Estrus synchronization
Approaches towards synchronizing estrus in livestock have to focus on either the manipulation of the luteal or the follicular phase of the estrous cycle. In the doe the window of opportunity is generally greater during the luteal phase, which is of longer duration and more responsive to manipulation. Different approaches have been concerned with either extending the luteal phase by supplying exogenous progesterone or with shortening this phase through removal of the corpus luteum. Successful techniques must not only establish synchrony, but also provide a reasonable level of fertility in the synchronized cycle (Table 3).
The treatment of choice for estrus synchronization, and also out-of-season breeding, in goats has been the intravaginal sponge, impregnated with 45-60 mg of a synthetic progesterone (Table 4). Sponges are widely used either in conjunction with pregnant mare serum gonadotropin (PMSG), FSH or prostaglandin to more tightly synchronize and/or induce a superovulatory response. Under research conditions sponges impregnated with natural progesterone in higher doses (400-500 mg) have been used and similar synchrony and fertility to that of commercial sponges were achieved. An alternative means of supplying continuous, exogenous progesterone has been the intravaginal pessary (CIDR-Gฎ) developed for goats in New Zealand. The CIDR device is constructed from a natural progesterone impregnated medical silicone elastomer molded over a nylon core. In large scale trials with cashmere goats in Australia CIDR devices were equally effective to intravaginal sponges in controlling ovulation and fertility following A.I.
A number of synchronization systems for goats have been evaluated under research conditions that use compounds approved for other species and/or applications (Table 4). One of these systems is based on the extra-label use of the norgestomet ear implant supplied with the estrus synchronization system Synchromate-Bฎ, developed for cattle. Does are implanted with the norgestomet implants for a period of approximately 14 days and a gonadotropin, either FSH or PMSG, is administered around the time of implant removal. There will usually not be an adequate response and synchrony of estrus without the gonadotropin treatment. The estradiol valerate injection provided in the product combination for cattle should not be used for goats due to their increased sensitivity to estrogens. Studies have indicated that the implant dose provided for cattle (6 mg norgestomet) can be reduced to 2-3 mg by cutting the implant. Following synchronization does and ewes come into estrus within 72 hours. Melengestrol acetate (MGA) is an orally-active, synthetic progestogen, approved for use in feedlot cattle, that can be used for the induction and synchronization of estrus in does in conjunction with zeranol and PMSG. Prostaglandin F2a, or rather its analogues, are widely used for estrus synchronization in cattle, but results have not been as satisfactory in goats. A functional corpus luteum is required for prostaglandin to regress, thus making this technique only suitable for synchronization during the breeding season. Synchronization with prostaglandin analogue generally produces a more synchronized estrus than that obtained with a progestogen-gonadotropin treatment, but subsequent fertility is somewhat reduced.
The application of estrus synchronization schemes requires an increased level of management either through the utilization of A.I. or the proper management of bucks. With a larger number of females showing estrus at the same time, the female : male ratio should not exceed 7:1, or alternatively, timing of the induced estrus should be staggered (i.e. spreading the removal of intravaginal sponges over several days). Hand mating of males, as a modification of A.I., can also be used. Fertility of the synchronized estrus is generally high, but responses to PMSG and prostaglandin co-treatment have at times been variable. The repeated use of PMSG in conjunction with progestogen treatment has resulted in reduced fertility in subsequent years and was attributed to an active immunization against PMSG.
ซิงโครไนส์ estrusวิธีต่อตรง estrus ในปศุสัตว์ต้องเน้นทั้งการจัดการนในหรือขั้นตอนการเจาะรอบ estrous ใน doe โอกาสเป็นมากขึ้นโดยทั่วไปนในระ ซึ่งเป็นระยะเวลานาน และตอบสนองได้มากกว่าการจัดการ วิธีต่างมีการเกี่ยวข้อง กับทั้งการขยายนในโดย supplying กระเทือนภายนอก หรือลดขั้นตอนนี้ผ่านการกำจัด corpus luteum เทคนิคประสบความสำเร็จต้องไม่เพียงแต่สร้าง synchrony แต่ยัง มีความอุดมสมบูรณ์ในระดับเหมาะสมของรอบการซิงโครไนซ์ (ตาราง 3)ทางเลือกสำหรับการซิงโครไนส์ estrus และยังเพาะพันธุ์ออกฤดู ในแพะมีฟองน้ำ intravaginal ด้วย 45-60 มิลลิกรัมเอกสารสังเคราะห์ (ตาราง 4) ฟองน้ำมีอย่างกว้างขวางใช้อย่างใดอย่าง หนึ่งร่วมกับครรภ์แมร์ซีรั่ม gonadotropin (PMSG), สูงหรือ prostaglandin เพื่อให้แน่นตรง หรือก่อให้เกิดการตอบสนอง superovulatory ภายใต้เงื่อนไขที่การวิจัย การใช้ฟองน้ำชุบน้ำยาที่ มีโปรเจสเตอโรธรรมชาติในปริมาณสูง (400-500 มิลลิกรัม) และทำคล้าย synchrony และภาวะการค้าฟองน้ำ ทางการขายอย่างต่อเนื่อง ภายนอกโปรเจสเตอโรได้ pessary intravaginal (CIDR Gฎ) พัฒนาขึ้นสำหรับแพะในประเทศไทย อุปกรณ์ CIDR คือสร้างจากยางซิลิโคนทางการแพทย์กระเทือนธรรมชาติชุบที่แม่พิมพ์กว่าแกนไนล่อน ในการทดลองขนาดใหญ่กับแพะแคชเมียร์ในออสเตรเลีย CIDR อุปกรณ์มีประสิทธิภาพเท่าเทียมกันกับฟองน้ำ intravaginal ควบคุมการตกไข่และความอุดมสมบูรณ์ต่อ A.I.A number of synchronization systems for goats have been evaluated under research conditions that use compounds approved for other species and/or applications (Table 4). One of these systems is based on the extra-label use of the norgestomet ear implant supplied with the estrus synchronization system Synchromate-Bฎ, developed for cattle. Does are implanted with the norgestomet implants for a period of approximately 14 days and a gonadotropin, either FSH or PMSG, is administered around the time of implant removal. There will usually not be an adequate response and synchrony of estrus without the gonadotropin treatment. The estradiol valerate injection provided in the product combination for cattle should not be used for goats due to their increased sensitivity to estrogens. Studies have indicated that the implant dose provided for cattle (6 mg norgestomet) can be reduced to 2-3 mg by cutting the implant. Following synchronization does and ewes come into estrus within 72 hours. Melengestrol acetate (MGA) is an orally-active, synthetic progestogen, approved for use in feedlot cattle, that can be used for the induction and synchronization of estrus in does in conjunction with zeranol and PMSG. Prostaglandin F2a, or rather its analogues, are widely used for estrus synchronization in cattle, but results have not been as satisfactory in goats. A functional corpus luteum is required for prostaglandin to regress, thus making this technique only suitable for synchronization during the breeding season. Synchronization with prostaglandin analogue generally produces a more synchronized estrus than that obtained with a progestogen-gonadotropin treatment, but subsequent fertility is somewhat reduced.The application of estrus synchronization schemes requires an increased level of management either through the utilization of A.I. or the proper management of bucks. With a larger number of females showing estrus at the same time, the female : male ratio should not exceed 7:1, or alternatively, timing of the induced estrus should be staggered (i.e. spreading the removal of intravaginal sponges over several days). Hand mating of males, as a modification of A.I., can also be used. Fertility of the synchronized estrus is generally high, but responses to PMSG and prostaglandin co-treatment have at times been variable. The repeated use of PMSG in conjunction with progestogen treatment has resulted in reduced fertility in subsequent years and was attributed to an active immunization against PMSG.
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