292 DIETETIC DEFKTEXCV. 



is of the Utmost importance, since many diseases liave from time 

 to time been regarded as causally related to a lack of minerals in 

 the diet simply because the disease affected the bones. Thus 

 in South Africa, for instance, the so-called " o.^teoporosis '' in 

 horses is conmionly regarded as due to dietetic deficiency, 

 whereas it is much more probable that it is of pureh infectioits 

 origin. 



Without going into the details of the starvation condition 

 arising when there is gross deficiency in the " energy value " of a 

 diet ( i.e., for practical puri)oses, a lack of carbohydrates and 

 fat), or where there is a marked deficiency in the protein content, 

 it may be mentioned that life may be indefinitely maintained on 

 a diet which is appreciably below the normal recpiirements of a 

 healthy animal. A half-starved condition or state of general 

 ill-nutrition then results, and the organism is incapable of the 

 normal " effort "' in res])onse to demand. 



As an illustration of im])erfect nutrition on a diet which lies 

 very near the normal. ])ut is deficient for the ]jur])ose in view, we 

 may take a case in which all the necessary food-constituents are 

 ])resent in fair amount, and in which the dynamic requirements 

 of the animal concerned are fullx- satisfied, but in which the com- 

 ponents are diff'erently balanced. Su})])ose a ration for dairy 

 cows in full milk be made up from silage, clover-hay, gluten meal, 

 and maize. Suppose that the gross energy re(|uirements calcu- 

 lated from the size and class of the animals be set down at 18.000 

 calories ]ier day — 



Ration T. Ration TI. 



lbs. Ihs. 



Maize Silagf 30 3" 



Clover I4ay 8 5 



Gluten [-"etd 4-66 3 



Ground Maize 2.2,?, 8 



Corresponding to — 



Discstiljle Protein 2.22 r.93 



Digestible F?t 0.40 0.51 



Digestilile Carbolndrate TI.7 13.0 



PLnergv value.. .'. 18,524 calories 21,130 calories 



These two rations, which hap])en to be e.xperimental diets 

 in certain American feeding trials, contain the same c()ni])onents. 

 but in dift'erent proportions. A batch of cows on Ration i 

 throve well. A batch on Ration 2 lost in condition in spite of the 

 higher energy value of their diet, and gave a milk yield of 

 approximately one-third less. So far as one can judge from the 

 diets, the dift'erence is to be attributed to the diiterence in protein 

 content, which in Ration 2 (0.29 lb. less) was inadequate to 

 meet the demands of the cows in milk. Here we have a defi- 

 ciency which, next to starvation, is the simplest in type. It 

 represents a mild form of protein starvation, resulting in loss 

 of condition, but not resuhing in disease. The ration given would 

 not have been deficient for store cattle. 



Suppose now that a diet be selected which is adequate in 

 respect both to energy requirements and to mere quantity of 



