Document Type : Research Paper
The present study was carried out on 120 repeat-breeder dairy cows belong to the breed Holstien-Frriesian , Animals of the study was divided into two equal groups, first group (A) involved 60 repeat breeder dairy cows expressed nervous excitation signs and elevated heart rate at the time of artificial insemination, while second group (B) involved 60 repeat-breeder dairy cows did not express nervous excitation signs and have normal heart rate. Each group was further subdivided into six equal subgroups: A1 and B1 (control) was injected with 5 ml of distilled water, A2 and B2 was injected with Oxytocin after artificial insemination, A3 and B3 was injected with hCG after AI, A4 and B4 was injected with Propranolol before AI, A5 and B5 was injected with Propranolol before AI in addition to injection of Oxytocin after AI, A6 and B6 was injected with Propranolol before AI in addition to injection of hCG after AI. The result revealed significant differences of the conception and pregnancy rate among the sixth subgroups inside each group. The percentage of repeat-breeder dairy cows belonging A1, A2, A3, A4, A5 and A6 were 0% ,10%, 30%, 40%, 70% and 50%, respectively. The statistical analysis showed significant increase (P<0.01) in subgroup (A5) (70%) followed by A6 (50%), A4 (40%), A3 (30%) and the lowest ratio was recorded in A2 (10%) compared with control (A1) which did not record any instance of pregnancy. While the ratios of the repeat-breeder dairy cows subgroups which did not expressed nervous excitation (B1, B2, B3, B4, B5 and B6) were 10%, 20%, 60%, 10%, 20% and 60%, respectively. The statistical analysis revealed significant differences (P<0.01) in the conception rate of B6 (60%) followed by B3 (60%), B2 and B5 (20%) while the lowest ratio was recorded in B4 (10%) and (control) (10%). On the other hand, in comparison between the groups (A and B), the results revealed higher ratios of all subgroups belong to A group at 0.01 level of significancy except A2 and B2 which revealed difference at 0.05 level of significancy, while A6 and B6 showed no significant difference. The result of present study stated that the better reproductive program to increase the conception and pregnancy rate in the first group A was by injection of Propranolol in addition to Oxytocin hormone, while second group B was by injection of hCG hormone only.