The Effect of Calcium Fluoride and Phosphate Rock on the Calcium Retention of Young Growing Pigs'

The experiments of Forbes and his associates (5) ^ at the Ohio Agricultural Experiment Station defined in a very complete fashion the relative efficiency of several mineral compounds as calcium supplements in swine nutrition. The minerals tested included limestone floats, precipitated bone flour, special steamed bone flour, rock phosphate floats, and precipitated calcium carbonate. As compared with a nonsupplemented ration, the bone and carbonate preparations did not differ greatly in their ability to increase retention of calcium and to induce the development of strong, dense bone. The rock phosphate, however, was distinctly inferior in these respects, for in hardness, density, and breaking strength, no differences were observed between the bones of pigs that received no minerals and those that received the rock phosphate supplement. The average ash content of the humeri of the pigs fed the various mineral supplements, expressed in grams of ash per cubic centimeter of volume, was as follows: Pigs fed calcium carbonate, 0.5148 gm. ; steamed bone flour, 0.5125 gm. ; precipitated bone flour, 0.4786 gm.; rock phosphate floats, 0.4459 gm.; no mineral supplement, 0.3756 gm.; control, killed at the beginning of the experiment, 0.4645 gm. The rock phosphate value is distinctly lower than the value for any of the other supplements fed. All the minerals used were fed in daily amounts equivalent to 5 gm. of calcium. Keed and Huffman (10y Í1) reported that when raw rock phosphate was fed to dairy cattle to the extent of 1.5 per cent or more of the grain mixture the animals went off feed, remained below normal weight, and their teeth became very soft and in some instances wore down to the gums. The mandibles of these cattle were much thicker and the surfaces were rougher than those of normal cattle. Buckner, Martin, and Peter {S, 4) foimd phosphate unsatisfactory as a mineral supplement for laying hens. Hens that received rock phosphate ad libitum were affected with diarrhea and their ^gg production was impaired ; the lot that received no minerals laid 60 per cent more eggs than those that received rock phosphate. Further evidence of the low value of rock phosphate as compared to bone meal is furnished by Tolle and Maynard {17), who found that white rats fed rock phosphate in quantities equal to 1.8 per cent of the ration gained in weight more slowly than rats fed bone meal. The teeth of the rats that received rock phosphate showed the changes first observed by McCoUum, Simmon ds, Becker, and Bunting (7) as being: due to fluorine in the diet. The