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

Document Type : Research Paper

Authors

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.

Abstract

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.

Keywords

Main Subjects

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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Iranian Journal of animal Science
Volume 56, Issue 1
March 2025
Pages 121-137

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History

  • Receive Date: 28 January 2024
  • Revise Date: 02 June 2024
  • Accept Date: 10 June 2024

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