234 Influence of Ventilation on Milk Yield, [june, 



average proportion of carbon dioxide in the air was thirty 

 parts in 10,000, while in the latter, with an average tempera- 

 ture of 49 0 F., varying from 32 0 to 65 0 , the proportion was 

 fifteen parts. It may be added that the difference in the degree 

 of ventilation was very noticeable in practice ; and the sensa- 

 tions of an ordinary observer would have led him to expect a 

 more considerable contrast than is shown by these figures. 

 Yet in spite of this the bad ventilation was by no means ex- 

 ceptional, and it is stated that even the worst ventilated of 

 these byres would have seemed cooler and better ventilated 

 than a large number in use throughout the country. 



The influence of temperature on milk-yield was not 

 specially considered, as no attempt was made to combine free 

 ventilation with a good temperature kept up by artificial 

 heat. The point investigated was whether in practice it 

 would not be better to ventilate cow-houses freely in winter 

 and ignore the necessarily lower temperature produced, and 

 the result is definitely in favour of ventilation. A com- 

 parison of the quantity of milk produced under the two 

 systems showed that the production of milk can be carried on 

 at least as profitably in byres ventilated down to 50 0 F. as in 

 those in which the temperature is kept ten degrees higher 

 by bad ventilation. 



Incidentally it has been brought out — 



(1) That any restriction of ventilation sufficient to bring 

 the temperature of a byre up to 6o° F. leads to a degree of 

 atmospheric impurity inconsistent with conditions of perfect 

 health. 



(2) That in byres in which the temperatures have been kept 

 down by thorough ventilation in autumn, cows do not suffer 

 either in health or milk yield even from very low temperatures 

 in winter. 



(3) That whatever waste of food may be entailed in the 

 maintenance of the body-heat of cows in colder byres is more 

 than counteracted by the influence of fresher air; while it is 

 evident that the health of animals is much more likely to be 

 promoted by active digestion than by the mere prevention 

 of loss of body-heat. It should also be observed that the 

 colder temperature in autumn causes the cows to grow and 

 retain thick coats of winter hair; so that it is not even certain 

 that the body-heat is better conserved in the less ventilated 



