GENERAL PROBLEMS IN DAIRY HUSBANDRY 357 



II. NUTRITIVE REQUIREMENTS OP DAIRY Cows 



569. Nutrients required by dairy cows. The general feed requirements 

 for milk production have been discussed in a previous chapter, and there 

 compared with the requirements for growing animals and for those which 

 are being fattened. (147-50) It is there pointed out that milk is rich 

 in protein and in mineral matter, especially calcium and phosphorus, and 

 that therefore the ration of the cow producing milk must contain an 

 abundance of these nutrients. It has further been emphasized that the 

 dairy cow in milk needs a ration high in net energy, due to the large 

 amounts of milk sugar and of butter fat she yields in her milk. There- 

 fore for continued high production she must receive a fairly liberal 

 allowance of concentrates, in addition to roughage of good quality. 



570. Vitamine requirements. Dairy cows which are fed well-balanced 

 rations, including plenty of good-quality legume hay, and are supplied 

 with good pasturage or other green feed during the summer will se- 

 cure an ample amount of the fat-soluble vitamine for health, for green- 

 leaved plants are rich in this vitamine and it is not destroyed by drying. 

 Furthermore, such rations will furnish plenty of the water-soluble vita- 

 mine, for as has been pointed out earlier, this is contained in ample 

 amounts in practically all common stock feeds. (104) Also, there will 

 be no deficiency of the anti-scorbutic vitamine. Cattle are not affected 

 by scurvy, as are man, monkeys, and guinea pigs, either because they do 

 not require this vitamine, or because it is contained in ample amount in 

 all rations. Therefore, except for the possible relationship of a vita- 

 mine to the assimilation of calcium, which is discussed later, the rations 

 ordinarily recommended for dairy cows apparently furnish an ample 

 supply of vitamines. 



571. Requirements for maintenance, growth, and pregnancy. A dairy 

 cow in full flow of milk needs nearly half the nutrients in the feed she 

 consumes merely for maintaining her body. In addition to these needs 

 for maintenance, if she is immature she will require additional nutrients 

 for the growth of her body tissues. During the time she is pregnant, 

 she will need nutrients for the building of the fetus. She can use in 

 actual milk production only the amount of nutrients which is left after 

 these needs have been met. 



It has been pointed out in Chapter VII that in computing rations for 

 a dairy cow by most of the modern feeding standards, first the mainten- 

 ance requirements are computed on the basis of her weight, and then to 

 these amounts of nutrients are added the requirements for the produc- 

 tion of the milk she is yielding. In the Wolf-Lehmann, Haecker, Savage, 

 Woll-Humphrey, and Morrison standards the daily maintenance re- 

 quirements per 1,000 Ibs. live weight are given as 0.70 Ib. digestible 

 crude protein and 7.925 Ibs. total digestible nutrients. In the Armsby 

 and Eckles standards the maintenance requirements of the 1,000-lb. cow 

 are stated as 0.50 Ib. digestible protein (not crude protein) and 6.00 



