Role of Calcium in the Nutritional Etiology of a Metabolic Disorder in Ruminants Fed a High Grain Ration ,

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Abstract
Four experiments involving 152 wether lambs were conducted to determine the nutritional factor(s) involved in the etiology of a metabolic disorder of cattle caused by feeding a high maize ration containing 0.3% phosphorus and 0.16 to 0.19% calcium. The calcium intake was inadequate to satisfy the needs of the growing-finishing lamb for calcium. Calcium deficiency signs observed were lack of appetite, decreased growth, emaciation, muscular stiffness, decreased plasma serum calcium concentration and rarefaction of bone. Phosphorus levels similar to those encountered in the field ration, in conjunction with the low calcium levels had a detrimental effect; plasma calcium levels were not maintained and plasma magnesium and inorganic phosphorus concentrations were increased. Death resulted from blockage of the urethra by sludge, or calculi, or both. The signs of the disorder were reversed by added calcium carbonate, but not by organic calcium sources or extra sodium as chloride or carbonate: bicarbonate and potassium. The evidence indicates that in the presence of phosphorus levels exceeding recommended levels, the calcium levels (expressed as a percentage of the diet) recommended by the National Research Council for lambs and probably for beef cattle are grossly inadequate. With these rations a Ca:P ration of 1.3:1 is borderline. The data suggest that ratios of 1.5:1 or 2:1 are more desirable.