28o 



Journal of Agricultural Research 



Vol. XV. No. s 



COMPARISON WITH KELLNER'S RESULTS ON STARCH 



As noted at the beginning of this article, Kellner has reported a number 

 of determinations of the net energy of starch. His results, expressed in 

 terms of energy and computed in a somewhat different manner than 

 that used by Kellner himself,^ are included in Table XIV. Two marked 

 differences appear. Kellner's metabolizable energy is lower than that 

 found in our experiment, while his heat increment is also less, the net 

 result being a higher net energy value. Kellner's rations, however, differ 

 quite materially from ours. As regards quantity (total organic matter) 

 our mixed ration was considerably above Kellner's in period i and much 

 below it in periods 2 and 4. As regards make-up it contained a much 

 larger proportion of hay and no concentrate except starch. The per- 

 centage of starch in the total ration was 31.2 as against 19.2 in Kellner's, 

 but the percentage of organic matter supplied by the hay was 69.8 as 

 compared with 40.9 in Kellner's experiments. As regards nutritive 

 ratio our ration was somewhat narrower than three of Kellner's rations 

 and somewhat wider than the other two. 



The difference in the metabolizable energy is due chiefly to a much 

 larger loss in the feces in Kellner's experiments, as Table X shows. If 

 this be eliminated, by computing the losses in urine and methane upon 

 the digested energy the following comparisons are obtained: 



Table XV. — Distribution of digested energy of starch 



Mean of periods 1,2, and 4 . 

 Kellner 's mean 



In urine. 



Per cent. 



— O. 26 



- -79 



InnxethanJ MetaboU- 



Per cent. 

 14- 50 

 II. 17 



Per cent. 

 85.76 

 89.62 



The higher digestibility of the starch in our experiment was accom- 

 panied (caused?) by a greater production of methane, so that a less 

 proportion of the digested energy was metabolizable. When thus com- 

 puted on the digested energy, our results in period i agree substantially 

 with Kellner's, while periods 2 and 4 show a considerably greater rela- 

 tive loss of energy in the methane. Period 3, as already noted, appears 

 exceptional. No obvious* explanation presents itself for the high heat 

 increment found in our experiment. The more extensive fermentation 

 of the starch may perhaps account for a portion, but by no means 

 all of it. 



1 ArmSBY, H. p. op. CIT., 191 7, p. 4SS-459, 474. 



