How to overcome respiratory diseases
OVERCOMING RESPIRATORY DISEASE: ACCURATE DIAGNOSIS OF BOVINE RESPIRATORY ILLNESSES REQUIRES MODERN UNDERSTANDING OF THEIR ETIOLOGICAL FACTORS
Protecting young cattle is a top priority for successful livestock farming. Respiratory diseases in cattle are one of the most significant challenges in modern animal husbandry, causing substantial economic losses for producers. Various infectious agents (viruses, bacteria, mycoplasmas) can trigger clinical signs of pneumonia in cattle. These pathogens often act in different combinations, contributing to complex disease progression. Among these, bacteria play a crucial role in the development of respiratory disease.
The Burden of Respiratory Disease.
Controlling respiratory diseases is one of the biggest economic burdens for cattle producers, especially in the beef industry. Bovine respiratory disease (BRD) is a multifactorial and multi-etiological complex. Normally, the respiratory system of cattle is resistant to disease, but under certain conditions, these illnesses emerge and pose a serious threat to calves.
Causes of Disease
The primary causes of respiratory disease in cattle can be grouped into:
- Management practices for rearing young stock
- Environmental influences
- Pathogenic microorganisms
Several factors influence the prevalence of respiratory diseases in dairy calves before weaning, including breed, age, region, and management practices (feeding, housing, vaccination, etc.) — both at the individual animal level and the herd level.
Management practices are key contributors, including feeding protocols, genetics (breed and herd structure), immune status (affected by age, colostrum intake, and vaccination), and co-existing illnesses.
Vaccination is Critical
Special attention should be given to immunizing the herd, including both adult animals and newborns. Vaccinating cows before calving helps maintain the dam’s immune status and ensures the transfer of antibodies through colostrum, building the calf’s early immunity.
Housing and Environmental Conditions
Housing conditions significantly impact the spread of respiratory diseases. While calf-rearing systems vary globally and each has pros and cons, it is vital to group calves by age. Mixing different age groups increases stress, competition for feed and water, and allows older animals to dominate younger ones.
Group size and animal density are also key. High density increases direct contact, which accelerates the spread of pathogens.
Environmental factors such as seasonal changes, temperature fluctuations, ventilation quality, and humidity levels also influence disease development. Peaks in disease incidence typically occur in autumn and early winter. It’s not the temperature itself, but the sudden changes in temperature that contribute most to illness.
Poor ventilation and hygiene in housing lead to high humidity and ammonia buildup, which harms the respiratory system. Ammonia levels rise when ventilation systems are absent or poorly maintained.
The Role of Pathogens
While all the factors above contribute to respiratory illness, pathogenic microorganisms remain the primary cause. BRD is often multi-etiological, involving multiple infectious agents—viruses, bacteria, and mycoplasmas—acting together.
- Viruses and mycoplasmas are usually primary agents
- Bacteria worsen the condition in an already weakened animal
Viruses may cause clinical symptoms on their own, but often they are considered co-infections or precede bacterial infections.
Many bacteria associated with pneumonia are actually part of the normal flora of the nasopharynx in cattle. On their own, they don’t cause disease in healthy animals and are considered opportunistic pathogens. However, stress factors such as poor housing, transport, and regrouping can activate these bacteria, leading to bronchopneumonia with clear clinical symptoms.
This underscores the need for vaccination and prophylactic antibiotic use, especially during transport and regrouping of animals.
Preventive Protocols
Based on veterinary experience, the following metaphylactic treatment protocol is recommended:
- During stressful periods such as:
- Moving calves from individual pens to group housing
- Switching feeds
- Forming new groups
- It is advised to administer:
- Tulathromycin (e.g., Macrosept)
- Long-acting penicillin combinations (e.g., Shotadin)
A single injection of these drugs can prevent diseases caused by Mycoplasma, Pasteurella, Streptococcus, and Staphylococcus (including diplococci).
Feeding calves with milk from cows with mastitis is another risk factor. Even pasteurization may not eliminate all microorganisms, increasing the risk of bacterial infections, including respiratory diseases.
Conclusion
Bacterial respiratory infections are one of the main challenges in modern cattle farming. The wide variety of bacterial pathogens complicates diagnosis. Therefore, a correct diagnosis, and thus the choice of effective antibacterial therapy, is impossible without up-to-date knowledge of the etiological agents, epizootiology, pathogenesis, and clinical features of respiratory illnesses.
Author: Yurii Naumenko, Doctor of Veterinary Medicine, "VETSINTEZ" LLC
Special thanks to Dr. Yurii Slon for assisting in the preparation of the article.
