44 ILLINOIS STATE DAIRYMEN'S ASSOCIATION 



in spite of the fact that the feed they were given supplied 

 what would appear to be ample amounts. For some rea- 

 son or other, the cows were unable to assimilate and re- 

 tain enough of the liberal supply of these mineral nutrients 

 in their feed to meet the heavy requirements in producing 

 the large amount of milk they yielded. 



Even when abundant amounts of calcium, or both cal- 

 cium and phosphorus, were added to their ration in such 

 forms as steamed bone meal, calcium carbonate, or calcium 

 lactate (a soluble form of calcium), the losses of these min- 

 eral constituents from the body continued. The reason for 

 this little-expected condition is still a problem. Possibly 

 the milk producing capacity of our dairy cows has been so 

 increased by selective breeding that it exceeds the ability 

 of high-yielding cows to assimilate sufficient mineral nu- 

 trients from their feed to meet the heavy demand in pro- 

 ducing the large flow of milk during the first part of the lac- 

 tation period. Later on in lactation, or when they are dry, 

 they are able to build up again the stores of these mineral 

 constituents in their bodies. 



In extensive experiments at the Wisconsin Experiment 

 Station by Professor Hart and his colleagues, it has been 

 found that dairy cows are able to assimilate calcium much 

 more completely from fresh green feed than from dried for- 

 age, such as hay. Furthermore, well cured alfalfa hay is 

 superior to that improperly cured. These trials indicate 

 that the best way of curing hay is to cure it in the bright 

 sun, getting it into the barn as soon as it is dry enough, by 

 means of using the side delivery rake, hay loader, etc. Hay 

 cured by such a method will contain the maximum amounts 

 of vitamins. 



All this work on the mineral requirements of dairy 

 cattle is so recent that we do not yet know just how far- 

 reaching the results may be in practical feeding. These 

 various trials, however, emphasize the importance of past- 

 ure and other green forage for dairy cows during the grow- 

 ing season, and of furnishing an abundance of legume hay 

 during the rest of the year. Also, the cows should be dried 

 off six to eight weeks before freshening, and during this 



