Comparison in dairy cattle of mucosal toxicity of calcium formate and calcium chloride in oil

AIM: Oral aqueous preparations of calcium chloride have been well established as causes of gastro-intestinal irritation in cattle. Recently another calcium salt, calcium formate, has been marketed as a treatment and prevention for hypocalcaemia, with the claim that it is non-irritant. The aim of this trial was to establish the safety of calcium formate in the target animal. METHODS: Nine Friesian milking cows were selected and separated at random into three groups. Three were treated with calcium formate, three with calcium chloride in soya bean oil as a positive control and three were negative controls. Cows were slaughtered 6 hours after the last administration and the rumen, reticulum, omasum and abomasum examined by an operator who was unaware of the experimental status of the animals. RESULTS: There was diffuse reddening and swelling of the abomasal mucosa in two of the three cows treated with calcium formate but no lesions in those treated with calcium chloride in soya bean oil or in the negative controls. Histology of the affected portions of abomasum showed areas of necrosis of the mucosa and some acute inflammation. The submucosa was also haemorrhagic with moderate numbers of polymorphonuclear neutrophils present. Histology on other animals was unremarkable. CONCLUSION: Calcium formate may not be a safe oral treatment for cattle. Further testing is required. CLINICAL RELEVANCE: Calcium formate, in the high concentrations required for therapy of hypocalcaemia may not be a safe treatment.