February to July. The first eight weeks of lactation is a critical time in which protein and energy are important. Beyond guidelines for those five periods, Laughlin suggested that producers always be alert to nitrate and prussic acid poisoning. Nitrate occurs in older leaves and lower parts in all plants. It can surface when animals consume lower plant parts.
Death usually occurs within four hours of digesting high nitrate forage.
Haying does not affect the level of nitrate. Ensiling can decrease the level somewhat. Death can come within minutes of consumption of the forage. Haying will dissipate some of the prussic acid over time. But ensiling does not affect the level.