Paper Information

Journal:   DYNAMIC AGRICULTURE   WINTER 2009 , Volume 5 , Number 4 (ANIMAL SCIENCE); Page(s) 404 To 393.
 
Paper:  ESTIMATION OF GENETIC AND ENVIRONMENTAL CORRELATIONS AMONG PRODUCTION AND REPRODUCTION TRAITS IN BALUCHI SHEEP
 
Author(s):  KHALILI D., GOLKHANDAN S.
 
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Abstract: 

The purpose of this study was to estimate genetic parameters for production body weight at birth, weaning, 6, 12, 18 months of age and greasy fleece weight at 18 months of age and ewe composite reproduction total number of lambs born and weaned, and total weight of lambs weaned per ewes joined over three parities traits for Baluchi sheep born from 1973 to 1998. Data consisted of 12328 lambs descending from 229 rams and 3677 ewes. Least-squares means for body weight at birth, weaning, 6, 12 and 18 months of age and greasy fleece weight at 18 months of age were 4.28±0.67 kg, 22.65±4.55 kg, 31.07±5.43 kg, 37.80±6.65 kg and 44.75±4.50 kg and 2.23±0.45 kg, respectively. These means for ewe composite reproduction traits were 3.08±0.79 lambs and 2.75±0.86 lambs and 61.99±19.31 kg, for total number of lambs born and weaned, and total weight of lambs weaned per ewes joined over three parities, respectively. Variance components resulting from direct additive genetic effects, maternal additive genetic effects, maternal permanent environmental effects, as well as, the covariance between direct and maternal additive genetic effects for production traits and direct additive genetic effects for ewe composite reproduction traits were estimated by REML procedures, fitting an animal models.
In addition to the direct additive genetic effects, maternal additive genetic effects, maternal permanent environmental effects and covariance between direct and maternal additive genetic effects were important for body weight at birth, weaning and 6 months of age. The direct heritability (h2a), maternal heritability (h2m), maternal permanent environmental variance as a proportion of phenotypic variance (c2) and correlation between direct and maternal additive genetic effects (ram) were 0.125
±0.020, 0.080±0.017, 0.110±0.015 and 0.473 for birth weight, 0.067±0.017, 0.035±0.015, 0.099±0.015 and 0.345 for weaning weight, and 0.109±0.022, 0.020±0.015, 0.047±0.019 and 0.904 for body weight at 6 months of age, respectively. For body weight at 12 months of age, besides the direct additive genetic effects, maternal additive genetic effects and covariance between these two effects were important. The direct and maternal heritability and correlation between direct and maternal additive genetic effects of this trait were found to be 0.247±0.045, 0.021±0.016 and 0.646, respectively. For body weight and greasy fleece weight at 18 months of age only direct additive genetic effects were important. On the basis of this model, direct heritability for these two traits were 0.322±0.150 and 0.142±0.033, respectively. Direct additive genetic variance for ewe composite reproduction traits were law. The corresponding estimates of direct heritabilites were 0.0106±0.035, 0.0079±0.035 and 0.0239±0.038, for total number of lambs born and weaned, and total weight of lambs weaned per ewes joined over three parities, respectively. The results of this study indicated that direct seletion for body weight at early stage of life, can improve ewe composite reproduction traits.

 
Keyword(s): BALUCHI SHEEP, GENETIC PARAMETERS, BODY WEIGHT, FLEECE WEIGHT, REPRODUCTION TRAITS, ANIMAL MODEL, REML
 
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