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Toxicity of Nitrates and Nitrites to Dairy Cattle

Federal Experiment Station, Agricultural Research Service, USDA, Mayaguez, Puerto Rico

ABSTRACT

During the past decade, the use of nitrogen fertilizers in the production of forage crops has become a wide-spread practice in many areas of the tropics. This practice has led to tremendous increases in yields of total digestible nutrients per acre. In tropical areas with 70–80 in. of rainfall annually, the yields of dry forage per acre can be increased from 4–5 tons per year to 25–30 tons per year. This increase in over-all yield is accompanied by a threefold increase in the per cent crude protein, resulting in an 18- to 20-fold increase in total crude protein per acre. These yields are phenomenal when compared to forage yields obtained in the temperate zones.

The utilization of these high protein grasses has presented problems. These grasses have a relatively high nonprotein nitrogen fraction, including nitrates, which leads to undesirable effects unless certain specified feeding practices are adopted (2, 5).

Recently, very severe losses from toxic agents of unknown origin occurred at two dairy farms in Puerto Rico.