ABSTRACT
Nitrate intoxication in livestock from some roughages has been of concern since W. B. Bradley et al. identified the toxic compound in oat hay as nitrate. Nitrates are ubiquitous in feed, food, and water, and are essentially nontoxic. Nitrate becomes toxic when reduced to nitrite. Nitrate reductase reduces nitrate to nitrite before further reduction to amino nitrogen. Nitrate reductase activity is influenced by many factors, including genetic control, intensity of light, hydration, and nitrate substrate. The combination of nitrate uptake at night and lack of reduction of nitrate by nitrate reductase during daylight hours, due to wilting and water loss, is an ideal combination for nitrate accumulation in plant tissues. Animals can adapt to relatively high nitrate levels in their diets if the levels of nitrate are increased gradually. Chronic nitrate toxicity has been associated with a variety of problems, including reduction in weight gains, decreased milk production, abortion, vitamin A deficiency, and hypothyroidism.
