ANNUAL REPORT, 1936 19 



included in the experiment, which will be continued for at least one complete 

 lactation period of all or practically all the individuals. Results will not be 

 available for at least another year. 



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

 V. A. Rice, and C. H. Parsons.) This project, recently organized, has for its 

 objectives answers to the following questions: 



(1) Can the amounts of the mineral elements normally presents in cows' 

 milk be significantly increased by modification of our feeding practices? 



(2) Can milk be "fortified" in those respects in which it is sometimes con- 

 sidered to be relatively deficient, by the feeding of certain elements such as 

 iron and manganese? 



(3) If these objectives can be accomplished, what significance have they from 

 the standpoint of human nutrition? In other words, what may be the effect 

 upon human well-being of milk so "fortified"? 



For the present, attention is concentrated on the element calcium. Ten 

 cows in the college herd have been divided into two groups of five each, in one 

 of which the cows are receiving supplemental calcium in the form of finely 

 ground limestone in amount roughly equivalent to that naturally occurring in 

 their rations. Composite milk samples are taken once a month for a two-day 

 period and the calcium determined by a method specially devised for the de- 

 tection of small differences. At the end of three months the groups will be 

 reversed so that the cows not now receiving supplemental calcium will receive 

 it for a similar three-month period later in the winter. 



The Effect of Artificial Light on Milk Production. (J. G. Archibald, 

 V. A. Rice, and C. H. Parsons.) The title of this project indicates its nature. 

 Some work done with poultry suggests that the stimulus to egg production which 

 results from the use of electric lights is not due entirely to the increased feed 

 consumption in the longer day made possible by the lights, but is due in part 

 to an indirect stimulus to the hen's reproductive system through the action 

 of light on the pituitary gland. The question naturally arises: if this is true 

 of hens, may not the light have a similar effect on cows. 



The idea is being tried out in a small way to begin with. Two Guernsey cows 

 of similar age, size, and productive ability, which freshened within a week or so 

 of each other in November 1936, are being kept in adjacent box stalls so 

 arranged that one of them is exposed only to such ordinary artificial light as is 

 necessary to milk, feed, and care for her generally; while the other is exposed 

 from dusk to dawn each night to the direct rays of a 1000-watt electric light. 

 Their feed and care in all other respects are identical. They are not confined 

 to the box stalls all the time but receive daily exercise in an adjacent yard. At 

 the end of a month they will be reversed with respect to the light and these 

 changes will be made at regular monthly intervals until the end of the barn- 

 feeding season in April. In this way it is hoped to obtain a measure of the effect 

 of the light, if there is any. 



Studies in the Chemistry of Pasture Grass. (J. G. Archibald. ) This 

 project has been continued throughout the year using the two series of plots 

 mentioned in the last report. Results from the second series will not be avail- 

 able until after the end of the 1937 growing season. Final conclusions on the 

 first series await the completion of this seasons' analytical work which is now 

 in progress. The following tentative conclusions are offered at this time: 



(1) The conclusions published in the Journal of Agricultural Research for 

 April 15, 1935, are in general confirmed by these later studies; viz., the high 



