14 MASS. EXPERIMENT STATION BULLETIN 362 



Gains in Weight 



All cows in the experiment were weighed on each of two successive days at 

 the beginning and end of each five-week feeding period. The average individual 

 gains for the entire trial were: 



On corn silage 46 pounds 



On grass silage 38 pounds 



On dry hay 33 pounds 



On grass silage 66 pounds 



Because of the usual considerable fluctuations in weight common to cows, the 

 difference of 8 pounds in favor of the corn silage has little if any significance. The 

 difTerence of 33 pounds in favor of the grass silage when compared with dry hay 

 is, however, of sufficient magnitude to be significant. This particular lot of hay, 

 at least, was' inferior to the grass silage for body gains. 



Average BiUterfat Test 



This was ascertained by means of three-day composite samples from each 

 group of cows, about midway of each five-week feeding period. The results 

 follow: 



Average fat test 



On corn silage 4.32% 



On grass silage 4.35% 



On dry hay 4.10% 



On grass silage 4 . 23 %, 



Since these tests represent the average of all cows, individuality of the animals 

 as a factor can be ruled out. The small difTerence between the tests when corn 

 silage and grass silage were compared is, of course, without significance. The 

 somewhat larger difTerence when grass silage was compared with dry hay may 

 possibly be of some significance as indicating a slightly favorable response in this 

 respect to the silage feeding. 



Vitamin A Content of the Milk 



This was determined by biological assay with white rats^ on the composite 

 milk samples taken during the second half of the winter; i. e., when grass was 

 being compared with dry hay. An assay for vitamin A in the milk was not made 

 during the first half of the season. Results appear below. 



Vitamin A 



(International Units 



per quart of milk) 



In March In April 



Cows receiving dry hay 2,172 1,514 



Cows receiving grass silage 3,407 1,703 



The much larger difference in favor of the grass silage in March than in April 

 is attributed to the fact that the lot of silage being fed at that time was probably 

 the highest in carotene content of any fed all through the season. It contained a 



'Acknowledgment is made of the cooperation of Dr. W. S. Ritchie and Dr. \Vm. B. Esselen, 

 who carried on this part of the work. 



