Genetic diversity in and conservation strategy considerations for Navajo Churro sheep

The objectives of this study were to 1) evaluate the genetic diversity of Navajo-Churro sheep using pedigree information; 2) examine the distribution of the Navajo-Churro population; and 3) evaluate the effect 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. Inbreeding coefficients were calculated for each individual animal using pedigree information. A geographic information system program was used to divide the United States into four regions and overlay breeder locations, flock size, and flock inbreeding level. The small correlation between level of inbreeding and flock size (r = -0.07, P = 0.07) indicated that inbreeding levels are not different across flock sizes. The mean flock inbreeding levels ranged from 0 to 11% across regions. The level of inbreeding did not differ among regions (P = 0.15), except for Region 4 (Kansas and Missouri; P = 0.001). The number of breeders registering sheep averaged 34 per year. Most of the breeders were transient, with only eight breeders maintaining ownership for more than 7 yr. Average inbreeding level for 2000 was found to be 1.2%, with a linear increase in inbreeding of 0.1%/yr over the period studied, suggesting a minimal loss of genetic diversity for the Navajo-Churro. However, given the relatively small effective population size (92) and the transient nature of the breeders, development of an ex situ cryo-preserved germplasm bank may be the best long-term strategy for maintaining this breed's genetic diversity.