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Using Medical Manipulation to Improve Reproductive Performance of Postpartum Dairy Cows in Taiwan
|摘要:||產後乳牛早期常有週期停止、濾泡不排卵或延遲排卵、黃體期延長或過短等問題，造成卵巢週期無法恢復，因此早期使用外源性內泌素進行處理，促使發情同期化則有利於卵巢週期的提早恢復。熱緊迫、產後發生胎衣滯留或子宮炎是造成乳牛繁殖性能下降的主要原因，不僅影響配種後精蟲的存活，並阻礙受精卵在子宮內膜的著床及胚胎發育。本實驗藉由改良之藥物處理模式促使產後乳牛提早恢復動情週期並進行人工授精，實驗組牛隻為實驗牧場全年分娩之母牛，包括產後正常乳牛（n = 22）及治療胎衣滯留的乳牛（n = 8），不進行任何處理的產後正常乳牛為對照組（n = 17），所有牛隻於配種後30天以超音波進行早期懷孕之診斷，未懷孕者則於下次發情時再配種。實驗組牛隻在產後150天內懷孕牛之比率較對照組高（56.7% vs 23.5%），且實驗組懷孕牛之空胎期較對照組短（121.7 ± 16.4天vs 198.8 ± 22.6天，P<0.05）。其中，產後發生胎衣滯留牛隻以oxytocin預防及ceftiofur治療之方法較傳統治療方式可減少懷孕牛隻的平均空胎期（102.8 ± 14.8天vs 251.9 ± 46.4天）及配種次數（2.5 ± 0.5次vs 4.7 ± 1.2次）。此外，本實驗組牛隻與該場乳牛前一年之空胎期相較有顯著性的縮短（121.7 ± 16.4天vs 207.8 ± 20.3天，P<0.01）。實驗組懷孕率為70.0%（21/30），其中有81.0%（17/21）懷孕牛於前三次配種時懷孕。此外，實驗牛隻的懷孕率、空胎期及平均配種次數於熱季及涼季之間的相較結果則無顯著性的差異，但本實驗再分別與前一年熱季及涼季比較，本實驗組之空胎期在熱季（119.8 ± 20.7天vs 234.0 ± 22.3天；P<0.01）及涼季（124.3 ± 27.9天vs 181.6 ±32.6天；P<0.05）皆有顯著性地縮短。本實驗結果顯示，實驗組牛隻較對照組有較好的產後繁殖性能，以藥物處理產後牛隻可顯著地改善其產後之繁殖性能。|
Reproductive problems including cessation of cycle, failure or delay of ovulation and inadequate luteal function, usually occur in lactating cows which lead to failure to resume normal ovarian cycle during the early postpartum period. Use of exogenous hormonal manipulation to synchronize postpartum dairy cows can facilitate cows to resume their normal ovarian cycle without delay. Heat stress and the occurrence of retained placenta and/or metritis are the major factors which decrease the reproductive performance of postpartum dairy cows in Taiwan. These factors not only influence the activity of spermatozoa in the genital tract after breeding, but also compromise fertilized eggs from attaching in the endometrium and subsequent embryo survival. In this study, medical manipulation was used to resume the estrous cycle of postpartum dairy cows to increase their fertility after breeding. Between March 2003 and February 2004, 47 Holstein dairy cows from the National Chung-Hsing University dairy farm were used after calving for this study. Of these, 22 normal postpartum dairy cows and 8 cows having retained placenta were divided into the experimental group, while the remaining 17 normal postpartum cows were divided into the control group. Ultrasound was used in all cows for early pregnancy diagnosis 30 days after artificial insemination. Cows which were diagnosed as non-pregnant were inseminated when they returned to estrus. The pregnancy rate of cows was higher in the experimental group than the control group within the first 150 days postpartum (60.0% vs 23.5%), and the days open were significantly lower than those of the control group (126.1 ± 15.9 d vs 198.8 ± 22.6 d, P<0.05). Of this group, oxytocin and ceftiofur were used to treat cows with retained placenta after calving, which resulted in a decrease in the mean days open (131.6 ± 31.1 d vs 251.9 ± 46.4 d, P<0.05) and breeding times (2.8 ± 0.5 vs 4.7 ± 1.2, P<0.05) when compared to cows that received conventional treatment. In addition, the mean days open of cows in the experimental group were significantly lower than cows of the same herd in 2003 (126.1 ± 15.9 d vs 207.8 ± 20.3 d, P<0.01). The pregnancy rate of cows in the experimental group was 76.7% (23/30), and of this, 78.3% (18/23) were pregnant from the first 3 services. In addition, there was a significant difference in the mean days open (119.8 ± 20.7 d vs 231.9 ± 25.7 d, P<0.01) between experimental and control groups during the hot season, however there was no difference in reproductive performance between experimental and control groups during cooler season. Thus the results of this experiment indicated that reproductive performance of postpartum dairy cows in the experimental group was better than that of the control group. It was concluded that using medical manipulation to treat postpartum dairy cows can significantly improve their reproductive performance during the postpartum period.
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