14 MASS. EXPERIMENT STATION BULLETIN 398 



was, however, very evident; the odor was mild and sweet, and the cows ate it 

 much more readily than they did a similar lot preserved with phosphoric acid in 

 the same silo the previous year. 



A second silo containing 75 tons of mixed grass was inoculated at five different 

 levels at filling time in June 1941, with a pure culture of Bacillus hulgaricus. No 

 other preservative was used. This silo was opened in January 1942; there was 

 considerable spoilage at the top and sides and the odor at first was very objec- 

 tionable, indicating formation of excessive amounts of butyric acid. The odor 

 improved after the top layers were fed off, but continued more sharply acid than 

 the odor of the molasses silage referred to above, although the pH was 4.4 in con- 

 trast to 3.9 for the molasses silage. The station bacteriologist was unable to recover 

 B. hulgaricus from the silage, which suggests that the inoculation may have 

 played little if any part in the fermentation. 



The silage was fed to young cattle; they ate it readilj' but made somewhat 

 smaller gains than when fed corn silage. This may have been due, however, to 

 inherent feeding value of the original material rather than to method of preserva- 

 tion. It would have been desirable to include another siloful of similar material 

 not inoculated, as a control. This has been done this year, but at this date 

 (Nov. 30) the silos have not been opened. 



In addition to the three large silos filled this year, using respectively molasses, 

 bacterial inoculation, and no preservative (control), sixteen miniature silos have 

 been filled, each containing approximately one and a half bushels of chopped 

 grass or alfalfa, and weighted with concrete blocks to produce a pressure of about 

 120 pounds to the square foot. Two crops, mixed grass and alfalfa, at two dif- 

 ferent moisture levels, have been ensiled in these miniature silos with the follow- 

 ing treatments: (1) no preservative, (2) inoculation with B. hulgaricus, (3) salt, 

 (4) B. hulgaricus plus salt. At date of writing (Nov. 30) six of these small silos 

 have been opened and their contents studied from a biochemical, and to a lesser 

 extent from a bacteriological standpoint. The outstanding facts thus far are: 

 (1) the excessive amount of butyric acid which has developed regardless of the 

 preservative used, and (2) the complete absence of lactic acid from these silages. 



A Study of Urea as a Partial Substitute for Protein in the Rations of Dairy 

 Cows. (J. G. Archibald.) This project has recently been discontinued for the 

 duration of the war. Final conclusions are not being drawn at this time, but 

 results of feeding trials extendmg over three years indicate that while the urea 

 has been utilized by the cows to some extent it has not proved equal to the stand- 

 ard protein concentrates as a source of nitrogen for milking cows. 



The Effect of Feeding Irradiated Dry Yeast on Reproduction and General 

 Health in Dairy Cows. (J. G. Archibald and J. D. Neville.) Two years' results 

 with sixty cows in the Gardner State Hospital herd show no differences of any 

 significance between the cows getting irradiated yeast and those on the control 

 ration. This lack of response may be due to the fact that this herd has always 

 been maintained at a rather high nutritional level. The level of vitamin D fed 

 was approximately 10,000 international units daily per cow. 



Determination of the phosphatase level in the blood of twenty of these cows 

 (ten in each group) at regular intervals during January-, February, and March 

 of this year showed no significant differences between the groups in this constit- 

 uent. Since a rise in blood phosphatase is considered to be a sensitive indicator 

 of vitamin D deficiency, it seems evident from these results that the cows in this 

 herd were not suffering from even a slight deficiency of this vitamin; therefore, 

 the lack of response to the feeding of irradiated 3'east is quite understandable. 

 The project in its present form and as involving the use of the Gardner herd has 

 been terminated. 



