Вестник аграрной науки, 6(69), 2017, http://dx.doi.org/10.15217/48484 UDC / УДК 619:616.89-008.454:636.237.23.082.252 INBREEDING DEPRESSION OF SIMMENTAL CATTLE IN THE SYSTEM OF GENETIC AND ENVIRONMENTAL FACTORS ASSESSMENT ИНБРЕДНАЯ ДЕПРЕССИЯ СИММЕНТАЛЬСКОГО СКОТА В СИСТЕМЕ ОЦЕНКИ ГЕНЕТИЧЕСКИХ И СРЕДОВЫХ ФАКТОРОВ Shendakov A.I., Doctor of Agricultural Sciences, Professor Шендаков А. <...> И., доктор сельскохозяйственных наук, профессор Federal State Budgetary Educational Establishment of Higher Education "Orel State Agrarian University named after N.V. Parakhin", Orel, Russia ФГБОУ ВО «Орловский государственный аграрный университет имени Н. <...> Парахина», Орел, Россия E-mail: bio413@ya.ru The article is devoted to the problems of inbreeding depression minimization in a herd of Simmental cattle. <...> The author analyses the data received during the experimental research of the evaluation of the intensity of Simmental calves growth using different degrees of inbreeding, including in-and-inbreeding, bottom crossing, top-cross inbreeding, in-breed-line-crossing. <...> The results of the experiment showed that at bottom crossing, top-cross inbreeding, in-breed-linecrossing the influence of genetic factors on live weight from birth to 6 months in bulls increases to 73.7-75.8%, also in 7, 8, 9 and 10 months heifers with Fx=25.0% left behind heifers with Fx= 0.781% and 24.8, 31.0, 41.7 and 43.2 kg, respectively (p<0.1-0.05). <...> Mating of inbred cows with outbreed bulls and outbreed cows with inbred bulls does not give the unambiguous results, however it can be assumed that the method of bottom-crossing can be applied to the large stud bulls only, while top-breeding and top-cross breeding can avoid serious consequences only in mating cases when a cow has a high live weight. <...> The genetic variability of live weight from the generation to 6 months was above heifers – from 1.588 to 16.428 kg; environmental variability was above in bull calves from the second month of cultivation (from 2.106 to 4.915 kg). <...> This can be the proof of the fact that the inbred bull calves needed the intensive feeding. <...> Key words: genetic factors, in-and-inbreeding, bottom crossing, top-cross inbreeding, inbreed-line-crossing, inbreeding depression, Simmental cattle. <...> Были проанализированы данные, полученные в ходе исследований интенсивности роста при использовании различных степеней инбридинга <...>