استفاده از فراتحلیل برای برآورد پارامترهای ژنتیکی صفات ماندگاری در گاوهای شیری

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه علوم دامی، دانشکده کشاورزی دانشگاه صنعتی اصفهان، اصفهان،ایران.

2 گروه علوم دامی، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران، کرج ایران

3 گروه علوم دامی، دانشکده کشاورزی، دانشگاه صنعتی اصفهان، اصفهان، ایران.

چکیده

در طراحی برنامه های اصلاح نژدای، وجود برآوردهای صحیح از پارامترهای ژنتیکی ضروری است. ماندگاری یکی از صفات مهم اقتصادی در پرورش گاو شیری است. به طور کلی، توانایی گاو برای ماندن در گله و حذف نشدن، بدون توجه به دلیل آن، ماندگاری تعریف می شود. به طور جزیی­تر میتوان ماندگاری را به صورت­های دیگر از جمله: استقامت، بقا، تعداد دوره شیردهی، طول عمرتولیدی و طول عمر گله تعریف کرد. طی سال های گذشته، برآورد پارامترهای ژنتیکی برای صفات گوناگون ماندگاری در گاوهای شیری گزارش شده است. با این حال، این برآوردها از مطالعات بر اساس جمعیت های مختلف گاو شیری به دست آمده که منجر به تنوع قابل توجهی در بین برآوردهای وراثت­پذیری و همبستگی ژنتیکی شده است؛ بنابراین، این مطالعه با هدف انجام یک فراتحلیل بر اساس یک مدل اثرات تصادفی برای ترکیب برآوردهای وراثت‌پذیری­های منتشر شده برای صفات ماندگاری و همبستگی ژنتیکی آنها با صفات تولید شیر، تیپ، روزهای باز و امتیاز سلول‌های سوماتیک انجام شد. در مجموع، 66 مقاله منتشر شده بین سال های 1984 تا 2023 در مطالعه حاضر مورد استفاده قرار گرفت. پس از جمع­آوری مقالات و استخراج پارامترها از آنها، برآورد پارامترهای ژنتیکی با روش فراتحلیل در نرم افزار Excel 2019 انجام شد. بررسی مطالعات انجام شده ناهمگنی زیادی را نشان داد بنابراین امکان استفاده از مدل با اثر ثابت وجود نداشت و از مدل با اثرات تصادفی استفاده شد. وراثت­پذیری برای صفات طول عمر تولیدی، طول عمر گله، تعداد دوره شیردهی، استقامت و نرخ بقا به ترتیب 10/0، 08/0، 07/0، 10/0 و 04/0 بود. همبستگی ژنتیکی بین صفات ماندگاری و صفات تولیدی بسیار متغیر بود، بیشترین همبستگی ژنتیکی بین تولید چربی و طول عمر گله بود (95/0). به طور کلی همبستگی ژنتیکی بین اکثر صفات تیپ و ماندگاری منفی و کم بود. بالاترین همبستگی ژنتیکی مثبت بین امتیاز کلی تیپ و استقامت یافت شد (62/0). همبستگی ژنتیکی بین امتیاز سلول‌های سوماتیک با استقامت و نرخ بقا به ترتیب 13/0- و 38/0- بود. همبستگی ژنتیکی بین روزهای باز با طول عمر گله و طول عمر تولیدی به ترتیب 40/0 و 54/0- بود. نتایج این تحقیق می­تواند در تدوین استراتژی­های انتخاب برای بهبود ماندگاری در گاو شیری مفید باشد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Using meta-analysis to estimate the genetic parameters of longevity traits in dairy cows

نویسندگان [English]

  • farzaneh shokri sangari 1
  • Ali Sadeghi-Sefidmazgi 2
  • saeed ansari mahyari 3
1 Department of Animal Science, College of Agriculture, Isfahan University of Technology, Isfahan ,Iran.
2 Department of Animal Science, College of Agriculture ‎and Natural Resources, University of Tehran, Karaj, Iran.
3 College of Agriculture, Isfahan University of Technology, Isfahan, Iran.
چکیده [English]

Designing effective breeding programs for dairy cattle relies on accurate estimates of genetic parameters for economically important traits. Extensive research over the years has explored genetic parameters associated with longevity in dairy cows. However, these estimates often come from studies using different cow populations, leading to significant variations in heritability and genetic correlations. Thus, this study aimed to conduct a meta-analysis based on a random-effects model to combine different published heritability estimates for longevity traits as well as their genetic correlations with milk production traits, type traits, days open (DO), and somatic cell score (SCS) in dairy cows. In total, 66 articles published between 1994 and 2023 were used in the present study. After gathering the articles and extracting the parameters, genetic parameters were estimated by meta-analysis method. pooled heritabilities for the productive life (PL), herd life (HL), Number of Lactation (NL), Stayability(ST), and Survival rate(SR) traits were 0.10, 0.08, 0.07, 0.10, and 0.04, respectively. Genetic correlations between most type and longevity traits were generally negative and low. The highest positive genetic correlation was found between the subjective score for type and ST (0.62). Genetic correlations between longevity (ST and SR) and SCS were -0.13 and -0.38, respectively. Genetic correlations between longevity (PL and HL) and DO were -0.54 and 0.40, respectively. Obtained results in the study can be useful to define animal breeding strategies to improve longevity in dairy cattle.

کلیدواژه‌ها [English]

  • Genetic correlation
  • Heritability
  • Holstein
  • production trait
  • type trait
  • Meta-analysis

Extended Abstract

Introduction

   Longevity is a complex trait with economic importance. Longevity in dairy cows has various definitions and includes characteristics that refer to the length of time a cow stays in the herd as a breeder or its ability to stay in the herd. The main goal in selecting and improving lifespan is to reduce early culling or forced culling. The reasons and strategies for culling are very broad, therefore, selection for longevity involves the improvement of many other traits. Also, greater longevity has a positive impact on the environmental footprint of dairy industry, better health and welfare status of the animals. In designing multi-breed programs and predicting response to selection, estimating the genetic parameters of the traits is a fundamental step, therefore it is necessary to have a correct estimate of the genetic parameters that enables accurate breeding value prediction. With meta-analysis of related studies, the results obtained from independent researches are combined with each other and heterogeneous sources are examined. Appropriate and correct use of meta-analysis method in animal studies can reduce the repetition of unnecessary work. The purpose of the present study is to combine the results of the parameter estimation of the studies conducted for longevity traits, using the meta-analysis method, and reach more accurate results.

 

Background and objectives

    Genetic parameter estimation in Holstein cows was done using the meta-analysis method to make estimates more accurate. To do this, we used information from 66 articles on genetic parameter estimation of longevity traits on Holstein dairy cows. Longevity traits were HL, NL, PL, ST and ST.

 

Materials and method

    Initially, estimates of heritability and genetic correlation were obtained from various articles. Subsequently, the collected data underwent preparation, and a meta-analytical model incorporating random effects was employed utilizing the Excel 2019 software. This approach aimed to estimate the weighted average of heritability, as well as genetic correlation while also determining the standard errors and 95% confidence interval for longevity traits.

 

Result

   The weighted averages of heritability for longevity traits in dairy cows were between 0.04 and 0.10. ST and PL had the highest (0.10) and SR had the lowest (0.04) heritability estimates among productive traits. Genetic correlations between most type traits and longevity traits were generally negative and low. The highest positive genetic correlation was found between the subjective score for type and ST (0.62). Genetic correlations between longevity traits (ST and SR) and SCS were -0.13 and -0.38, respectively. Genetic correlations between longevity traits (PL and HL) and DO were -0.54 and -0.40, respectively.

 

Conclusion

   The meta-analysis carried out in this study provided the possibility of providing consolidated estimates of the heritability of longevity traits and their genetic correlation with production traits, type traits, open days, and the somatic cell score in dairy cows. The obtained results showed that meta-analysis by combining the results of various studies and increasing the sample size reduces the standard error of the estimates, and thus increases the accuracy of genetic parameters estimation, except in cases where the number of studies conducted is small. The results of this meta-analysis study indicated the existence of favorable genetic correlations for durability traits with production traits, type traits, open days, and somatic cell score.

Author Contributions

Conceptualization, F.S.S. and A.S.S.; methodology, F.S.S. and A.S.S; software, F.S.S.; validation, F.S.S., A.S.S. and S.A.M..; formal analysis, F.S.S; investigation, F.S.S., A.S.S. and S.A.M.; resources, F.S.S.; data curation, F.S.S.; writing—original draft preparation, F.S.S.; writing—review and editing, F.S.S., A.S.S. and S.A.M.; visualization, A.S.S. and S.A.M.; supervision, F.S.S., A.S.S. and S.A.M.; project administration, F.S.S.; funding acquisition, A.S.S.

Data Availability Statement

Data available on request from the authors.

Acknowledgement

The authors would like to thank all participants of the present study.

Ethical considerations

Not applicable.

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