April. 1921. 



SCIENTIFIC AGRICULTURE 



IS'i 



chromatiu of cell imilein in combination with nucleo- 

 proteiiis. 



There are good reasons for believing that iron com- 

 pounds of tlie cell act as catalysts to the oxidizing en- 

 zymes. 



Iron compounds besides furnishing iron for the syn- 

 thesis of hemoglobin appear to exert a stimulating ef- 

 fect on the production of hemoglobin — (Hense the value 

 of medicinal iron compounds in anemia). 



The mineral elements are intimately involved in the 

 maintenance of the acid-liase (piilibrium of the body. In 

 the opinion of many this function is one of greate.st im- 

 portance and is considered one of the determining 

 factors in proper balancing of rations of farm animals. 



Their Metabolism. 



Higher mammals contain from 2 to 5 percent of ash, 

 about % of which is contained in the skeleton. The 

 mineral requirement of the animal organism, especially 

 of growing or pregnant animals, is largely determined 

 l)y the composition of the skeleton. 



In bone, mineral matter is deposited almost entirely 

 in inorganic combinations. Growing or pregnant ani- 

 mals require relatively large amounts of calcium and 

 phosphorus, which may be supplied to them in inor- 

 ganic form. 



Small portion of the mineral elements absorbed from 

 the intestines is built up into complex organic com- 

 pounds. 



In the case of lactating animals, consideral)lc quan- 

 tities of calcium may be combined with casein and with 

 lactic acid produced in the manunary gland and excreted 

 in the milk as calcium caseinate and lactate. 



Much of the mineral material ingested with the food is 

 in excess of the body's requirements and is promptly ex- 

 creted — almost entirely as inorganic salts. If absorbed 

 in organic combination, the organic radicle is generally 

 oxidized and the inorganic ions combined with other 

 ions to form salts previous to elimination from bodj'. 



The method of excretion of mineral elements from the 

 body depends largely upon the character of the mineral 

 elements. 



1. Iron is almost entirely excreted through the in- 

 testinal wall and ultimately leaves the body in the 

 feces. The urine rarely contains more than a trace of 

 this element. 



2. In lierbivora most of the Calcium is excreted in the 

 feces. It is well kno^vn that calcium of the feces comes 

 from the body as well as the food. 



Elimination through the intestinal wall has been 

 proven for Ca as for iron, and during fasting or under- 

 nutrition the principal way in which calcium salts are 

 lost from the body is through the walls in the intestine. 



3. The excretion of ]\Ig and P runs more or less closely 

 parallel to that of calcium. 



4. Na, K and CI and S are excreted largely through 

 the urine, this being true especially the last two avious. 



In Ohio experiments with pigs (Bulletin 27) it was 

 shown that from 97 to 99 percent of clilorine excretion 

 appeared in the urine. 



Also that 'A to 78 percent sulfur excretion, 



67 to 87 percent Na excretion, 



.)7 to 83 percent K exci'etion, occur in the urine. 



And only 9 to 20 percent Ca, 



10 to 19 percent Mg, 



19 to 43 percent P, 

 excretion occurred in the urine. 



In general : — the magnesium of the fixid is shown to 

 be a factor in the partition of phosphorus between urine 

 and feces. 



An increased proportion of Mg to P in food increases 

 the proportion of fecal phosphorus to urinary phos- 

 phorus. 



A high ^Ig intake seems also to be detrimental to Ca 

 retention. Mendel and Benedict have slio-mi that in- 

 jection of Mg salts into dogs produced an increased 

 elimination of Ca in the urine. 



Hart and Bteenbock at the Wisconsin Experiment 

 Station fed a pig a ration of corn, wheat bran and oil 

 meal, and determined the excretion of calciimi in urine 

 and feces. 



The addition to the day's ration of 6.08 grams of 

 either Mg CL or MgSO^ caused a marked rise in the ex- 

 cretion of calcium in the urine, with no appreciable 

 effect on the fecal calcium. 



.4 positive calcium balance thus by the addition of 

 Magnesium was converted into a negative balance. 



There is no evidence therefore that the limited utiliza- 

 tion of calcium by milk producing cows is due to the 

 limited solubility of calcium compounds of the ration. 



The fact that heavily milking cows lose calcium at the 

 same time that they receive a readily assimilable supply 

 greatly in excess of the amount utilized, shows that the 

 calcium stores of the body are more readih- accessible 

 for use in milk production of the cow. 



In comparison with the extent of the change of intake 

 in Forbe's Experiments, it becomes apparent that the 

 mineral metabolism of the well fed, heavily milking cow 

 is not intimately and directly dependent upon tlie min- 

 eral nutrients of the ration during lactation, but that 

 it is determined by (A) the inherited impulse to .secrete 

 mUk, (B) by the mineral reserve of the animal body, 

 (Q) only thirdly by the minerals in food supply. 



■Value of Organic and InorgaJiic Compounds of Min- 

 eral Elements in Nutrition. 



The body requirement for mineral salts is largely in- 

 organic. There is little question that inorganic salts of 

 food can meet the body requirements for mineral ele- 

 ments in inorganic combinations. 



It is a question, hoivever, whether the inorganic salts 

 ingested in, or ivith the food can be built up in the body, 

 into organic combinations. 



The field of usefulness of inorganic salts would seem 

 to be restricted by the fact that the union between their 

 ions is more stable than that between either ion and the 

 organic complexes with which it might otherwise be com- 

 bined in metabolism. 



For example: — KsPO^ is probably not well suited for 

 all the needs of the organism for phosphorus, simply be- 

 cause the potassium has a stronger affinity for the phos- 

 phorus, than it does for glycerol, or for the nitrogenous 

 bases with which it might otherwise be combined in the 

 synthesis of phospholipins. 



In favor of this explanation is the fact that the nature 

 of the organic compound containing a given mineral 

 element seems to be a matter of indifference as far as 

 its value in nutrition is concerned. Thus casein, nucleic 

 acid, or lecithin can furnish the body with phosphorus 

 in a form suitable, to cover all types of phosphorus re- 

 quirements. 



Acid Base Equilibrium. 



Temperature and neutrality are physico-chemical con- 

 ditions vitally connected with the proper working of 

 physiological processes in higher mammals. 



In all tissue of the body during life, there occurs a 

 continuous production of acids — final products of met- 

 abolism. They are carbonic, sulfuric and phosphoric 

 acids. 



