SELECTIVE BREEDING TAKING INTO ACCOUNT THE LIMITING FACTORS IN THE HERD OF THE HEREFORD BREED

Abstract

The purpose of this work was to create a “model” group of Hereford bull calves, taking into account the limiting selection factors. The research was carried out in the breeding farm of JSC “Belokopanskoe” in the Stavropol Territory in 2023-2024. The object of study was bull calves (n = 60) and servicing bulls (n = 3) of the Hereford breed. A “model” group of Hereford bull calves was selected as successors of the genealogical lines of servicing bulls, taking into account the selection and genetic parameters and the composite index (CI), which was constructed on the basis of the Harrington’s desirability function. The selection-significant traits were determined and ranked, taking into account the reliable correlation dependence (r² = 0,38–0,81). The coefficient of repeatability of live weight at 8 and 12 months, 8 and 15 months was 0,72–0,84 units, which suggested that the testing of bull calves for their own productivity would be completed at an earlier age. The bulls had a highly significant genetic effect on the live weight of their offspring at 15 months of age and on meat forms (η² = 0,46 units and η² = 0,52 units). The dimensionless relative numerical value of the composite index of the Harrington’s function showed that 25% of the population had the value of the CI with the established selection criteria: sacrum height at the age of 15 months was 123 cm, constitution and exterior were 4 points or more, live weight was the “elite” class and higher, lifetime evaluation of meat qualities was 54 points or more. Among the offspring of the “improver” bulls, a “model” group of successors was selected, which surpassed their herdmates: in live weight – by 42,9 kg (10,2%; α ˂ 0,001), in average daily gain – by 165,2 g (16,4%; α ˂ 0.001).