12 BULLETIN 945, U. S. DEPARTMENT OF AGRICULTURE. 





nutriment in the course of the year than the feeding standards call 

 for. 5 



There is one other aspect of the case which must be discussed. 

 Quite apart from the question of the feed cost per pound of milk 

 when a cow's yield is reduced by feeding a ration deficient in one 

 or more necessary constituents, is the question of the effect of this 

 process on her capacity to resist disease. The Beltsville herd has 

 suffered severely in the last three years from contagious abortion. 

 The relation between the incidence of this disease and the manner 

 in which the cows have been fed is being carefully studied at present, 

 and the results of this study will be reported later. The results 

 already obtained, however, are sufficient to justify a strong sus- 

 picion that abortion has occurred more frequently among the animals 

 that were less adequately fed. But, whatever the final results of this 

 study may be, it is obviously bad practice to allow a cow to deplete 

 her body stores of important materials for long periods of time, 

 even though milk may thereby be temporarily more economically 

 produced. The ideal method is clearly to keep the yearly supply 

 of raw materials in the food equal to the demand for milk produc- 

 tion. 



SUMMARY. 



Feeding cows for several years according to the commonly ac- 

 cepted standards with little or no additional pasture, has resulted in 

 their milk yield being reduced much below the optimum. The con- 

 dition of reduced milk yield so brought about may be corrected by giv- 

 ing the animal a dry period of two months, and feeding during that 

 period a ration containing legume hay and grain with a high phos- 

 phorus content and with three or four times the amount of protein 

 required for maintenance, and two or three times the total nutri- 

 ment. The milk yield in the subsequent lactation period may some- 

 times be doubled by this treatment. 



In the case of cows of which the milk yield has been reduced by 

 several years' standard feeding, a greatly increased yield can be 

 brought about by feeding " alternated rations with phosphate " dur- 

 ing the dry period. This is taken to mean that the ordinary rations 

 are more likely to be deficient in one or both of the principal bone- 

 building elements than in any other constituent, 



E Feeding cows* heavily before they calve, of course, introduces the risk of milk fever. 

 But if this disease is properly treated, the mortality is not high, and there are appar- 

 ently no enduring bad effects. A well-managed dairy farm should be equipped for deal- 

 ing with milk fever. Our experience at Beltsville shows that the risk even of the 

 appearance of the disease is not very great. In the last five years there have been 

 something over 30 cases of cows fed two to four times the maintenance requirement of 

 protein and total nutriment before they calved, and milk fever has appeared only twice. 

 One of these cases was in a young cow, but was mild ; the other was in a cow 15 

 years old. 



