108 FEEDS AND FEEDING 



in the body weight, would have required the improbable increase in the 

 body of 104 Ibs. of water and intestinal contents. ' ' 



Jordan concludes that not over 17 Ibs. of the fat produced during 

 the trial could possibly have been produced from the protein supplied 

 in the food. It is most evident that a large part of all the. fat produced 

 by this cow must have come from the carbohydrates in her feed, and so 

 a long disputed question was at length settled. 



147. Nutrients required for milk production. To aid in showing the 

 nutrients required for the production of milk, let us compute the amount 

 of product yielded by a well-bred dairy cow in the course of a year. 

 Such an animal, of no unusual ability, should yield 8,000 Ibs. of milk 

 of average quality. Taking the composition shown in a previous table 

 (115), we find that she will produce annually in her milk 272 Ibs. of 

 protein, 296 Ibs. of fat, 392 Ibs. of milk sugar, and 56 Ibs. of mineral 

 matter. This is 56 per ct. more protein, 30 per ct. more non-nitrogenous 

 nutrients and 19 per ct. more mineral matter than is contained in the 

 entire body of a fat 2-year-old steer weighing 1,200 Ibs. (29) 



Thus each year the cow yields more protein and mineral matter than 

 has been built into the body of the steer during its entire life. At 

 the same time she is also storing considerable protein and mineral matter 

 in the developing body of her unborn calf. It is therefore evident that, 

 far different from the requirements of the mature horse at work or of a 

 mature fattening animal (141, 129), the cow needs a liberal supply of 

 protein and mineral matter. To yield the great amount of nutriment in 

 the milk, a ration supplying a large amount of net nutrients is also neces- 

 sary, for energy used up in the mastication, digestion, and assimilation 

 of such feeds as straw is of no value for the formation of milk. 



148. Protein requirements for milk production. We have seen (118) 

 that for growth individual proteins have widely different values. Hart 

 and Humphrey 11 have found in recent metabolism experiments with 

 dairy cows at the Wisconsin Station that proteins from various sources 

 may sometimes be of different worth for milk production. When fed 

 with corn stover as the only roughage, protein from gluten feed or 

 from the entire corn or wheat grains (much of which is unbalanced 

 in composition) was distinctly inferior to milk protein or to the protein 

 of linseed meal or distillers 7 dried grains. However, with clover hay and 

 corn silage as the roughages, there was little difference in the efficiency 

 of gluten feed, linseed meal, distillers' grains, or cottonseed meal as 

 sources of protein. With alfalfa hay and corn silage, distillers' grains 

 were slightly superior and cottonseed meal slightly lower in efficiency 

 than gluten feed or linseed meal. Where legume hay forms a consider- 

 able part of the roughage for dairy cows, there is probably not much 

 difference in the feeding value of a pound of digestible crude protein in 

 the common protein-rich concentrates. (573) 



"Jour. Biol. Chem., 21, 1915, p. 239; 26, 1916, p. 457; 31, 1917, p. 445; 35, 1918, 

 p. 367. 



