Simple and Constrained Selection Indices with and without Calving Interval Included in Selection Goal Function for Holstein Cows of Iran
محورهای موضوعی : Camel
ا. دارنگ
1
(
Agriculture Jihad Organization of Guilan, Guilan, Rasht, Iran
)
ع.ا. شادپرور
2
(
Department of Animal Science, Faculty of Agricultural Science, University of Guilan, Rasht, Iran
)
م. گلشنی
3
(
Agriculture Jihad Organization of Guilan, Guilan, Rasht, Iran
)
کلید واژه: Holstein, calving interval, constrained selection index, genetic growth,
چکیده مقاله :
Two selection goals of inclusion or exclusion of calving interval (CI) in the selection goal function for Holstein cows in Iran, besides milk yield, milk fat percentage, and milk protein percentage, were studied. Four selection indices were composed of using the information on production traits, CI and / or days from calving to first insemination (DFI). The results of the predicted genetic growth in selection goals showed that the index composed of all production and reproduction traits generated the greatest genetic growth. Although CI had a negative coefficient in the selection goal, it is genetic mean increased in any case. However, the magnitude of this undesirable increase was lower in the CI included selection goal. This implies that the inclusion of CI in the selection goal is necessary to control the undesirable growth of this trait. The comparison of indices in this goal reflected that the inclusion of CI along with the production traits resulted in a smaller undesirable change in this trait. Constraining the genetic change in CI in the selection goal impaired the selection efficiency. So, this constraint is not recommended for breeding programs.
در این تحقیق دو نوع تابع هدف انتخاب با و بدون دخالت فاصله دو زایش در کنار صفات تولیدی شامل تولید شیر، درصد چربی شیر و درصد پروتئین شیر برای گاوهای هلشتاین ایران مورد بررسی قرار گرفت. برای هر تابع هدف چهار نوع شاخص انتخاب مرکب از صفات تولیدی، فاصله دو زایش و نیز فاصله زایش تا اولین تلقیح تشکیل شد. بررسی رشد ژنتیکی پیشبینی شده در توابع هدف نشان داد که شاخص مرکب از همه صفات تولیدی و تولید مثلی بیشترین رشد ژنتیکی را ایجاد کرد. گرچه فاصله دو زایش ضریب منفی در تابع هدف داشت، میانگین ژنتیکی این صفت در هر حالت افزایش یافت. اما میزان این افزایش نامطلوب در تابع هدف دربرگیرنده صفت فاصله دو زایش کمتر بود که نشان میدهد حضور فاصله دو زایش در تابع هدف برای کنترل رشد نامطلوب این صفت ضروری است. در مقایسه شاخصها در این تابع، حضور صفت فاصله دو زایش در کنار صفات تولیدی سبب تغییر نامطلوب کمتری برای این صفت شد. اعمال محدودیت تغییر ژنتیکی در صفت فاصله دو زایش در تابع هدف منجر به کاهش کارایی انتخاب شد و لذا این اعمال محدودیت در برنامههای اصلاحی قابل توصیه نیست.
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