lesions, measuring at least one centimetre, appeared in 94 animals, or nearly three quarters of those studied. Pneumonia progressed without any visible signs in 97 percent of the affected calves.

The researchers initially left lesions measuring one to two centimetres untreated. The condition worsened over time in nearly three out of five cases, while only about a quarter of the calves recovered without intervention. Among calves with more serious lung damage measuring more than three centimetres, immediate antibiotic treatment increased the chance of recovery several dozen times.

The problems affecting young calves were linked to several factors. The farms had bovine coronavirus and several types of bacteria. Viruses can first damage the lining of the lungs, making the animals more vulnerable to bacteria that cause deeper lung damage. Calves also have weaker immunity during their second and third weeks of life, as protection received from their mothers begins to decline before their own immune systems have fully developed.

Environmental and management-related stress also contributed. The researchers observed a new wave of pneumonia shortly after the calves were moved into larger groups.

Hidden pneumonia also affected growth. Calves with damage in three or four areas of the lungs gained less weight during their first month than those with healthier lungs. Because visible symptoms are usually absent, the researchers said early ultrasound examinations are becoming increasingly important for preventing poor growth and later economic losses.

The researchers published their findings in the Journal of Dairy Science.