4 MASS. EXPERIiMENT STATION BULLETIN 357 



The maximum length of storage between mixing and feeding of the grain was 

 two months. The interval was much shorter than this for the most part. During 

 the period from February 1935 to October 1936 the supplement was guaranteed 

 to contain 2500 U. S. P. units of vitamin A and 250 units of vitamin D per gram. 

 From October 1936 to April 1937 the guarantee was 3000 U. S. P. units of vitamin 

 A and 350 units of vitamin D per gram. 



Translated into ordinary usage this means that a cow receiving an average 

 amount of ten pounds of grain daily would obtain 28,350 U. S. P. units of vitamin 

 A from the earlier lot of the concentrate and 34,020 U. S. P. units daily from the 

 later lot. Converse and Meigs in their latest published work-^ conclude that an 

 average of 144,000 U. S. P. units daily (the equivalent of 90,000 gamma of pure 

 beta carotene), is necessary for normal calving. This means that most of the 

 necessary vitamin A must have come from the feeds rather than from the supple- 

 ment. As there were no indications of vitamin D deficienc>' in the herd, a study 

 of the elTects of the supplement in this respect was not made. 



Vitamin A assays were made on the supplement, and carotene determinations 

 were made on the various feeds used in the course of the experiment. The usual 



Table 2. — Comparison of Reproductive Function before and during 



THE Experiment for Cows in the Herd Previously and Continuing in 



THE Herd during most or all of the Experimental Period. 



Group Group not 

 Receiving Receiving 



Vitamin A Vitamin A 



Supplement Supplement 



Before During Before During Before During 

 Expt. Expt. Expt. Expt. Expt. Expt. 



Time from calving to first 



heat Days 44 49 45 49 40 



Services required for concep- 

 tion Number 2 . 



Length of gestation Days 283 



Cases of retained placenta. . Percent 8. 



Abortions Number 2 



Calves born dead Number 2 



Calves died some time after 



birth Number 1 



Cases of milk fever Number 4 



*One of these was due to B. abortus infection. 

 Other abnormalities, all occurring during the experiment, include: 



One case of aversion of the uterus in the group receiving the vitamin A supplement. 

 Two cases of nymphomania, one in each group. 



Two cases of cystic ovaries, both in the group not receiving the supplement. 

 One cow in the group not receiving the supplement stopped coming in heat for no apparent 

 reason. 



^Converse, H. T., and Meigs, E. B. The carotene requirements for normal reproduction. (Ab- 

 stract) Jour. Dairy Sci. 21 (No. 5):114. 1938. 



