الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
A total of 4745 normal lactation records of Egyptian buffaloes, kept at three experimental farms (MehalletMousa, El-Nattafe El-Gaded and El-Nattafe El- Kadem), belonging to the Animal Production Research Institute, Ministry of Agriculture ,Cairo, Egypt, over a period of 35 years from 1980-2014 were each record included cows, sires and dams identification, date of used. Calving (season, parity, year), lactation period (LP), total milk yield (TMY) days open. Traits studied of Egyptian buffaloes. Data were analysis by the general linear model procedures (GLM) of SAS (2003) to estimate the fixed effects which were parity of the dam, season of calving and the parity. The differences between means were tested (P<0.05) using Duncan (1955) test, In addition, genetic parameters ,Direct heritability, genetic correlation, maternal Heritability, genetic correlations for maternal, genetic correlations between direct and maternal, Permanent environmental correlations, Residual correlations, phenotypic correlation for different traits studied. Were analyzed using multi-traits animal model of VCE6 computer package (Groeneveld et al., 2010) for Variance component estimates for six different models. The present study can be summarized as the following: Means for TMY, LP, DO, were 1445.30kg, 220.60day, and 184.34day respectively.Season, parity and year of calving had a significant effect on TMY, LP, and DO. Direct Heritability estimates for TMY, LP and DO for six models were 0.15±0.021 to 0.57±0.15, 0.16±0.047 to 0.56±0.026, 0.13±0.020 to 0.20±0.02, respectively.Estimates of genetic correlation rg between traits study TMY, LP and DO, LP are positive and highly significant and ranged from 0.53 to 0.84, 0.30 to 0.94 respectively, while the genetic correlation between DO and TM is moderate and ranged from -0.15 to 0.58 for all models.Estimates of maternal heritability were very low in six models for LP, TMY and DO and ranged from 0.18E-09±0.79E-05 to 0.055±0.026; 0.52E-09±0.13E-04 and 0.081±0.029 and from 0.83E-09±0.12E-04 to 0.053±0.01, respectively.Estimates of phenotypic correlations (rp) between traits study TMY and LP are positive and highly significant in all models and ranged from 0.76 ±0.74, the phenotypic correlations (rp) between DO,LP and DO, MY was lower and ranged from 0.29±0.27 , 0.20±0.17 respectively in all models.The present results showed that the estimates of traits under investigation in unconditioned range with other studies in Egyptian buffaloes. The influence of the maternal genetic effect for traits studied was lowest thereby no relative efficiency of improvement. Viceversa, direct heritabilities for TMY and LP were efficiency, therefore considerable rate of genetic improvement these traits under investigation. Genetic betterment for LP following up improves each TMY and DO. The estimates of heritability were low for DO indicated that the major part of the variation in this trait was environmental and selection may not prove effective in bringing about genetic improvement. Therefore, preferable improving management can play a major role in this trait.It was concluded that using the Multiple - Trait animal model 6, analysis is recommended to obtain more accuracy genetic parameters value for the studied traits because it makes use of all the information about the lactation and the covariances among then as well as the relationships between the relatives in the different traits.