Genetic and phenotypic relationships between chick quality and some yield characteristics in japanese quail

The one day old chick quality is the great economic importance as it directly affects the quantity of salable products. In commercial production, the chick quality is determined by some quantitative and qualitative methods.Tona and Pasgar score methods which are among qualitative methods have attracted the attention of researchers in recent years. In this study, using the Tona and Pasgar score methods in one-day-old chicks in Japanese quail, it was aimed to determine the quality scores and other yield characteristics, their estimates of heritability, genetic and phenotypic relationships among them. In the literature, there are no studies on the heritability estimates of the values obtained from the determination of the chick quality by the qualitative methods for poultry species, their yield characteristics and the genetic relationships between them. In the research, 867 quail obtained from 42 male and 126 female breeder quail, which have not been subjected to any selection before, constituted the animal material of the experiment. Chicks from hatch were waited until they dry and then the wing number was attached and then chick quality scores were determined using Tona and Pasgar methods. Pedigree records were created with the wing numbers attached to the chicks, all weekly weighing from hatch to eighth week age and slaughter-carcass measurements performed at the age of eight weeks were obtained individually during the trial using these wing numbers.The growth curves of quail were analyzed by Gompertz nonlinear regression function. In the study, the mean quality scores of the daily quail chicks using Tona and Pasgar score methods were found to be 98.69 and 9.80, respectively. Body weight averages from hatch to eighth week age were also found as 8.06, 22.77, 36.45, 55.48, 76.36, 95.05, 114.59, 132.51, and 150.71 g, respectively. While the averages for the β0, β1 and β2 parameters of the Gompertz model were found as 253.25, 3.25, 0.038, respectively. The average values for the inflection point age and weight of the model were 35.60 days and 93.37 g, respectively. In the trail, the average weight of quails slaughtered at the age of eight weeks old was found as 108.27, 3.77, 1.44, 3.22, 1.62 and 8.44 g. Cold carcass weight average is 112.89 g, breast, leg and back-neck weight averages are 42.98 g, 25.94 g and 33.41 g respectively. In the study, the average of hot carcass yield was 71.79 % and the average value of cold carcass ratio was 74.86 %. For the chick quality characteristics determined by the Tona and Pasgar score methods, the heritability levels estimated by both the single-trait method and the multi-trait method were found to be low and were 0.08 and 0.09, respectively. The heritability estimates of Japanese quail chicks from hatch to eight weeks age were found to be 0.41-0.40; all of the heritability estimates for the weekly live weights (0.42-0.58) are high. Similarly, moderate to high levels of haritability are estimated for the weights of hot carcass, cold carcass, edible internal organs and carcass parts, while the estimated heritability for abdominal fat weight was low. Genetic relationships of chick quality traits with other yield traits were also low and estimated between -0.10 and 0.10. In addition, the fact that the phenotypic and genetic correlation coefficients between the values obtained by Tona and Pasgar methods at one day age were found positive and strong (both 0.82) showed the consistency between the results obtained by these measurement methods. Considering the results obtained from the study, it is not possible to say that there are not statistically significant relationships with the quality of chicks and most of the yield characteristics in Japanese quail. It is thought that it is difficult to add to the selection indexes in genetic improvement studies, since the chick quality characteristics determined by Tona and Pasgar methods have a very low level of heritability. When the variation that occurred for the chick quality trait was examined, 4.06 % of the total variance for the Tona score of the total variance and 4.48 % of the total variance for the Pasgar score were found to be 95.94 % and 95.52 %, respectively. In this case, instead of using the breeding value of this trait in order to improve the chick quality in these breeding studies, it may be advised to focus on improving environmental conditions such as humidity temperature affecting chick quality.