الفهرس 
INTRODUCTION
Factors affecting reproductive traits of ewesOnly 14 pages are availabe for public view
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Abstract
The objective of the present study was to improvement reproductive traits for ewes and weights of lambs at birth and weaning in Farafra sheep by estimating genetic parameters including heritability and genetic correlations for reproductive traits of Farafra sheep and lambs weights at birth and weaning because the genetic characterization of the native breeds is required for the conservatory consideration and building up efficient selection and breeding schemes.
Data used in the present study was collected during the period from 1995 to 2009 on Farafra sheep (1072 ewes and 3151 lambs). Farafra breed was raised in Mallawi research station (latitude 28◦ 07 and longitude 30◦ 33 E) which is located in the north of Upper Egypt and belonging to Animal Production Research Institute (APRI).
Reproductive traits for ewes were basic traits and composite traits, basic traits include: conception rate (CR), number of lambs born (NLB), number of lambs weaned (NLW), total litter weight at birth (TLWB) and total litter weight at weaning (TLWW). Composite traits were: number of lambs born per ewe exposed (NLB/EE), number of lambs weaned per ewe exposed (NLW/EE), total litter weight at birth per ewe exposed (TLWB/EE) and total litter weight at weaning per ewe exposed (TLWW/EE). Lambs traits were: (BW and WW).
The fixed effects ( year of mating, season of mating, age of ewe at mating, type of birth of ewe, year of lambing, season of lambing, age of ewe at lambing, type of birth for lamb, litter size born, litter size weaned and sex) were performed to SAS (2004) to calculate the significancy of studied factors.
Heritability (h2a), additive maternal effect (h2m), genetic(rg) and phenotypic(rp) correlations and permanent environmental effect (c2) were estimated using the Multiple Trait Derivative Free Restricted Maximum Likelihood program (MTDFREML), a set of programs employing the simplex procedure to locate the maximum of the log likelihood (-2loglik-) for each parameter.
Lastly, variance components and further phenotypic and genetic parameters for the basic and composite traits with discrete numerical observation (CR, NLB, NLB/EE, NLW, and NLW/EE) were estimated using of the Multiple Trait Gibbs Sampling in Animal Models (MTGSAM).
Year of mating (Yr(m)) and Age of ewe at mating (Age(m)) were significant (p<0.01) sources of variation on CR, NLB, NLB/EE, TLWB and TLWB/EE. Season of mating (Sn(m)) was significant (p<0.01) source of variation on CR, NLB, NLB/EE and TLWB, and was significant (p<0.05) source of variation on TLWB/EE.
Type of birth for ewe was significant (p<0.01) source of variation on NLB and NLB/EE. Litter size born LSB was significant (p<0.01) source of variation on TLWB, TLWB/EE, NLW and NLW/EE. Sex of lamb was significant (p<0.01) source of variation on TLWB, TLWB/EE, TLWW and TLWW/EE. Year of lambing (Yr(l)) was significant (p<0.01) source of variation on NLW, NLW/EE, TLWW and TLWW/EE. Season of lambing (Sn(l)) was significant (p<0.01) source of variation on TLWW, and was significant (p<0.05) source of variation on TLWW/EE.
Age of ewe at lambing (Age(l)) was significant (p<0.01) source of variation on NLW, TLWW and TLWW/EE. Litter size weaned (LSW) was significant (p<0.01) source of variation on TLWW and TLWW/EE.
Year of lambing (Yr(l)), season of lambing(Sn(l)), age of ewe at lambing (Age(l)), type of birth for lamb (TBL) and sex of lamb (sex) were significant (p<0.01) sources of variation on BW and WW of lambs .
Direct heritability estimates for CR, NLB, NLB/EE, TLWB, TLWB/EE, NLW, NLW/EE, TLWW and TLWW/EE were 0.06, 0.10, 0.07, 0.02, 0.05, 0.03, 0.01, 0.13 and 0.11, respectively. Maternal effect for the same traits ranged from 0.008 to 0.04 (Table 36).
The heritability estimates by Bayesian analysis for CR, NLB, NLB/EE, NLW, and NLW/EE tented to be larger than MTDFREML estimates, threshold estimates were, 67%, 60%, 71%, 67%and 50% larger than MTDFREML estimates (Table 38).
Genetic correlation between reproductive traits ranged from -0.21 to 0.98 and phenotypic correlations estimates between the investigated traits ranged from -0.06 to 0.65 (Table 37).