26 MASS. EXPERIMENT STATION BULLETIN 344 



SUMMARY 



Three lines of Rhode Island Reds with respect to egg size were carried 

 through nine generations to study the genetic behavior of egg weight, egg 

 shape, shell texture, shell porosity, and shell pigmentation. Some of the more 

 important deductions made were as follows: 



Part I. Egg Weight 



1. Egg weight to January first was a very good criterion of prospective egg 

 weight in February or March. The mean egg weight to January first should 

 not fall below 53 grams (22.5 ounces to the dozen) if 56.7-gram eggs (24 ounces 

 to the dozen) are expected in February or March. 



2. Winter egg weight showed an intimate correlation with both hatching- 

 season egg weight and annual egg weight, with strictly linear regression. 



3. Hatching-season (February and March) egg weight was intimately cor- 

 related with annual egg weight. The data showed that birds averaging 56.7- 

 gram eggs (24 ounces to the dozen) for the full year should lay eggs weighing 

 about 58.2 grams (24.7 ounces to the dozen) in the hatching season. 



4. The basis for selecting breeders did produce a significant difference in 

 hatching-season and annual egg weight between line A and lines B and C, but 

 not between line B and line C. 



5. In all three lines, maximum egg weight occurred in March, or at a mean 

 age of about eleven months. 



6. The mean annual egg weight was significantly greater in line B than in 

 lines A or C and slightly greater in line C than in line A. 



7. The data in general indicated that there is no advantage in selecting for 

 hatching purposes, pullet eggs that weight more than 26 ounces to the dozen. 



8. Most satisfactory breeding females for large eggs were those attaining 

 standard egg weight within sixty days. 



9. Egg size depends in inheritance upon three dominant genes A, B, and C. 

 Gene A is epistatic to both B and C and produces small eggs. Either gene B 

 or gene C gives an egg weight above 24 ounces to the dozen in the normal 

 hatching season. Genes B and C acting together give very large egg size. 



Part II. External Egg Characters 



1. Ridged shell condition is not inherited, but the sandy shell character does 

 depend on recessive genes. 



2. High shell porosity depends largely on one recessive gene (po). 



3. Available data do not indicate that egg shape is governed by inheritance. 



4. Shell flecking is probably independent of inheritance. 



5. Multiple factors are concerned in shell pigmentation. Eight shades of 

 color were observed ranging from white to vinaceous cinnamon. From the 

 white or near white there was a gradation to pinkish tints and from pinkish 

 tints to brown tints. 



6. A shade of color near light pinkish cinnamon or light vinaceous cinna- 

 mon is probably most desirable, and females laying such eggs gave very few 

 daughters laying light colored eggs. 



