Measurements of telomere length at different life stages as predictive biomarkers of health, reproduction and longevity in dairy cattle

Lead Research Organisation: SRUC
Department Name: Research

Abstract

The key concept of the proposed work is based on three tenets:

1. Health, reproduction and longevity are key factors influencing the sustainability and profitability of the livestock industry in the UK and internationally. In addition to bearing considerable economic significance, these factors affect animal welfare, the environmental footprint of livestock operations, and the acceptability of animal products by consumers. Therefore, improvement of these traits will yield multi-faceted benefits.

2. Given the complexities and time requirements affecting the accurate recording of these traits, there is a need for reliable, early-life predictors that could provide early warnings for poor health, reproduction and longevity, effectively contributing practical tools for improvement.

3. Recent advances in human and laboratory animal research have revealed potentially useful biological markers that are associated with lifespan, as well as age and age-related conditions.

The proposed project aims to identify an early-life biomarker to predict health, reproduction and longevity in dairy cattle.

For this reason, the project will use a comprehensive database of cows raised in the experimental herd of the Crichton Royal Farm in Scotland. Animals belong to two different genetic lines (selected for high vs. average production) and two diet groups (high vs. low protein intake) and are closely monitored from the time of birth until they die or are removed from the herd. The database comprises records of individual animal pedigree, performance, feed intake, disease and reproductive events, and longevity. Detailed environmental descriptors associated with these records are also included in the database.

Approximately 1,000 animals from this herd have already been blood sampled at birth and then in 6-month intervals. These samples will be used to measure the length of the telomeres of each cow across her lifetime. Telomeres are small structures capping the chromosomes' ends in the animal cells and are known to be associated with aging in humans. Changes in telomere length measures obtained in the proposed study will be monitored throughout the animals' life and analysed together with data pertaining to health events, reproductive issues and length of productive life. These analyses will establish the link between animal telomere length and health, reproduction and longevity.

To achieve its objectives, the project will draw on complementary expertise in animal science, genetics, biotechnology, physiology and biology.

The potential applications and benefits of this study are as follows:

1. This is the first ever study in food producing animals that looks at the way telomeres change across time and how this change may relate to important animal traits. Also for the first time the effect of many genetic and environmental factors on telomeres and longevity will be examined.

2. The outcome of the project will bring a better understanding of the process of ageing of milk producing cows and will identify an early-life indicator that predicts the animals' future health, reproduction and longevity.

3. The end result will be an easily applicable, animal-friendly biomarker that could be used as a management and selection tool to improve the robustness, welfare and survival of dairy cattle, and reduce the rate of involuntary removal of high yielding animals from the herds. Further ramifications of the envisaged improvement include a healthier background for the production and consumption of animal products, and a lower environmental footprint of the sector as a whole.

4. Knowledge acquired in this project may have longer reaching consequences for animal conservation programmes to improve survival of rare animal breeds and endangered species, as well as detailed studies to better understand the aging process in other species including humans.

Technical Summary

We propose the first ever longitudinal study of telomere length (TL) in relation with health, reproduction and longevity (HRL) of dairy cattle. Key objectives include:

1. Examination of the genetic and environmental factors affecting TL.
2. Evaluation of the link of TL with animal production and HRL.
3. Identification of an early-life TL measure as a predictive biomarker of HRL.
4. Demonstration of the utility of the biomarker in breeding programmes.

A resource population of 1,000 dairy cows raised at the SRUC research herd will be used. Animals are split into two equally sized genetic lines (high vs. average genetic merit for production) and two diet groups (high vs. low protein intake) as part of an on-going selection and feeding experiment. Animals are closely-monitored on a daily basis from birth to death or removal from the herd. A dense phenotypic database including individual animal performance, feed intake, metabolic load, health status and reproductive events is already in place.

Blood samples have been taken from these animals at 6-month intervals starting at birth. These samples will be used to extract DNA from blood cells and measure TL with a quantitative Polymerase Chain Reaction. Repeated measures of TL for each animal will determine the telomere attrition rate. The bovine TERT gene locus will be sequenced and influential polymorphisms will be determined with association analyses.

Mixed statistical models will be developed for data analyses to:

1. Portray the TL profile across an animal's lifetime.
2. Quantify the effect of genetic and environmental factors on TL.
3. Estimate heritability of TL.
4. Estimate genetic and phenotypic correlations of TL with production and HRL.
5. Assess the predictive capacity of TL as a biomarker of HRL.

Cross-validation will be used to identify the most accurate telomere predictor. A simulation study will be designed to demonstrate the optimal way of incorporating this into breeding programmes.

Planned Impact

The sustainability and profitability of dairy farms depend on cows producing milk normally for at least 3-4 years. Given that dairy cows start producing milk when they calve for the first time (approximately 2 years old) the desirable length of life in the herd is at least 5-6 years. Cows that leave the herd earlier due to diseases or poor fertility incur considerable costs for the farmer. Currently, nearly 20% of dairy cows in the UK fail to reach their first calving and onset of milking whilst many more leave the herd before achieving their full production potential.

This project offers an innovative approach, utilises unique data and combines complementary scientific expertise in order to develop knowledge and practical, early-life tools to predict health, reproduction and longevity of dairy cows. The project will also investigate and propose optimal ways of incorporating these tools in the national breeding and genetic improvement programme. Thus, the outcomes of this project will contribute directly to the reduction of health and reproductive problems, the enhancement of dairy cow longevity and, consequently, the improvement of animal welfare. Benefits would apply to individual cow, farm and population levels.

In this respect, the impact of the proposed work is expected to be multi-faceted:

1. Early identification of animals prone to repeat health and reproductive problems will assist selection and replacement strategies, and minimise animal suffering.

2. Dairy farmers will directly benefit from improved cow longevity as cost of replacements (i.e. young animals kept in the herd to replace older animals at the end of their productive utility) will decrease. More offspring will then be obtained from animals with high genetic merit. The intensity of selection will increase as there will be more selection candidates to choose from. Fewer health and reproductive problems will also signify enhanced animal welfare.

3. The dairy industry will benefit from advances and optimisations of the genetic improvement programmes brought about by outcomes of the proposed project. Currently, the economic benefits of such programmes in the UK are worth nearly £106 million/year; more than half of this is being realised by improvements in cow health, reproduction and longevity.

4. Improved health and longevity of the milking cows will enhance the health profile of their products and, eventually, the image of the sector and acceptability by consumers.

5. Benefits in the dairy industry will permeate the entire food producing animal sector, where outcomes from this project could be used as models for pertinent activities.

6. Environmental benefits are expected to accrue because of the reduced number of on-farm replacements, the latter accounting for 27% of the methane produced on-farm.

7. Policy makers and government can use outcomes and evidence from this project in the formulation and regulation of actions aiming at animal welfare and the social acceptability and environmental image of the livestock sector.

8. Considerable scientific benefits are anticipated which are described in detail in the Academic Beneficiaries section. Staff hired for the project will have the opportunity for training, attend courses and conferences, and develop scientific and professional skills in the laboratory, computer, numerical and quantitative analyses.

9. The UK as a whole will benefit through the links between the scientific partners in the project and their industry contacts, ensuring quick uptake and implementation of the research results, contributing to the enhancement of farm output, health and living standards.

This is a 3-year project whose benefits are expected to start materialising as soon as the first results become available and continue long after the completion of the project.
 
Description 1. Methodology to extract DNA suitable for telomere length (TL) measurement has been developed and tested. Commercially available kits were optimised based on in-house protocols in order to enhance the applicability and cost efficiency of the methods. Experiments were conducted to demonstrate the method suitability for TL measurements with the appropriate calibration. The final method chosen was successfully used on 2,202 cattle samples for the purposes of the project.
2. A quantitative real-time PCR (qPCR) approach has been adapted to measure TL. A high throughput procedure has been established and applied successfully on approximately 2,202 cattle samples.
3. A project database has been established including TL and individual animal records from the SRUC research farm. An individual "animal diary" consisting of daily observations on each cow in the project has been set-up including all information required to meet the objectives of the study.
4. The longitudinal profile of TL was examined across the animals' lifetime in the resource population. No significant (P>0.05) impact of genetic line or feeding group on TL was found. Date of birth, date of sampling and age of animal at sampling had the most significant effects on TL measurements. Telomere length declined almost linearly during the first 14 months of age and stabilised afterwards. Decline in TL seemed to stop at approximately the time the animals entered their reproductive cycle for the first time and inseminations started.
5. Random regression models were developed and tested to derive smoothed curves of TL across the time trajectory and assess the attrition rate. Estimates of genetic and non-genetic co-variances between successive measurements have been derived.
6. Heritability estimates of TL at various ages have been derived and ranged from 0.23 to 0.48 (P<0.01). Heritability estimates were higher at earlier ages. Significant genetic variances were estimated suggesting that telomere measures are under genetic control. Significant maternal effects were also estimated demonstrating the impact of the dam on the TL profile of the offspring. In some cases, maternal effects accounted for nearly as much variance as the additive genetic effects.
7. Genome-wide association studies were conducted revealing the presence of Single Nucleotide Polymorphisms (SNPs) on bovine chromosomes 1 and 23 with significant effects on TL at birth.
8. A series of bivariate analyses between TL and various longevity, survival and health measures were conducted. Positive genetic correlations were derived, ranging between 0.58 and 0.63 (P<0.01), indicating a favourable correlation between long telomeres with increased survival. Also a favourable environmental correlation was found between TL and mastitis.
9. A platform for assessing TL as predictors of health, reproduction and longevity has been established including regression analyses of health, reproduction and longevity on TL at birth, as well as relevant cross-validation routines. A significant positive regression of survival to the first year on TL at birth was found.
10. A stochastic simulation platform of a dairy cattle population undergoing genetic selection was developed and tested.
Exploitation Route Outcomes can inform breeding programmes aiming to enhance animal longevity and health.
The methods developed can be used by other groups conducting telomere research in other species.
Sectors Agriculture, Food and Drink,Pharmaceuticals and Medical Biotechnology

 
Description Outcomes will enhance animal longevity and health, and, consequently, welfare. An additional impact is the improved image of the livestock industry in the general public. This was manifested during participation and presentation of the project in public engagement activities such as the Royal Highland Show in Edinburgh. Outcomes can be also applicable to rare breeds and endangered populations, thereby bearing additional societal and cultural benefits.
First Year Of Impact 2016
Sector Agriculture, Food and Drink
Impact Types Cultural,Societal,Economic

 
Description AVTRW (Association for Veterinary Teaching and Research Work) travel bursary
Amount £250 (GBP)
Organisation Association for Veterinary Teaching and Research Work 
Sector Charity/Non Profit
Country Unknown
Start 08/2015 
End 08/2015
 
Description Additional predictive biomarkers of survival and performance in dairy cattle
Amount £78,507 (GBP)
Organisation Scotland's Rural College 
Sector Academic/University
Country United Kingdom
Start 04/2016 
End 03/2017
 
Description GCRF-IAA
Amount £10,000 (GBP)
Funding ID BB/GCRF-IAA/06 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 11/2016 
End 01/2017
 
Description Murray Black Award
Amount £600 (GBP)
Organisation British Society of Animal Science 
Sector Learned Society
Country Unknown
Start 09/2015 
End 09/2015
 
Title High-throughput method for qPCR measurement 
Description We have developed a high-throughput protocol for measurement of leukocyte telomere length by qPCR using cattle blood samples, and also developed a method that allows us to account for variation associated with DNA extraction method amongst samples within this protocol. 
Type Of Material Technology assay or reagent 
Year Produced 2016 
Provided To Others? No  
Impact We used this method to process 2,202 samples for the purposes of the project. 
 
Title qPCR analysis for bovine telomere measurement 
Description A quantitative Polymerase Chain Reaction method was developed to measure the length of telomeres in bovine leukocytes. Three DNA extraction methods, four control gene primers and two telomere primers were tested. The method was applied to 58 samples on 4 identical plates across 2 days. All samples passed LinRegPCR Quality Control. Well-specific efficiencies and within-plate repeatability were very satisfactory. The method was shown to be robust for large-scale application. 
Type Of Material Biological samples 
Year Produced 2016 
Provided To Others? No  
Impact The method was applied to 2,202 longitudinal telomere measurements within the project. 
 
Title List of bovine blood samples 
Description The database combines historic and current blood samples of cattle raised in the Crichton Royal Farm, Scotland. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? No  
Impact These data were used to estimate telomeree lentgh of 735 animals (totally 2,202 measurements) that were then merged into the project database and used for analysis purposes. 
 
Title Project database 
Description The database included detailed information of animal management, performance, health, reproduction and longevity, along with measurements of their telomere length for 735 animals (2,245 records in total). 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? No  
Impact The database was used to extract data in order to assess the relationship between telomere length and animal erformance, health, reproduction and longevity. 
 
Description Telomeres in African cattle 
Organisation International Livestock Research Institute (ILRI)
Country Kenya 
Sector Charity/Non Profit 
PI Contribution We contribute analytical skills and methodology developed for large-scale measurement of telomere length in cattle.
Collaborator Contribution The partner has access to valuable local bovine resources.
Impact We have held discussions on the development of a project that will investigate the utility of telomere length measurements as a practical biomarker for cattle productivity and adaptability to climatic variability in Sub-Saharan Africa. We are currently seeking appropriate funding avenues for this activity.
Start Year 2016
 
Description Scottish Ecological Ageing Research Group (SEARG) meeting 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Study participants or study members
Results and Impact A presentation entitled "The effect of DNA extraction method on telomere length measurement by qPCR" was delivered at the meeting. We shared the outcomes of our research and demonstrated how the developed methodology may be used by other groups.
Year(s) Of Engagement Activity 2015
 
Description 2016 Workshop on Diversity in Telomere Dynamics, Edinburgh 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Outcomes of the project were presented at an international workshop on "Understanding diversity in telomere dynamics" that took place in Edinburgh, 31 October - 3 November, 2016. The workshop brought together scientists from different backgrounds, and at different career stages, with research interests in the causes and consequences of variation in telomere length. The meeting forms part of a workshop series conducted as part of an international network on telomere dynamics, funded by the Leverhulme Trust.
Year(s) Of Engagement Activity 2016
URL https://storify.com/adrbart/2015-workshop-on-the-comparative-biology-of-telome
 
Description Association for Veterinary Teaching and Research Work annual meeting in London. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact A presenation was given at the Association for Veterinary Teaching and Research Work annual conference, entitled "Telomere length and longevity in dairy cattle". The topic is directly related to outcomes of this award and reached a number of post-graduate students and young professionals from across the UK.
Year(s) Of Engagement Activity 2015
URL http://www.avtrw.co.uk/events/
 
Description Diversity in Telomere Dynamics Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact This workshop brought together researchers from across the globe who work on different facets of telomere dynamics. Delegates heard from human medical researchers, behavioural ecologists, and evolutionary biologists studying organisms ranging from human to planarians, birds to marsupials. Informal discussions in the evening, combined with engaging speakers throughout the day, ensured that all delegates left with new insights about telomere research and new ideas for collaborations and research.
Year(s) Of Engagement Activity 2014
URL http://www.gla.ac.uk/researchinstitutes/bahcm/research/sigs/garner/events/headline_370573_en.html
 
Description International Conference on Understanding Diversity in Telomere Dynamics 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact The event took place on 2 Nov 2017 in Edinburgh and was attended by about 60 scientists from various universities and research institutes internationally who have an interest in telomere lentgh dynamics. The interaction included exchange of results and views of future research and practical application.
Year(s) Of Engagement Activity 2017
 
Description Royal Highland Show, Edinburgh 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact A project booth was set up at the Royal Highland Show, 23-26 June 2016. The booth included a video for the general public, posters for the industry and scientists, and interactive material for younger audience. Interest was stimulated in all cases leading to discussions that mostly aimed at increasing awareness about the main concept (telomeres as biomarkers in cattle) and identifying application opportunities in practice.
Year(s) Of Engagement Activity 2016
 
Description SRUC and Royal (Dick) School of Veterinary Studies Postgraduate Conferences 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact A poster showing the work was set-up at the event. Post-graduate students from different disciplines approached, disussed and became familiar with the work.
Year(s) Of Engagement Activity 2015
 
Description Telomere Network UK 2018 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Telomere Network UK was formed to promote interaction among scientists and professionals working in the area of telomeres. The group is multi-disciplinary and promotes synergies in areas of common interest. The first meeting took place in Newcastle on Sep 11-12, 2018. The BBSRC award on cattle telomeres featured in the programme.
Year(s) Of Engagement Activity 2018