POULTRY FOODS 203 



such foods need to be used with caution, when their natural form 

 is changed, as by cooliing. 



Mineral foods. The mineral elements (ash) in foods, disregarded 

 in calculations of food values, are of great importance in nutrition 

 and more important to poultry than to any other kind of domestic 

 creature. The rate of growth of young poultry is very much more 

 rapid than that of young horses, cattle, sheep, and swine. A chick 

 weighing i jounces when hatched, and 27 ounces at ten weeks of 

 age, has in the ten weeks multiplied its original weight eighteen 

 times. In ducks and geese the rate is even more rapid. In all 

 young poultry adequately supplied with material for making bone, 

 the rate of growth of the skeleton is more rapid than that of the 

 flesh (muscle). The adult female laying regularly requires (for the 

 shells of the eggs) much larger percentages of lime in her food 

 than any other creature consumes. Although (as the tables of analy- 

 ses show) nearly all foods contain some mineral elements, and many 

 contain quite large proportions of these elements,-' green bone is 

 the only common article of food carrying a percentage of mineral 

 matter large enough to make it valuable for its special supply of ele- 

 ments of this kind. Because green bone (from its limited use) is not 

 a dependable source of supply of mineral foods, it is usual to supply 

 pure mineral foods, sometimes in small quantities finely ground in 

 mashes, but more generally in coarser form in receptacles from 

 which the birds take what they want as appetite directs. Dry bones, 

 shells, and various kinds of rock ground or crushed to convenient 

 size are used for this purpose. Charcoal is also commonly used 

 as an accessory to poultry rations. The actual need of these ac- 

 cessories and the quantities needed depend in any case upon the 

 amounts of mineral elements that the birds may secure in other 

 foods, or may pick up for themselves. The subject has not received 

 much attention from investigators, and nearly all studies along this 

 line have included observations on grit based on the assumption that 

 the primary function of grit is to grind food in the gizzard. From 

 such investigations as have been made, and from common observa- 

 tion, it appears that in ordinary good feeding of mixed rations 

 under good conditions (range) young birds get quite all the mineral 



1 Some foods low in protein and fat are especially valuable for their ash con- 

 tent; thus, bran is rich in phosphorus in an especially useful condition. 



