20 MASS. EXPERIMENT STATION BULLETIN 378 



Overwintering of Common Tobacco Mosaic Virus in Soil Under Natural 

 Conditions. (C. V. Kightlinger.) This project has been completed. The 

 purpose was to determine whether common tobacco mosaic virus could 

 overwinter in soil under natural conditions in the Connecticut Valley, 

 and if so, then to determine how much mosaic would develop in suc- 

 ceeding tobacco crops with the overwintered virus as a source of inoculum. 

 B}^ wa}^ of summary of experimental results, it may be stated that 

 the mosaic virus overwintered abundantly in the soil but that only a small 

 percentage of the tobacco plants grown on the land developed mosaic. 



DEPARTMENT OF ANIMAL HUSBANDRY 

 Victor A. Rice in charge 



The Effect of Complex Mineral and Vitamin Mixtures on Milk Pro- 

 duction, General Health, and Reproductive Efficiency in Dairy Cattle. 

 (J. G. Archibald.) This project was completed during the past year. A 

 confidential report was furnished to all interested parties, but release of 

 the results in a general publication is not contemplated. No benefits 

 from the feeding of two of the three complex mixtures investigated over 

 a two-year period, were in evidence. Slight positive results were obtained 

 from the third supplement fed. The following paragraphs are quoted 

 from the confidential report on this particular supplement: 



Although only one, or possibly two, of the diflferences between the 

 groups of cows are of significance, nevertheless the general trend of the 

 evidence slightly favors the group which received the supplement. These 

 cows maintained their general condition slightly better than the controls 

 did; they gave slightly more milk (1.4 lbs. daily); they required a signif- 

 icantly smaller number of services to get them with calf; and they had 

 somewhat less trouble at calving time with retained afterbirth. 



It is impossible, of course, to say definitely whether the supplement as 

 a whole produced this desirable efifect, or whether it was due to some one 

 ingredient of what was a rather complex proprietary mixture, and, if the 

 latter, what particular ingredient. It is our opinion, however, that the 

 ingredient most likely to have been responsible for the slight benefits 

 noticed was the cod liver oil the supplement contained. Results of a some- 

 what similar magnitude and trend were obtained a few years ago in an 

 extensive trial of the merits of a cod liver oil concentrate added to the 

 grain mixture for about half the milking herd of cows at the Massachu- 

 setts State College. 



It seems probable that the price of the supplement (9 cents a pound 

 at the time it was purchased in 1936) would prohibit its use by the average 

 farmer. Fed at the rate of two percent of the grain mixture, it would 

 add $3.60 to the cost of each ton of mixed grain. If, as we believe, the 

 beneficial effect of the supplement is due to the cod liver oil it contains, 

 sufficient cod liver oil concentrate to furnish 30,000 additional U. S. P. 

 units of vitamin A per cow daily (an amount that along with the potential 

 vitamin A in average quality roughage provides a reasonable margin over 

 requirements) can be purchased for not more than $1.00 of additional cost 

 per tc>n of mixed grain. 



A Study of the Mineral Elements of Cow's Milk. (J. G. Arcliil)aid and 

 C. H. Parsons.) For reasons outlined in last year's report, tlie work 



