Small, compartmentalized, poorly vascularized… The lungs of cattle have everything to attract respiratory diseases. Especially in meat breeds.
THE respiratory disorders are part of the lot of all breeders. Mortality in young calves, growth retardation in weanlings… But why do cattle cough so easily? Unfortunately for them, their lung morphology is not to their advantage. And if the problem is so widespread, it is because cattle are ” respiratory failure chronicles”.
Natural respiratory failure
Cattle have small lungs in relation to their build. The lungs of an adult man have an average capacity of 4 litres, whereas the lung capacity of a 500 kg bovine is around 12 litres. At equal weight, the respiratory volume cattle is half that of humans. The horse, of comparable build, has a lung volume of 42 litres!
To make matters worse, the lungs of cattle have low vascularization. THE capillariessmall vessels where red blood cells are loaded with oxygen, are less numerous in cattle than in horses.
Highly compartmentalized lungs
Cattle lungs are quite compartmentalized. The right lung is divided into 6 lobes, and the left into 3 lobes. This organization certainly makes it possible to compartmentalize the development of pathological foci, but it limits the capacity of the lungs to modify their volume.
And above all, in the presence of lesions, the compartmentalization condemns a part of the lung as soon as it is located downstream of a bronchial obstruction. By comparison, human lungs have collateral pathways to ensure good ventilation despite obstructions.
Cattle also have a trachea and of bronchi quite narrow. Thus, when cattle breathe, the airflow is up to three times faster than in other mammals. This anatomical peculiarity makes the animal vulnerable. Indeed, the respiratory tract has the role of conditioning the ambient air to the sterile universe of the lungs. The speed of the air flow then makes the mucous membranes particularly sensitive to irritation.
A compensatory respiratory rate
To compensate for its weaker physiological capacities, cattle have a ventilation more important. THE volume of air mobilized with each breath represents 30% of the total volume of the lungs, compared to 11% in humans. Her respiratory rate, at a rate of 15 to 35 movements per minute is also higher. Thus, for the same level of blood oxygenation, cattle use up to twice as much air volume as other mammals.
Particularly sensitive weanlings
This fragility is even more pronounced in cattle typed meat. The more the animal’s weight increases, the greater the muscle mass to be oxygenated at a fixed lung volume. THE malesgenerally heavier and more conformable than females, are more affected by respiratory disorders.
Subjected to the same effort, beef cattle show less oxygen and more carbon dioxide in the blood than dairy cattle of the same age.
THE assholes also have fairly narrow airways, which provides so much resistance to airflow. A benign respiratory disease in a dairy cattle may have more serious consequences on a cattle with the culard gene.
Finally, the young animals are particularly sensitive to respiratory disorders, because the maximum efficiency of gas exchange is not reached until the animal is 1 year old.