Estimation of co-variance components, genetic parameters and genetic trends of reproductive traits in community-based breeding program of Bonga sheep in Ethiopia
The objectives of the study were to evaluate reproductive performance and selection response through genetic trend of community-based breeding programs (CBBPs) of Bonga sheep.
Reproduction traits data collected between 2012 and 2018 from Bonga sheep CBBPs. Phenotypic performance was analyzed using the General Linear Model procedures of SAS. Genetic parameters were estimated by univariate animal model for age at first lambing (AFL) and repeatability models for lambing interval (LI), litter size (LS) and annual reproductive rate (ARR) traits using restricted maximum likelihood method (REML) of WOMBAT. For correlations bivariate animal model was used. Best model was chosen based on likelihood ratio test (LRT). The genetic trends were estimated by the weighted regression of the average breeding value of the animals on the year of birth/ lambing.
The overall least squares mean ± SE of AFL, LI, LS and ARR were 375±12.5, 284±9.9, 1.45±0.010, and 2.31±0.050, respectively. Direct heritability estimates for AFL, LI, LS and ARR were 0.07±0.190, 0.06±0.120, 0.18±0.070, and 0.25±0.203, respectively. The low heritability for both AFL and LI showed that these traits respond little for selection program rather highly depend on animal management option. The annual genetic gains were -0.0281days, -0.016days, -0.0002 lambs and 0.0003 lambs for AFL, LI, LS and ARR, respectively.
Implication of the result to future improvement program was improving management of animals, conservation of prolific flocks and out scaling the CBBP to get better result.