680 GENERAL THERAPEUTIC MEASURES 



Proteids consist of carbon, hydrogen, oxygen, nitrogen, and 

 sulphur, united in different proportions. Carbohydrates are 

 composed of carbon, hydrogen and oxygen. Fat is similar 

 in composition to carbohydrates, but in its combustion outside 

 the body yields two and a quarter times as much heat as that 

 produced by an equal weight of carbohydrate. Fat as a nutrient 

 is therefore empirically regarded as equivalent to two and a 

 quarter times the same weight of carbohydrate material. 



Hitherto computation of the food requirements has been 

 based simply on the pounds of digestible nutrients and the pro- 

 portion of proteids to carbohydrates, this proportion being known 

 as the nutritive ratio. 



Now scientific feeding is founded on the fuel value or 

 energy value of food. The fuel value means the amount of 

 heat that is given out by food in its combustion in the body. 

 There is much less heat formed by the combustion of food 

 within the body — on account of losses in food undigested and 

 fermented in the bowels and escaping incompletely burned in the 

 urine— than would occur in food burned outside the body. The 

 heat or energy value of food is measured in calories or therms. 

 A calorie is the quantity of heat necessary to raise 1 gram of 

 water 1° C. A therm is the amount of heat required to raise 

 1 kilo, of water 1° C. Tables based on the most elaborate ex- 

 periments showing the actual amount of fuel or energy 

 value of foods, together with the amount of digestible protein 

 and dry matter contained in them*, must be consulted in calcu- 

 lating daily rations. 



Thus, for maintenance of animals of 1,000 lbs. live weight 

 per diem, it has been found that cattle require 0.5 lb. digestible 

 protein and food of the energy value of 6.0 therms. Horses 

 require 1.0 lb. digestible protein and food of a fuel 'value equal 

 to 7.0 therms. 



The daily food requirements of grown cattle are such that 

 for each pound of digestible protein there should be 8 to 10 

 lbs. of carbohydrates and 20 to 30 lbs. of total dry matter. 

 More important still, it has been found that there are necessary 

 ^-in addition to the maintenance reqmrements of cows — 0.05 

 lb. of digestible protein and 0.3 therm in energy value in the 

 daily ration for each pound of milk produced. 



As a practical applicatioii of the foregoing, suppose that we 

 compute a ration for cows giving 25 lbs. of milk daily and 

 weighing 850 lbs. Consulting a table. showing maintenance re» 



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