الفهرس 
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Abstract
Data used in this investigation were collected from 2692 records of 753 Friesian cows were daughters of 53 sires which belong to Shobratana Animal Production Society, located in the North Part of Delta region near Tanta city in Egypt, from 1985 to 2003. The following five productive and reproductive traits were analyzed: total milk yield (305-dMY, kg), dry period (DP, day), lactation length (LL, day), days open (DO, day) and calving interval (CI, day). Data were analyzed using the two methods, firstly, data analyzed by using Linear Mixed Model Least Squares and Maximum Likelihood (LSMLMW) computer program of Harvey (1990). Secondly, MTDFREML program of Boldman et al., (1995), using the multiple models were included the additive genetic effect of animal, maternal genetic effect and the maternal effect due dam (permanent environmental).The objectives of this study were to: 1-Estimate the effect of non-genetic factors effecting on productive traits such as: 305-day milk yield (dMY), lactation length (LL) and Dry period (DP) ) and reproductive traits such as: (calving interval (CI) and Days open (DO)).2- Estimates of genetic parameters for 305-day milk yield (dMY), lactation length (LL), Dry period (DP), calving interval (CI) and Days open (DO) by statistical programs. The results obtained from the analysis of these study could be summarized as follows:1-The overall means, for 305 day milk yield (305dMY), lactation length (LL), dry period (DP), days open (DO) and calving interval (CI) in a commercial herd of Friesian cows in Egypt were 4897 k g, 327 d., 66.30 d, 120 d and 401.16d, respectively. 2- Sire had highly significant (P<0.01) effect on all traits studied under investigation. 3-The month of calving highly significant (P < 0.01) on all traits under investigation and the highest estimates of all traits for Autumn months (October, November and December), vice versa in Winter month (January, November and March)4- The year of calving highly significant (P<0.01) on all traits under investigation, which the highest values of 305dMY, LL, DO and CL found in years (1994, 1995 and 1996) and the highest value of DP estimated in years (1993, 1994 and 1995).While the lowest values for all traits estimated in years (1987, 1988 and 1989).5- Parity highly significant (P < 0.01) effect on dry period, significant (P<0.05) effect on day open and calving interval but no significant effect on 305dMY and LL, whereas MY and LL increased with increased lactation and reached maximum level in the four lactation of milk yield but maximum of LL in three lactation. The lowest estimated of DP and CL for 5th lactation while the highest value of DO found in same lactation.6- Age at first calving as linear and quadratic regression coefficient had significant (P<0.05 or P<0.01) on all traits under investigation except effect quadratic regression on DO and effect linear regression CI. 7-The estimates of heritability using sire model for 305-dMY, LL, DP, DO and CL were (0.44 ± 0.08, 0.29 ± 0.09, 0.31 ± 0.08, 0.25 ± 0.11 and 0.22 ± 0.09), respectively
8- The estimates of genetic correlations between different traits studied ranged from (-0.30 to 0.98), which the genetic correlation among 305-dMY, LL, DO and CL were positive and high (0.76 to 98). The highest value between DO and CL (0.98), while the lowest estimated found between DP and CL (0.09). 9-The estimate of residual using sire model for studied traits ranged from (0.66 to 0.78). While the estimated of residual ratio among studied traits ranged from (-0.18 to0. 67), which the highest ratio found between CL and LL (0.67), but the lowest ratio between DP and LL (-0.18).10-The estimates of phenotypic correlations among milk production and reproductive traits by using sire model varies (-0.21 to 0.94), which the highest value found between LL and CL (0.94), succeeding by phenotypic correlation between DO and CL (0.90) and then the correlation between 305dMY and CL (0.88), while the lowest value and negative found between LL and DP (-0.21). 11-The estimates of direct heritability for 305-dMY (0.38) was moderate, while for LL, DP, DO and CI were stingy, being 0.13, 0.11, 0.14 and 0.16, respectively by animal model. 12-The low estimates of maternal heritability for 350d MY, LL, DP, DO and CI, were also obtained; being 0.13, 0.18, 0.14, 0.23 and 0.21, respectively 13- The estimate of genetic correlations between 305dMY and each of LL, DP and CI were positive and high (0.79, 0.92 and 0.98). Also the estimates genetic correlation between LL and each of DO and CI were (0.91 and 0.95) respectively. The genetic correlations between DP and both of 305dMY and LL were negative 14-Estimates of maternal correlations (rm) between MY and traits (LL, DO and CI) were moderate and positive, while the maternal correlations between DP and other studied traits were negative. The estimates of correlations between direct and maternal genetic effects were negative, except among 305dMY, LL and DO were positive 15-The estimates permanent ratiod for traits, 305dMY, LL, DP, DO and CL were 0.19±0.11, 0.21±0.09, 0.04±0.02, 0.28±0.18 and 0.09±0.03, respectively. The permanent environmental ratios among 305dMY, DP and DO were moderate and negative, while the ratio between CI and (all traits) were positive (0.29, 0.04, 0.26 and 0.64), respectively. Also between LL each of 305dMY, DP and DO were positive (0.09, 0.50 and 0.06) respectively. 16- Estimates of residual ratio from different studied traits using animal model Table 43 were 0.30±0.02, 0.48±0.30, 0.71±0.19, 0.35±0.09, 0.54±0.16), respectively. While the ratios among studied traits round (-45 to 0.90). 17-The phenotypic correlation between 305dMY and each of LL, DO and CI were positive and high ranged from (0.81 to 0.99) and the phenotypic correlation between DO and CI was (0.91) 18-The predicted breeding value of sires, cows and dams for studied traits 305dMY, LL, DP, DO and CI, range of predicted breeding value (PBV’s) of sires were 462 kg, 1.05 d, 0.24 d, 5.93 d and 2.26 d, for 305dMY, LL, DP, DO and CI, respectively. PBV’s of cows of the mentioned traits was 1123 kg, 2.92 d, 1.64 d, 5.93 d and 2.92 d respectively. Corresponding PBV’s of dams for the above same traits were 510 kg, 1.42 d, 0.80 d, 7.20 d and 3.00 d, respectively. Accuracy of (PBV’s) ranged from 38 to 88, 73 to 88 and 39 to 89% for sires, cows and dams, respectively; CONCLUSION The heritability estimates for 305-dMY emphasized of realizing a considerable rate of genetic improvement in this trait under investigation. The estimates of heritabilities were low for some traits studied indicated that the major part of the variation in these traits was environmental. Therefore, better management can play a major role in improving these traits. The estimates of maternal heritability shown that maternal effects need to be considered in the analysis model and selection for productive and reproductive traits. The accuracies of predicted breeding values, similarly for sires, cows and dams indicate that genetic improvement could be attained through any bath of sires or cows or dams.