GENETIC-PARAMETERS FOR EGG NUMBER, EGG WEIGHT, AND EGGSHELL COLOR IN 3 CATALAN POULTRY BREEDS

Heritabilities for egg number, egg weight, and eggshell color (percent age light absorbance) at 39 wk of age, and the genetic correlations be tween them were estimated by restricted maximum likelihood in three Ca talan poultry breeds: Penedesenca Negra (PN), Prat Lleonada (PL), and Empordanesa Roja (ER). Additive genetic differences between these bree ds were also estimated. Data were from the IRTA Poultry Genetic Conser vation Program and consisted of records from 1,309 PN, 1,466 PL, and 1 ,440 ER hens, which were obtained from 80 contemporary batches per bre ed hatched between 1987 and 1992. Estimates of heritability for egg nu mber, egg weight, and eggshell color were, 0.20, 0.59, and 0.49 for PN , 0.31, 0.18, and 0.53 for PL; and 0.33, 0.50, and 0.27 for ER. Estima ted genetic correlations between egg number and egg weight, egg number and shell color, and egg weight and shell color were, for PN, -0.22, -0.03, and 0.00; for PL, -0.21, -0.06, and 0.09; and 0.19, -0.29, and 0.30 for ER. Heritability for eggshell color and genetic correlation b etween eggshell color and other traits showed a different genetic patt ern in ER breed. Significant additive genetic differences (P < 0.05) w ere found between ER and PN base populations for egg number (3.89), eg g weight (0.91), and eggshell color (-3.50); and between ER and PL for egg number (6.69) and eggshell color (35.39). The PN and PL breeds di ffered significantly (P < 0.05) for eggshell color (38.22), which was darker in PN. These results could be taken as the expected genetic dif ferences for these breeds.