12 



MASS. EXPERIMENT STATION BULLETIN 357 



Table 9. — Effect of the Vitamin A Supplement on the Fat Content 

 OF the Milk. 



Group Receiving Group not Receiving 



Vitamin A Supplement Vitamin A Supplement 



Average Number of Average Number of 



Fat Test Records Fat Test Records 



Records during the experi- 

 ment of cows in the herd 

 previously 



a. Shorthorns 4.05 



b. Ayrshires 4.09 



c. Holsteins 3 . 62 



d. Guernseys 4.82 



e. Jerseys 5.96 



Weighted average 



fat test 4 . 59 



Total number of 

 records 



Records of group previous 

 to the experiment 



a. Shorthorns 4.15 



b. Ayrshires 4.19 



c. Holsteins 3.67 



d. Guernseys 4.90 



e. Jerseys 6.02 



Weighted average 



fat test 4 . 67 



Total number of 

 records 



43 



4.69 



22 



42 



19 



NOTE: It should be clearly understood that in all cases the records before and during the ex- 

 periment are for identical cows. The larger number of records in some instances for the period 

 covered by the experiment is due to the fact that occasionally only one record was available for 

 a cow previous to the experiment, while during the experiment two records were available in almost 

 all cases. 



Effect of the Supplement on the Vitamin A Content of the Milk 



This topic is perhaps of most interest from the standpoint of human nutrition, 

 but it may also be of significance in the successful rearing of caKes. Biological 

 assays of the milk from the two groups of cows were made at two difTercnt times 

 during the course of the experiment — once during the winter of 1936 and again 

 during the winter of 1937.^ The tests were made on three-day compfjsilc- samples 

 of the milk. Results appear in Table 10. 



^Acknowledgement is made to Dr. W. S. Ritcliie and Dr. \V. B. Esselen of the Experiment 

 Station staff, who made the assays for carotene in feeds and vitamin A in milks. 



