Estimates Of Genetic Parameters, Genetic Trends And Optimizing Community Based Breeding Of Abera Sheep Breed, Ethiopia
Views
0% 0
Downloads
0 0%
Open access
Citation
Amelmal Alemayehu. (19/12/2022). 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.
