178 EXPERIMENT STATION EECOED. 



DAIRY FARMING— DAIRYING. 



Milking machines: EfEect of method of handling on the germ content of 

 the milk, H, A. Harding, J. K. Wilson, and G. A. Smith {New York ^tate Sta. 

 Bill. J/7, 2)1). 25S-2!)2, i)ls. //). — This bulletiu repoi'ts original iuvestigatious 

 witli uiillcing niacbiiios and reviews other Investigations, on the same subject. 



The point that is emphasized by these studies is that the quality of milli 

 obtained from the milking machine depends largely upon its care and manipu- 

 lation. " The most important item in this connection is the careful immersion 

 of the milking parts in a brine or similar solution between milkings. This has 

 been shown to be many times more efficacious than the most careful steaming. 

 While there is room for improvement in this particular, a 10 per cent solution 

 of common salt is fairly satisfactory for immersing the tubes. The limit to 

 which the germ content of the milk can be reduced turns largely upon the 

 efficiency of the air filters and these have varied widely upon the different 

 types of machines which have been studied." 



The trials with the Globe milking machine in 190G did not remove all of the 

 milk and the bacterial count was abnormally high. Later trials, reported in 

 this bulletin, were with the B-L-K machine. 



AVhen the teat cups and rubber parts were immersed in a 10 per cent salt 

 solution between milkings the number of germs per cubic centimeter averaged 

 17,086; when not so immersed, 188,580. An inspection of the tubes in the 

 preliminary work showed that they contained air in considerable quantities. 

 Thereafter the condition of the tubes was inspected at 10 o'clock each day on 

 which samples were to be collected at the night milking, and the air which was 

 practically always found in the tubes was expelled. Later an attempt was 

 made to measure the effect of allowing air to remain in the tubes, and it was 

 found that when the air was excluded the count was 1,990; when left in the 

 tubes, 4,740. 



In experiments with cotton filters when the vacuum was broken at the 

 stanchion cock the germ content on the suction filter side was 19,856, and on 

 the other side 8,290. Without the filter the figures were 51,600 and 12,650, 

 respectively. In using cotton filters when the vacuum was broken through the 

 teat cocks the germinal count on the filter side was 4,383 ; on the other side 

 7,764. Without the filters the counts were 10,758 and 7,177, respectively. 

 These results indicate that the larger suction filter is .capable of removing the 

 germs from the air which rushes in at the time the stanchion hose is removed 

 from the stanchion cock. 



Later experiments were made with a new type of machine in which no 

 unfiltered air w-as admitted to the milk chamber, and in l^e relief filters the 

 cup for cotton was much larger than in the type used in the previous experi- 

 ments. With this machine the average bacterial count was 3,210 as compared 

 with 8,340 with the older type. Two later machines were tested which differed 

 from the preceding form in that they did not have a relief filter on the dome 

 of the milking machine, and the relief filters at the teat cup connectors had 

 correspondingly larger openings for the entrance of air. In one of the ma- 

 chines the filter was in the form of a cone, which admits the air into the teat 

 cup connector in front of the opening coming from the forward pair of teats. 

 The filtering cotton was prevented from entering this cone by a perforated 

 sheet of metal. The object of this change was to equalize the milking action 

 of the 4 teats. The test was intended to determine whether this change in form 

 influenced the filter action when the capacity of the filter remained constant. 

 The results were slightly better on the average with the filter supplied with 

 a coue, but the difference was not marked. 



