Development of an additional criterion for evaluating the genetic apparatus of cattle for selected chromosomal defects in order to optimise production performance

In cattle, the most frequently diagnosed aberration is Robertsonian translocation. It may be inherited from parents or arise de novo. Its occurrence has a direct impact on reducing fertility and extending the calving period, which is associated with financial losses.

So far, cytogenetic work on the carriage of this translocation has been carried out based on metaphase plates obtained from peripheral blood. This method requires the involvement of a veterinarian and immediate processing of the material.

In the project, the karyotype analysis will be performed on sperm, without time and place limits (possibility of working on frozen and dead semen) and on blood lymphocytes from dairy cows, which is the innovation of this project.

The goal of the project is to develop and implement an additional criterion for controlling the genetic apparatus of cattle in the semen of bulls and in the blood of heifers and dairy cows which will enable the elimination of individuals carrying the translocation and optimization of cattle production results.

Project activities

The project will be implemented in close cooperation between the consortium members. Blood and semen from selected individuals will be analyzed for the carriage of chromosomal aberrations using molecular cytogenetics techniques, and the results will be used to eliminate carriers from breeding.

The main benefits of the project

The application of the project results in cattle breeding will allow the elimination of translocation carriers and improvement of fertility parameters, which may result in a measurable, positive financial effect.

• Breeders who want to implement the project results will be able to use the database of bulls free from disorders when selecting semen and thus reduce losses related to the need to perform subsequent insemination procedures, extension of the calving interval and reduced efficiency in cows.

Practice summary

• Translocations in cattle are disorders that may have a negative impact on fertility. Their occurrence forces breeders to repeat insemination procedures due to the lack of calving, may be associated with a prolonged inter-calving period, loss of embryos and low milk yield. This translates into financial losses, and stress related to the lack of explanation for failures.
• Selecting bulls for insemination that are healthy in terms of chromosomal aberrations will reduce the need for additional, costly procedures. 
•  Increasing awareness among breeders can reduce stress in the event of calving failure, as they will know the possible explanations for this situation, examination of the problematic individual and obtain the information necessary for further work.

Results achieved

The aim of the project was to develop and implement an additional criterion for controlling the genetic apparatus of cattle in the semen of bulls and in the blood of heifers and dairy cows, enabling the elimination of translocation carriers, which consequently affects the optimization of cattle production results. The implementation of the assumed goal took place in close cooperation between the consortium members. The blood and semen from selected individuals provided for testing were analyzed in terms of the carriage of chromosomal aberrations, focusing on sex chromosomes and chromosomes of pairs 1 and 29. Abnormalities of these chromosomes have a direct impact on reduced fertility and an extension of the inter-calving period, which is associated with financial losses. The research used molecular cytogenetics techniques to analyze the correctness of the karyotype of heifers and to observe selected chromosomes in sperm, which is an innovative element of this project, and the obtained results were passed on to breeders.
Additionally, as part of the project, a database of bulls with a correct karyotype, free from translocations, was created. This database will be updated with further studies and made available to farmers who want to implement the developed project results. The implementation of the project contributed to increasing the level of awareness among cattle breeders, which may open new opportunities for cooperation between the scientific community and practitioners.

A tangible effect for breeders is information on the karyotype of the tested individuals and the elimination of potential translocation carriers from breeding, and therefore a beneficial financial effect by reducing the risk of occurrence and spread of chromosomal abnormalities carriers, which affect fertility and production features such as milk yield. Another effect is the establishment of a molecular cytogenetics laboratory and the production of molecular probes specific to selected chromosomes, which can be used to diagnose chromosomal defects in spermatozoa, but also for quick and precise karyotype assessment of dairy cows. The benefit of the project is a database of bulls with correct karyotype, free from translocations. This database will be updated with subsequent tested animals and made available to farmers who want to implement the developed results of the project. The main research effect of the action is to obtain knowledge on the degree of spread of Robertsonian translocation in the population of young bulls and cows - obtaining detailed information on the number of carriers and the number of their potential offspring in the population. The research results were the basis for 2 engineering works and are being developed in the form of a doctoral dissertation and scientific publications. Additionally, the project's effect is to increase the education of breeders by disseminating the research results and creating a network of connections with recipients through presentations, exhibitions, and training.

Additional comments

Close cooperation with the breeder and MCB will facilitate access to research material. Additionally, the project will create a database of bulls with a normal karyotype, free from translocations. This database will be updated with subsequent research and made available to breeders who want to implement the developed project results. The database will be gradually expanded to include additional tested animals. The implementation of the project will contribute to increasing the level of awareness among cattle breeders, which may open new opportunities for cooperation between the scientific community and practitioners.