North American Veterinary Licensing Examination (NAVLE) Practice Test 2025 - Free NAVLE Practice Questions and Study Guide

The most effective treatment for nitrate poisoning in cattle grazing Sudan grass is methylene blue. Nitrate poisoning occurs when cattle consume plants that contain high levels of nitrates, which can be converted to nitrites in the body. These nitrites interfere with the ability of hemoglobin to transport oxygen, resulting in methemoglobinemia—a condition where hemoglobin is altered such that it can no longer effectively bind to oxygen, leading to tissue hypoxia.

Methylene blue works by reducing methemoglobin back to functional hemoglobin, effectively reversing the methemoglobinemia. It serves as a reducing agent, donating electrons to methemoglobin and facilitating the conversion back to its oxygen-carrying form. This process restores the animal’s ability to transport oxygen, making it a targeted and effective treatment for this specific type of poisoning.

In contrast, while the other options listed have their uses in veterinary medicine, they do not specifically address the mechanism of action needed to remedy nitrate poisoning effectively. Digitalis is used primarily in cardiac conditions, sodium thiosulfate is more commonly used for cyanide poisoning, and vitamin B12 plays a role in various metabolic processes but does not directly counteract the effects of nitrate toxicity. Thus, methylene blue is recognized as the