پديد آورندگان :
رستمي، بهنام دانشگاه زنجان - علوم دامي , حاجي زاده، رحمان دانشگاه زنجان - دانشكده كشاورزي - علوم دامي , شهير، محمدحسين دانشگاه زنجان - علوم دامي
كليدواژه :
hCG , پس از جفت‌گيري , عملكرد توليدمثلي , ميش
چكيده فارسي :
زمينه مطالعاتي: تلفات اوليه روياني يكي از مشكلات اصلي توليدمثلي دام هاي مزرعه اي است. توليد ناكافي پروژسترون از جسم زرد در اوايل آبستني يكي از علل عمده اين تلفات است. هدف: هدف از انجام اين آزمايش تعيين اثرات تزريق عضلاني 400 واحد بين المللي hCG، در روز 11 پس از قوچ اندازي بر روي عملكرد توليدمثلي ميش هاي آميخته افشاري × مرينو بود. روش كار: در مطالعه حاضر، تعداد 24 راس ميش آميخته افشاري × مرينو به صورت تصادفي در دو گروه 12 راسي قرار گرفتند. جهت همزماني فحلي، تمامي ميش ها سيدرهاي پروژستروني را به مدت 12 روز دريافت كردند. در روز 11 پس از قوچ اندازي، ميش هاي گروه hCG، 400 واحد بين المللي hCG به صورت عضلاني دريافت كردند و ميش هاي گروه كنترل هيچ درماني را دريافت نكردند. جهت اندازه گيري غلظت هورمون پروژسترون در روزهاي 7، 12، 17 و 22 پس از قوچ اندازي از ميش ها خون گيري به عمل آمد. نتايج: نتايج اين مطالعه نشان داد كه غلظت هورمون پروژسترون در روزهاي 12 و 17 پس از قوچاندازي در ميشهاي گروه hCG به طور معنيداري بالاتر از گروه كنترل بود (0/05 >P). ميشهاي گروه hCG سه و چهارقلوزايي بيشتري نسبت به گروه كنترل داشتند كه در نتيجه تعداد بره متولد شده و تعداد بره به ازاي هر ميش در گروه hCG بالاتر بود. ميزان تلفات روياني تا زمان از شيرگيري در گروه (hCG (3/6% از گروه كنترل (11/8%) كمتر بود (05/0>P). نتيجه گيري نهايي: به طور كلي نتايج بدست آمده از اين تحقيق نشان داد كه تجويز hCG در اوايل آبستني با بهبود عملكرد لوتئال و احتمالا با كاهش تلفات روياني، عملكرد توليدمثلي را در ميش هاي آميخته افشاري × مرينو بهبود مي بخشد.
چكيده لاتين :
Introduction: Embryonic death occurs during early stages of pregnancy in mammalian species and is one of the most common causes of economic loss in the sheep industry. Almost 40% of sheep embryos fail to survive during the first month of pregnancy and 70–80% of this total loss occurs between days 8 and 16 after conception (Michels et al. 1998). Insufficient luteal function and low concentration of maternal progesterone is one of the major reasons of this mortality. Progesterone (P4) has a critical role in production of different endometrial secretions that are essential for embryonic growth and plays a major role in establishment and maintenance of pregnancy (Spencer et al. 2004a). Suboptimal P4 concentration after breeding, leads to a small and underdeveloped embryo not capable of producing sufficient amounts of interferon-tau (IFN-τ) on the days of maternal recognition of pregnancy (MRP) (Spencer et al. 2004b). In sheep, insufficient luteal function and consequently low concentration of maternal P4 is one of the main causes of embryonic mortality (Michels et al. 1998). hCG has been used in order to increase P4 production and to enhance reproductive performance. In the ewe, a single injection of hCG on Day 11.5 after breeding stimulated uterine secretions and increased IFN-τ (MRP protein) concentrations and conceptus growth (Nephew et al. 1994) and, when given on Day 12, improved reproductive efficiency (Khan et al. 2007). Contradictorily, hCG treatment on Day 12 after mating did not improve the reproductive efficiency in ewe lambs (Khan et al. 2009). One of the breeding programs which has been extensively supported by the government is the marker-assisted introgression of Fec B gene from Booroola Merino (originated in Australia and NewZealand) to Afshari (originated in Iran) sheep. This study is designed to evaluate the effects of such hormonal treatments on reproductive efficiency of these cross-continental crossbred ewes. Therefore, the purpose of this study was to investigate the effect of hCG given on day 11 after breeding on the conception rate, litter size, and P4 concentration in highly prolific Iranian crossbred (Afshari × Booroola Merino) ewes. In addition, the effects of these treatments on birth weight and survivability of offspring were also studied. This study was conducted to investigate the efficiency of hCG administration after breeding to increase the maternal progesterone (P4) concentrations and also to study the role of such hormonal treatment to enhance fertility in ewes.
Material and methods: The experiment was conducted during the breeding season (September 2014–April 2015) at the experimental herd of the University of Zanjan (latitude: 48° 31′ 21″ N; longitude: 36° 40′ 13″ E; altitude: 1663 m), Iran. Twenty-four cyclic and healthy Afshari × Booroola Merino crossbred ewes of 2.5 years old, weighing 69.9 ± 1.1 kg, were used in the experiment. They were fed Lucerne hay supplemented with grain pellets (CNCPS 2003) and givenwater ad libitum. After oestrus synchronization, the ewes were mated with fertile rams and were assigned to two groups. Ewes in hCG group (n=12) received an i.m. injection of 400 IU hCG on day 11 post-mating (day of oestrus = day 0) and ewes in the control group (n=12) did not receive any treatment. Blood samples were collected from all animals on days 7, 12, 17 and 22 post-mating.
Results and discussion: Plasma P4 concentrations were higher at days 12 and 17 post-mating in hCG treated ewes than that in control ewes (P < 0.05). The ewes in hCG group produced more quadruplets (P < 0.05) and triplets and consequently they had a larger litter size. The lamb mortality rate by weaning in hCG group (3.6 %) was less than that in control (11.8%; P < 0.05), groups. Results from the present study indicated that hCG administration increased maternal P4 concentration, particularly during day 12 after breeding, which coincides with the critical time of maternal recognition of pregnancy (day 12 to 13; Spencer et al. 2004b) in sheep. Gonadotropins like hCG have been previously used in several experiments to improve the reproductive efficiency of ewes (Khan et al. 2003; Cam and Kuran 2004; Lankford et al. 2010). hCG is a luteogenic/luteotrophic hormone and has a luteinizing hormone (LH) activity which binds to the LH receptors on corpus luteum cells and has a longer half-life than LH in mammals and it may be useful for increasing P4 production, and elevates maternal P4 in sheep (Farin et al. 1988). This, in turn, prevents luteolysis and maintains viable the developing embryo. Considering the fact that day12 is a critical time to MRP, and to prevent luteolysis, we selected the day 11 post-mating as an optimum time to administration of hCG. The timing of such hormonal treatments might be important
Conclusion: In conclusion, the results of present study demonstrated the efficiency of hCG administration after breeding to increase the maternal P4 concentrations and also revealed the possible beneficial effect of such hormonal treatments as a management tool that may enhance fertility by improving luteal function in ewes.
