GENETIC DIFFERENCES, CONSERVATION AND UTILIZATION OF TUNIS SHEEP IN TUNISIA AND THE UNITED STATES
Plant And Animal Genetic Resources Preservation Research Unit
2011 Annual Report
1a.Objectives (from AD-416)
To determine genetic differences between the Tunis/Barbarine sheep in the US and Tunisia and compare phenotypic performance of the progeny sired by Tunisian and US rams.
1b.Approach (from AD-416)
During the 1800’s Barbarine sheep from Tunisia were imported to the US as gifts from that government. This breed, now called Tunis in the US, has been maintained as a relatively pure breed in the eastern part of the US. However, its population is relatively small with only 700 animals registered in 2000. In a genetic distancing study performed by NAGP it was determined that the present Tunis are unique compared to other US and Kazakhstan breeds. This result has led us to the following question: how different have the Tunis sheep become from the Barbarine sheep in Tunisia, and how does their phenotypic performance vary for economically important traits? Cooperators will determine the genetic distance between the Tunis and Barbarine. Genetic distances for 28 US breeds have already been completed, therefore the same set of genetic markers will be used on samples from Tunisian Barbarine sheep and the results will be merged with the US results for analysis. The National Gene Bank in Tunisia has the laboratory capabilities to conduct the needed laboratory work on the Barbarine. The analysis of the merged data will be performed jointly by ARS/NAGP and Tunisian scientists. Cooperators will also collect and cryopreserve semen from US Tunis sheep for exportation to Tunisia. This will require the assimilation of Tunis rams at a central facility for quarantine, collection and cryopreservation. NAGP and Virginia State University in Petersburg, VA have facilities which can be used for the described purposes. NAGP staff will cryopreserve the ram semen. Ten rams for this study will either be purchased or borrowed from Tunis breeders known to maintain breed purity (contacts with US breeders have already been established). The cryopreserved semen will be shipped to Tunisia where it will be inseminated into synchronized ewes. Either a NAGP or VSU scientist (or other trained professional) will assist with the inseminations. A like number of Barbarine rams will be mated to ten ewes each. The performance of the resulting progeny will be compared for phenotypic traits, such as, birth weight, weaning weight, growth rates, and wool characteristics. The anticipated results from this project are multiple. Quantification of the genetic similarity or dissimilarity between the Tunis and Barbarine sheep that will increase our understanding about gene flow between countries and how imported populations are subject to genetic drift and selection pressure over time. Understanding the genetic differences will assist ARS and the National Gene Bank of Tunisia in knowing if there are genes of interest in the Barbarine/Tunis sheep populations. The phenotypic comparison of performance traits will serve to inform breeders of both countries of the potential for exchanging genetic resources. The project will strengthen the collaboration between ARS/NAGP and scientists at the National Gene Bank of Tunisia, a process started during the ARS sponsored workshop in 2009.
DNA from U.S. Tunis sheep has been extracted and sent to Tunisia for laboratory analysis via the FAO panel of microsatellites for sheep. This analysis has been combined with the Barbarine samples from Tunisia. The results of the laboratory analysis have been reviewed by scientists in both countries and it was determined some genotyping errors had occurred. These are currently being rectified so that the statistical analysis can proceed. Work on correcting the allele calls will proceed. ADODR monitoring for this project was done via email and phone.