VITAMIN A FOR DAIRY CATTLE 5 



factor (1.6) was used in converting gamma of carotene found into U. S. P. units of 

 vitamin A as given hereafter. 



Using these values together with the average daih- ration fed. calculation shows 

 that the average intake of vitamin A by individual cows in the group receiving 

 the supplement was approximately 174,000 TJ. S. P. units daily, while in the group 

 which did not receive the supplement it was approximately 142,000 U. S. P. units 

 daily. These figures indicate that if the standard set by Converse and Meigs 

 is correct for our conditions, the group of cows receiving the supplement had an 

 excess of approximately 21 percent of vitamin A above requirements in their 

 daily ration, while those not receiving the supplement were experiencing a slight 

 deficiency of the vitamin in comparison with the standard. 



A very careful record of the reproductive function of all the individuals was 

 kept throughout the experiment. Growth of the heifers was followed b^' means 

 of live weights obtained at intervals of not more than two months during each 

 barn feeding season. The average of two weights on consecuti\e days, or on 

 days with only one day intervening, was the figure used at an\ particular time. 

 Complete milk records were available as a matter of routine practice in the herd. 

 All calves dropped during the period were weighed at birth and were graded for 

 condition by an experienced herdsman. Those saved for the herd were weighed 

 again at one month of age. Effects on growth and reproductive function are 

 summarized in Tables 2 to 5 inclusive. 



T.\BLE 3. — Record of the Milking Herd during the Experiment. 



Group Receiving 

 Vitamin A 

 Supplement 



Records Number 

 during of 



Experiment Records 



Group not Receiving 

 Vitamin A 

 Supplement 



Records Number 



during of 



Experiment Records 



Number of individuals . 



Regularity of heat 



Interval between heats. Days 



Time from calving to first 



heat Days 



Services required for 



conception Number 



Length of gestation .... Days 



Cases of retained pla- 

 centa Percent 



Abortions Number 



Calves born dead Number 



Calves died some time 



after birth Number 



Cases of milk fever .... Number 



44.9 



51.0 



41 



*One of these wa? due to B. abortus infection. 

 Other abnormalities the same as reported in the footnote to Table 2, except for one additional 

 case of eversion of the uterus which occurred in the group receiving the Vitamin A supplement. 



