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The objectives of this study was to evaluate the effects of GnRHPGF2α– GnRH protocols (on 0, 5 and 7 d, respectively) and artificial insemination (AI) within 24-28 h post the 2 GnRH injection, on reproductive performance of crossbred ewes, in reference with comparing the same AI dose once versus twice or once AI with low versus high concentration. Total of 40 ewes 1/2 Finnish Landrance x 1/2 Rahmani (F x R) and 1/2 Finnish Landrance x 1/2 Ossimi ewes (F x O) during January breeding season 2012 were used in this study. Animals were divided into four experimental groups (10 in each, 5 from each crossbred). In the 1 group, ewes were exposed to fertile ram without treatment (G1, control). Ewes in treatment groups were i.m. injected (d 0) with 1 ml GnRH analogue (Receptal), followed 5 d later by i.m. injection with 0.7 ml PGF2α (Estrumate). A second dose of 1 ml GnRH was given on d 7 and AI was carried out after the 2 GnRH injection based on the experimental design. Ewes in the treatment groups received the same hormonal protocol, but differed in sperm concentration of AI dose, being about 300 x 10 /ml/once after 24 h from the 2 GnRH injection (G2), 300 x 10/ml/twice after 20 and 28 h from the 2 GnRH injection (G3) and 400 x 10/ml/once after 24 h from the 2 GnRH injection (G4). Results revealed that estrus rate was the highest (70%) in G2, moderate in G3 (60%) and the lowest in G4 (50%) (P<0.05), being higher (P<0.05) in F x O than in F x R within each group. No pronounced differences were detected among groups or crosses in the time of incidence and duration of estrus. Lambing rate based on treated ewes decreased (P≥0.05) by increasing number of AI (once vs. twice) from 50% in G2 to 40% in G3, however, it decreased (P<0.05) from 40 to 20% by increasing AI dose from 300 to 400 x 10 sperm/ml/once AI in G3 and G4, respectively. Lambing rate based on estral ewes increased (P<0.05) by increasing AI number (50 vs. 66.7%) in G2 and G3, respectively; while it decreased (P≥0.05) from 50 to 40% by increasing AI dose in G3 and G4, respectively. There was higher lambing rate of F x R than that of F x O in G2 and G4 and G1. All treatments shortened lambing period as compared to the control group, ranging between 1-5 d in treatment groups and averaged 33 d in the control one. Lambs were numerous in G2 as compared to G1 (7 vs. 6 lambs). Litter size was higher (P<0.05) in G2 than in G1 and lower in G3 (1.25) than in G4 (1.50, P<0.05). Litter size was higher (P<0.05) in F x R than in F x O. Ovarian activity was higher in G2 and G3 than in G4 as well as in F x R than in F x O ewes. On day of 1 GnRH injection, P4 concentration was elevated in all groups, increased post-1 GnRH injection, decreased postPGF2α injection and at AI and showed marked increase 5 days post-AI. Loss cases was higher (P<0.05) in G3 than in G4 (37.5 vs. 25%), moderate in G2 (30%). Overall rate of loss was 31.8% in all treatment groups. In conclusion, using GnRHPGF2α–GnRH protocols (on 0, 5 and 7 d, respectively) and AI 24 h post the 2 GnRH injection during breeding season give high sufficient of estrous synchronization and lambing as well as the lowest reproductive losses , in particular for F x R ewes.

journal of animal and poultry production

EFFECT OF NUMBER AND SPERM CONCENTRATION OF ARTIFICIAL INSEMINATIONS ON THE REPRODUCTIVE PERFORMANCE OF GnRH-PGF2α-GnRH TREATED CROSS-BREED EWES IN THE BREEDING SEASON.