Aug. i6, 1915 Prickly-Pears as a Feed for Dairy Cows 409 



specific gravity by using Farrington and Woll's table (3, p. 264, tab. 6). 

 At the end of each lo-day period the yield of the milk of each cow was 

 totaled, and the number of pounds of fat for the period was determined. 

 This yield of fat was then used as the basis for computing the grain 

 ration to be fed for the next 10 days. 



Every 20 days samples of the ordinary prickly-pear, chopped and 

 thoroughly mixed, were put into quart jars (chloroform being used 

 as a preservative) and sent to the Dairy Division for analysis by Mr. 

 R. H. Shaw. 



While this method of determining the relative values of feeds is by 

 no means perfect, it is an improvement on the ordinary feeding experi- 

 ment, because the factor of live weight was controlled and a direct 

 comparison of the feeds in question made possible on the basis of fat 

 production. It would be well, too, if a comparison could be made 

 on a basis other than that of fat; this, however, owing to the variation 

 in the composition of the milk caused by the feed, is impossible without 

 conducting more experiments. The alternating system of feeding, such 

 as was used in this experiment, favors the poorer feed. If any feed 

 under comparison has a tendency to stimulate production more than 

 another, the cows which receive the better feed for the second period 

 are placed at a disadvantage, as they must begin the second period 

 at a lower level of production than the cov/s that are to receive the 

 poorer feed. The feeding periods were continued long enough to reduce 

 the experimental error to an insignificant factor. 



Cow 7, in the group receiving grain, hay, and the medium prickly-pear 

 ration, died from acute indigestion, but in the opinion of all those con- 

 nected with the experiment its death can not be ascribed to the prickly- 

 pear any more than to the other ingredients of the ration. In calculating 

 the results of the experiment, therefore, the data for this animal were 

 disregarded. 



OUTLINE OF the; SECOND YEAR'S TESTS 



As the first-year's work had shown that prickly-pear fed in medium 

 amounts gave best results, it was fed the second year at the rate of 

 75 pounds a day to each cow in the groups that were used for comparing 

 prickly-pear with other feeds. Two groups were fed to compare the 

 relative values of prickly-pear and the sorghum silage and two to com- 

 pare the relative values of these cacti and cottonseed hulls; one addi- 

 tional cow was fed to study the effect of prickly-pear when fed for a 

 long period; another cow was fed on prickly-pear without any sup- 

 plementary ration to ascertain whether it would be possible to maintain 

 an animal upon this feed alone. The cottonseed hulls were such as are 

 ordinarily purchased in the open market. The sorghum silage was below 

 the average in quality, as the sorghum had been sown broadcast and 

 was not fully mature at the time of putting it into the silo. In order to 



