68 



FEEDING EXPERIMENTS WITH ISOLATED FOOD-SUBSTANCES. 

 Table XXXII (from Waters, Table VI). Sub-Maintenance. 



Steer No. 591. Grade Hereford. Born May 15, 1907. Experiment began Feb. 26, 1908. 



Age of animal at beginning of experiment, nine and a half months. 



Full fed four months before trial began and was in good condition. 



Weight at beginning of trial, 572.7 lbs. Weight at close of trial, 490.4 lbs. 



Total loss in weight, 82.3 lbs. Average daily loss 0.43 lb. Denotes loss. 



Date. 



I C)08. 



Depth of Width of 

 chest. chest. 



cm. 



57 

 57-5 



5S 



57 



57-5 



58 



50-5 



58 



n 



cm. 



38.5 



34-5 



35 



33 



33 



33 



31-5 



20.5 



20 



- 9-5 



24.6 



The following is from Waters, in regard to a series of compara- 

 ble cattle maintained by him on different nutritive planes, desig- 

 nated as sub-maintenance, maintenance, and super-maintenance: 



It is to be observed that there is no appreciable difference in the rate of 

 growth in height of these three animals on widely different nutritive planes, 

 from the beginning of the experiment (February) to the end of June. At 

 this time the curve of the sub-maintenance animal flattens perceptibly. A 

 month later, the maintenance animal is apparently responding to the in- 

 fluence of the low nutritive plane. As would be expected, in the case of 

 the super-maintenance animal, the rate of growth remains unchanged. 

 It may be surprising to many [Waters writes elsewhere] that an animal 

 on maintenance, much less on sub-maintenance, should show any increase 

 whatever in the width of hip or length of leg . . . Apparently the animal 

 organism is capable of drawing upon its reserve for the purposes of sustain- 

 ing the growth process for a considerable time and to a considerable extent. 

 Our experiments indicate that after the reserve is drawn upon to a con- 

 siderable extent to support growth the process ceases, and there is no further 

 increase in height or in length of bone. From this point on the animal's 

 chief business is to be to sustain life. This law applies to animals on a 

 stationary live weight as well as those being fed so that the live weight is 

 steadily declining, and indeed to those whose ration, while above main- 

 tenance and causing a gain in live weight, is less than the normal growth 

 rate of the individual. Such an animal will, while gaining in weight, be- 

 come thinner, because it is drawing upon its reserve to supplement the 

 ration in its effort to grow at a normal rate.* 



More recently Aronf has made comparable studies on growing 

 dogs. He formulated his problem in the following words: 



"Was wird geschehen, wenn furkurzereoderlangereZeitinderNahrung 

 nur so viel Energie usw. zugefiihrt wird, wie erforderlich ist, umden Erhalt- 



*H. J. Waters: How an animal grows. Kansas State Board of Agriculture, Seven- 

 te?nth Biennial Report, 1909-1910, 1, p. 208. 



jAron: Biochemisehe Zeitsehrift, 1910, xxx, p. 207. 



