238 MASS. EXPERIMENT STATION' BULLETIN 257 



dish and 2 or 3 cc. of vaccine were taken, and so on until all birds were 

 vaccinated. A number of brushes were kept at hand and used alternately, 

 with each group of 35 to 50 birds. 



About the third or fourth day after vaccination the majority of the 

 follicles showed a slight swelling which gradually became more pronounced, 

 until on the eighth to tenth day after vaccination, individual follicular scabs 

 began to de\elop which later becanie coalesicent in most of the cases. The 

 sca^bs began to drop off on or a,bout the eighteenth to twentieth day after 

 vaccination, and were usually entirely gone by the twenty-eighth to thirty- 

 first day. At this time the inmiunity was complete. 



The cutaneous vaccine should not be used in a flock unless the disease 

 was prevalent in former seasons and it is reasonably certain that it will 

 appear again. All the young stock on the premises should be vaccinated. 

 The cutaneous vaccine is unattenuated and, therefore, will serve to introduce 

 the infection to unvaccinated, susceptible birds by contamination of litter, 

 feed, water, etc. Yearlings or older birds may or may not be treated. As 

 a rule, they have developed a resistance against the disease during a pre- 

 vious outbreak. 



Preventive Flock Vaccination and Its Effect on Early Egg Production 



During the last four years opportunity has been given to study fowl pox, 

 aivian diphtheria, roup, and colds as they occurred in the spontaneous or 

 natural form in the two flocks maintained at this institution. These out- 

 breaks have occurred annually during this period at a time when egg pro- 

 duction was at its peak. Pens would drop in total egg production to an 

 alarming degree. This also occurred in other flocks throughout the State, 

 The economic situation was serious. An imposing annual loss and disar- 

 rangement of breeding programs were necessarily anticipated from year to 

 year. Experimental vaccines, bacterins (8), and one conunercial vaccine had 

 been used in several of these flocks with some success. By late sunruner of 

 1928 such confidence had been placed in the cutaneous vaccine that it was 

 decided to use it on the two important flocks above mentioned. 



Flock 1. 



This flock, maintained by the College poultry department for teaching, 

 breeding, and commiercial purposes, contained, aside from the older stock, 

 1511 birds which were hatched during the late winter and spring of 1928. 

 They consisted for the most part of Rhode Island Reds and one or two pens 

 each of White Leghorns and Barred PljTiiouth Rocks. They were all trap- 

 nested and some were pedigreed. They were cutaneously vaccinated as they 

 were brought in from the range to the laying houses. The first lot of the 

 1511 pullets and cockerels was housed on September 5; the last lot on October 

 11. The yearlings and older birds were not vaccinated because they had 

 either gone through the disease during the previouis year or, in the opinion 

 of the writer, had developed enough resistance to withstand a natural out- 

 break of the infection. 



The birds were first bled for the detection of pullorum disease {Salmon- 

 ella pullorum infection) bj^ means of the agglutination test as they were 

 taken from the crates. Next they were handed to the operator who vac- 

 cinated them. After this they were placed in the laying pens. A varying 



