110 FEEDS AND FEEDING 



furnished in abundance, it is undoubtedly wise to add calcium and 

 phosphorus in such forms as steamed bone meal, bone flour, bone black, 

 or ground rock phosphate. 



These trials indicate, furthermore, that a liberal supply of pasture 

 or other fresh green feed during a good share of the growing season aids 

 materially in securing continued high production, year after year, from 

 dairy cows. 



It has been mentioned previously that serious results follow when 

 common salt is withheld from dairy cows for a long period. Hence 

 salt should always be regularly supplied. (653) 



150. Vitamines and milk production. So far as we now know, the 

 usual type of balanced ration recommended for dairy cows, in which 

 there is plenty of good-quality legume hay, will furnish an ample supply 

 of vitamines for the health of the cows, with the possible exception, just 

 pointed out, of the anti-rachitic vitamine, which apparently aids in 

 the assimilation of calcium. Hart and Steenbock have found in trials 

 at the Wisconsin Station 15 that milk from cows on pasture is much 

 richer in the anti-scorbutic vitamine and also somewhat richer in the 

 fat-soluble vitamine than milk produced by cows fed winter rations of 

 hay, silage, and concentrates. These results indicate that the udder 

 has no power of forming these vitamines that are now recognized as so 

 important in proper nutrition, but that these substances are secured 

 from the supplies in the feed and concentrated by the cow in her milk. 



Since most of the scientific studies of the factors influencing the pro- 

 duction of milk have been conducted with the dairy cow, the discussion 

 of milk production as relating to that animal is continued in Chapters 

 XXI to XXV. The requirements of the mare, ewe., and sow for the 

 production of milk are also treated in the respective chapters of Part III. 



III. WOOL PRODUCTION 



151. Composition of wool Aside from moisture and dirt, "wool" is 

 made up of pure wool fiber and yolk, the latter including the suint and 

 the wool fat. The wool fiber is practically pure protein, and is of the 

 same chemical composition as ordinary hair, but differs in being covered 

 with minute overlapping scales. The suint, chiefly composed of com- 

 pounds of potassium with organic acids, forms from 15 to 50 per ct. or 

 more of the unwashed fleece, being especially high in Merinos. As 

 suint is soluble in water, most of it is removed by washing the sheep or 

 fleece, and less is present in the wool of sheep exposed to the weather. 

 The fat, often incorrectly called yolk, is a complex mixture of fatty sub- 

 stances, insoluble in water, and may make up 8 to 30 per ct. of the weight 

 of a washed fleece. 



152. Requirements for wool production. Owing to the large amount of 

 protein stored by sheep in their fleece, their ration should contain some- 



15 Wis. Bui. 323, p. 20 ; information to the authors. 



