شبیه سازی طرح اصلاح نژادی گروهی هسته باز برای بهبود ژنتیکی وزن شش ماهگی گوسفند نژاد کرمانی

نوع مقاله : مقاله پژوهشی

نویسنده

گروه علوم دامی، دانشکده کشاورزی، دانشگاه شهید باهنر کرمان، کرمان، ایران

چکیده

هدف اصلی ازمطالعه حاضر با استفاده از شبیه‌سازی، تعیین مناسب‌ترین اندازه نسبی هسته و نرخ‌ انتقال میش‌های جایگزین از گله‌های تجاری پایه به هسته در یک طرح اصلاح نژادی گروهی هسته‌باز برای بهبود ژنتیکی وزن شش ماهگی گوسفند نژاد کرمانی بود. مدل سازی ساختار هرم اصلاح نژادی شامل گله‌هایی در دو لایۀ هسته و پایه با 5000 رأس میش و 143 رأس قوچ با نسل‌هایی هم پوشان، 6 گروه سنی میش و 3 گروه سنی قوچ در هر دو لایۀ هسته و پایه، تولد اولین فرزندان در 2 سالکی، انتخاب جایگزین‌ها به روش "انتخاب فرزندان" برای وزن 6 ماهگی، انتقال جایگزین‌ها بین دو لایه در مسیرهای انتخابی 5 و 6 گانه، تأمین تمام قوچ‌های جایگزین در دو لایه از هسته، بدونِ- و با انتقال میش از هسته به پایه انجام و با احتساب اثر انتخاب بر واریانس و پیشرفت ژنتیکی، با رویکرد قطعی شبیه‌سازی شد. تعداد 8 اندازه نسبی هسته به فواصل 0/02، از 0/04 تا 0/18 منظور و برای هر یک نرخ انتقال بهنیه میش از پایه به هسته با استفاده از گزینۀ راه حل تکاملی موجود در افزونه داخلی سالور ضمیمه برنامه اکسل به دست آمد. پیشرفت ژنتیکی سالیانه و تأخیر ژنتیکی گله‌های پایه با نرخ بهینه انتقال میش به هسته برای هر اندازه‌ نسبی هسته محاسبه و مناسب‌ترین اندازه نسبی هسته تعیین شد. بهترین اندازه نسبی هسته 0/12 بود اما مناسب‌ترین اندازه نسبی (اقتصادی) هسته 0/08 بود، تعداد 400 میش در هسته و 4600 رأس در گله های پایه با 64 میش جوان برای انتقال به هسته و 3/51 سال لنگش ژنتیکی پایه نسبت به هسته پیش‌بینی شد. هم چنین، در کاهش اندازه نسبی هسته 0/08، 33 درصد از اندازه نسبی هسته کاسته و به اندازه نسبی پایه 5 درصد افزوده شد. افزایش تعداد میش‌های جوان انتقالی به هسته 3 رأس بود. لنگش ژنتیکی گله های پایه 0/36 سال بیش‌تر شد. مزیت انتخاب در طرح هسته‌باز در اندازه نسبی هستۀ 0/12 در مقایسه با انتخاب در تمام گله های مردمی بدون هسته بررسی شد. شبیه‌سازی قطعی برای تعیین مناسب‌ترین اندازه هسته که منجر به پیشرفت ژنتیکیِ وزن شش ماهگی کاملأ نزدیک به حالت بهینه، کاهش هزینه های طرح و شمول تعداد هرچه بیش‌تر گوسفندان در پایه خواهد شد، کاملا مؤثر بود.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Simulation of the open nucleus group breeding scheme for genetic improvement of six-month weight of Kermani sheep breed

نویسنده [English]

  • Heshmatollh Askari Hemmat
Department of Animal Science, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran
چکیده [English]

The main objective of the present simulation study was to determine the most appropriate relative nucleus size and transfer rate of the replacement ewes from the base commercial flocks to the nucleus in an open nucleus group breeding scheme for improvement of six-month weight of Kermani sheep. Modeling the structure of the breeding pyramid including flocks in nucleus and base tiers including 5000 ewes and 143 rams with overlapping generations, 6 ewe age groups and 3 ram age groups in both nucleus and base tiers, the birth of first progeny at 2 years old, selection of replacements by the method of "progeny selection" for 6-month weight, transfer of replacements between two tiers in 5 and 6 selection paths, provision of all replacement rams in two tiers from nucleus, without- and with the transferring of ewes from nucleus was carried out, and it was simulated using a deterministic approach with account of the selection effect on the genetic variance and progress. Eight relative nucleus size considered at intervals of 0.02, from 0.04 to 0.18, for each of which the optimal transfer rate from the base to the nucleus was obtained. The annual genetic progress and the genetic lag of base flocks with optimal ewe transfer rate to nucleus calculated for each relative nucleus size and the most suitable relative nucleus size was determined. The best relative nucleus size was 0.12, but the most appropriate economic relative nucleus size was 0.08, 400 ewes in nucleus and 4600 in base flocks with 64 young ewes to be transferred to nucleus and 3.51 years genetic lag for base compared to nucleus predicted. When reducing the relative nucleus size to 0.08, 33% of relative nucleus size reduced and 5% was added to the base relative size. The increase in number of young ewes for transferring to nucleus was 3 heads. The genetic lag of base flocks increased by 0.36 years. The advantage of selection in the open nucleus scheme at the relative nucleus size of 0.12 in comparison to selection in all community flocks without a nucleus investigated. Deterministic simulation was quite effective for determining the most suitable nucleus size leading to genetic improvement of six-month weight quite close to optimal state, reducing costs of scheme and including as many sheep as possible in base.

کلیدواژه‌ها [English]

  • Deterministic simulation
  • Group breeding
  • Breeding nucleus
  • Six-month weight
  • Kermani sheep

مراجع

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فصلنامه محیط زیست جانوری
دوره 15، شماره 2
مرداد 1402
صفحه 113-120

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