THE NUTRIENTS AND NUTRITION 321 



While the different nutrients have differing coefficients in 

 different feedstuff's and under different conditions, as a rule 

 the nutrients rank in the following order of digestibility for 

 poultry: Nitrogen-free extract, protein, fat, and crude fiber. 



Variations in Digestibility and Their Cause. — It would seem 

 that it should l)e a comparatively easy matter to determine 

 the digcsti\c coefficients of a nutrient aside from the physi- 

 ological and chemical difficulties already described. As a 

 matter of fact there are many causes of variation in the diges- 

 tion of foods which make accurate determinations that may 

 have general application difficult. A knowledge of the more 

 important known and probable causes should be had by a 

 practical feeder as well as by the investigator. These are 

 (1) the mechanical condition of the feed; (2) the combination 

 of feeds; (3) amounts of feed consumed; (4) the source of the 

 feed, whether vegetable or animal; (5) the concentration of 

 the feed; (6) its palatability; (7) cooking and wetting the 

 feed; (8) age and exposure of the grain or grass when cured, 

 and (9) age, species, and individuality of the bird fed. 



Mechanical Condition of Feed. — While for some of the larger 

 animals grinding certain of the grains increases their digesti- 

 bility, this does not hold true for poultry. Fields and Ford' 

 found that chickens digested kafir and corn more completely 

 when the grain was fed whole than when it was ground into 

 meal. It will be noted in Table XXXVII that over 3 per cent 

 more organic matter from whole corn was digested than when 

 the corn was cracked or ground into meal. The increased 

 digestibilitjf brought about by grinding for larger animals is 

 usually because hard grains are not well masticated. With 

 poultry the grinding of the feed is involuntary and, unless 

 grit is not available, consistently thorough. 



Because of the fact that corn or any other grain is less 

 digestible for poultry when ground it must not be assumed 

 that it is less profitable and therefore bad practice to feed 

 a part of the ration in ground form. (For further discussion 

 see page 336.) 



' Oklahoma Bulletin No. 46. 



