PRODUCTION OF WORK, MILK, AND WOOL 109 



149. Mineral matter required for milk production, It was formerly as- 

 sumed that when dairy cows were fed common well-balanced rations 

 containing plenty of protein and a liberal amount of legume hay, there 

 could be no deficiency in calcium (lime) or in phosphorus, for legume 

 hay is rich in calcium, and protein-rich feeds are in general high in 

 phosphorus. Surprising results have, however, been secured in ex- 

 tensive experiments at the Ohio Station 12 by Forbes, in which high pro- 

 ducing cows have been fed such excellent winter rations as alfalfa or 

 clover hay, corn silage, and corn with such high-protein concentrates 

 in addition as wheat bran, cottonseed meal, linseed meal, dried distil- 

 lers' grains, or gluten feed. On these rations the cows in most instances 

 lost calcium, phosphorus, and also magnesium from their bodies, being 

 able to assimilate and retain so small a portion of the liberal supply 

 in their feed that it was insufficient to meet the requirements in pro- 

 ducing the milk. Even when abundant amounts of calcium, or both 

 calcium and phosphorus, were added to the ration in such forms as 

 steamed bone, calcium carbonate, or calcium lactate (a soluble form 

 of calcium), the losses of these mineral constituents from the body 

 continued. The cause of this 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 nutrients from their feed to meet the 

 heavy demand in producing the large flow of milk during the first 

 part of the lactation period. Later on in lactation, or when they are 

 dry, it was found that they are able to build up again the stores of these 

 mineral constituents in their bodies. 



In experiments at the Wisconsin Station 13 by Hart and Steenbock, 

 dairy cows and also milk goats have shown greater ability to assimilate 

 calcium from fresh green feed than from dried forage. They have sug- 

 gested that such fresh green forage contains larger amounts of the 

 anti-rachitic vitamine, which aids in assimilating calcium from the food. 

 This would emphasize the importance of pasture or other fresh green 

 forage for milk cows. In trials by Meigs of the United States Depart- 

 ment of Agriculture, 14 the production of cows which had but little 

 pasturage thruout the year was increased in the following lactation 

 period by feeding sodium phosphate when they were dry. (104, 574) 



It is impossible as yet to predict the ultimate outcome of such studies 

 or the manner in which they may modify our common feeding practices. 

 At present, these results emphasize the necessity of supplying dairy 

 cows with plenty of calcium and phosphorus, especially by the use of 

 legume hay, not only in the period of high production, but also later 

 on in lactation and when the cows are dry. When legume hay is not 



I2 Ohio Buls. 295, 308, and 330; Proceedings Am. Soc. Anim. Prod., 1917-20, pp, 

 32-40. 



13 Wis. Bui. -323, p. 17; Res. Bui. 49, p. 18; information to the authors. 

 "Address before Am. Soc. Anim. Prod.; Dec. 1920; U. S. D. A. Bui. 945. 



