GENERAL PROBLEMS IN SWINE HUSBANDRY 603 



least, to a lack of minerals in their rations. It has been pointed out pre- 

 viously that common salt should always be supplied to swine, as well as 

 to horses, cattle, and sheep, and that calcium is the mineral nutrient 

 which is most apt to be lacking, in addition to common salt. (95-100) 

 Phosphorus may be deficient in amount if unbalanced rations, low in 

 protein, are fed. If the ration contains plenty of protein, the supply 

 of phosphorus will usually be ample for good results, because most 

 protein-rich feeds are high in phosphorus. In some sections it may also 

 be necessary to add iodine to the ration to prevent hairless pigs. (917) 

 Tho pigs require less salt than the other farm animals, they should 

 be supplied with it regularly. In a trial by Evvard at the Iowa Station 3 

 pigs allowed free access to salt made better gains than those receiving 

 no salt or others getting allowances of one sixty-fourth, one thirty-second, 

 or one-sixteenth ounce per head daily. Salt may be supplied in a trough 

 or a small self-feeder. If pigs have not had free access to salt they may 

 at first overeat if allowed free access to it. (100) 



If pigs are fed well-balanced rations on such pastures as alfalfa, clover, 

 or rape, good results will be secured without the addition of any mineral 

 supplement except common salt. Indeed, if plenty of skim milk, butter- 

 milk, tankage, or fish meal is fed to balance the ration, there is no definite 

 proof that there is any advantage whatsoever in adding a mineral 

 supplement to furnish additional calcium or phosphorus where swine are 

 on good pasture. Likewise if brood sows are fed well-balanced rations 

 in winter, including legume hay and also a protein-rich feed of animal 

 origin, such as skim milk or tankage, there is no conclusive evidence that 

 there is any benefit from adding supplements to furnish more calcium 

 or phosphorus. 



Where less ideal rations than these are fed either to pigs or to brood 

 sows, there may be an advantage in adding mineral supplements supply- 

 ing calcium, and perhaps phosphorus also. For example, in a trial by 

 Evvard at the Iowa Station 4 pigs fed corn and a mixture of 40 parts of 

 linseed meal, 40 parts of corn germ meal, and only 20 parts of tankage 

 made slightly more rapid and economical gains when such mineral sup- 

 plements as ground limestone or spent bone black were supplied in addi- 

 tion. One of the primary reasons why forage crops are so indispensable 

 in pork production is that they are, in general, rich in mineral matter, 

 especially lime, in addition to being rich in protein of good quality. 

 In view of the limited amount of data on the mineral requirements of 

 swine at present, it is probably wise to supply a simple and cheap mineral 

 mixture for all swine not on pasture, except perhaps when they are fed 

 excellent well-balanced rations, including calcium-rich feeds of animal 

 origin, such as skim milk or tankage, and also legume hay. 



Many different mineral mixtures have been suggested by various 

 authorities, and several proprietary mixtures are being advertised exten- 

 sively by commercial concerns at the present time. Some of these pro- 

 information to the authors. 'Information to the authors. 



