68 PRINCIPLES OF FEEDING FARM ANIMALS 



keen appetite, resulting from hard work, enables an animal 

 to make greater use of the feed provided. Within reason- 

 able limits, however, work has no effect upon the digestibihty. 

 However, it has been found that very hard work decreases 

 the digestibility. Also it was found that horses working at 

 a quick trot did not digest their rations as well as when work- 

 ing at a walk or when resting. 



The individuality of the animal may have considerable 

 effect upon the digestibility of the ration. In other words, 

 animals kept under the same conditions and fed the same 

 ration may have different powers of digestibihty. Thus 

 at the Ilhnois Experiment Station,^ Grindley, Carmichael 

 and Newlin conducted forty digestion experiments, each of 

 ten days' duration, on four pigs. All conditions of the 

 experiments were practically the same. The pigs were 

 litter mates and had been fed together from birth. It was 

 found that some of the coefficients of digestibihty of certain 

 pigs were uniformly higher than those of other pigs on the 

 same ration. This difference sometimes amounted to as 

 much as five per cent. 



Palatability of the Ration. — Increased palatabihty of the 

 ration probably has a sUght beneficial effect upon the digest- 

 ibility. The secretion of the digestive juices is partly under 

 the control of the nervous system ; thus, Pawlow, a great 

 Russian physiologist, found that the smell or taste of food 

 stimulates the nervous system and causes a flow of the diges- 

 tive juices, which would tend to increase the thoroughness of 

 digestion. The experienced feeder knows well the value of 

 stimulating the appetites of his animals by means of attrac- 

 tive mixtures. Too much stress should not be placed upon 



1 Unpublished data. 



