MAINTAINING FARM ANIMALS 57 



wise to add a supply to the ration. Calcium may be furnished 

 cheaply in ground limestone or wood ashes, and both calcium and 

 phosphorus in ground rock phosphate, ground bone, or bone ash. As 

 shown in Chapter XXVII, it is wise to keep a supply of mineral 

 matter before pigs at all times, especially when confined to pens. 



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

 for periods as long as a year. After varying lengths of time, a com- 

 plete breakdown occurred, marked by loss of appetite, lusterless eyes, 

 a rough coat, and a rapid decline in body weight and milk yield. 

 When salt was supplied, recovery was rapid. 



Animals allowed free access to salt or supplied with it at frequent 

 and regular intervals will take only enough to meet the needs of the 

 body. Animals that have not been supplied with salt for some time 

 and are then allowed all they will eat, may consume too much. This 

 creates an abnormal thirst and causes excessive drinking, which may 

 lead to digestive disturbances. Cows in milk and sheep show the 

 greatest need of salt, horses, fattening cattle, dry cows, and stock 

 cattle require less, and pigs but little. The needs of each class of 

 farm animals for salt are discussed in the respective chapters of 

 Part III. 



IV. Additional Requirements of Animals 



We have thus far considered in detail only the requirements of 

 farm animals for crude protein, carbohydrates, fat and mineral 

 matter. However, just as vital as the demands for fuel and repair 

 material, which are met by these nutrients, is the need for air and 

 water. 



Air. — ^While animals survive starvation for considerable periods, 

 lack of air brings immediate death, since a continuous supply of 

 oxygen is required for all vital processes. Each hour a cow breathes 

 in about 117 cubic feet of air, making over 2,800 cubic feet each 

 21: hours. For health, a stable where animals are confined should 

 not contain more than 3.3 per et. of air which has been previously 



3 Wis. Rpt. 1905. 



