نوع مقاله : مقاله پژوهشی
نویسندگان
گروه علوم دامی، دانشکده کشاورزی، دانشکدگان کشاورزی و منابع طبیعی، دانشگاه تهران، کرج، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
This study presents a meta-analysis comparing the effectiveness of short-term and long-term progesterone-based protocols for estrous synchronization in sheep, focusing on pregnancy rates. The primary aim was to evaluate whether short-term protocols, which are more practical, yield comparable results to traditional long-term methods in terms of pregnancy success. The study is based on a meta-analysis of 22 independent studies conducted between 2010 and 2023, which examined various progesterone-based estrous synchronization protocols in different seasons. The data was collected from Scopus, PubMed, OpenAlex, and Google Scholar databases using keywords such as "progesterone", "P4", "estrous”, “synchronization," "sheep," and "ewe." The results revealed no significant difference between short-term and long-term protocols concerning pregnancy rates. This suggests that both protocols are equally effective, with short-term protocols offering logistical and cost benefits. However, the analysis also highlighted moderate heterogeneity among the studies, indicating that factors like breed, nutrition, and environment might influence outcomes. This meta-analysis provides valuable results into the effectiveness of short-term versus long-term progesterone-based estrous synchronization protocols in sheep. The findings indicate that short-term protocols are just as effective as long-term protocols in achieving pregnancy, offering significant advantages in terms of cost and labor efficiency. Additionally, potential publication bias was identified, underscoring the need for further research in this area to refine these reproductive strategies.
کلیدواژهها [English]
Extended Abstract
Introduction
In sheep breeding, lamb production is more important than milk production. The primary factor influencing profitability is the number of lambs born and the successful rearing of these lambs. One of the most effective ways to enhance reproductive efficiency is through estrous synchronization. This process allows breeders to synchronize the estrous cycles of ewes, ensuring that they all come into heat at the same time, thus enabling scheduled breeding and lambing seasons. The synchronization of estrus is achieved through the administration of hormonal treatments, primarily based on progesterone, which can either mimic or manipulate the natural estrous cycle of the sheep. While long-term protocols have been traditionally used for estrous synchronization, recent research has suggested that short-term protocols might offer similar results with fewer logistical challenges and reduced costs. This study aims to evaluate the effectiveness of both short-term and long-term protocols, focusing on pregnancy rates in sheep.
Materials and Methods
The study is based on a meta-analysis of 22 independent studies conducted between 2010 and 2023, which examined various progesterone-based estrous synchronization protocols in sheep. The data was collected from Scopus, PubMed, OpenAlex, and Google Scholar databases using keywords such as "progesterone," "P4," "estrous synchronization," "sheep," and "ewe." The studies were selected based on strict inclusion criteria, such as being peer-reviewed, focusing on sheep, and comparing at least two different estrous synchronization protocols. Studies that did not report quantitative data or involved outdated or unconventional methods were excluded. The meta-analysis compared short-term and long-term progesterone-based protocols for estrous synchronization in sheep, assessing the pregnancy rates as the primary outcome. The data from each study were extracted, including the year of publication, sample size, pregnancy rates, and whether the study was conducted during or outside the breeding season. The extracted data were then analyzed using statistical methods to determine the overall effectiveness of short-term versus long-term protocols.
Results
The meta-analysis revealed that there was no statistically significant difference between short-term and long-term progesterone-based protocols in terms of pregnancy rates. Both protocols yielded comparable pregnancy success rates, suggesting that short-term protocols are just as effective as long-term protocols for estrous synchronization in sheep. The overall effect size was 0.07, indicating that the difference in pregnancy rates between the two protocols is negligible. One of the key findings of this study is that short-term protocols, typically lasting 5 to 7 days, can achieve pregnancy rates similar to those achieved by long-term protocols, which traditionally last between 12 to 14 days. This has significant implications for sheep farmers, as short-term protocols are not only less labor-intensive but also more cost-effective, requiring less time and resources to administer. The study supports previous research, which has shown that short-term progesterone treatments can be just as effective as long-term treatments, while offering practical advantages in terms of ease of use and economic efficiency. The analysis also found moderate heterogeneity among the studies, with an I² value of 47.85%. This suggests that factors other than the duration of the progesterone treatment, such as breed, nutrition, and environmental conditions, may influence the success of estrous synchronization protocols. For example, some breeds may respond better to shorter treatments, while others may require longer protocols to achieve optimal pregnancy rates. Additionally, differences in the nutritional status of the ewes or variations in environmental conditions, such as temperature and daylight, could also affect the success of the synchronization protocols. Furthermore, the meta-analysis compared the effectiveness of short-term and long-term protocols in different seasons. The results indicated that there was no significant difference between the two protocols in either the breeding or non-breeding seasons. During the breeding season, the overall effect size was 0.19, suggesting a slight, non-significant preference for short-term protocols, while in the non-breeding season, the effect size was -0.03, indicating a similarly non-significant preference for long-term protocols. These findings suggest that both short-term and long-term protocols can be effectively used for estrous synchronization, regardless of the season.
Discussion
The findings of this study have important implications for sheep breeders. Given that short-term protocols are equally effective in achieving pregnancy rates as long-term protocols, breeders can consider adopting short-term protocols to reduce labor and costs associated with estrous synchronization. Short-term protocols are easier to implement, as they require fewer days of hormone administration and reduce the need for extended management of ewes during the synchronization process. Despite the clear advantages of short-term protocols, the moderate heterogeneity observed in the study indicates that further research is needed to identify the specific factors that influence the success of estrous synchronization protocols in different breeds and environments. Factors such as breed, nutritional status, and environmental conditions should be considered in future studies to develop more tailored protocols that maximize reproductive success in different sheep populations. Additionally, the potential for publication bias identified in the funnel plot suggests that more comprehensive and balanced research is needed to fully understand the effectiveness of estrous synchronization protocols. Future studies should aim to address this bias by including a wider range of studies from different regions and with varying methodologies.
Conclusion
This meta-analysis provides valuable insights into the effectiveness of short-term versus long-term progesterone-based estrous synchronization protocols in sheep. The findings indicate that short-term protocols are just as effective as long-term protocols in achieving pregnancy, offering significant advantages in terms of cost and labor efficiency. While the moderate heterogeneity observed suggests that additional factors may influence the success of these protocols, the overall conclusion is that short-term protocols are a viable and practical option for estrous synchronization in sheep. Further research is needed to explore the underlying factors contributing to the variability in success rates and to address potential publication biases in the existing literature.
Mahdi Zhandi: Conceptualization, Validation, Supervision, Writing - Review & Editing, Project administration,
Omid Bouzari: Methodology, Software, Formal analysis, Investigation, Writing - Original Draft
All authors contributed equally to the conceptualization of the article and writing of the original and subsequent drafts.
The data supporting reported results are collected and used from published articles, to them we have referred in the manuscript.
The authors would like to thank all participants of the present study.
The study was approved by the Ethics Committee of the University of ABCD (Ethical code: IR.UT.RES.2024.500). The authors avoided data fabrication, falsification, plagiarism, and misconduct.
The author declares no conflict of interest.
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