34 N. H. Agr. Experiment Station [Bulletin 304 



Seasonal variations in basal metabolism of dairy bred cows (not lae- 

 tating) amounting to as much as 50 per cent, and higher have been ob- 

 served. The highest level of metabolism invariably occurred during 

 May, June, and July, that is, during the period of longest sunlight when 

 the extra heat is least necessary suggesting that this factor may play a 

 dominant effect on stimulus of the body tissues. It is conclusive evi- 

 dence that under ordinary conditions of environmental temperature 

 the rate of heat loss from the body does not determine the rate of its 

 production as has been believed heretofore. 



Physiologically a fundamental study of metabolism and food utiliza- 

 tion involves a study of many specific factors which may affect the pro- 

 duction of heat or the disposal of excess heat under unusual conditions. 

 Thus our studies in metabolism during the past year have also been 

 carried out on the relatively little explored subject of the effect of en- 

 vironmental temperature on the metabolism of the various species of 

 farm live stock, including cattle, sheep, goats, and the pig. 



In a series of thirteen metabolism measurements of two Jersey cows 

 kept under very carefully controlled conditions of temperature, feed 

 and water intake, it was found that the basal metabolism increased from 

 two to three per cent, for each degree drop in temperature below about 

 18° C. (64° F.) which is approximately the most comfortable tempera- 

 ture for adult cattle under ordinary conditions of feeding. The ef- 

 fect of blanketing at environmental temperatures of 8.5 to 9.5° C. re- 

 duced the heat production of these Jersey cows, when regularly fed, 

 by four per cent. Numerous measurements of the relative amount of 

 heat lost by vaporization indicated much lower values for the heat loss 

 by this path than have been previously reported for cattle. 



Metabolism measurements were also made of sheep at various tem- 

 perature levels both before and after shearing. At a normal tempera- 

 ture of 18 to 22° C. shearing increased the basal heat production about 

 10 per cent., but when the environmental temperature was dropped to 

 about 11° C. the heat production increased 33 per cent, above the level 

 before shearing. Similar experiments with goats indicate somewhat the 

 same metabolic reaction to temperature as does the sheared sheep. 



A series of similar experiments begun with an adult Chester White 

 sow is still in progress. 



The technique and design of apparatus required for a study of these 

 new problems in physiology constitute no small part of the efforts of 

 research. Thus, our preliminary attempts to evolve a technique for 

 the metabolism of the horse in action by means of a treadmill have 

 found technical limitations which make this method of procedure un- 

 suitable. This has led to the design of a special type of mask, based on a 

 new principle of application. This mask is at present well along to- 

 ward completion, and if satisfactory will be used to measure the energy 

 production of the horse in action at different speeds. 



During the year a manuscript has been prepared on the researches 

 in metabolism and nutrition carried out primarily on cattle during the 

 last eighteen years. This will be published in the monograph series of 

 the Carnegie Institution of Washington under the title "Nutritional 



