Modeling latent variables of body size, hump development, and thoracic capacity in dromedary camels (Camelus dromedarius): a confirmatory factor analysis approach.

This study modeled body size (BS), hump development (HD), and thoracic capacity (TC) as latent variables using confirmatory factor analysis (CFA). The latent variables were computed using records of nine morphometric traits from 136 adult camels reared in southern Kerman Province, Iran. The morphometric traits were body length (BL), height at withers (HW), height at hump (HH), abdominal girth (AG), hump girth (HuG), hump width (HuW), hump length (HuL), chest girth (CG), and chest depth (CD). A three-factor CFA model comprising BS (4 indicators), HD (3 indicators), and TC (2 indicators) was fitted using robust maximum likelihood estimation (MLR) in the lavaan package of R. The comparative fit index (CFI = 0.96), Tucker-Lewis index (TLI = 0.92), root mean square error of approximation (RMSEA = 0.07), and standardized root mean square residual (SRMR = 0.06) indicated acceptable model fit. HuW and HuL exhibited the strongest phenotypic association (r = 0.77, P < 0.001). The most representative indicators of BS were BL and AG, whereas HuL and HuW showed the highest loadings for HD. BS was positively correlated with HD (r = 0.43, P < 0.001) and TC (r = 0.68, P < 0.001), while the relationship between HD and TC was not significant (r = -0.13, P = 0.13). The proposed latent variable framework may contribute to improved phenotypic characterization and provide useful information for future breeding and selection programs in dromedary camels. However, given the moderate statistical power for detecting small correlations, confirmation in larger samples is warranted.