Nov. 4, 1918 Net Energy Values of Alfalfa Hay and Starch 281 



SUMMARY 



In seven respiration calorimeter experiments on a steer the digesti- 

 bility and metabolizable energy of different amounts of alfalfa hay and of 

 a mixture of alfalfa hay and commercial starch the gaseous excretion 

 and the heat production were determined. 



By a comparison of periods in which different amounts of the same 

 ration were fed, the heat increments consequent on feed consumption 

 and the net energy values of the rations were computed. 



The digestibility of the rations, the losses in the urine, and the extent 

 of the methane fermentation showed a distinct increase as the total 

 amount of the ration was reduced. 



The greater loss of energy in the urine and methane on the lighter 

 rations more than compensated for the smaller losses in the feces, so that 

 the proportion of the total energy metabolizable was somewhat less than 

 on the heavier rations. 



The metabolizable energy of the starch was 10 per cent greater than 

 the average computed from five experiments by Kellner, the difference 

 being due chiefly to smaller losses in the feces. Starch caused the usual 

 depresion in digestibility. 



The average heat increment caused by the consumption of alfalfa 

 hay was 999 Calories per kilogram of dry matter as compared with 981 

 Calories found for the same hay in the previous year and with an average 

 of 1,169 Calories in six previous experiments on three different samples. 



The average heat increment for the starch was 1,692 Calories per 

 kilogram of dry matter as compared with 1,248 Calories computed from 

 Kellner's experiments. 



The net energy values of the starch was about 9 per cent lower than 

 that computed from Kellner's experiments, only 49 per cent, as com- 

 pared with 59 per cent of the metabolizable energy being utilized by 

 the animal. 



APPENDIX 



The principal numerical data obtained in the experuments are recorded in the 

 following tables. The computations involved have been carried out beyond the 

 probable limit of accuracy of the experimental methods in order to guard against 

 a possible accumulation of arithmetical errors. 



