THE NUTRIENTS AND DIGESTION 323 



those feeds upon which trustworthy work has been done is 

 given in Table XXIX. 



Digestive Powers of Chickens. — ^The different structure of the 

 alimentary tract of chickens as compared with other farm 

 animals would lead one to suspect a different digestive 

 capacity and different digestive coefficients. In comparison 

 with other animals, fowls show digestive powers most 

 nearly comparable with swine, except that in the digestion 

 of fat they correspond most closely to the ruminants. Unlike 

 ruminants, they digest very little crude fiber. 



While they consume over twice as much feed as is required 

 by the same weight in cattle, they cannot make use of the 

 coarser kinds of -feed, such as hay and fodder. They must 

 be fed a concentrated ration made up quite largely of grains 

 and their by-products. 



While the different nutrients have differing coefficients in 

 different feedstuffs 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 be a comparatively easy matter to determine 

 the digestive 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' 



' Oklahoma Bulletin No. 46. 



