152 



MASS. EXPERIMENT STATION BULLETIN 230 



the institute, as a result of his own experiments and those eondueted in 

 Europe, deduced a formula for determining net energy, based upon chemical 

 analysis, total energy and metabolizable energy. In the experiments here 

 reported, we have made use of this formula after having determined the 

 composition and the total and metabolizable energy in each feedstuff, as well 

 us its digestibility; and it is these two units of measurement — net energy, 

 expressed in therms', with diyeslih'diiy as an aid — that we have used in 

 getting at the relative values of the feeds studied. 



Method of Pkoleiuti:!; 



Two horses were used in each trial. Each feed was analyzed and its total 

 energy determined. Definite amounts drily were fed, the feces and urine 

 collected, and the energy contamed in tliem determined and subtracted from 

 the total energy of the feed, winch gives the nictal)olizable energy. By the 

 a])plication of the formula mentioned above, the net energy was estimated. 

 In the al)Ove procedure we were alile also to determine digestibility. Each 

 actual experiment required about three weeks for its completion, in addition 

 to a large amount of work in the chemical laboratory and in the calculation 

 of the results. 



Some Results of the Experiment 



The Story of Alfalfa. 



Two different lots of alfalfa were tested, one grown in New York state 

 and tiie other on the Experiment Station grounds. The New York sample 

 contained 11.7 per cent protein and 35.2 per cent fiber, while the Station 

 sample contained 17.7 per cent protein and 27.5 per cent fiber. It is evident 

 that the former sample was more mature than the latter. 



Average Digestion Coefficients and Net Energy Values 



These results indicate that the New York sample was more mature and less 

 utilized by the horses than the Massachusetts .sample; while the net energy 

 values show that the horses had to expend considerably more energy to digest 

 the New York, or late-cut sample. 



The comparison of the digestibility of alfalfa by horses and cattle, given in 

 the table, shows that cattle are able to digest alfalfa to a greater degree than 

 are horses, although the protein is well and about equally digested by both 

 classes of animals. 



^ The therm represents the amount of heat required to raise 1000 kilograms of water 

 1 degree Centigrade, and is used as a unit of measurement for energy. 



