Open Veterinary Journal, (2025), Vol. 15(5): 2112-2121

Research Article

10.5455/OVJ.2025.v15.i5.29

Reproductive disorders in Simmental cattle: Enhancing fertility through a hormonal protocol

Musdalifa Mansur^1,2, Athhar Manabi Diansyah^3*, Rahmat Rahmat⁴, Muhammad Fajar Amrullah³, Andi Muhammad Alfian³, Ahmad Alfaruqi Syahrandi Adam¹ and Aeni Nurlatifah⁵

¹Graduate School, Hasanuddin University, Makassar, Indonesia

²Animal Husbandry Study Program, Faculty of Science and Technology, Muhammadiyah Sidenreng Rappang University, Sidenreng Rappang, Indonesia

³Faculty of Animal Science, Hasanuddin University, Makassar, Indonesia

⁴Faculty of Agriculture, Lambung Mangkurat University, Banjarbaru, Indonesia

⁵Department of Nutrition and Feed Science, Faculty of Animal Science, Gadjah Mada University, Yogyakarta, Indonesia

*Corresponding Author: Athhar Manabi Diansyah. Faculty of Animal Science, Hasanuddin University, Makassar, Indonesia. Email: athhar.md [at] unhas.ac.id

Submitted: 30/01/2025 Revised: 26/03/2025 Accepted: 29/04/2025 Published: 31/05/2025

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ABSTRACT

Background: Reproductive disorders, including abortion, endometritis, and silent estrus, present significant challenges to fertility and productivity in semi-intensive farming systems. These conditions disrupt physiological and hormonal functions, leading to impaired reproductive outcomes.

Aim: This study aimed to evaluate the effectiveness of hormonal protocols in addressing these disorders by assessing reproductive tract size, cervical mucus characteristics, and fertility outcomes in cattle with varying reproductive health statuses.

Methods: Healthy cattle exhibited optimal reproductive performance and were characterized by high-quality cervical mucus, normal uterine horn dimensions, and superior fertility outcomes. This finding highlights the importance of balanced endocrine function in supporting optimal reproductive efficiency.

Results: In contrast, cattle with abortion disorders and endometritis experienced disrupted uterine health, enlarged uterine horns, and diminished cervical mucus quality, resulting in significantly reduced fertility. Silent estrus showed intermediate results, reflecting suboptimal estrus expression and hormonal imbalances that affected reproductive efficiency despite hormonal interventions. Strong positive correlations were observed between cervical mucus characteristics, such as viscosity, acidity, and ferning patterns, and fertility outcomes, indicating their critical role in facilitating sperm survival, motility, and fertilization. Conversely, uterine horn dimensions exhibited a negative correlation with fertility, reflecting the impact of chronic inflammation and structural abnormalities on reproductive success.

Conclusion: Although hormonal protocols were effective in synchronizing estrus and inducing ovulation, their efficacy varied depending on the severity of reproductive disorders and environmental management practices. These findings demonstrate that hormonal protocols can partially mitigate the physiological disruptions caused by reproductive disorders; however, integrated reproductive management strategies are essential. Combining hormonal interventions with targeted nutritional support, improved environmental management, and enhanced estrus detection practices is critical for optimizing reproductive performance. This study provides a framework for addressing reproductive challenges in Simmental cattle, supporting sustainable livestock production in semi-intensive systems in resource-limited settings.

Keywords: Simmental cattle, Reproductive disorders, Reproductive tract size, Cervical mucus, Hormonal protocols.

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Introduction

Reproductive efficiency is a critical determinant of productivity and profitability in cattle farming, particularly in beef production systems. In Indonesia, Simmental cattle are extensively utilized for their superior growth performance and meat quality, making them one of the most economically significant breeds in the livestock industry (Terry et al., 2021). However, reproductive disorders, such as abortion, endometritis, and silent estrus, present substantial challenges in achieving optimal fertility, calving intervals, and herd productivity (Bisla et al., 2018). These issues not only delay conception but also lead to increased culling rates and financial losses for farmers, particularly in semi-intensive farming systems prevalent across Indonesia.

Abortion disorders disrupt pregnancy and reduce reproductive efficiency because of their multifactorial etiology, including infectious agents, metabolic imbalances, and hormonal dysregulation (Andrade and Simões, 2024). Effective management is required to clear uterine contents, restore ovarian cyclicity, and prepare cows for subsequent breeding (Consentini et al., 2021). Endometritis, characterized by uterine inflammation, typically arises postpartum and significantly affects conception rates (CRs) by impairing uterine function and embryo survival (Pascottini et al., 2023). Silent estrus, defined by the absence of detectable estrus behavior despite normal ovarian activity, complicates estrus detection and timing of artificial insemination (AI), which is critical in beef production systems that depend on optimal reproductive performance (Gilbert, 2016; Arero, 2022).

The use of hormonal protocols, such as gonadotropin-releasing hormone (GnRH), prostaglandin F2α (PGF2α), and progesterone-releasing devices [e.g., controlled internal drug release (CIDR)], has been established as an effective approach to address reproductive disorders in beef cattle. These hormonal protocols regulate ovarian function, synchronize estrus, and improve the timing of AI, thereby enhancing fertility outcomes (Mansur et al., 2020; Yusuf et al., 2024a,b). However, the success of these treatments can vary depending on the specific reproductive disorder, environmental factors, and management practices. Evaluating the efficacy of such protocols in Simmental cattle under semi-intensive systems in Indonesia is essential for improving reproductive performance and supporting sustainable beef production.

This study aimed to assess the impact of hormonal protocols on reproductive outcomes in Simmental cattle according to reproductive health status. The evaluation included reproductive tract size (RTS), cervical mucus characteristics, and fertility rates in cows with normal reproductive health, abortion disorders, endometritis, and silent estrus. The findings of this research are intended to provide practical insights for improving reproductive efficiency in Simmental cattle and addressing the challenges of beef production in Indonesia, which has unique environmental and management conditions.

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Materials and Methods

Experimental design

The study used a total of 150 Simmental cow aged 4–8 years and raised under semiintensive systems were selected based on their reproductive health status (Fig. 1). The cattle were categorized into four experimental groups: Group 1 (cows with normal reproductive health), Group 2 (cows diagnosed with abortion disorders), Group 3 (cows with endometritis disorders), and Group 4 (cows with silent estrus disorders). Observations included reproductive tract assessments, cervical mucus analysis, and fertility rate evaluation.

Hormonal protocol

The hormonal protocols for each experimental group of Simmental cattle were designed to address their specific reproductive health conditions and optimize fertility outcomes.

Fig. 1. Reproductive status distribution.

Fig. 2. Hormonal protocol for normal reproductive health.

Fig. 3. Hormonal therapy protocol for abortus disorders.

Group 1: normal reproductive health

A synchronization protocol was applied to maximize fertility and ensure effective timed artificial insemination (TAI). On Day 0, GnRH (100–250 µg) was intramuscularly administered to induce ovulation and initiate a new follicular wave, followed by PGF2α (25 mg) on Day 7 to lyse the corpus luteum and synchronize estrus. A second dose of GnRH (100 µg) was administered on Day 9 to trigger ovulation, and TAI was performed 16–24 hours later (Yusuf et al., 2024a,b) (Fig. 2).

Group 2: abortion disorders

The primary goals were to clear the uterine contents, reset the reproductive cycle, and prepare for breeding. On Day 0, PGF2α (25 mg) was intramuscularly administered to induce uterine contractions and facilitate the expulsion of retained fetal membranes or debris. If the corpus luteum was detected 10–14 days later, a second dose of PGF2α was given to ensure complete luteolysis. After confirming uterine involution (21–30 days postpartum), a synchronization protocol was initiated, starting with GnRH (100–250 µg) to stimulate follicular development, followed by PGF2α (25 mg) 7 days later, and another GnRH injection (100 µg) 48 hours after PGF2α. TAI was performed 16–24 hours after the second GnRH injection (Yusuf et al., 2024a,b) (Fig. 3).

Group 3: endometritis disorders

The primary focus was on treating uterine infection and restoring reproductive health. On Day 0, PGF2α (25 mg) was intramuscularly administered to induce luteolysis and promote uterine drainage. The uterine health was reassessed 14 days later, and if the infection persisted, a second dose of PGF2α was administered. Once the infection resolved, a synchronization protocol was initiated with GnRH (100–250 µg) on Day 0, followed by PGF2α (25 mg) on Day 7 to lyse the corpus luteum, and another GnRH injection (100 µg) on Day 9 to induce ovulation. TAI was conducted 16–24 hours later (Mansur et al., 2020) (Fig. 4).

Group 4: silent estrus disorders

Hormonal therapy aimed to stimulate and synchronize estrus. The insertion of a CIDR device containing progesterone on Day 0 was combined with GnRH administration. The CIDR was removed on Day 7, and PGF2α (25 mg) was administered. GnRH (100 µg) was administered on Day 9 to induce ovulation, and TAI was performed on Day 10 (Yusuf et al., 2010) (Fig. 5).

Assessment of RTS

The RTS was evaluated using a modified procedure based on the study of Miller and East (2020) through rectal palpation during estrus. Measurements included the diameter of the uterine horn and the dimensions (length, width, and height) of the ovaries. Ultrasonography (USG) equipment (Honda, Japan) was used to enhance the accuracy of the assessment and provide detailed imaging of the reproductive tract.

Assessment of the cervical mucus

Cervical mucus samples were collected from Simmental cows 5–30 minutes before AI during estrus. The evaluation followed a modified protocol by Yusuf et al. (2024a,b), focusing on parameters such as appearance, viscosity, spinnbarkeit, acidity, and ferning pattern (FN) (Table 1).

Fig. 4. Hormonal protocol for endometritis disorders.

Fig. 5. Hormonal therapy for silent estrus disorders. Correlation between RTS, cervical mucus characteristics, and fertility rate.

Table 1. Assessment score of cervical mucus.

Table 2. RTS according to reproductive status.

Table 3. Characteristics of mucus cervical cancer according to reproductive status.

Fertility rate assessment

The fertility rate was assessed by calculating the CRs following TAI. CRs was defined as the proportion of inseminated cows that became pregnant after a single AI procedure, providing a reliable measure of reproductive efficiency. Pregnancy diagnosis was conducted using transrectal USG between 45 and 60 days after AI to confirm successful conception, as described by Diansyah et al. (2022).

Statistical analysis

The data collected in this study were organized and tabulated using Microsoft Excel before statistical analysis. A one-way analysis of variance was performed to compare RTS, cervical mucus characteristics, and fertility rates among the experimental groups. Pearson’s correlation analysis was used to determine the relationships between the evaluated parameters. All statistical analyses were performed using SPSS software (version 25) for Windows (IBM Corp., Chicago, IL). Statistical significance was determined at a level of p < 0.05.

Ethical approval

All procedures adhered to ethical standards for animal welfare and were approved by the Animal Ethics Committee of the National Research and Innovation Agency (Approval No. 104/KE.02/SK/05/2023).

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Results

Reproductive tract size

The RTS of Simmental cattle, as presented in Table 2, exhibited significant variations across groups based on reproductive status. G1 exhibited a consistent RTS, representing optimal physiological conditions. Significant differences (p < 0.05) were observed between the groups, highlighting the impact of reproductive disorders on both ovarian and uterine dimensions. G2 showed a slight reduction in ovary dimensions compared with G1, with significant differences in ovary width (p < 0.05). However, their uterine horn diameter was significantly larger than that of G1 (p < 0.05). In G3, the most pronounced changes were observed, particularly in the uterine horn diameter, which was significantly larger than in the other groups (p < 0.05). Ovarian dimensions in G3 were also significantly reduced in G3 compared with G1 (p < 0.05). In G4, all ovarian dimensions (length, width, and height) were significantly smaller than those in G1 (p < 0.05); the uterine horn diameter in G4 was similar to G1 (p > 0.05) but significantly smaller than those in G2 and G3 (p < 0.05).

Characteristics of the cervical mucus

The cervical mucus characteristics of Simmental cattle, as presented in Table 3, showed significant variations across groups based on reproductive health status. G1 exhibited optimal cervical mucus characteristics, representing healthy reproductive conditions. Significant differences (p < 0.05) were observed between groups. In G2, all parameters of cervical mucus were significantly lower than in G1 (p < 0.05), with appearance, viscosity, spinnbarkeit, acidity, and FN values reduced to minimal levels. Similarly, G3 exhibited even lower values for these parameters compared with G1 (p < 0.05). There were no significant differences between G2 and G3 for most parameters (p > 0.05). In G4, cervical mucus parameters were intermediate between those in G1, G2, and G3. All parameters in G4, including appearance, viscosity, spinnbarkeit, acidity, and FN, were significantly lower than those in G1 (p < 0.05) but significantly higher than those in G2 and G3 (p < 0.05).

Fig. 6. Fertility rate based on reproductive status; Means with different superscripts differ significantly at p > 0.05;G1: healthy group; G2: abortion group; G3: Endometritis group; G4: Silent Estrus group.

Fertility rate

The CRs of Simmental cattle, as presented in the Figure 6, demonstrated significant differences across groups based on reproductive health status. G1, representing healthy cows, exhibited the highest CRs (81.81%). This value was significantly higher (p < 0.05) than in the other groups. In contrast, G2 and G3 had similar CRs of 35.74% and 35.36%, respectively, with no significant difference between the two groups (p > 0.05). In G4, an intermediate CRs of 50.91% was recorded, which was significantly lower than that of G1 (p < 0.05) but significantly higher than that of both G2 and G3 (p < 0.05).

The correlation matrix shows several statistically significant relationships among the reproductive parameters (Fig. 7). Positive and significant correlations were observed between viscosity and conception rate (r=0.83, p < 0.01), ferning pattern (r=0.75, p < 0.01), and acidity (r=0.74, p < 0.01). Similarly, the FN was positively correlated with the CRs (r=0.81, p < 0.01) and acidity (r=0.73, p < 0.01). Significant positive correlations were also noted between appearance and the CRs (r=0.74, p < 0.01), the FN (r=0.75, p < 0.01), and the viscosity (r=0.70, p < 0.01). Additionally, acidity exhibited a strong positive correlation with the perception rate (r=0.80, p < 0.01). In contrast, significant negative correlations were found between the uterine horn diameter and several parameters, including the perception rate (r =−0.72, p < 0.01), appearance (r=−0.69, p < 0.01), viscosity (r=−0.65, p < 0.01), acidity (r=−0.67, p < 0.01), and FN (r=−0.63, p < 0.01). Additionally, ovary height was negatively correlated with acidity (r=−0.24, p < 0.05).

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Discussion

This study evaluated the physiological impacts of reproductive disorders and the effectiveness of hormonal protocols in improving fertility in Simmental cattle raised under semi-intensive systems. By analyzing RTS, cervical mucus characteristics, and fertility outcomes, this research provides critical insights into how reproductive disorders alter physiological function and how targeted hormonal interventions can mitigate these effects. Comparisons with previous studies and their quantitative data strengthen the interpretation of the findings. Cattle with normal reproductive health demonstrated optimal reproductive performance, with a CR of 81.81%, comparable to the 82.5% reported by Crowe et al. (2018) and Fernandez-Novo et al., (2020) for healthy beef cattle under intensive management systems. High-quality cervical mucus in this group, characterized by a viscosity score of 2.47 and a FN score of 2.48, reflects robust estrogenic stimulation. Previous studies have shown that viscosity scores above 2.0 and FN scores near 3.0 are strongly associated with CRs exceeding 80% (Ferdiansyah et al., 2022). Furthermore, the normal uterine horn diameter (22.53 mm) observed in healthy cattle aligns with findings by Gutierrez et al. (2014) and Hindman et al. (2022), who reported values ranging from 21 to 23 mm. These physiological benchmarks highlight the role of balanced endocrine function in optimizing cervical mucus quality and uterine receptivity.

Fig. 7. Pearson’s correlation coefficient between RTS, cervical mucus characteristics, and fertility rate.

In cattle with abortion disorders, fertility outcomes were significantly lower, with a CRs of 35.74%. This percentage is comparable to the 36.2% reported by Markos et al. (2019) in cattle with postpartum complications under similar farming systems. Enlarged uterine horn diameters (25.39 mm) in this group suggest delayed uterine involution and persistent inflammation, consistent with findings by Gutiérrez-Reinoso et al. (2022), who observed horn diameters exceeding 24 mm in cattle with unresolved uterine infections. Cervical mucus quality was also compromised, with a viscosity score of 0.61 and acidity score of 0.61. These values are significantly lower than the optimal ranges reported for healthy cattle, indicating impaired estrogenic stimulation and suboptimal conditions for sperm survival and motility. This finding aligns with that of Yusuf et al. (2024a,b), who noted that poor mucus quality, defined by viscosity scores below 1.0, was associated with CRs below 40%.

Cattle diagnosed with endometritis exhibited the most severe disruptions in reproductive physiology, with a CRs of 35.36%, similar to the 34.8% reported by Yusuf et al. (2024a,b) for cows with chronic uterine infections. Enlarged uterine horns (32.76 mm) reflect significant structural and functional damage caused by chronic inflammation, as previously described by Gautam et al. (2009), who reported horn diameters >30 mm in cattle with severe endometritis. Cervical mucus quality was markedly diminished, with a viscosity score of 0.59 and a FN score of 0.45. These findings align with research by Maher et al. (2018) and Jain et al. (2022), which demonstrated that poor mucus quality in endometritis cases is driven by systemic inflammation, oxidative stress, and disrupted hormonal signaling, all of which reduce estrogen receptor activity and estrus expression.

Silent estrus was associated with intermediate reproductive parameters and fertility outcomes, with a CRs of 50.91%. This value is slightly lower than that reported by Devkota et al. (2022) in cattle with subclinical estrus disorders in intensive systems, reflecting the challenges of estrus detection and hormonal synchronization in semi-intensive environments. Cervical mucus quality in this group, with a viscosity score of 1.41 and acidity score of 1.68, indicates partial estrogenic stimulation. Previous studies have shown that suboptimal mucus parameters in silent estrus are often linked to delayed follicular development and incomplete ovulation (Pérez-Marín and Quintela, 2023; Yusuf et al., 2024a,b). The intermediate uterine horn diameter (22.49 mm) suggests that silent estrus is less associated with structural uterine pathology but more influenced by hormonal dysregulation, which complicates the timing of AI and reduces fertility outcomes.

The correlations observed in this study emphasize the physiological interconnections within the reproductive system and are supported by findings from previous studies. Strong positive correlations between cervical mucus characteristics such as viscosity (r=0.83, p < 0.01), acidity (r=0.80, p < 0.01), and FNs (r=0.81, p < 0.01) and CRs highlight the central role of estrogen-driven changes in optimizing the reproductive environment. Yusuf et al. (2024a,b) similarly reported strong correlations between cervical mucus quality and fertility in healthy cattle. Optimal mucus viscosity and alkaline acidity facilitate sperm motility, capacitation, and survival, whereas FNs enhance sperm transport by aligning mucus glycoproteins (Siregar et al., 2019). Conversely, uterine horn diameter exhibited a strong negative correlation with fertility outcomes (r=−0.72, p < 0.01), consistent with findings by Binelli et al. (2021), who reported similar parameters in cattle with uterine inflammation. Enlarged uterine horns, indicative of chronic inflammation or fibrosis, impair endometrial receptivity, and disrupt hormonal feedback mechanisms. This dual disruption reduces fertilization and implantation efficiency. The interplay between cervical mucus quality and uterine health highlights the systemic impact of reproductive disorders. Poor uterine health diminishes estrogen signaling, leading to suboptimal mucus production and barriers to successful reproduction.

This study provides critical insights into the management of reproductive disorders in semi-intensive Simmental cattle, but several limitations should be noted. The findings are specific to semi-intensive simularial cattle, which may limit their applicability to other breeds and production environments. Additionally, although strong correlations between reproductive parameters and fertility were observed, causality could not be fully established because of the cross-sectional study design. Longitudinal studies are needed to confirm these relationships and to better understand the mechanisms underlying these relationships. Furthermore, external factors such as nutritional status, immune responses, and environmental stressors were not directly assessed, but they likely influenced fertility outcomes. Addressing these factors in the future will provide a comprehensive understanding of how reproductive efficiency can be optimized in semi-intensive systems. Despite these limitations, this study lays a solid foundation for integrated reproductive management strategies that combine hormonal protocols with improved nutritional, environmental, and health management practices. These approaches have the potential to enhance reproductive performance and ensure sustainable livestock production in resource-limited settings.

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Conclusion

In conclusion, this study demonstrated that reproductive disorders substantially disrupt reproductive physiology and reduce fertility outcomes in Simmental cattle under semi-intensive systems. Healthy cattle exhibited optimal cervical mucus quality and uterine horn dimensions, leading to superior fertility outcomes, whereas cattle with abortion disorders and endometritis experienced enlarged uterine horns, poor mucus characteristics, and significantly lower fertility. Silent estrus showed intermediate results, reflecting hormonal imbalances that partially impaired reproductive efficiency. Positive correlations were identified between cervical mucus parameters such as viscosity, acidity, FN, and fertility, whereas negative correlations were observed with uterine horn dimensions. These findings highlight the physiological disruptions caused by reproductive disorders and the role of hormonal protocols in mitigating these effects. However, the variability in outcomes emphasizes the importance of integrated management strategies that combine hormonal interventions with targeted nutritional and environmental improvements to optimize reproductive performance in semi-intensive systems.

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Acknowledgments

The first author is a doctoral student and is supported by the Beasiswa Pendidikan Indonesia (BPI) No. 2021011222685 Ministry of Education, Culture, Research, and Technology and Lembaga Pengelola Dana Pendidikan (LPDP) Ministry of Finance, Republic of Indonesia.

Conflict of interest

The authors declare no conflict of interest.

Funding

This study was supported by Beasiswa Pendidikan Indonesia (BPI) No. 2021011222685 Ministry of Education, Culture, Research, and Technology and Lembaga Pengelola Dana Pendidikan (LPDP) Ministry of Finance, Republic of Indonesia.

Authors’ contributions

M Mansur, A.M Diansyah, and A Nurlaifah conceptualized and designed the experiment, conducted the literature review, and wrote the first draft of the manuscript. A Baharun, A.M Diansyah, R Rahmat, and A.M Alfian edited and revised the manuscript draft, M.F Amrullah, A.M Alfian and A.A.S Adam collected data and data analysis. All authors read and approved the final manuscript.

Data availability

All data supporting the findings of this study are available in the manuscript.

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