41 8 Journal of Agricultural Research voi. iv, no.s 



DIGESTION TRIALS 



Toward the close of the first year's work it became apparent that the 

 heavy prickly-pear ration was not used as efficiently as the medium. 

 In order to ascertain whether the heavy ration was rushed through the 

 digestive tract too rapidly to allow sufficient time for digestion and 

 absorption, and also to check previous work of that kind which had not 

 been altogether satisfactory, some digestion trials were conducted in 

 May and June, using cows that were accustomed to the different classes 

 of roughage fed during the previous year's work. 



The plan was to use two cows in each trial and to conduct five trials 

 for a period of lo days each, with a preliminary period of 4 to 7 days 

 during which time the ration was to be exactly the same in kind and 

 quantity as during the digestion trial. This plan was rigidly adhered to, 

 except that in one of the trials data for 9 days instead of 10 were used. 



The four different rations used were as follows: Sorghum hay and 

 grain; sorghum hay, medium quantities of prickly-pear, and grain; sor- 

 ghum hay, heavy rations of prickly-pear, and grain; and prickly-pear 

 alone. The grain in every case consisted of equal parts by weight of com 

 meal, cottonseed meal, and wheat bran. 



The sorghum hay was run through a cutter, thoroughly mixed, and a 

 sample taken for analysis. Samples of the com meal and other grains 

 were taken before the grain mixture was prepared. The prickly-pear 

 was sampled by taking a representative portion each day, chopping it 

 into fine pieces, mixing and weighing out about 100 gm. on a chemical 

 balance. This portion was then dried on a hot-water bath. The dried 

 samples for 10 days were placed together in a tight jar and sent to Wash- 

 ington for analysis with the other samples. 



The feces were collected by attendants who were with the cows day and 

 night throughout the trials. No urine was collected. The cows were 

 kept in ordinary rigid stanchions. The wooden gutter behind and the 

 rear portion of the platform on which the cows stood were covered with 

 white oilcloth, so that in case the attendant failed to catch the feces at the 

 time they were passed, they could be easily collected from the cloth. In 

 order to avoid any possibility of including urine with the feces, water was 

 used to wash it out of the gutter. An ordinary shovel was used in catch- 

 ing the feces, except in the case of the cows receiving prickly-pear alone, 

 when, owing to the extreme looseness of the bowels, it became necessary 

 to use a large tub. The feces were placed in large cans, weighed each day 

 at the same hour, and, after being thoroughly mixed, an aliquot portion 

 was taken and composited for chemical analysis. These samples were pre- 

 served with chloroform and kept on ice. At the end of 10 days a portion 

 of the composite was weighed on the chemical balances and then dried 

 over the hot-water bath in the same way as the prickly-pear. Owing to 

 the loss in nitrogen when feces are dried, the samples for nitrogen deter- 



