68 FEEDS AND FEEDING 



cipitated calcium carbonate, finely ground limestone, or chalk. Both 

 calcium and phosphorus may be supplied in steamed bone meal, bone flour, 

 bone black, precipitated bone, or even ground rock phosphate, tho the 

 latter is probably somewhat less soluble in the digestive tract than the 

 other forms. When animals are allowed to help themselves to the 

 mineral supplement, it is best to use one of the phosphates, for they are 

 usually more palatable than the carbonates, such as ground limestone, 

 and also they may be eaten in much greater quantity without causing 

 any disturbance in digestion. In supplying a mineral supplement, it is 

 a good plan to mix the supplement with the concentrates. The amounts 

 recommended for the various classes of stock ar.e stated in later chapters 

 of this volume. The use of expensive proprietary mineral mixtures is 

 unnecessary and generally uneconomical. (292) 



100. Common salt. In spite of the well-known hunger of herbivorous 

 animals for salt, practical men have differed as to the necessity or 

 advantage of adding it to the ration. It is now agreed, however, that 

 salt should be supplied regularly to farm animals. It not only serves 

 as a spice to whet the appetite and add to the palatability of many 

 feeds, but it also stimulates the digestive glands and prevents digestive 

 disturbances. At least for cows in milk, a supply of salt in addition to 

 that contained in the feed is absolutely necessary for health. This was 

 shown in experiments by Babcock and Carlyle at the Wisconsin Station 15 

 in which dairy cows, well fed otherwise, were given no salt for periods 

 as long as a year. After 2 or 3 weeks, they showed abnormal appetites 

 for salt, but their health was not usually affected for a much longer 

 time. Finally, a complete breakdown occurred, marked by loss of ap- 

 petite, lusterless eyes, rough coat, and a very rapid decline in both live 

 weight and yield of milk. If salt was supplied recovery was rapid. 

 In one case potassium chlorid was given instead of common salt (sodium 

 chlorid). Recovery followed as quickly as when common salt was sup- 

 plied, showing that not the lack of sodium but the lack of chlorin was 

 responsible for the troubles. 



Cows in milk and sheep need the largest amounts of salt; fattening 

 cattle, horses, dry cows, and stock cattle require less ; and pigs but little. 

 The salt requirement will vary considerably in different localities. Soils 

 which contain large quantities of salt doubtless produce feeds contain- 

 ing more salt than those poor in this ingredient; and also the water of 

 streams and wells varies in salt content. The needs of each class of 

 farm animals for salt are discussed in the respective chapters of Part III. 



101. Iodine. Especially in certain sections of the northwestern states, 

 during recent years heavy losses have been experienced of new-born 

 pigs, lambs, kids, calves, and foals, due to goitre or "hairlessness." The 

 young so affected are born dead or weak, are frequently hairless, and 

 commonly have enlarged necks. This is due to the thyroid gland in the 

 neck being diseased and enlarged, just as in the case of humans suffer- 



"Wis. Rpt. 1905. 



