Abstract
The purpose of the present study was estimation of genetic parameters and genetic trends of early growth traits using Bayesian approach by Gibbs3f90 software in Iranian Afshari sheep. The data set [birth weight (BW), weaning weight (WW) and pre-weaning daily weight gain (PWDG)] were collected during the period 1999 to 2010 from Agriculture Jahad of Zanjan province, Iran. The fitted fixed effects were herd-year-season as interactions, sex (male, female), birth type (single, multiple) and age of dam. Based on Derivative Information Criteria (DIC), for studied traits the most appropriate model was determined. Therefore, based on the most appropriate fitted model, the direct additive heritabilities estimate for BW, WW and PWDG were 0.32?0.02, 0.05?0.01 and 0.24?0.02, respectively. The estimates of maternal heritabilities were 0.17?0.04, 0.07?0.02 and 0.12?0.05 and total heritabilities 0.11?0.05, 0.08?0.02 and 0.08?0.03 for BW, WW and PWDG, respectively. Direct genetic trends were positive for all traits but only significant for BW 0.75?0.31 g/year (P <0.05). Also, maternal genetic trends were for all traits negative and was significant for BW -0.63?0.27 g/year (P <0.05). The moderate estimates of heritabilities for early growth traits indicate that in Afshari sheep faster genetic improvement through selection is possible for these traits. Furthermore, the results genetic trends in this current study indicated that genetic improvement through selection is suitable only for BW in Afshari sheep.
Highlights
An advantage of a breeding program can be assessed by change in breeding value expressed as a proportion of expected theoretical change of the mean breeding value for the trait under selection (Mokhtari and Rashidi, 2010).Sheep meat production is one of the most important parts of Iranian livestock industry
The moderate estimates of heritabilities for early growth traits indicate that in Afshari sheep faster genetic improvement through selection is possible for these traits
The results genetic trends in this current study indicated that genetic improvement through selection is suitable only for birth weight (BW) in Afshari sheep
Summary
An advantage of a breeding program can be assessed by change in breeding value expressed as a proportion of expected theoretical change of the mean breeding value for the trait under selection (Mokhtari and Rashidi, 2010).Sheep meat production is one of the most important parts of Iranian livestock industry. Improving growth performance by selection programs is an important method to increase meat production in lamb breeding herds (Gholizadeh and Ghafouri-Kesbi, 2015). In this regard, one of the heavy, fat-tail, meat and high lamb growth rate breeds in Iran is Afshari sheep. One of the heavy, fat-tail, meat and high lamb growth rate breeds in Iran is Afshari sheep This sheep has high potentials of growth and reproduction and adapt to cold climate and must be considered in breeding program (Ghavi Hossein-Zadeh, 2012; Mohammadi et al, 2009). The purpose of Afshari sheep breeding were selection for increasing body weight and phenotypic characteristics. In Afshari sheep faster genetic improvement through selection is possible for body weight (Eskandarinasab et al, 2010)
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