15 



disease-free sources, and the owner of this flock bought hatching eggs 

 from a disease-free source, but made the mistake of having Ihem custom 

 hatched by a hatcheryman who, according to our records, did not have 

 his own flock tested. 



The remaining 15 owners either purchased their stock from known 

 infected sources, or imknown sources, or a combination of infected and 

 non-infected sources. Two flocks included in this group are of particular 

 interest. One poultryman had both White Rocks and Barred Rocks. The 

 White Rocks were purchased from known disease-free sources in Mass- 

 achusetts and were non-reacting to the agglutination test. The Barred 

 Rocks were purciiased from a well-known Barred Rock breeder in another 

 state. One of the authors has had opportunity to examine chicks and 

 test several groups of Barred Rocks from this same source, and in every 

 instance infection has been found. The second flock belongs to a poul- 

 tryman who purchased Barred Rocks from known, disease-free sources in 

 Massachusetts, and Rhode Island Reds both from known infected and from 

 unknown sources. The Barred Rocks were without infection, while the 

 Rhode Island Reds had several reactors reported among them. 



Of the 21 flocks with previous testing histories, 11 were 100 per cent 

 tested, and 10 less than 100 per cent tested. All but three of the 21 

 flocks had been tested for two or more consecutive years. Only one of the 

 entire group had been previously reported as non-reacting. The probable 

 cause of infection in this flock was the change of breeds. White Leghorns 

 were introduced, and there was 33 per cent infection in the White Leg- 

 horns, while the Barred Rocks, which had previously been non-reacting, 

 had 2.21 per cent infection. 



None of the 21 flocks had retesting histories until 1928-29. In three of 

 the group having 12.99, 14.66, and 23.42 per cent infection, respectively, 

 on the first test, this was reduced to less than 10 per cent on the second 

 test. None of the three had more than one retest. 



Summarizing the discussion on the 6 to 10 per cent infection group, the 

 histories of the flocks in this group are not different from those in the 

 groups above 10 per cent. The majority of the flocks came from infected 

 sources, or have not been following an intensive retesting program. As 

 has been mentioned previously, it is almost impossible to eliminate the 

 disease by a single test in a year. 



Eleven to Fifteen Per Cent Infection 



Tliere were 19 flocks that had from 11 to 15 per cent infection. Twelve 

 of these flocks were tested for the first time in the 1928-29 season, while 

 seven had earlier testing histories. All but one of the 12 originated either 

 from known infected sources, from unknown sources, or from a combin- 

 ation of known infected and non-reacting sources. The owner of the one 

 flock which originated from two non-reacting sources, has furnished no 

 history indicating whether or not infection was on the premises when the 

 stock from non-reacting sources was added. 



Of the seven flocks with previous testing histories, three were 100 per 

 cent tested, and two of the three have been tested consecutively for two 

 or more years; while five were only partially tested. None of these flocks 

 had been retested previous to 1928-29, and all but one, that had been 

 tested consecutively, had infection at the last previous test. One flock 

 which was negative in 1927-28, but infected in 1928-29, had added birds 



