General and specific combination abilities of live weights in japanese quail (coturnix coturnix japonica) lines with diallel crossbreeding

In this thesis, the growth characteristics of four different Japanese quail (Coturnix coturnix japonica) lines, distinguished by feather color, were studied. The aim was to examine the growth traits, genetic parameters, and combination abilities of the hybrids formed through diallel crossbreeding. For this purpose, the research was conducted using Japanese quail lines from the Poultry Breeding Unit within the Agricultural Research and Application Farm of Isparta University of Applied Sciences, Faculty of Agriculture. In the study, the parent quail were crossbred using the Griffing diallel crossbreeding method. Following the diallel crossbreeding analysis with the Griffing method, the general and specific combining abilities between lines with different feather colors were evaluated. The weekly live weights of the parents and hybrids were examined, and growth performance was analyzed using the Gompertz growth curve model. Additionally, additive and non-additive genetic effects were evaluated by estimating genetic parameters. As a result of the study, specific combining ability (SCA) and general combining ability (GCA) were analyzed, and the superiority of different lines was determined along with the heterosis effects. Based on the results obtained in the study, the highest average live weights for all weeks were obtained from the white feather color (BEY) parent population (the averages for 4 and 5 weeks of age were 246.40 and 295.68 g, respectively). Furthermore, according to the results of the diallel crossbreeding, the best crossbreeding combinations were found to be those made with the BEY line. These results support the preference for the BEY line and its hybrids in terms of meat yield in quail farming. In the study, the BEY genotype exhibited the highest positive GCA values across all age groups and showed the best performance in terms of live weight. The other genotypes (SAR, SIY, and YAB) generally showed negative GCA values. SCA, on the other hand, produced the highest values from combinations of BEY x SIY, BEY x SAR, and BEY x BEY. Additive genetic variance was found to be high for all weeks, with additive genetic effects being dominant on live weight. Maternal effects were found to be statistically significant in some age groups, but their overall contribution was limited. The estimated narrow-sense heritability (h²) values ranged from 0.55 to 0.74, while the broad-sense heritability (H²) values ranged from 0.67 to 0.81. This study provides valuable information for genetic breeding programs and offers suggestions to enhance the commercial potential of Japanese quails. Keywords: Japanese quail, Griffing diallel crossing, General and specific combining ability, Genetic parameters, Gompertz model, Heterosis.