Genetic monitoring: the bulls retirement reasons analysis

The purpose of the study is to analyze the reasons for the retirement of bulls and to identify the degree of its hereditary conditionality. Tasks - to study the spectrum of reasons for leaving; to conduct a comparative analysis of culling by species and areas of productivity; to study the influence of ecogenesis on the example of bulls of local selection and imported animals. Bulls of the Red-and-White and Black-and-White Holstein breeds were studied, including local types (Yenisei and Krasnoyarsk), Simmental, Hereford and Aberdeen-Angus breeds (n = 783). The spectrum of reasons for retirement is highlighted: sufficient sperm accumulation (SSA), breeding sale (BS), poor sperm quality (PSQ), andrological diseases (AD), diseases of the digestive system (DDS), diseases of the cardiovascular system (DCS), limb diseases (BC), limb injuries (LI), violent temper (VT), other reasons (OR). In general, the planned culling, reflecting a high level of livestock safety, amounted to 57.1 % (47.4 % - SSA and 9.7 % BS). The dynamics of the spectrum indicates an increase in the share of planned retirement by 23.7 % (from 33.4 % in the previous period). This was due to a slight increase in the share of breeding sale (by 2.6 %) and sperm accumulation (by 21.3 %). The highest level of genetic load for reasons of hereditary causes of disposal is observed in bulls of the combined direction (60 % of the disposal), less - in the dairy direction (40 %). The number of bulls with poor sperm quality has increased - 21.2 % of the dropouts, i.e. manifested recessive genes in the homozygous state. This, in turn, indicates the ongoing process of drift of mutant genes remaining in a heterozygous state. Bulls of local types have great health in relation to cardiovascular diseases and diseases of the digestive system. They are stable in relation to loads on the limbs.