DIFFERENTIAL EFFECT OF WEIGHT-CLASS AND SEX ON CORRELATION BETWEEN ZOOMETRIC TRAITS IN YOUNG JAPANESE QUAIL (Coturnix japonica)

Abstract

The present study examined whether early growth rate and sex perturb the direction of correlation between body weight and length of body parts of young Japanese quail aged 1-6 weeks. Sixty quail of mixed sexes were studied. Zoometric traits including Body weight at hatch, and Body weight, BW (g); Body length, BL (cm); Body girth, BG (cm); Wing length, WL (cm); and Shank length, SL. (cm) at age 16 weeks and their intervallic growth rates were determined. Birds were classified based on body weight growth potential in the period spanning age 0-3 weeks such that birds with a growth rate equal to or greater than I standard deviation point above the group mean were classified as "Heavy", birds with a growth rate equal to or lower than I standard deviation point below the group mean were classified as "Light", while with a growth rate between (above I standard deviation below the group mean and below I standard deviation above the group mean were classified as "Medium" weight. The sex of each bird was determined based on the appearance of secondary sexual characteristics between age 4 and 6 weeks. All zoometric trait data were subjected to Pearson's bivariate correlation analysis by use of SPSS 21 (IBM SPSS). Formal Logic arguments were used to interrogate the correlation matrixes to determine the number and percentage of instances in which there was concordance/discordance in the direction of correlation between trait pairs across Weight classes. The resulting data was subjected to Chi-squared analysis. The direction of correlation between traits was significantly (p<0.05) perturbed by sex, and weight class. There was a significant (p<0.05) bias towards concordance of the direction of correlation between weight classes and between sex classes than might be observed by chance, which points point to the operation of shared mechanisms underpinning correlation between traits across classes. Body weight class and Sex significantly (p<0.05) differentially perturbed the direction of correlation between weight classes. specifically, there was a greater tendency for concordance (in the direction of correlation) between sexes than between body weight classes. Generally, the significant (p<0.05) perturbation of the direction of correlation of body weight at each of age 16 weeks and other zoometric traits was similar in both sexes. These results reveal that the application of general notions of correlation between body weight and zoometric traits to a specific set of contexts such as sex or weight class subgroups during animal breeding or management processes is far from ideal and should be avoided as it should lead to unreliable predictions and accordingly, outcomes.