НОВЫЙ ПОДХОД В ОЦЕНКЕ БЫКОВ-ПРОИЗВОДИТЕЛЕЙ ПО КАЧЕСТВУ ПОТОМСТВА

Abstract

The repeatability of the results of evaluating sires by the offspring quality according the conventional methods of daughter-herd (basic) and daughter-dam (clarifying) comparison for production is low and does not always correspond to the assigned categories. The records of evaluating eight sires of different genotypes by the offspring quality based on the daughter-dam comparison for production were investigated. To this end, daughters’ dams were assigned to seven groups by milk yield for 305 days of the first lactation, with a class interval of 500 kg in comparison with the daughter’s milk yield in each group, and the daughter-dam difference for production was established. The second stage involved assigning sires’ daughters, in the same manner, to the similar seven groups, for comparison with dams. The procedure aimed to establish which dams by milk yield produced different groups of daughters; compared with the dams the daughters came from. The proposed method for evaluating sires based on compatibility with the breeding stock of different milk yield classes has several advantages over the conventional method of the daughter-herd comparison. The new approach allows establishing the limits for dams based on the milk yield within which a sire has a significantly improving effect; selecting a class of dams by milk yield that gave birth to the highest-yielding daughters. The method eliminates the need to rank the tested sires as improving, neutral and worsening types with numerous variations and makes it possible for the breeder to set up a plan for selection – assigning dams to a sire. The study suggests the following selection plan of assignment (sires – dams with a milk yield for 305 days of the first lactation): Arzamas 8815 – from 3700 to 4700 kg, Gir 1883 (ceased), Grilyazh 6977 – from 4000 to 4500 kg, Iman 314 – limited to 4000 kg, Knor 45026 – from 4000 to 5000 kg, Twist 76849 – from 3000 to 4500 kg, Tibul 3728 – from 4000 to 5000 kg, and Torpan 2739 – with all classes up to 6001 kg and above.