ANNUAL REPORT, 1938 23 



the phosphorus content of their milk only slightly (from .089% when they did 

 not receive it to .090% when it was fed daily in their grain ration). This slight 

 increase was not significant. The averages are based on 96 determinations of 

 the element in the milk — 48 when the cows were receiving the supplement and 

 48 when they did not receive it. 



This season the effect of supplemental iron on the iron content of milk is being 

 studied. 



The Effect of Artificial Light on Milk Production. (J. G. Archibald and C. H. 

 Parsons.) The preliminary trials on this project have been completed. During 

 the winters of 1936-37 and 1937-38, two Guernsey cows were alternately e.xposed 

 to the direct rays of a 1000-watt electric light throughout the hours of darkness 

 for successive 30-day periods. These cows were similar in age, breeding, and 

 stage of lactation and were handled identically except for the exposure to light. 

 Their production records, when converted to a 4 percent fat basis, showed greater 

 production (1.43% the first year and 0.64% the second year) during the periods 

 when they were exposed to the strong light than when they were kept under 

 ordinary conditions. 



Studies in the Chemistry of Pasture Grasses. (J. G. Archibald.) The chemical 

 studies originally planned for this project were brought to completion during the 

 year and correlation and interpretation of the results are in progress. The pal- 

 atability tests with cows were repeated this season and extended to the second 

 series of plots. The results substantiate those obtained last year. The cows 

 showed a decided preference for timothy, the bent grasses (Agrostis spp.), and 

 orchard grass; they were quite indifferent to bluegrass as long as the others were 

 in good supply; and they left sheep fescue {Festuca ovina) practically untouched. 

 The verdict of the cows confirms the judgment of the nutritive value of the grasses 

 based on their chemical composition. 



The Vitamin Content of Certain Pasture Grasses. (W. S. Ritchie and J. G. 

 Archibald. Cooperative with Chemistry.) This project has been completed. 

 The report appears under the Department of Chemistry. 



Investigation of the Merits of Legume and Grass Silage for Massachusetts 

 Agriculture. (J. G. Archibald and C. H. Parsons.) The feeding trials conducted 

 during the winter of 1937-38 showed that this type of silage was equal to corn 

 silage and superior to dry hay for milk production. Flavor and carotene content 

 of the milk were improved. 



No difficulty was experienced in getting the cows to eat the silage. Two lots 

 of it stored in 1937 consisted largely or entirely of alfalfa. The cows relished the 

 alfalfa silage keenly and increased somewhat in their milk flow while it lasted. 

 Experience thus far in feeding such material, however, leads to the belief that it 

 cannot completely take the place of dry hay. The cattle seem to crave dry rough- 

 age after they have been without it for a time. 



In June of this year approximately 80 tons of the material were preserved with 

 molasses and 117 tons were stored in another silo with phosphoric acid (18 pounds 

 to each ton of green grass) as the preservative. At date of writing (December 

 1938), the phosphoric acid silage is being fed in comparison with corn silage. 

 Later in the winter it will be compared with the molasses silage. 



The phosphoric acid silage seems to be quite well liked by the cows, but it 

 has not kept as well in storage as the molasses silage did last year. Flakes and 

 pockets of mold are encountered rather too frequently, but this may possibly 

 be due to the type of silo (a square concrete structure with rough inside walls) 

 rather than to inefficiency of the preservative. 



