الفهرس 
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Abstract
The present study was carried out in sheep farm at Animal Reproduction Research Institute (ARRI), Giza province. The study was conducted on a total 40 multiparous, non-pregnant Barki ewes aged 3-5 years and weight 35-45 kg.
The ewes were randomly allocated into 2 groups (A & B) of equal numbers (n=20 ewes/each group). group A were treated with polyurethane vaginal sponges impregnated with 25 mgmedroxy-progesterone acetate (MAP) and left in situ for 14 days. On the day of sponge’s withdrawal the ewes were randomly reassigned according to eCG dose into three subgroups (A1, A2 and A3). group A1 (n=6), served as control, without eCG injection, while groups A2 and A3 (n=7 ewes/each group) were injected intramuscularly (IM) with 300 and 500 IU/eCG, respectively, once at the time of sponge removal. The ewes of group B (n=20 ewes) were inserted vaginally with polyurethane sponges containing 50 mgof MAP for 14 days. At the day of sponge removal, the ewes of group B were subdivided into 3 subgroups (B1, B2 and B3). group B1 (n=6), used as control, without eCG injection, while groups B2 and B3 (n=7 ewes/each group) were injected IM with 300 and 500 IU/eCG, respectively, at the time of sponge withdraw as groups B2 and B3.
The occurrence of estrus was monitored 8h after sponge withdrawal for a period of 30 min, three times daily for 5 days, using three fertile rams with highly sexual desire. Rams were introduced and subjected to run with the treated ewes for heat detection and natural mating. Ewes started to have responded to the treatment when they have showing estrus signs during the observation periods (extended to 120h after sponges withdraw) and stood to allow the ram to mount, and the end of estrus was defined by the antagonistic behavior of ewes to the rams. The pregnancy was assured by trans-rectal ultrasonography on day 35-40 following the mating.
To studying the pattern of progesterone in the blood for each treatment group, blood samples were taken immediately before sponge insertion and every 2 days to the end of sponge application. As well as, on day 17 post mating, for determining the level of progesterone for pregnancy check. Also blood samples were taken from all treated groups 9 hours after eCG injectionand every 3h up to 74h latter for LH and estradiol-17β assay.
The following parameters were included in the study
• Estrus response: Number of ewes exhibiting estrus/total ewes in each treatment group x 100.
• Time to onset estrus (h):It’s the time elapsed between the cessation of the treatment (sponge withdrawal) to the middle of the time interval between the last rejection to be mounted and the first tolerance of rams mounting. The onset of estrus was estimated to begin half time between the last negative and the first positive signs of estrus.
• Duration of estrus (h):It’s the period of sexual receptivity and mating which characterized by distinct behavioral symptoms of estrus and estimated from first to last signs of estrus. The duration of estrus was estimated as the time extended from the first positive signs of estrus to the half time between last positive and first negative signs.
• Pregnancy rate: (pregnant ewes/ewes mated) x100.
• Lambing rate: (lambed ewes/pregnant ewes) x 100.
• Fecundity rate: (number of lambs born/number of pregnant ewes) x 100.
• Prolificacy rate: (lambs born /lambed ewes) x 100
• Progesterone (P4) assay
• Estradiol (E2) assay
• Luteinizing Hormone (LH) assay
The results can be summarized as follows:
Parameters related to estrus synchronization
Estrus Response (%): The incidence of estrus response were 74.60±9.71and 79.37±9.71 for groups A (25 mg MAP) and B (50 mg MAP), respectively. Irrespective to MAP sponge concentrations, the estrus response in ewes injected with 500 IU/eCG (A3B3) was higher (92.86±11.58%) than group A2B2 (71.43±11.58%) which treated with 300 IU/eCG and control group A1B1 without eCG (66.67±12.51%).
Time to estrus (h):The onset of estrus in ewes of group A was significantly shorter (P<0.05) than group B (36.23±3.18 h vs 46.10±3.41 h). Regardless of MAP, the onset of estrus in control ewes (without eCG) was significantly longer (56.02±4.70 h;P<0.01) than ewes treated with 300 IU/eCG, (36.20±3.82 h) and 500 IU/eCG (31.27±3.49 h).
Duration of estrus (h):The means of estrus duration in ewes of group A which received sponge containing 25 mg MAP were slightly longer (33.03±1.72 h)than group B (30.10±1.96 h) of high concentration (50 mg MAP) with no significant differences between values. Similarly, no significant effect of eCG on the estrus duration, and the mean values were 32.13±2.68, 31.53±2.25 and 31.04±1.74 h for ewes groups A1B1, A2B2 and A3B3, respectively.
Parameters related to reproductive performance
Pregnancy rate: The pregnancy rate was higher in ewes of group A (83.33±10.55%) than group B (65.24±10.34%) but no significant differences between values. Regardless of MAPdose, the pregnancy rate of ewes were higher in group A3B3(92.86±11.21%) than groups A1B1andA2B2 (50.00±14.24 and 80.00±12.74%), respectively, with significant differences at P<0.05.
Lambing rate:The lambing rates were 87.78±11.09 and 88.89±11.92% for animal groups A (25mg MAP) and B (50mg MAP), respectively, and were 100.00±17.87, 73.33±13.05 and 91.67±10.32% for groups A1B1 (without eCG), A2B2 (300 IU/eCG) and A3B3 (500 IU/eCG), respectively. Neither MAP nor eCG has been a significant effect on the lambing rate.
Fecundity rate:The fecundity rates were 93.33±17.36 and 105.56±18.65% for animal groups A and B, respectively, and were 100.00±27.97, 90.00±20.43 and 108.33±16.15% for groups A1B1, A2B2 and A3B3, respectively.
Prolificacy rate:The prolificacy rates were 106.67±12.25 and 122.22±13.58 % for animal groups A and B, respectively, and were 100.00±18.86, 125.00±16.33 and 118.33±11.42% for groups A1B1, A2B2 and A3B3, respectively.Neither MAP nor eCG has been a significant effect on the prolificacy rate.
Blood Hormonal Assay
Progesterone (P4) assay: The mean level of plasma progesterone on the day of sponge insertion for group A (25 mg MAP) was 1.52±0.24 ng/mL followed by gradually increases reaching to its maximum levels on days 6 (1.97±0.49) and 8 (2.00±0.45) and then begins to decrease until reach to its minimum level on day 14 (1.08±0.20). This means about 29.34 and 32.11% of the started progesterone level increased on days 6 and 8, respectively followed by dramatically decline to be below the beginning level with -28.95%at day 14 (day of sponge withdraw). On the other side, the patterns of plasma progesterone changes in ewes group B (50 mg MAP) were likewise group A, but the beginning level was 1.67±0.29 ng/mL then forcefully increased to reaches 2.40±0.40 and 2.47±0.36 on days 6 and 8 accompanied with progressively increases 43.62 and 47.52% , respectively, of the started level. However, the plasma progesterone declining in group B not like group A, in the sense, after day 8, the rate of plasma progesterone decreases in group B was gradually and reached to minimum level (1.61±0.33) on day 14 to be lower than started level with -3.42% only.
The mean level of plasma P4 on day 17 of mating were significant lower (P<0.05) in non-pregnant ewes (0.65±0.10) than ewes pregnant in single (6.56±1.36) and twins (8.00±0.36). However, no significant difference was detected between two later groups.
Luteinizing hormone (LH) assay:The time from sponge withdraw to LH surge was significantly shorter (P<0.05) in-group A (25 mg MAP) than group B (50 mg MAP), (42.89±4.07h vs 54.07±3.49h). Whereas, the concentrations of LH surge were 21.83±1.94 mIU/mL and 19.80±1.78 mIU/mL, for groups A and B, respectively with no significant differences. The time extended from sponge removal to LH surge was significantly (P<0.01) longer in ewes of group A1B1 (without eCG) control (61.00±4.32h) than groups A2B2; 300 IU/eCG (47.63±4.46h) and A3B3; 500 IU/eCG (41.71±5.11h). On the other side, the means of LH surge concentrations were 20.56±2.13 mIU/mL, 20.72±2.28 mIU/mL and 20.95±2.42 mIU/mL for ewes of groups A1B1, A2B2 and A3B3, respectively with no significant differences.
Estradiol-17β (E2) assay:The time from sponge withdraw to estradiol-17β surge needs a longer period (P<0.05) for ewes in-group B (50 mg MAP) than group A (25 mg MAP), (51.13±3.90h vs 40.56±4.63h). Whereas, the concentrations of estradiol-17β surge were 8.90±0.76 pg/mL and 7.74±0.72 pg/mL, for groups A and B, respectively with not significant differences.The time extended from sponge removal to estradiol-17β time surge was significantly (P<0.01) longer in ewes group A1B1; control (58.38±4.99h) than groups A3B3; 500 IU/eCG (39.14±5.72h) and A2B2; 300 IU/eCG (44.88±4.99h). In contrast, ewes of group A3B3; 500 IU/eCG (11.50±1.02 pg/mL) showed higher level surges (P<0.01) of estradiol-17β than ewes of groups A1B1 (6.46±0.90 pg/mL) and A2B2 (7.06±0.79 pg/mL).
Conclusion: Neither MAP nor eCG hada significant effect on the estrus response or its duration,whiletheir effects were appeared clear at the time of onset estrus. Concerning to parameters related to reproductive performance, neither MAP nor eCG had significant effects on thelambing, fecundity and prolificacy. However, eCGhad a significantly higher pregnancy rate than ewes treated without eCGand as eCG doses increased the pregnancy rate increased.
Recommendations:Forimprovingthe estrus responseand pregnancy rate in synchronized Barki ewes,sponges impregnated with 25mg MAP for 14 days with injection 300-500 IU/eCG at the day of sponge withdrawcan be used. This protocol of estrus synchronization is more economic and suitable for Barki ewes under Egyptian conditions.
Further Study: Different doses of eCG more than those used in this study (300 and 500IU) should be investigated in Barki ewes toincrease twinning and subsequently fecundity and prolificacy rates.
Based on previous studies, ovulation occurs in sheep about 14 hours after reaching the LHsurge, so when used eCG hormone (300 to 500 IU) in the synchronization of estrus inBarki ewes advised to mated ewes about 55-61 hours after sponges removal, as in the caseestrus synchronization by using progesteroneonly (without eCG) it recommended a delay of mated to about 75 hours aftersponges removal for high rates of fertility.