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SCIENTIFIC AGRICULTURE 



Mineral Feeds for Farm Animals 



By .). S()T()1>A. Aiiiuuil Nutrition Dfiiartincul "f 



Animal Husbandry, State College of 



Washjng:tou. 



April. 1921. 



INTRODUCTION. 



Among the numerous problems of animal nutrition 

 those bearing upon mineral metaliolism are assuming an 

 interesting aspect. Comparatively recent developments 

 in the field, especially in connection with the dairy cow 

 and the hog, have tended to stress the importance of 

 mineral matter in the rations of these animals. 



The requirements for minerals are secondary to the 

 larger needs for protein and energy, but higher stand- 

 ards in animal production as evidenced l)y the increasing 

 numbers of pure bred livestock, and keener competition 

 in the methods of feeding have magnified the impor- 

 auce of all points which tend toward greater economy 

 of production. 



It has been shown that the mineral content ot soils 

 affects more or less directly the mineral content of the 

 grains and roughages produced on such soils. Animals 

 with rickety symptoms have been identified with sec- 

 tions where soils are infertile, where the calcium and 

 phosphorus content of the soils is especially low. In 

 such regions devitalization, sterility and complication at 

 time of parturition have l)een traced to lack of minerals, 

 especially to that of calcium and phosphorus. 



The riiaterial here presented is treated under two 

 general sub-heads. Part I, Mineral Metabolism, deals 

 with the conversion of minerals in feeding stuffs into 

 body substances, with a general review of the functions 

 of mineral elements in the animal economy. Part II. 

 How to Feed Minerals to Livestock, is treated with the 

 view of pointing out some of the practical applications 

 of this sub.ject. 



PART I. 



Mineral Metabolism. 



Method of AssimUatioii. — The various elements as 

 Sodium, Potassium, Calcium, Magnesium, Iron, Sulfur, 

 Phosphorus and Chlorine enter the body in organic and 

 inorganic form. In digestion numerous reactions occur. 



Calcium salts as calcium lactate, reacting with Na-CO^. 

 of juices poured into intestine or with K soaps from di- 

 gestion of fats, would be precipitated in insoluble form. 



Similarly Iron salts may react with H.S (a product of 

 putrefaction of proteins) to form insoluble iron sulfids. 



In protein digesticm inorganic radicles or complexes 

 may or may not be liberated. 



(1) Calcium caseiuate of milk would yiehl Calcium 

 and H^PO^ on complete digestion. 



(2) Phosphoric acid of uncleo proteins would also be 

 liberated. On the other hand the iron of hemoglobin 

 would probably not be split off from hematin. 



Food phospho-lipins are partly split in the digestive 

 tract, giving rise to glycero-phosphoric acid — but proli- 

 ably no free phosphoric acid. 



Sulfur ingested is mostly combined in the unoxidized 

 form in proteins of the feeds — only small amounts of 

 sulfates occuring as inorganic salts. Sulfur is absorbed 

 as sucli in the mercapto group of cystine, (a derivative 

 of i)ropionic acid). Some of the sulfur, however, is 

 lost as metallic sulfids. 



Theory of Bergheim : — Insoluble mineral salts in in- 

 testine — as Ca3 (PoJ. may be dissolved and absorbed 

 through the agency of many leucocytes which are known 

 to migrate into tlie intestinal lumen during digestion. 



The leucocytes are rich in nucleic acid, and other phos- 

 plioric acid compounds — and it is suggested' that 

 through the action of enzymes (phospho nucleases), 

 phosphoric acid is liberated from them — which form 

 soluble acid phosphates cf the insoluble CaalPOJ,. The 

 calcium gains access to the body in combination in the 

 leucocyte. 



Functions of Mineral Elements 



(A) They are constituents of tissues and fluids. 



(B) In osseous tissue phosphates and carbonates of 

 Ca and Mg give rigidity. 



(C) Na^HPO, and Na.CO,— transport CO, from 

 tissue to lungs. 



(D) Iron containing hemoglobim of erythrocytes sup- 

 plies tissue with oxygen. 



(B) Ca of blood is essential to blood coagulation. 



(F) Hooker has .shown that Ca produces contraction 

 of the muscular coat. Potassium and Sodium cause re- 

 laxation. 



(G) If the salt content of blood is changed — there is 

 an effect on heart action. Potassium salts slow up heart 

 and may stop it. (in condition of diastole). If heart is 

 jierfused with fluid containing no calcium, muscular 

 contraction is impossible. Abnoi'mal amounts of Ca 

 may stop heart in condition of systoe. Sodium ions in 

 blood are essential to heart action. Their absence des- 

 troys eontractibility and irritability. Sodium salts in 

 physiological salt concentrations produce relaxation of 

 heart muscles. 



The above illustrations tend to emphasize antagonism 

 of Ca ions vs Na and K ions. The first favors contrac- 

 tion, the latter relaxation. 



(H) Transmission of nervous impulses and trans- 

 ference of impulses from nerve to mu.scle are dependent 

 on the presence of inorganic ions. 



(I) Mineral substances play a role in digestive juices. 

 They provide suitable H ions and OH ion concentration 

 for optimum functioning of enzymes. 



The endocellular enzymes — to which are due many 

 chemical transformations of cellular metabolism would 

 probably be inactive in the absence of electrolytes. 



(J) Inorganic salts preserve and regulate proper os- 

 motic pressure of body fluids. NaCl is particularly con- 

 cerned in this function. Inorganic salts are concerned 

 in the movement of lifjuids and dissolved substances into 

 or out of cells — because of their capacity of modifying 

 the permeability of the cell or cell membrane. 



Example -. — If Sodium iodide is injected intravenously 

 into dogs, fluid is exuded into the pleura and edema of 

 lungs results. If Ca CI., is injected simultaneously, no 

 exudation occurs and the pleural cavity remains dry. 

 The Ca salts appear to decrease the ])ermeability of 

 blood vessels by increasing consistency of colloids of 

 cells comprising walls of the vessels. 



In general Ca possesses the property of increasing the 

 rigidity or viscosity of colloidal ."systems. 



The imi)ortance of iron in the body is entirely out of 

 proportion to the small amounts of iron contained in 

 tissues and fluids. 



A man weighing (i()-70 kgs — contains approximately 

 about 3 grams of iron, 80 percent of which exists as a 

 constituent of hemoglobin. The rest of it is in the 



