170 EXPERIMENT STATION EECOED. 



pounded as follows, in percentages of net thermal energy values (not weights) : 

 Ration 1, silage, cotton-seed meal, and starch, 100 : : ; ration 2, : 100 : ; 

 ration 3, 10 : 30 : ; ration 4, 50 : 50 : ; ration 5, 34.5 : 34.5 : 31 ; ration 6, 

 69 : : 31 ; ration 7, 30 : 70 : ; ration 8, 15.8 : 36.9 : 47.3 ; ration 9, 52.7 : : 47.3. 

 High-grade yearling Shorthorn steers were used, and the digestion trials were 

 of 10 days' duration with a suitable interim between each trial. 



It was found that starch, when fed in excessive amounts, seemed to exert 

 a depressing effect upon the digestibility of the nitrogen and crude fiber, even 

 when the excess was not great. When 47.3 per cent of the net energy of the ra- 

 tion was supplied in the form of starch there was also a depression in the di- 

 gestibility of the total ash. These depressions in digestion of nitrogen, crude 

 fiber, and ash were accompanied by a rise in the digestion of fat, which was 

 quite noticeable in the high starch rations. The depression in the digestibility 

 of the several nutrients brought about by the addition of starch was largely 

 overcome, and in some instances completely overcome by the addition of cotton- 

 seed meal, even though the quantity of starch remained constant. Increasing 

 the quantity of crude fiber in tlie ration did not exert a depressing effect upon 

 the dige.stibility of the nitrogen-free extract, but tended rather to increase the 

 percentage of niti'ogen-free extract digestetl. 



The variability of the results from different steers, due either to the in- 

 dividuality of the animals or to the Imperfections of the usual methods of 

 conducting metabolism experiments, was so great as to obscure in many ca.ses 

 the variations resulting from the influence of food combinations. The nearer 

 the rations approached what is generally considered a normal ration, such as 

 a ration in which 70 per cent of the net energy is supplied in the form of 

 silage and 30 per cent in the form of cotton-seed meal, the smaller were the 

 variations among individuals. 



Steers when changed from one ration to another apparently do not at first 

 secure all of the nutriment from the ration that they will secure after they have 

 been on the feed for a time. Especially does this seem to be true when the 

 change is from a rich to a poorer diet. Even when as nmch as 47.3 per cent of 

 the net energy of the ration was supplied in the form of starch the iodin test 

 did not indicate the presence of starch in the feces. Within certain limits the 

 total quantity of nitrogen excreted by the feces was fairly constant, despite 

 marked changes in the nitrogen intake and digestibility. A 200-kg. steer will 

 excrete by the feces as much as 5.84 gm. daily of metabolic nitrogen for a con- 

 siderable period (25 days). 



The figures obtained relative to the actual coefficients of digestion, as com- 

 pared with the calculated, so far as the silage and cotton-seed meal rations are 

 concerned, indicate that for most nutrients a fair degree of reliability can be 

 placed upon the calculated coefiicients of digestion. For the dry matter the 

 variation was never over 5 per cent ; for the nitrogen, never over 7 i)er cent ; for 

 the crude fiber, never over 10 per cent ; for the fat, never over 14 per cent ; and 

 for the ash, never over 30 per cent. In the case of the silage and cotton-st^ed 

 meal rations, modified by the addition of starch, much less reliability could be 

 placed upon the calculated coefiicients of digestion. For the dry matter the 

 variations amounted to as much as 20 per cent ; for the ash, 35 per cent ; for the 

 nitrogen, 73 per cent ; for the crude fiber, 45 per cent ; for the nitrogen-free 

 extract. 15 per cent ; and for the fat, 55 per cent. 



Cotton-seed cake vs. cold-pressed cotton-seed cake for beef cows. Mixed 

 grain vs. cotton-seed cake for growing' beef cattle. A. D. P^aville (Wyominff 

 Sta. Bui. 106 (1915), pp. 11). — In part 1 of this bulletin it is shown that in an 

 experiment with two lots of four beef cows each 2.4 lbs. of cotton-seeil cake. 



