eg, Telephone: + 202 3378 6729, Fax: + 202 3569 4049, Cellular phone: + 2 012 2340 9079 SUMMARY Milk production and processing in Egypt is a basically function of buffalo and cattle. Various reasons justify sterility and low reproductive performance in livestock, among them chromosomal aberration which is highly considered. The present study was undertaken to investigate the association between semen characteristics and cytogenetic structure as an early indicator of fertility in Egyptian

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... bulls. Data and samples were collected during September and October, 2015 on 116 ejaculates of 29 randomly selected bulls (age from 22 to 26 months and body weight from 250 to 300 kg). Animals were classified into two groups based on semen quality: group 1 (G1) composed of 10 animals with low semen quality characteristics and group 2 (G2) that included 19 bulls with normal semen quality characteristics. Polyploidy accounted for 9.6% of total numerical aberrations in G1 compared to 1.2% in G2, while aneuploidy represented 5% and 0.4% in G1 and G2, respectively. G1 and G2 differed significantly (P < 0.05) in the percent of polyploidy and aneuploidy. Structural chromosomal aberrations identified were deletion, break, gap, fragmentation, ring, centromeric attenuation and centric fusion, which varied significantly (P<0.05) between G1 and G2. Such aberrations in metaphase chromosomes may have a direct relevance on fertility as they were consistent. All estimates of genetic correlation were significant (P<0.05), except that were related to centromeric attenuation. Chromosomal aberrations correlated negatively with motility, live sperm, hypo-osmotic swollen (%) and testosterone level; whereas their correlation coefficients with sperm abnormality were positive. Genetic correlations ranged from -0.391 between motility and polyploidy to 0.341 between sperm abnormality and polyploidy. The results obtained suggest screening buffalo bulls for chromosomal aberrations prior to their use in natural or artificial insemination.