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A MANUAL OF VETERINARY PHYSIOLOGY 



No one can say with any degree of certainty how much hay a 

 horse will digest in any given period, as may be seen from the 

 following observations : 



It is known, however, that as a rule more will be digested in the 

 first hour, less in the next, still less in the third, and so on until 

 the stomach empties itself, or until what exists in the stomach 

 is actually pushed out by the arrival of the next feed. Assuming, 

 however, that the animal is purposely starved, the stomach may 

 not empty itself for fifteen, eighteen, twenty-four, or even thirty- 

 six hours. It is impossible to say, either at the end of twelve 

 or of thirty-six hours, that the stomach has passed the whole of 

 its contents into the intestine. The writer has found hay in the 

 stomach fifteen and eighteen hours after being given, and under 

 identical experimental conditions the stomach at the fifteenth 

 hour has been found empty. 



Colin's elaborate researches furnish very complete data on 

 the question of hay digestion in the horse. In one experiment 

 carried out on fourteen animals he divided them into two groups, 

 each horse receiving 2*5 kilogrammes (5*5 pounds) hay. One 

 groups had long, the other chaffed hay. The following table 

 shows the percentage digested at each period : 



This shows that the rate of digestion falls off after the second 

 hour, so that even at the end of eight hours there is still food left 

 in the stomach. Only one animal digested as much as 90 per 

 cent., and this was at the fifth hour. With this exception the 

 results are fairly uniform, and they further demonstrate that 

 chaffing hay does not increase its rate of digestion. 



The influence of water on the digestion of hay was tested 



