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Ammonia Toxicity in Cattle. IV. Effects of Unprocessed or Extrusion-Cooked Mixtures of Grain and Urea, Biuret, or Dicyanodiamide and Liquid Supplements on Rumen and Blood Changes Associated with Toxicity¹

Kansas State University, Manhattan 66506

Abstract

Mixtures of unprocessed grain and urea were more toxic than extrusion processed mixtures of grain and urea when given to cattle not adapted to urea. Also, ammonia toxicity occurred sooner (P<.001) when the animals received unprocessed grain and urea than when they were given any of the processed mixtures. No differences were observed in rumen ammonia-N between processed samples that were toxic or nontoxic, but rumen pH and blood ammonia were higher (P<.001) with the toxic samples. Extruded grain with dicyanodiamide, and unprocessed grain with biuret, produced almost no change in rumen and blood ammonia-N and rumen pH, suggesting that degradation of the N source was limited in the rumen. Processed grain with biuret significantly increased those variables. Considerable biuret was converted to urea during extrusion cooking. Toxicity was observed when the cattle were dosed with liquid supplements containing urea. Toxicity was prevented when 3% phosphoric acid was incorporated in the liquid supplement. Neither prevention nor regression of signs of ammonia toxicity in cattle given urea intraruminally was accomplished by intravenously administering an electrolyte solution containing Ca, Mg, K and dextrose. No significant changes in serum total Ca, Mg, and K were observed in animals dosed with extruded grain and urea, dicyanodiamide, or liquid supplements. However, serum Ca²⁺ decreased (P<.05) after the animals were dosed with extruded grain and urea or with liquid supplements. Serum Ca²⁺ and serum total Ca were not correlated.

¹ Contribution 949-J, Department of Dairy and Poultry Science; contribution 950-J, Department of Grain Science and Industry; and contribution 265-J, Department of Statistics, Kansas Agricultural Experiment Station, Manhattan.