GENETIC DIVERSITY IN AND CONSERVATION STRATEGY CONSIDERATIONS FOR NAVAJO-CHURRO SHEEP

Authors: MAIWASHE, NORMAN - COLORADO STATE UNIVERSITY; Blackburn, Harvey

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2004
Publication Date: 9/1/2004
Citation: Maiwashe, N., Blackburn, H.D. 2004. Genetic diversity in and conservation strategy considerations for navajo churro sheep. Journal of Animal Science. 82:2900-2905.

Interpretive Summary: The objectives of this study were to: evaluate genetic diversity of the Navajo-Churro sheep using pedigree information, examine the distribution of the population, and evaluate the impact of breeder dynamics on genetic conservation of the breed. Pedigree data and breeder information (city and state) were obtained from the Navajo-Churro Sheep Breed Association. The U.S. was divided into four regions in order to characterize breeder distribution. Inbreeding coefficients were calculated for each individual breeder using pedigree information. A geographic information system (GIS) program was used to overlay breeders, flock size, and flock inbreeding level. The correlation between level of inbreeding and flock size (r=-0.07, P>0.05) indicated that inbreeding levels are not different across flocks. The mean for flock inbreeding levels ranged from 0 to 11% across regions. The level of inbreeding did not differ among regions except for the region with the fewest breeders. Number of breeders registering sheep averaged 34 per year. Most of the breeders were transient, with only 8 breeders maintaining ownership for more than seven years. The rate of inbreeding was 0.1% per year indicating a linear increase over the period of time studied. Effective population size was calculated at 92 head. Considering the minimal level of inbreeding in this population, it is clear that the loss of genetic diversity has not yet reached critical levels; however, an effective population size of less than 100 head indicates breeders need to be concerned about genetic diversity in this breed. Given the in-situ population and the transient nature of the breeders, development of cryopreserved germplasm may be the best long-term strategy for maintaining this breed's genetic diversity.

Technical Abstract: The objectives of this study were to: evaluate genetic diversity of the Navajo-Churro sheep using pedigree information, examine the distribution of the population, and evaluate the impact of breeder dynamics on genetic conservation of the breed. Pedigree data and breeder information (city and state) were obtained from the Navajo-Churro Sheep Breed Association. The U.S. was divided into four regions in order to characterize breeder distribution. Inbreeding coefficients were calculated for each individual breeder using the pedigree information. A geographic information system (GIS) program was used to overlay breeders, flock size, and flock inbreeding level. The correlation between level of inbreeding and flock size (r=-0.07, P>0.05) indicated that inbreeding levels are not different across flocks. The mean for flock inbreeding levels ranged from 0 to 11% across regions. The level of inbreeding did not differ among regions except for the region with the fewest breeders. Number of breeders registering sheep averaged 34 per year. Most of the breeders were transient with only 8 breeders maintaining ownership for more than seven years. The rate of inbreeding was 0.1% per year indicating a linear increase over the period covered in this study. Effective population size was calculated at 92 head. Considering the minimal level of inbreeding in this population, it is clear that the loss of genetic diversity has not yet reached critical levels, within the time frame studied. Given the in-situ population and the transient nature of the breeders, development of cryopreserved germplasm may be the best long-term strategy for maintaining this breed's genetic diversity.