8 MASS. EXPERIMENT STATION BULLETIN 312 



SUMMARY 



1. Three inbred lines were established using the following standard in the 

 selection of female breeders: 



Sexual maturity — 215 days or less. Broodiness — none during the pullet 



Weight at first egg — 5 pounds or over. year. 



Winter pause — not over 4 days. Persistency — 315 days or more. 



Winter clutch size— 2.6 or over. Hatchability — 85 per cent or more. 



Egg weight — a minimum average of 52 grams to January 1. 



Range mortality — not above 10 per cent in family. 

 Check females were selected each year from the general flock according to these 

 standards and were mated to the inbred males. Female offspring from the 

 most desirable families were retained and trapnested for a full year. One of 

 the inbred lines failed to give any satisfactory breeding females in the third 

 generation and was discontinued. The other two inbred lines were intercrossed 

 in 1932 and 1933 and also bred as such. 



2. Inbreeding increased range mortality, retarded sexual maturity, increased 

 the percentage of birds with winter pause, reduced intensity, had no effect on 

 broodiness, decreased persistency, reduced hatchability, increased winter egg 

 weight, consistently reduced annual egg production without reducing its variabil- 

 ity, and increased laying-house mortality. 



3. Crossing inbred lines decreased range mortality in the first cross only, 

 hastened sexual maturity, reduced the proportion of birds with pause, greatly 

 increased intensity over that of the inbreds, improved persistency, increased 

 hatchability, improved egg size, raised the annual egg production level above 

 that of the inbreds but did not affect variability in egg production, and reduced 

 the laying house mortality rate over that of the inbreds. 



4. In no respect were the inbreds or inbreds crossed found to be superior 

 to the general flock. Apparently nothing is to be gained from the standpoint 

 of fecundity by inbreeding. 



REFERENCES 



Dunkerly, J. S. 1930. The effect of inbreeding. Proc. Fourth World's Poultry 



Cong. p. 46. 

 Dunn, L. C. 1923. Experiments on close inbreeding in fowls. Conn. Agr. 



Expt. Sta. Bui. 111. 

 Hays, F. A. 1924. Inbreeding the Rhode Island Red Fowl with special refer- 

 ence to winter egg production. Amer. Nat. 58:43-59. 

 Hays, F. A., and Ruby Sanborn. 1927. Intensity or rate of laying in relation to 



fecundity. Mass. Agr. Expt. Sta. Tech. Bui. 11. 

 Hays, F. A. 1929. Inbreeding in relation to egg production. Mass. Agr. 



Expt. Sta. Bui. 258. 

 Hays, F. A. 1933 a. Relation between body weight and age at sexual maturity. 



Poultry Sci. 12:23-25. 

 Hays, F. A. 1933 b. Characteristics of non-broody and intense broody lines of 



Rhode Island Reds. Mass. Agr. Expt. Sta. Bui. 301. 

 Jull, M. A. 1933. The effects on various characters of close inbreeding and of 



intercrossing inbred lines of White Leghorns. Jour. Heredity 24:93-101. 



Publication of this Document Approved by Commission on Administration and Finance 

 3M-10-'34. No. 2621. 



