Body volume modeling by linear features of the Irmen type cattle

The results of modeling the variability of the complex trait "body volume" by linear traits measured on a 10-point scale in accordance with the current instructions for cattle grading of dairy and dairy-beef breeds are presented. The object of research is the complex indicator "body volume" of Irmen type cattle. The exterior of the livestock was evaluated by experts on a collegial basis. The models obtained made it possible to identify a group of exterior features associated with the variability of the studied trait and to identify errors in the work of the evaluators. The tasks were solved using multiple linear, polynomial, power and logarithmic regression models. It was found that multiple linear regression models accurately describe the norm reaction of the body volume response. Residue distribution diagrams made it possible to control the quality of appraisers' assessment and adjust their further work. The logarithmic model was marked as closest to linear. The residues in most cases turned out to be close to zero, which was explained by the low level of variability of the traits used. It was revealed that the use of different levels of power orders in modeling the variability of the body volume in points can lead to the emergence of biologically inexplicable relationships with such linear features as the location of the front teats, the location of the rear teats, attachment of the anterior lobes and the position of the bottom of the udder. The construction of the scatter diagram revealed a high level of variation in the residues and led to the conclusion that it was inexpedient to introduce power series models into the practical work of livestock breeders. The insignificant contribution of the studied linear features to the variation of the complex feature under study is shown. High intra-group variance in the construction of second- and fourth-order polynomial models was reflected in the lowest values of the Fisher criterion.