Estimates Of Genetic Parameters, Genetic Trends And Optimizing Community Based Breeding Of Abera Sheep Breed, Ethiopia

Abstract

Three combined investigations were carried out with the objectives of 1) estimating the genetic parameters and genetic trends for growth traits of Abera sheep in six breeder cooperatives established under community-based breeding programs (CBBPs); 2) participatory basis of comparison of breeding objectives and selection criteria of farmers from CBBPs and farmers from traditional sheep breeding practices; and 3) optimization of CBBPs of Abera sheep targets to increase genetic gain and economical profits with nine different breeding alternatives, considering number of candidate breeding ram and male to female sex ratio. A total of 2901 birth weight (BWT) 2626 weaning weight (WWT), 2261 six-months weight (SMWT) and 1603 yearling weights (YWT) records were collected between the year 2013 and 2019 were used for the analysis. General linear model consisting of the fixed effects of sex, breeder cooperative, season and birth type was used to analyze growth traits. As sheep in each CBBP is bred with by its own breeding ram, variance components and resulting genetic parameters were estimated, within each breeder cooperative, using univariate animal model based on restricted maximum likelihood method using WOMBAT software. Multivariate analysis was also employed to compute correlation estimates among growth traits. Six different models, by including or excluding maternal additive genetic effects, maternal permanent environmental effect, and covariance between direct-maternal additive genetic effects were fitted and the most appropriate model was selected based on a Log-Likelihood Ratio Test (LRT) and Akaike’s Information Criterion (AIC) were then used to select the most appropriate univariate model for each trait, which was finally used to estimate the studied parameters. Results indicated that all fixed effects influenced (P<0.05) the growth traits. The overall least squares means for BWT, WWT, SMWT and YWT were 2.9, 15.5, 20.8 and 27.9 kg, respectively. Based on the best fitted univariate model, the direct heritability (h2) for WWT and SMWT in the six breeder cooperatives were in the ranges of 0.12 to 0.38 and 0.20 to 0.49, respectively. Low to high (0.14 to 0.99) genetic correlations were observed for SMWT and other growth traits in all locations except negative association of SMWT with BWT and WWT in Abera Doko and Bonchesa Gobi communities. The WWT and SMWT showed positive genetic trends over the selection years in all breeder cooperatives/sites except Abera Doda breeder cooperative. Positive genetic progress was also achieved in most of the Abera sheep breeder cooperatives. Breeding objectives and selection criteria were defined using participatory own-flock ranking experiment and a structured questionnaire were under taken to assess sheep breeding practices of different sheep from community based breeding and traditional breeding practices of 3 sheep breed/type namely Doyogena, Abera and Dauwro from Sothern, Sidama and South-west regions of Ethiopia. Farmers selected purposively from community based breeding program (CBBP) and traditional breeding practices, accessibly and sheep production experience. A survey and own flock ranking experiment involving 300 households and 360 head of sheep were used. Data on size and appearance, lamb growth, lamb survival and reproduction traits were recorded for each ewe. From survey study, qualitative and quantitative data were obtained from flock ranking measurements and significant (p<0.05) variation was observed on rank, breed and membership of community based breeding program (CBBP) on body weight and most of studied traits including price of ewe. Farmers from both member of CBBP and non-member community breeding program emphasized traits on body size and appearance, reproduction and mothering ability and body condition as their breeding objective. A simulation study was conducted to optimize for genetic progress and profitability of Abera sheep CBBP based on candidate number and sex ratio. Six-month weight (kg) were identified as selection criteria trait, 9 breeding alternatives or schemes were simulated and evaluated for Abera Bongodo breeder village based on different candidate number and sex ratio. The annual genetic gain (AGG) for SMWT ranged from 0.06 to 0.16 kg, annual monetary genetic gain (AMGG) ranges $ 0.27 to 0.64 and discounted profit per ewe ranges $-0.04 to 1.87. Scheme 9 is recommended over all other schemes. So, shifting the current male to female ratio 1:9 to 1:27 (Scheme 9) with increased number of proved lambs for selection up to 150 maximized the genetic progress and profitability of the breeding program than the former breeding scenario in Abera sheep CBBP.