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اثرات خطا و نقص شجره‌ بر پیش بینی ارزش اصلاحی و رتبه‌بندی حیوانات در گاوهای شیری

نوع مقاله: مقاله پژوهشی

نویسندگان

1 استادیار، گروه علوم دامی، دانشکده کشاورزی، دانشگاه کردستان

2 دانشجوی سابق کارشناسی ارشد، گروه علوم دامی، دانشکده کشاورزی، دانشگاه کردستان

3 استادیار، گروه علوم دام و طیور، پردیس ابوریحان دانشگاه تهران

چکیده

وجود شجره کامل به عنوان یکی از فرضیات ارزیابی ژنتیکی حیوانات با معادلات مختلط است. در این پژوهش، با هدف تأثیر روابط خویشاوندی بر ارزیابی ژنتیکی، از اطلاعات شجره و تولید 100 گله بزرگ گاو شیری تحت پوشش مرکز اصلاح نژاد دام ایران استفاده شد. داده ها مربوط به 302860 رأس گاو در دوره اول شیردهی بودند که شجره کامل این حیوانات توسط نرم‌افزار DMUTrace  ردیابی و استخراج شد. به منظور اعمال خطا و نقص در شجره، به کمک برنامه R و به‌طور تصادفی سطوح 4، 8، 12، 16، 20، 24 درصد از مشخصات ثبت شده­ پدران حذف و یا با اطلاعات سایر پدرها جابجا شد. هر کدام از سناریوها پنج مرتبه تکرار و با نرم­افزار DMU آنالیز شدند. تأثیر میزان کامل بودن شجره بر رتبه­بندی حیوانات بر اساس معیار همبستگی رتبه­ای و در چهار سطح %1، %5، %10 و 20% از نرهای برتر، با استفاده از نرم­افزار SAS  برآورد شد. وراثت‌پذیری با شجره کامل 29/0 و در شجره­های دارای نقص و خطا به ترتیب به  26/0 و 27/0 برآورد شد. در سطح 12 درصد و برای 1000 دام برتر، همبستگی رتبه­ای شجره کامل با شجره دارای خطا 60/0 و با شجره ناقص 65/0 بود (01/0P<). با افزایش خطا و نقص، اثربخشی انتخاب به عنوان معیار نرخ اشتراک حیوانات برتر در سناریوهای مختلف، روند نزولی داشت. نتایج نشان دهنده اثرات نامطلوب شجره ناکامل و دارای خطا بر ارزیابی ژنتیکی و پیامد آن ایجاد اریبی در رتبه­بندی حیوانات است.

کلیدواژه‌ها


عنوان مقاله [English]

Effects of misidentification and paternity errors on prediction of breeding values and ranking of animals in dairy cattle

نویسندگان [English]

  • Mohammad Razmkabir 1
  • Farid Fathi 2
  • Rostam Abdollahi-Arpanahi 3
1 Assistant Pprofessor, Department of Animal Science, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
2 Former M. Sc. Student, Department of Animal Science, Faculty of Agriculture, University of Kurdistan, Sanandaj, Iran
3 Assistant Professor, Department of Animal and Poultry Science, Campus of Aburaihan, University of Tehran, Tehran, Iran
چکیده [English]

Genetic evaluations are computed to assess the genetic merit of animals based on mixed model equations. An important assumption for setting up these equations is that all genetic relationships among animals are available and correct. The objectives of the present study were to estimate the effects of incomplete pedigree and paternity errors on genetic evaluation. Data and pedigree of 100 dairy herds were obtained from Animal Breeding Center of Iran. Final data edited included milk yield records from 302860 first lactation Holstein cows. DMU Trace program was used for tracing ancestors and creating the full pedigree of animals. To simulate incomplete and wrong pedigrees, different scenarios including 8, 12, 16, 20, 24 percent of paternal identification numbers were removed or replaced using R program. Breeding values for milk yield was predicted by animal model using DMU program. Spearman's rank correlation was estimated for superior animals in different scenarios using SAS software. Estimates of heritability for full, incomplete and wrong pedigrees were 0.29, 0.26 and 0.27, respectively. The results showed a high variation in ranking of animals and determination of superior animals (P<0.01). As an example, at 12% level scenario, Spearman's rank correlation of BVs predicted from full pedigree with incomplete and wrong pedigrees were 0.65 and 0.60, respectively. Selection effectiveness, defined as the ratio of common superior animals in alternative scenarios, was decreased by increasing the rate of misidentification and errors (P<0.01). Incorrect pedigree and misidentification of animals could reduce accuracy of breeding values and consequently bias in animals ranking.

کلیدواژه‌ها [English]

  • Parentage misidentification
  • pedigree errors
  • rank correlation
  • relationship matrix
  • selection effectiveness
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