Excess rumen product anions in cattle. II. Toxic and lethal effects with butyrate.

Toxicity to butyrate was observed in 100-250 kg male Holstein calves following intravenous injection of 0.7-3.6 mmole/kg body weight, intravenous infusion with 0.12-0.53 mmole/min/kg body weight and intraruminal dosage with 19.4 mmole/kg body weight butyrate. Lower doses produced ataxia and serous nasal discharge. Higher doses produced sudden flaccid paralysis and death from asphyxia. No postmortem lesions, gross or histological, were observed. Plasma K+ was reduced to 2.2-2.5 mEq/L. When infusions were stopped, rapid recovery preceded clearance of butyrate and low K+ remained. Nerve depolarization in the central nervous system may be the cause of the toxic effects. Butyrate acidosis is suggested as a factor in unexplained sudden deaths in ruminants.