الفهرس 
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Abstract
This study was carried-out to investigate the effect of crossbreeding between Egyptian native cows (Baladi) and Brazilian Zebu bull on:- 1-Productive This study was carried-out in the farm of the Faculty of Veterinary Medicine Alexandria University at Edfina city-Rosetta Line-Behaira Governorate-Egypt. During the period extended from August 2008 to September 2014. performance:- which include body weight at different age, average daily gain, puberty age of Baladi calves, F1 and F2 calves. 2-Reproductive performance:- which include, gestation period, days open, calving interval and conception rate for Baladi calves, F1 and F2 calves. 3-Molecular study on growth hormone gene to reveal polymorphism in this gene in Baladi cattle, F1 and F2 with Brazilian Zebu cattle using, PCR-RFLPs and DNA sequencing. The animals used in this study :- 1-Baladi cattle:-Baladi cattle were purchased from animals markets based on phenotypic characteristics of Baladi cattle and were maintained for research under supervision of Gynacology and Obstetrics Department at the Faculty farm. 2-Zebu cattle:-Frozen semen straw of genetically improved selected sire were obtained from Brazil in an Egyptian – Brazilian Project for improving Egyptian cattle. (Improving the genetic characters of Egyptian cattle through crossing between Egyptian cattle and Brazilian Bulls).Through co-operation between Faculty of Veterinary Medicine Alexandria University and Association Brazilian Cattle Zebu breeders (ABCZ). This animals under study was divided into 3 groups: a-Group I: Sire: Baladi (100 %) Baladi sire were naturally mating with baladi cow. Dam: Baladi(100%) :30 cows. b-Group II: ( zebu-50%): Sire: Pure zebu. Dame: 81 Pure Baladi cow. c-Group III F2 (Zebu-25%): Sire: Result from the cross between F1 (50 % Zebu X 50 % BaladiDam): 25 pure Baladi cow. 2-Parameters studied: 2.1-Productive efficiency parameters which include: Birth weight, weaning weight, body weight and body weight gain. 2.2. Reproductive efficiency parameters: Which includes: Age of puberty, adult age, days open, calving interval, number of services per conception and conception rate. 3-The data was analyzed statistically for determination of the significant of the parameters studied among the different breeds studied. The results of this study showed that: 1-Crossing of Zebu sire with Baladi cattle improved birth weight, weaning weight, One year body weight, 1.5 year body weight, body weight gain, average body weight gain and two year body weight , puberty age, gestation period, conception rate observed in F1 (Zebu-50%), followed by F2 (Zebu-25 %) and both of them higher in its body weight than that of (Baladi-100 %) calves. 2-The effect of genotype on sex of the calf cleared that, the results indicated that, the higher incidence of male sex observed in F2 (Zebu-25 % ), followed by F1 (Zebu-50 %) and the lowest male incidence observed in (Baladi-100 %) calves. While, the incidence of Femal sex in (Baladi-100 %) was higher followed by F1 (Zebu-50 %) and the lowest incidence observed in F2 (Zebu-25 %). 3-The higher level of milk production per year observed in F2 ( Zebu-25%) , followed by F1 (Zebu-50 %) and the lowest milk production per year observed in (Baladi-100 %). 4-This results cleared that, the best generation for crossing zebu cattle with Baladi cattle is the F1 (Zebu-50%) as the crosses showed a higher body weight, body weight gain, milk yield and best reproductive performance parameters. The aim of molecular study was to detect the polymorphism in intron 3 and part of exon 4 of GH gene in Baladi cattle and F1 hybrid (Baladi×Zebu) and F2. Blood samples were obtained from animal under study. Sequence analysis of 329 b p of G.H revealed high similarity of sequence of GH gene among the Baladi, Zebu (50%) and Zebu (25%). Only five SNPs are detected at the 3rd intron, four SNPs are recorded in tow animals and the fifth SNP at 59 C < T is a recognition site of MSPI. Digesion of 329 bp of GH.gene with MSPI revealed 3 genotypes. AA genotype with one undigested fragment, BB genotype with tow fragment (224-105bp) and AB genotype with three fragments (329, 224 and105). Following restriction analysis, the animals were ranked according to their corrected weaning weight, breeding value, genotype and the results showed that, The heterozygous genotype (AB) has higher corrected weaning weight in Baladi (100%), Zebu (50%) and Zebu (25%) compared other genotype. from the previous results this study may concluded that, crossing of Zebu bull with Baladi cows improved productive and reproductive efficiency parameters, the higher level of milk production per year observed in F2 (Zebu-25%), followed by F1 (Zebu-50 %) and the lowest milk production per year observed in (Baladi-100 %), The results cleared that, the best generation for crossing zebu bull with Baladi cattle is at the F1 (Zebu-50%), and PCR sequence analysis of growth hormone gene showed minor differences in growth hormone gene in animal breeds under study, furthermore, The heterozygous genotype (GH) has highest body weight in each breed.