22 MASS. EXPERIMENT STATION BULLETIN 347 



With respect to the average experimental results given above for the several 

 items of data, it should be stated that the respective results for the two replica- 

 tions of the experiment were very similar, with only small differences existing 

 between corresponding items of data. 



DEPARTMENT OF ANIMAL HUSBANDRY 

 Victor A. Rice in Charge 



The Effect of Feeding a Vitamin A Concentrate on Reproduction in Cattle. 



(J. G. Archibald, V. A. Rice, and C. H. Parsons.) This project was brought to 

 completion during the year. A preliminary report of results was given at the 

 annual meeting of the Eastern Section, American Dairy Science Association in 

 September. Conclusions drawn at that time are as follows: 



Taken individually none of the differences between the groups are significant. 

 However, the evidence as a whole shows a slight trend in favor of the group which 

 received the vitamin A concentrate. Twenty comparisons of various phases of 

 reproductive function are available for the duration of the experiment. Of these, 

 eleven favor the group receiving vitamin A concentrate, six favor the other group, 

 and three are evenly divided. 



The effect of the supplement is reflected principally in the birth weight of the 

 calves dropped during the experiment and in a much smaller percentage of still- 

 born calves. 



Since these cattle probably were on better than average rations, it is conceivable 

 that the vitamin supplement might show a more positive effect in some herds, 

 especially where silage is not fed and the hay is of poor quality. The indiscrim- 

 inate feeding of such supplements regardless of conditions should not be practiced. 

 The individual farmer should study his own particular conditions and decide for 

 himself whether grain mixtures containing vitamin A concentrates are worth 

 the additional cost, bearing in mind always that if for winter feeding he has 

 plenty of early-cut, properly cured hay and well-made corn silage that has not 

 been frosted, and if he has good pasturage in the summer, he will not need to 

 supply additional vitamin A to his cattle. 



The Effect of Complex Mineral and Vitamin Mixtures on Milk Production, 

 General Health, and Reproductive Efficiency in Dairy Cattle. (J. G. Archibald.) 

 This project has been continued throughout the year in accordance with the plan 

 outlined in last year's report. Regular quarterly visits have been made to each 

 of the three herds in order to grade the cattle for general appearance and condition, 

 and to exercise proper supervision over the work and the keeping of records. 

 The feeding trials will be terminated during the coming year and the records will 

 then be studied in detail. 



A Study of the Mineral Elements of Cows' Milk. (J. G. Archibald, V. A. 

 Rice, and C. H. Parsons.) Supplemental calcium in the form of ground limestone 

 fed to a group of eight cows in the college herd during the winter of 1936-37 did 

 not increase the calcium content of their milk. On the contrary the average 

 calcium content of monthly samples of milk taken in each month from November, 

 1936, through April, 1937, was slightly lower when the cows received the supple- 

 mental calcium than when they were on the standard ration, although the differ- 

 ence was so slight that it was not statistically significant. 



This season the effect of supplemental phosphorus on the amount of that 



