1909.] Summary of Agricultural Experiments. 755 



contains less than '01 per cent., the source of the boric acid is to be 

 looked for in the food of the cow, whilst between 'i and *oi per cent, 

 the origin would be uncertain. 



Milk Sampling. — (Durham C.C., Education Com., Offerton Bull., 

 No. 3). — Careful experiments were made on the variation in the com- 

 position of the milk due to sampling. The changes which take place 

 even within a short time owing to the cream rising were very marked. 

 Thus in hot weather a sample from the top of a churn which had stood 

 a quarter of an hour, contained 7*25 per cent, of fat, while one from 

 the bottom of the churn contained only 2*27 per cent. At the end of 

 an hour the variations were still more marked. In cool weather, 

 however, the change was much less rapid. 



Influence of Temperature on the Milk Yield. — (Highland and 

 Agric. Soc. Transactions, Fifth Series, vol. xxi., 1909). — It has been, 

 and still is, a common belief that milk cannot be profitably produced 

 in our climate in winter unless the cows are kept warm. This 

 warmth, however, is only secured by the exclusion of fresh air, the 

 temperature being raised by the heat from the animals' bodies, with 

 the result that the air becomes much polluted. It was pointed out 

 that this was likely to be injurious to health, and experiments were 

 therefore undertaken under the direction of the Highland and Agricul- 

 tural Society for the purpose of testing by accurate records the influence 

 of free and of restricted ventilation on the milk yield of cows. 



The experiments were carried out on five farms with 100 cows in 

 all, divided into two lots on each farm. One lot on each farm was 

 kept in a freely ventilated byre, and the other lot in a byre without any 

 special system of ventilation. Arrangements were made for the milk to 

 be weighed and sampled, and for recording' the temperature and the 

 moisture of the air, for testing the carbonic acid in the air, and for 

 taking samples of the air for chemical and bacteriological examination. 



The conclusions which may be drawn from the results at this stage 

 of the enquiry suggest that fresh air is a much more important factor 

 in the production of milk in mid-winter than is generally supposed, 

 but in order that the greatest advantage may be derived from the fresh 

 air, the animals should at no time have the ventilation restricted in 

 autumn, but should be kept as cool as possible, so that they may not 

 only retain all their hair, but, if necessary, increase it. There is no 

 difficulty, much less impossibility, in producing milk in freely-ventilated 

 byres in the coldest weather likely to be met with in this country, if 

 the cows are allowed free ventilation and kept sufficiently cool in early 

 autumn. 



The experiment showed that rather more milk was produced under 

 conditions of free ventilation than where ventilation was restricted, but 

 this may not invariably happen. The percentage of fat was about the 

 same. 



Any saving in food which is effected by keeping the animals at a 

 higher temperature is equalled, if not exceeded, by improved digestion 

 when they have plenty of fresh air but a lower temperature. 



There is reason to believe that both mammitis and tuberculosis may 

 be reduced to a minimum if cows are kept in freely ventilated byres 

 in winter. . 



Variations in the Composition of Milk. — (Dumbarton C.C., Report 



3 G 2 



