الفهرس 
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Abstract
Genetic analysis for improving productive and reproductive traits using 2181 normal lactation records of Friesian cows at Sakha Experimental Farm belonging to the animal production Research Institute, Egypt during the period from 1996 to 2002. Data divided into four groups, group one was first lactation records only, group two was first and second lactation records, group three was first, second and third lactation records, group four was all data. Traits studied in all groups were milk yield (MY), fat yield (FY) and protein yield (PY). While, age at first calving (AFC) and calving interval (CI) studied in group one only. Analysis was carried out using MTDFREML. The model included year and season of calving and parity as fixed effects, individuals permanent environmental and errors as random effects. The means were, 2570, 99, 77 kg 32.80 mo and 428 d for MY, FY, PY, AFC and CI respectively. While for MY, FY and PY were 2973, 107 and 83 kg for group two, and were 2983, 103 and 79 kg for group three, and were 2806, 102, 79 kg for group four respectively. heritability estimates were, 0.42, 0.12, 0.30, 0.35 and 0.26 for MY, FY, PY, AFC and CI respectively for group one, h2 tended to decrease with increasing parity. For group four h2 were 0.29, 0.24 and 0.29 for MY, FY and PY respectively. For group one all genetic and phenotypic correlations were positive and high (0.41 to 0.94) while genetic correlations between MY and AFC, MY and CI, AFC and CI were low and negative. The phenotypic and genetic (co) variances for milk traits studied (MY, FY and PY) for group four were used to estimate direct and correlated response to selection for one generation of cow selection, the results showed that selection for MY would resulted in correlated changes in different traits studied more than the direct selection of each of FY and PY. Four selection indices for improving traits studied were constructed including all combinations of two or three traits studied. The indices constructed using two sets of relative economic values (actual economic values and one standard deviation) for group one, group two, group three and group four. When using the actual relative economic values (set1) for group one the expected genetic change per generation ranged between 294 kg and 323 kg for MY. 2.48 kg and 5.13 kg for FY, 6.69 kg and 8.25 kg for PY. While ranged between 294 kg and 322 kg for MY, 2.08 kg and 5.13 kg for FY, 6.74 kg and 8.60 kg for PY when using one standard deviations (set2) as economic value. For second combination MY, AFC and CI the expected genetic gain per generation for MY ranged from 195 to 272 kg for set 1 and from 211 to 222 kg for set2, for AFC ranged from <U+2013>0.94 mo to <U+2013>1.17 mo for set1 and from <U+2013>0.57 to 0.81 mo for set2, for CI ranged from <U+2013>2.55 to 7.06 d for set1 and from <U+2013>12.81 to <U+2013>15.99 d for set2.the results showed that the differences between the two methods of relative economic values were small. In the original indices for group one the results showed that there is a little differences in expected genetic gain in both sets of analysis in different combinations (MY, FY and PY) or (MY, AFC and CI) Similar trend was found for milk traits when used group two, group three and group four. The results showed that uses of different methods of economic values giving the same trend in expected genetic gain and most cases the same accuracy. The results indicated that the effect of variation in economic weights on efficiency of selection might be quite small and the two different sets of relative economic values are succeeded in constructing different selection indices, but the method of one standard deviation appear to be most realistic and easy in calculation. Index I1a, I1b or I1b, I1c which included MY, FY and PY or MY, AFC and CI was the best (RIH=0.71, 0.74 or 0.65, 0.63) and recommended for genetic improvement of Friesian cows if the selection was exercised at the end of the first lactation