18 University of New Hampshire [Sta. Bull. 331 



probably supply us eventually with a yardstick of comparative endur- 

 ance which is one of the first assets of a good horse. 



We have also measured the comparative basal metabolism of sheep, 

 goats, and pigs to determine their comparative energy requirements. 

 Selective breeding has also had an effect in modifying, or as we call 

 it improving, these species to a point where they offer some unique 

 contrasts in food utilization and in their economic adaptation. Of 

 these species, the pig is in a class by itself as it is capable of an ex- 

 traordinary rate of growth. It can increase its weight a hundred 

 fold during the first year as compared to about 15-fold for the sheep 

 or from 5- to at most a 10-fold for the calf. Our data also show that 

 the pig possesses an extraordinary superiority over other farm live- 

 stock in the relative proportion of the digestible food energy which it 

 stores due in part to its labile adaptation to environmental conditions 

 and probably to a low hormone activity, which results in a low basal 

 energ}^ requirement. 



This study of the comparative basal metabolism of different spe- 

 cies, and of types possessing different functional adaptation has sup- 

 plied many new facts. The concept held for many years that the 

 rate of metabolism, or basal heat production, is conditioned solely by 

 the rate of heat loss to the environment, is untenable. It has been 

 shown that basal metabolism is affected by seasonal influences and 

 particularly by genetic factors which are essential to actuate the in- 

 herited (specialized) function to which the organism is adapted. 



Publications 



In addition to the progress reported year by year in the annual 

 reports of this Station and in the Year Books of the Carnegie Insti- 

 tution of Washington the results of our investigation in nutrition 

 and in breeding have been made public in the four large monographs, 

 technical bulletins, the Journal of Agricultural Research, and through 

 the medium of scientific societies in both this country and abroad. A 

 number of popular bulletins on sheep breeding based largely on the 

 general result of these researches were also prepared by E. G. Ritz- 

 man for publication by the New Hampshire Sheep Breeders' Asso- 

 ciation. The list is as follows — 



Publications in Nutrition 



TECHNICAL BULLETINS, N. H. AGRICULTURAL EXPERIMENT STATION 



No. 16, April, 1920 — A Respiration Chamber for Large Domestic Animals^ 

 No. 26, June 1924 — ^The Effect of Varying Feed Levels on the Physiological 



Economy of Steers. 

 No. 43, June, 1930 — ^The Energy Metabolism of Sheep. 



No. 45, April, 1931 — The Heat Production of Sheep under Varying Conditions. 

 No. 52, June, 1932 — An Automatic Method of Collecting Solid and Liquid 



Excreta from Cows in Digestion Balances. 

 No. 64, May, 1936 — The Heat Production of the Sheep and Pig before and 



after Castration. 

 No. 66, July, 1936— Basal Metabolism of the Goat. 



No. 75, June, 1941 — Traits that Determine the Efficiency of the Pig as a 



Transformer of Energy, 



* Also published in French: A. M. Leroy. Une chambre respiratoire pour animaux domes- 

 tiques de grande taille. Bulletin de la Societie Scientifique D'Hygiene Alimentaire Vol, 

 19:500-523. 1921. 



