22 MASS. EXPERIMENT STATION BULLETIN 355 



made at successive 15-day intervals each season, beginning as soon after the time 

 of setting the tobacco as it was possible to inoculate the plants. The inoculum 

 used in the experiments was obtained by expressing juice from mosaic-diseased 

 tobacco plants, and it was applied to the leaves of the plants to be inoculated by 

 means of the fingers. Except for the difference in time of inoculating the plants, 

 uniform treatments were employed throughout the experiments each season. 



By summarizing the experimental results for the two years, it was found that 

 mosaic infection resulting from the inoculations reduced the yield of tobacco 

 below that grown on the control plots, which was 1924 pounds per acre. Quality 

 and value of the tobacco were also reduced as follows: 



Time of Inoculation Reduction due to Mosaic Infection 



At time of setting. . . 

 15 days after setting. 

 30 days after setting. 

 45 days after setting. 



DEPARTMENT OF ANIMAL HUSBANDRY 

 Victor A. Rice in Charge 



The Effect of Feeding a Vitamin A Concentrate on Growth and Reproduction 

 in Dairy Cattle. (J G. Archibald and C. H. Parsons.) The final detailed report 

 on this project has been prepared and will be published as an experiment station 

 bulletin. 



The results obtained, although favorable to the vitamin A concentrate in their 

 general trend, were not marked. It should be borne in mind, however, that the 

 cows were on better-than-average rations, some of them being fed for Advanced 

 Registry records. It seems reasonable to assume that response to the concentrate 

 might be more marked under average farm conditions than it was in this case. 



It seems justifiable to recommend for average New England conditions the 

 inclusion of some form of supplemental vitamin A in the rations of dairy cattle 

 during that period of the year when they are not on pasture. The practice will 

 be of most value on farms where silage is not fed and the hay is of poor quality. 

 If New England dairymen could feed good quality alfalfa hay through the winter 

 and if they could always be sure of having well-preserved corn silage stored 

 before frost, it is probable that their cows would not need additional vitamin A. 

 But since for most of them such a state of affairs is not attainable, some other 

 source of the vitamin must be relied upon. 



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

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

 The feeding trials connected with this project were brought to completion during 

 the year, and records extending over a period of two years are in process of de- 

 tailed study. Conclusions cannot be drawn at this time, but from superficial 

 observation the animals receiving the supplements do not appear to be superior 

 to those in the control groups. 



A Study of the Mineral Elements of Cows' Milk. (J. G. Archibald and C. H. 

 Parsons.) Supplemental phosphorus in the form of disodium phosphate, fed to a 

 group of eight cow^ in the college herd during the winter of 1937-38, increased 



