الفهرس 
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Abstract
Egyptian buffaloes are considered one of the most important dual purpose farm animals that represent 44% of dairy animals in Egypt. During the last 5 years, Ministry of agriculture (MOA) allowed the importation of Italian buffalo bulls with the aim to significantly improve the genetic makeup of the Egyptian buffaloes for economic traits, i.e. increasing milk and meat production. This study aims to evaluate the reproductive capacity of such bulls. Four native and four Italian buffalo bulls belonging to the Abassia Frozen Semen Center, General Organization for Veterinary Services were used in this study. Depending on age, these bulls were divided into young (< 4 years of age), adult (6-9 years of age) and old (≥ 12 years of age). Ones scrotal circumference and body weight were measured at monthly intervals, while libido (reaction time and libido score) and semen characteristics were assessed weekly over four seasons of the year 2013. The overall mean values of scrotal circumference (33.3±1.9 vs 29.2±1.6 cm), body weight (795.0±17.0 vs 762.5±14.8 kg) and reaction time (33.7± 3.8 vs 29.3±2.5 sec.) were significantly (p< 0.05) higher in native compared with Italian buffalo bulls. However, the difference in overall mean value of libido score (0-6) was non-significant between the two bull breeds (4.3±0.4 vs 4.2±0.4). Concerning semen characteristics, overall mean values of semen consistency scores (1.46±0.06 vs 1.31±0.05), volume (3.9±1.2 vs 2.9±1.0 ml), pH (6.50±0.03 vs 6.79±0.04), mass activity score (3.7±0.6 vs 2.4±0.5), initial progressive motility (61.5±6.3 vs 46.3±4.1 %), sperm concentration (1577.9±152.6 vs 1285.4±138.3 ×10⁶/ml), sperm abnormalities (primary: 2.51±1.26 vs 4.82±1.29 %; secondary: 6.07±1.21 vs 7.82±1.70 %), living percentage (69.5±7.9 vs 54.6±6.3 %), post-thawing motility (46.7±2.0 vs 32.5±3.2 %) and sperm freezability (71.8±6.6 vs 63.5±5.2%) were all in the favor of native compared to Italian bulls, respectively. All of the studied reproductive parameters were significantly affected by age of bull and season of the experiment, the differences were in favor of adult bulls during autumn and winter. More studies are recommended for the assessment of productive, reproductive and genetic diversity of crossbred populations before the enhancement of crossbreeding Italian and native activities on a national level.