FEEDING STANDARDS— CALCULATING RATIONS 99 



protein, and total digestible nutrients, the latter term including the 

 digestible protein, the digestible carbohydrates, and the digestible 

 fat X 2.25. This simplification agrees with the uses made of the dif- 

 ferent nutrients in the animal body, for, as we have already learned, 

 carbohydrates and fat in general perform the same functions in the 

 body. Likewise, after there has been supplied the minimum amount of 

 protein needed for the repair of body tissues and the formation of milk 

 protein, any additional amount serves the same purposes as do the 

 carbohydrates and fat. The requirements of a 1,000-lb. cow, according 

 to this system,^ are shown in the following table. The allowance for 

 maintenance is the same as in the Haecker standard : 



W oil- Humphrey standard for 1,000-lb. dairy cow 



Digestible Total 



Dry crude digestible 



matter protein nutrients 



Lbs. Lbs. Lbs. 



Dry COW 12.5 0.70 7.9 



Cow yielding 1.0 lb. fat per day 22.3 2.02 15.4 



Cow yielding 1.5 lbs. fat per day 27.3 2.86 19.2 



Cow yielding 2.0 lbs. fat per day 30.9 3.42 23.0 



This system of expressing the requirements of dairy cows has been 

 found convenient in practice. It is not strictly accurate, however, 

 when applied to milks varying widely in the percentage of fat con- 

 tained. Haecker 's table places the requirements for a pound of butter 

 fat in rich milk considerably lower than for a pound in milk low in fat. 

 For example, for 100 lbs. of 3 per ct. milk there are required 4.7 lbs. 

 protein, 20.0 lbs. carbohydrates, and 1.7 lbs. fat, while for 50 lbs. of 

 6 per ct. milk, containing the same amount of fat, only 3.3 lbs. protein, 

 16.0 lbs. carbohydrates, and 1.4 lbs. fat are required. This is due to 

 the fact that, tho the 6 per ct. milk contains twice as much fat as the 

 3 per ct. milk, it is not twice as rich in sugar and protein. 



The Savage standard. — From trials at the New York (Cornell) 

 Station ° Savage concludes that for maximum production the nutritive 

 ratio of rations for dairy cows should not be wider than 1 :6. He has 

 accordingly modified the Haecker standard by increasing the protein 

 requirement per pound of milk from 18 to 20 per ct. His standard 

 is also simplified by being stated in terms of dry matter, digestible 

 crude protein, and total digestible nutrients (or as Savage terms it 

 "total nutriment"), in the same manner as in the Woll-Humphrey 

 standard. The requirements according to this standard are shown in 

 the next table. 



5 Table as revised by Humphrey, unpublished data. 

 6N. Y. (Cornell) Bui. 323. 



