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Rapidly Growing Forages and Atypical Interstitial Pneumonia

Cattle that are moved off a dry, sparce pasture onto one that has abundant lush growth can cause atypical interstitial pneumonia (AIP). The disease is also known as fog fever, pulmonary emphysema, bovine asthma, acute bovine respiratory distress syndrome, or acute bovine pulmonary emphysema and edema. The disease usually impacts mature animals 5 to 10 days after they are turned out into lush pastures.

When forages grow rapidly, tryptophan, (an amino acid) is produced in high amounts. After lush forage is consumed by cattle, tryptophan is degraded by a two-step process into 3-methylindole. It is then transported via the bloodstream to the lungs. Once in the lungs, it is converted into 3-methyeneindolenine. It is this form that causes extensive damage to the lungs. Symptoms include open mouth breathing, head and next extension, and a swayed back appearance. Rapid, shallow breathing occurs. A grunt sound occurs when the animal exhales. Coughing is not usual.

Fifty percent of affected animals recover from the ailment. There is no effective treatment for this condition. Prevention measures such as feeding minerals with Bovatec six days prior to turnout reduces the number of bacteria in the rumen that convert tryptophan to 3-methylindole. Continue feeding Bovatec while pastures are actively growing.

This disease may become more prevalent because more seeded annual pastures include brassica species in the cover crop mixture. Turnip tops, kale, rapeseed, and cabbages all have high tryptophan content.

To reduce the risk of AIP, introduce the animals to the lush pasture gradually. Use an electric fence to limit access or limit grazing time in the new paddock. Start the animals off slowly on the new pasture with consumption limited to 25% of dry matter intake. Gradually increase to full feed over 10 to 14 days. Supplement lower quality dry hay to make up the shortfall. If there are concerns with animal health, consult with a veterinarian.

Contact Barry at 403-741-6032 or, for additional information on grazing lush pastures and Bovatec usage.


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