Assessment of the significance of new phenotype parameters of Russian meat merino sheep by principal component analysis

Phenotype assessment is an important process in breeding practice and for studying the influence of genes that shape the productive qualities of sheep. As a result of many years of selection and breeding work, the existing indicators fixed in the breed have lost their supposed potential, which dictates the need to search for new indicators that more accurately characterize the meat productivity of sheep. The aim of the work is to assess the informativeness of phenotype parameters in Russian meat merino sheep by the method of principal component analysis, for further use in genomic selection programs, as well as applicable for in vivo assessment of meat productivity. For the first time, new methods of assessing the exterior and interior for the study of meat productivity have been proposed and their efficiency has been determined for russian meat merino (RMM) sheep. The possibility of determining the size of individual muscle groups using such parameters as the girth of the shoulder, forearm and thigh by instrumental methods, as well as measuring the thigh muscle thickness and fat thickness (TMT and FT) in the lumbar region using ultrasound was studied. The object of the study was the one-year -old rams (n = 50) of the Russian Meat Merino (RMM) breed. To assess the significance of the proposed measurements, in comparison with those used in existing practice, the principal component method and correlation analysis were used. In the course of the work carried out, it was found that measurements: thigh volume, forearm girth had the most significant correlations with all parameters describing the exterior of the PMM breed. Based on the analysis of the main components, it was determined that the first six components in our study explained more than 80% of phenotypic variability. Thus, the proposed parameters determined by ultrasound: TMT and FT are advisable to use for the phenotypic assessment of the conformation of sheep of the RMM breed, especially when searching for genomic associations with productive qualities.