June i, 1921 
Some Fundamentals of Stable Ventilation 
349 
investigators on this subject (3, p. 312) shows that the critical external 
temperature for the horse is high as compared with that of ruminants, 
so that a ration which is sufficient for maintenance in summer may be 
insufficient in winter. The critical temperature for swine has been like¬ 
wise found to be comparatively high (68° to 73 0 F.), which means that 
exposure to low temperatures may be expected to increase the actual 
maintenance ration and the heat production of swine, and this has been 
confirmed by experimental results. On the other hand, the results on 
cattle seem to indicate that their critical temperature is rather low 
(much below 56°), which means that cattle can be exposed to lower 
temperatures than horses or swine before their maintenance require¬ 
ment will be affected and their heat production stimulated. 
EFFECT OF LOW THERMAL SURROUNDINGS ON PRODUCTIVE FEEDING 
The production of meat or milk implies the consumption of large 
quantities of feed. Since the latter is the source of a large amount of 
heat, due to the “work of digestion,” which has to be removed at a cor¬ 
respondingly rapid rate, it appears that heavy producers are better 
adapted to relatively cold thermal surroundings. Furthermore, since 
it is the aim in feeding such animals to induce them to eat as much 
feed as can be economically converted into useful products, it seems 
desirable, on the one hand, that the thermal surroundings should be 
low in order to maintain the appetite of the animals and, on the other, 
not so low as would cause wasteful oxidation for simple heat production. 
The question whether winter feeding for fattening can be accom¬ 
plished to better advantage in the stable than in the open shed has 
interested many investigators, and a considerable amount of experi¬ 
mental work is on record. The results (1) show in general that cattle 
are best adapted to exposure—that is, they produce as good results when 
exposed as when stable fed. Swine are least adapted to exposure, the 
gain of the animals exposed to severe weather being frequently negative, 
while sheep seem to take an intermediate place. These results are in 
full harmony with the findings given above as regards the critical temper¬ 
ature. Less decisive results have been obtained with dairy cows, but 
it appears fairly well established that for well-fed animals the need for 
warm stables has been somewhat overemphasized. 
optimum stable) temperature 
Both theoretical considerations and the results of experience show 
that a certain excess of heat production over that absolutely required 
to maintain the body temperature is likely to be advantageous, both by 
promoting the comfort of the animal and as providing a margin of safety. 
On the other hand, an unnecessarily high temperature tends to affect 
the appetite and general health of the animal. From this it follows that 
the best thermal surroundings for animals lie between these limits— 
