FEEDS AND FEEDING 



39 



In calculating a ration for a dairy cow according to the Armsby stand- 

 ard, one adds to the requirements for maintenance, 0.05 pounds of digest- 

 ible protein and 0.3 therm of net energy for each pound of milk produced. 

 For example, one wishes to calculate a ration for a 900-pound cow giving 

 22 pounds of milk. According to Table IV the requirements are as follows : 



The ration is then calculated in the manner previously described. 



The Haecker Standard for Dairy Cows holds that the requirements 

 of the dairy cow vary not only according to her weight and the quantity 

 of milk yield, but also according to the quality of the milk. According to 

 Haecker, a 1000-pound cow requires for maintenance 0.7 pound of digestible 

 crude protein, 7.0 pounds of digestible carbohydrates, and 0.1 pound of 

 digestible fat. For each pound of 4 per cent milk the Haecker standard 

 requires the addition of 0.054 pound of digestible crude protein, 0.24 pound 

 of digestible carbohydrates, and 0.021 pound of digestible fat in addition 

 to the maintenance requirement. If the milk contains less than 4 per cent 

 of fat, smaller amounts of nutrients are prescribed. The amounts of 

 digestible nutrients to produce one pound of milk containing various per- 

 centages of butter fat are given in Table V. 



For example, to calculate a ration according to the Haecker standard 

 for a 900-pound cow giving 20 pounds of milk daily containing 5 per cent 

 of butter fat, the process is as follows: (1) determine the maintenance 

 requirement for a 900-pound cow; (2) add to the maintenance require- 

 ment the requirement to produce 20 pounds of 5 per cent milk; and (3) 

 calculate a ration to conform with this standard. Thus a cow weighing 

 900 pounds requires 0.63 pound of digestible protein, 6.30 pounds of 

 digestible carbohydrates and 0.09 pound of digestible fat for maintenance. 

 According to Haecker, to produce one pound of 5 per cent milk requires 

 the consumption of 0.060 pound of digestible crude protein; 0.28 pound 

 of digestible carbohydrates, and 0.024 pound of digestible fat, in addition 

 to the maintenance requirements. Thus the total requirement to produce 

 20 pounds of 5 per cent milk is calculated as follows: 



The ration is then calculated in the same manner as described under the 

 discussion of the Wolff-Lehmann standards. 



