VITAMIN A FOR DAIRY CATTLE 9 



alternative is to present the results corrected so far as possible, and explain the 

 reason for most of the apparent difference. 



It should not be concluded from the preceding paragraph, however, that the 

 supplement was without effect on milk production. There is good reason to 

 believe that it did have some positive effect in this respect as indicated by the 

 following evidence: 



1. When the results are broken up into sub-groups according to breeds the 

 differences in production during the experiment are in favor of the supplement 

 for all five breeds of cattle, and this situation holds true whether all the cows in 

 the experiment are considered, or only those that were in the herd previously. 

 The fact that none of the breed differences in themselves are of significance, is 

 due in part to the comparatively small number of records for each breed. The 

 trend is certainly suggestive of positive effect. 



Of more significance is the fact that the breed records previous to the experi- 

 ment do not show any such definite trend in favor of the group that later received 



T.\BLE 7. ^Corrected Milk Production by Breeds, both before and 



DURING THE EXPERIMENT (COMPLETE LACTATIONS ONLY). 



Average Daily Production 

 per Cow, in Pounds 



Group Group not 



Receiving Receiving 



Vitamin A Vitamin A 



Supplement Supplement 



1. Records of all cows during the experiment 



a. Shorthorns 



b. Ayrshires 



c. Holsteins 



d. Guernseys 



e. Jerseys 



2. Records during the experiment of cows in the 



herd previously 



a. Shorthorns 



b. A^'rshires 



c. Holsteins 



d. Guernseys 



e. Jerseys 



3. Records of group 2 previous to the experiment 



a. Shorthorns 



b. Ayrshires 



c. Holsteins 



d. Guernseys 



e. Jerseys 



25.93 

 37.01 

 40.93 

 30.93 

 31.00 



27.44 

 36.32 

 41.41 

 31.84 

 30.71 



30.94 

 35.74 

 33.46 

 27.60 

 33.16 



24.96 

 30.98 

 39.70 

 30.31 

 20.59 



26.09 



28.78 



33.67 



30.31* 



20.59* 



27.40 

 41.57 

 36.42 

 31.51 

 26.55 



*It so happened that all the Guernseys and Jerseys in group 1 not receiving the supplement 

 had been in the herd previously; hence the identical values for these breeds in groups 1 and 2. 



