100 percent tested and nonreacting contained 917,521 or 97.10 percent of the total ' 

 birds tested. All tested breeding flocks were classified as negative at the termina- 

 tion of the season. 



During the past year 79, or 29.37 percent, of the flocks tested in 1957-58 were 

 not tested. Annual testing of breeding flocks is required by the National Poultry 

 Improvement Plan and by the Massachusetts Department of Agriculture. If a flock 

 owner finds it necessary to discontinue the production of hatching eggs for his own 

 replacements, he should make certain that stock is obtained from an officially 

 clean source for his replacement flock. 



APPEARANCE OF INFECTION IN FLOCKS PREVIOUSLY NEGATIVE 



Fortunately, no infection was detected in tested flocks that had been negative 

 the previous season. Table 3 lists the incidence of "breaks" among Massachusetts 

 tested flocks during the past 18 years. Flock owners and hatcherymen should ob- 

 serve constantly the strictest vigilance against the introduction and spread of the 

 disease. 



Table 3. Incidence of "Breaks" Observed During the 

 Past Eighteen Years 



Flocks with Less than 

 0.5 Percent Infection 



The following measures have been effective in establishing and maintaining a 

 pullorum-free flock. 



1. All the birds on the premises should be tested each year. 



2. If infection is present, the entire flock should be retested within four to six 

 weeks until a negative report is obtained, provided the value of the birds justifies 

 the expenditure. 



