38 BULLETIN 642, U. S. DEPARTMENT OF AGRICULTURE. 
THE THREE MOST ESSENTIAL FACTORS IN THE PRODUCTION 
OF MILK OF LOW BACTERIAL CONTENT. 
In connection with the term “ production of milk” as used in this 
paper, it is evident that there are three essential factors which most 
influence the bacterial content. Named in the order of their im- 
portance they are, first, the use of sterilized utensils; second, clean 
cows, particularly the udders and teats; third, the use of the small- 
top pail. By the use of these factors it has been possible to produce 
milk of a low bacterial count and practically free from visible dirt 
in an experimental barn which represents a poor type found in this 
country. In fact, the counts obtained were so low that only 2,000 to 
3,000 bacteria per cubic centimeter were introduced through external 
contamination. A large number of factors not considered in this 
paper are responsible for this contamination. Some of them have 
been extensively studied by Stocking (1), Harding (9), Ruehle (10), 
and Prucha (11). 
It is evident, therefore, that the three simple factors mentioned 
prevent most of the contamination of milk. It is possible, however, 
that under some circumstances low-count milk can not be produced 
by means of these few factors. It has been shown that they prevent 
most of the external contamination and that by their use it is possible 
to produce milk with a bacterial content very nearly as low as that 
drawn directly from the udder. If milk drawn directly from the 
udder is high in bacteria, it 1s impossible under any conditions to 
produce a low-count milk. 
It is well known that freshly drawn milk from some cows is some- 
times high in bacteria; if there are, therefore, a number of such cows 
in a herd, the bacterial content of the mixed milk will be relatively 
high. Asan example it may be well to mention a case in which milk 
produced in a sanitary barn from clean cows and with sterilized 
utensils averaged 5,096 bacteria per cubic centimeter for 28 samples. 
In the herd there were cows whose milk occasionally was abnormal, 
in that it contained a few small clots and the last milk sometimes was 
slightly stringy. The milk from these cows was kept separate from 
the regular herd milk, with the result that 28 samples of it, produced 
at the same time as the other samples, averaged 137,786 bacteria 
per cubic centimeter. It is therefore evident that with cows of that 
type it would be impossible under any conditions to produce a low- 
count milk. 
It is not known how common such cows are in this country, and 
the point is mentioned merely to show why it is sometimes impossible, 
even with the three essential factors, to produce milk of low bac- 
terial count. 
The criticism may be raised that the value of the essential factors 
was determined under experimental conditions which do not repre- 
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