56 MASS. EXPERIMENT STATION BULLETIN 293 



for selectinsj pullet breeders to produce this last generation was the ability to lay 

 52-p;ram, 57-gram and 59-grani eggs during the month of November. Previously 

 these egg weights applied for the month of December. The daughters in these 

 three lines are mated to three full brothers of distantly related stock each year. 

 Egg size is being increased in all three lines but at a very slow rate in the 52-gram 

 group. 



DEPARTMENT OF VETERINARY SCIENCE 



J. B. Lentz in Charge 

 Poultry Disease Elimination Law. (H. Van Roekel, K. L. Bullis, O. S. 

 Flint, and Miriam K. Clarke.) During the 1931-32 pullorum disease testing 

 season, 420,861 blood samples were tested by the macroscopic tube agglutination 

 method. This number represented 377,191 chickens in 455 flocks. Among the 

 samples tested, 0.90 per cent were positive. This is the lowest percentage of 

 positive tests ever attained in this State. No positive tests were recorded in two 

 counties. In six other counties there were less than 1 per cent of positive tests. 

 The number of non-reacting flocks was increased to 355. Of these, 180 flocks, 

 representing 157,516 birds, were 100 per cent tested. No reactors were detected 

 among 1,034 birds other than chickens. These birds were distributed among 25 

 flocks. Chickens were tested on 19 of these premises, and reactors were found in 

 five of the chicken flocks. Necropsies were performed on 117 birds for 61 flock 

 owners. The necropsy service has been found valuable in determining the pull- 

 orum disease status of a flock in which only doubtful reactors are detected. 



Pullorum Disease Investigations. (H. Van Roekel, K. L. Bullis, O. S. 

 Flint, and Miriam K. Clarke.) Results of recent investigations concerning jellied 

 blood samples, susceptibility of pheasants and guinea fowl, agglutinins in young 

 chicks, avenues of infection, a comparison of diagnostic tests, and the most effi- 

 cient use of the agglutination test in eradication are reported in Control Bulletin 

 63. 



Laboratory Service - Pathology. (G. L. Dun lap and K. L. Bullis.) During 

 the year, 1,042 specimens were examined for 263 people, of whom 96 made personal 

 calls at the laboratory. The specimens were distributed as follows: — 1,013 

 chickens, 3 pigeons, 8 guinea pigs, 4 swine, 6 rabbits, 2 turkeys, 2 ducks, 1 calf, 

 and 1 mink. The diseases encountered most frequently were pullorum disease, 

 rachitis, so-called "range paralysis", parasitism, and tumors. Tuberculosis was 

 diagnosed in one turkey and in one hen. 



Farm and Station Bang Disease. In assisting this project, the laboratory 

 tested 1,371 blood samples by the tube agglutination method. 



Infectious Laryngotracheitis. (C. S. C.ibbs.) The studies on chronic 

 carriers of infectious laryngotracheitis have been completed, and 22 chronic 

 carriers have been found in approximately 1,000 birds examined by intratracheal 

 swabs. The length of time virus was eliminated by these carriers varied from 

 37 to 741 days. 



Immunity studies have been continued through the year. It has been deter- 

 mined that immunity to infectious laryngotracheitis is acquired by direct contact 

 with the causative agent and is not transmitted to the offspring, except in rare 

 instances where the hens have laid eggs for hatching while passing through the 

 acute stages of the disease. Also it has been found that infectious laryngotrachei- 

 tis is primarily a flisease of pullets and cockerels, older birds being more or less 

 immune to it. This natural resistance should not be confused with artificial 

 imnmnity. 



