کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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2095350 | 1082101 | 2012 | 8 صفحه PDF | دانلود رایگان |
The objective was to determine the effects of the duration of progesterone exposure during the ovulatory wave on fertility (pregnancy rate) in beef cattle. We tested the hypothesis that short-progesterone exposure during the growing and early-static phase of the ovulatory follicle (analogous to the ovulatory wave of 3-wave cycles) is associated with higher fertility than a longer duration of exposure (analogous to the ovulatory wave of 2-wave cycles). Three to 5 days after ovulation, beef heifers (n = 172) and suckled beef cows (n = 193) were given an intravaginal progesterone-releasing device (CIDR) and 2.5 mg estradiol - 17β +50 mg progesterone im to induce a new follicular wave. Cattle were allocated to short- or long-progesterone exposure groups (for 3 and 6 d after wave emergence, respectively) after which prostaglandin F2α was administered and CIDR were removed. Forty-eight hours later, all cattle were given 12.5 mg pLH and artificially inseminated (AI) with frozen-thawed semen. The diameter of the two largest follicles and the corpus luteum were measured by transrectal ultrasonography at CIDR removal, insemination, and 36 h after insemination. Pregnancy diagnosis was done ultrasonically 38 and 65 d post-AI. There was no difference in pregnancy rates in short- vs long-progesterone exposure in heifers (53 vs 47%, P = 0.44) or cows (63 vs 58%, P = 0.51). However, the diameter of the ovulatory follicle at CIDR removal and AI was smaller in short- than in long-progesterone groups (P < 0.02), and larger in cows than in heifers (P < 0.006). In conclusion, short-progesterone exposure during the growing and early-static phase of the ovulatory follicle (similar to 3-wave cycles) was not associated with higher fertility than a longer progesterone exposure (similar to 2-wave cycles).
Journal: Theriogenology - Volume 77, Issue 2, 15 January 2012, Pages 437–444