14 



partly from negative sources, and partly from infected or unknown 

 sources. The one flock which originated from a non-reacting source had 

 1.26 per cent infection. No information was obtained in regard to earlier 

 condition of the plant, or whether or not poultry had been kept on the 

 premises previous to the addition of stock from non-reacting sources. 



To emphasize the need for buying stock from non-reacting sources, and 

 to show the danger of introducing infection into flocks by adding birds 

 from unknown or untested sources, a few interesting examples are dis- 

 cussed. One flock having two breeds had 1.21 per cent infection among 

 the Rhode Island Reds, which came from a disease-free flock; and 10.09 

 per cent infection among the White Leghorns, which came from a flock 

 with no testing history. 



One test on a flock of Barred Rocks and White Wyandottes showed 

 no infection in the White Wyandottes, and 4 per cent infection among the 

 Barred Rocks. The White Wyandottes came from a non-reacting source, 

 while the Barred Rocks came from one which was known to have had in- 

 fection in 1927-28. 



A third flock consisting of Rhode Island Reds and Barred Rocks had 

 infection among the Rhode Island Reds, which originated from a source 

 that had an outbreak of the disease in 1927-28. The Barred Rocks, which 

 came from a known, disease-free flock, were without infection. 



In the group of 29 having previous testing histories, 16 were 100 per 

 cent tested, and 13 were partially tested. All but two of the 29 flocks 

 were tested in 1927-28. In the group wliich iiad been tested in 1927-28, 

 two of the partially tested flocks and one of the 100 per cent tested 

 flocks were non-reacting in 1927-28. No history was available on one of 

 the partially tested flocks, but the other had been sold since the previous 

 test and untested birds were added to this flock by the new owner. Like- 

 Vtise no history, which would indicate the reason for the infection in 

 the 100 per cent tested flock in 1928-29, has been obtained. Again, the 

 importance of annual 100 per cent testing is shown. 



Two of the flocks had previous retesting histories, though neither of 

 them retested long enough to obtain a non-reacting report. One of these 

 flocks had a total of seven reactors left in it from 1927-28 until the 

 1928-29 test. The other flock was retested by the so-called pen method 

 (llie infected pens only retested), which has not proved successful. 



The two flocks which were not tested in 1927-28 were only partially 

 tested at an earlier season. One was non-reacting in 1925-26, and no 

 history was obtained regarding what took place in the flock from that 

 season until the 1928-29 test. The second flock having intermittent 

 testing history had infection at the previous test in 1924-25. 



The classification of seven flocks in the 1 to 5 per cent group was 

 based upon the results of retesting. Four of the seven had over 20 per 

 cent infection on the original test in 1928-29, and three had between 5 

 and 10 per cent infection. By one retest on these flocks the infection 

 \sas reduced to less than 5 per cent. 



Six to Ten Per Cent Infection 



There were 37 flocks that had from 6 to 10 per cent infection. Pre- 

 vious testing records are available on 21 of these flocks, while 16 were 

 tested for the first time. Nine of the 16 were partially tested, and seven 

 were tested 100 per cent. Only one of the 16 originated from known 



