448 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



When different feeds are added to a basal ration, the productive 

 value should not be altered by other compensatory additions. For 

 example, if cottonseed meal is compared with gluten meal, and 

 straw is added to increase the nitrogen-free extract for cotton- 

 seed meal, the experiment would be unfavorable to cottonseed 

 meal, because the nitrogen-free extract of straw is not equal to 

 that of gluten meal. The rations should be weighed out for each 

 animal, and fed in such order or with such preparation that they 

 will be completely consumed. 



The live weight varies very much on account of irregular ex- 

 cretion of dung, irregular elimination of urine, unequal con- 

 sumption of water from day to day, etc. The animals should be 

 weighed three days in succession, just before the midday meal, 

 every ten days. Since the first weighings are usually of little 

 value, on account of the animals being excited, the animals should 

 be accustomed to the weighing as early as possible. 



The feeding period should not be too short. Two months is 

 the minimum for fattening and work animals, but it is better 

 to continue the experiment with fattening animals, until they are 

 fully fat and then to make a slaughter test on them. Important 

 observations are sometimes made only when the experiment 

 is continued a long time. 



When comparing two feeds, equal quantities should be fed. If 

 one feed is more palatable than the other, and the animals allowed 

 to eat more, they will have a larger excess over their maintenance 

 requirements, and the results will be more favorable to the more 

 palatable food. 



Standards for Fattening Rations. Since fattening animals put 

 on little flesh, it would appear that they require little more pro- 

 teids than animals on a maintenance ration. The heavy ration 

 fed, however, demands a quantity of digestive fluids composed 

 largely of proteids. Since the digestibility of the food is de- 

 creased if the nutritive ratio is too wide, the nutritive ratio 

 should not be wider than 1 : 10. A ratio narrower than i : 4 in- 

 creases the oxidation of matter in the body, and so decreases the 

 production of fat. Numbers of experiments have been made 



