Population genetic structure analysis of Shall sheep using pedigree information and effect of inbreeding on growth traits

Abstract

The objective of this study was to use pedigree analysis to describe the population structure, genetic variability and inbreeding to quantify their effects on growth traits in Shall sheep. The analysis was based on the pedigree information of 64,964 animals. Data and pedigree information used in this study were collected from 1982 to 2012 by the Animal Breeding Centre of Iran. Growth traits included were birth weight (n = 12,786), 3-month weight (n = 9521), 6-month weight (n = 5106), average daily gain from birth to three- (n = 8543) and 6-month of age (n = 4,303) and their corresponding Kleiber ratios (n = 8543; n = 4,303, respectively). The CFC program was applied to calculate pedigree statistics and the population genetic structure of the Shall sheep. Also, the INBUPGF90 program was used for calculating inbreeding coefficients for individuals. The pedigree analysis indicated that the inbreeding coefficient ranged from 0 to 38% with an average of 1.62%. The average coancestry was 0.0072% and the generation interval was 3.755 years. Inbreeding depression was observed for all growth traits in this population of sheep. Based on the estimate of effective population size (910.25), it is expected to have enough genetic variability in the understudy population. On the other hand, the ratio of the effective number of founders to the effective number of ancestors (1.001) indicated no genetic bottleneck in Shall sheep. Breeders must do their best to prevent the mating between closely related animals and use this as an appropriate strategy to maintain the inbreeding under control in this sheep breed.HIGHLIGHTS The average coefficients of inbreeding and coancestry were low in Shall sheep. Enough genetic variability was available in Shall sheep and no genetic bottleneck occurred in this population. Inbreeding depression was observed for growth traits in this population of sheep.

Keywords

• coancestry coefficient
• effective population size
• fat-tailed sheep
• genetic variability
• generation interval