AIR AND VENTILATION 



85 



may be supplied. Given a warm, comfortable and dry bed, a 

 sufficiency of food and a rug or two if necessary, the temperature 

 of the stable may be ignored however low it may fall, provided that 

 wind is shut off. Under these conditions and with free ventilation 

 cold air can do no harm. What does harm is cold air so entering 

 a stable or byre as to cause a draught. 



It is impossible to raise the temperature in animal quarters 

 by restricting the ventilation without at the same time causing an 

 increase in both the absolute and relative humidity, as animals are 

 continually discharging moisture from their bodies into the atmos- 

 phere, and there is always a potential source of moisture on the floor 

 in urine and in the faeces. If the ventilation is inefficient the air 

 becomes surcharged with moisture and the relative humidity raised. 

 For mankind it is considered that the optimum degree of humidity 

 lies between 70 and 80 per cent, of the maximum that it could hold 

 at any temperature. This probably applies equally to animals. 

 Spiers,* when investigating during the winter months the influence 

 of temperature on milk yield, found that in a set of freely ventilated 

 byres the relative humidity ranged 80 to 94 per cent., and that in 

 another set of buildings where the ventilation was restricted it 

 ranged from 85 to 96 per cent, the average for the former was 88-3 

 and for the latter 92-7 per cent. Undoubtedly in many byres the 

 air is practically saturated with moisture. 



The atmosphere in a building heavily laden with moisture is 

 stagnant and oppressive, and it holds a greater amount of organic 

 matter than does drier air. 



The effect on the animal body of an excessively humid atmos- 

 phere is the prevention of free respiratory and cutaneous outlet 

 of waste heat and products of metabolism. Under such conditions 

 health is impossible. 



When the temperature of the air in a building is appreciably 

 lower than that of the animals, there is a loss of body heat by radia- 

 tion and convection. This loss lessens as the temperatures approxi- 

 mate. Evaporation of moisture from the body can only take place 

 when the surrounding atmosphere is unsaturated. 



The fatter the animal or the more intensively it is fed, the 

 greater is the metabolism and the greater need for facility to elimin- 

 ate waste products. The fatter the animal the less able is it to with- 

 stand high temperatures as fat is a bad conductor of heat. 



Warmth with humidity is above all conditions to be avoided; 

 unquestionably this combination is the greatest evil in badly ventil- 

 ated animal houses. 



* Trans. High, and Agric. Soc., 1909. 



