Inflammation in Calves
Inflammation is a normal immune response to infection. This local response to cellular injury results in capillary dilation, leukocytic infiltration, redness, heat, and pain and serves as a mechanism to initiate the elimination of toxins and damaged tissue.
Enteric Inflammation
Most pathogens that wreak havoc on young calves attack the digestive system. At this point in time, young calves have both an underdeveloped digestive system and an underdeveloped immune system. An overabundance of pathogenic bacteria colonizing the gut can lead to infection and disease.
Enteric pathogens bind to and destroy villi cells at different degrees, but all create inflammation and activation of the arachidonic acid cycle. Scours are typically a result of both the malabsorption caused by damaged villi and excretion of sodium chloride, bicarbonate, and water as byproducts of the inflammation pathway. Severity of the diarrhea will depend upon the severity of infection and amount of damage done to enteric cells.
Lung inflammation
Bovine respiratory disease (BRD) is the leading cause of morbidity and mortality of both dairy and beef young stock and is a major animal welfare issue with extensive economic implications. Similarly, to enteric disease, respiratory disease is caused by infection of cells in the respiratory tract. Damage to these cells leads to inflammation, and if not resolved quickly may lead to lasting damage.
Recent studies have shown that an imbalanced immune reaction is an important factor to clinical symptoms and lung lesions associated with BRD. The animal’s immune response is necessary to fight the infection and restore lung homeostasis. A dysregulated immune response is held responsible for excessive lung damage and overwhelming of the anti-inflammatory immune capacity to heal lung lesions and restore lung function.
HPA-Immune Axis (Hypothalamopituitary Adrenal and Inflammatory Axis)
The HPA Axis modulates the immune system. Adult animals utilize adaptive immunity to help control the innate immune response by minimizing the amount of proinflammatory cellular responses. Youngstock lack a developed adaptive immune system and rely on the HPA axis as the primary regulator and modulator of immunity.
Stress hormones play an important role in the immune response and calves that are resilient and immunocompetent have well-regulated HPA-activity and coping behaviors in the presence of multiple stressors.
Early life enteric disease may influence the ability to detect respiratory disease later in life. Severe dehydration and septicemia seem to affect the regulation of the HPA axis and the inflammatory response. Calves that have experienced severe early-life infections may have less of a febrile (fever symptoms) and behavioral response to respiratory pathogens.
Early detection of disease is vital to the success of treatment. Any action taken to lighten the pathogen load, support anti-inflammatory pathways, and provide nutrients for cell restoration and function will give the animal the opportunity to recover from the infection quickly and fully.
Written by: Mariah Gull, M.S.
Sources: Hulbert, Lindsey and Sonia J. Moisa, 2016, Stress, Immunity, and the management of calves, J. Dairy Sci. 99:3199-3216.
Osorio, Johan. S., 2020, Gut health, stress, and immunity in neonatal dairy calves: the host side of host-pathogen interactions, Journal of Animal Science and Biotechnology, 11:105.
Dr. Wayne Hagan, DVM