Prevalence and Risk Factors of Postpartum Health Disorders in Dairy Cattle: First Report in Algeria

1.Introduction
The postpartum transition period in dairy cows is critical, affecting both the animal’s health and the overall herd productivity. Postpartum disorders, such as hypocalcemia, ketosis, retained fetal membranes, mastitis (MAS), and uterine diseases (endometritis and metritis), are strongly associated with reduced fertility and pregnancy rates, increased embryonic loss, and decreased milk production. These disorders, associated with metabolic and immunological imbalances, significantly impact on animal welfare and the economic performance of dairy farms. Its can reduce conception rates, prolong calving intervals, and increase culling rates [1, 2]. Recent studies have highlighted that factors such as peripartum nutrition, metabolic status, and management practices strongly influence the prevalence of these disorders [3, 4]. Notably, subclinical hypocalcemia has been identified as a major predisposing factor, compromising cows’ resilience during the early days of lactation [5]. Similarly, thermal management during the prepartum period, particularly in hot climates, has been shown to significant affect postpartum inflammatory diseases [6].
In the Algerian context, dairy farming holds a strategic position, contributing to food security and rural economic development. However, production systems often face challenges related to management practices, nutrition, climate, and limited infrastructure [7]. These constraints can increase the prevalence of postpartum disorders, the management a critical issue for improving farm performance.
Despite the importance of this subject, specific data on the prevalence and risk factors of postpartum health disorders in Algerian dairy farms remain scarce. Understanding the underlying causes, whether related to genetics, the environment, or management practices, is essential for developing appropriate prevention and intervention strategies tailored to the local context.
Based on field-collected data, this study seeks to provide a scientific foundation to improve management practices and support the sustainable development of dairy production in Algeria. Therefore, to the best of our knowledge, for the first time in Algeria this study aims to examine the frequency of postpartum health disorders in dairy farms and identify the associated risk factors.

2. Material and Methods
2.1. Study area and population 
This study was based on field data collected between April 2023 and July 2024 from 7 dairy herds located in 7 different regions in Algeria (Oran, Tipaza, Setif, Mila,M’sila, Ghardaia and Medea). Oran is located in the northwest of Algeria on the Mediterranean coast, while Tipaza is lies in the north-central region, also along the seafront. Sétif and Mila are situated in the northeast. M’sila is located in the center, in a region of semi-arid high plains. Ghardaïa lies in central Algeria, at the heart of the Sahara in the M’zab Valley, and Médéa is situated in the Tell Atlas of northern Algeria (Figure 1).

A total of 1153 dairy cows of two breeds were enrolled: Holstein (79.37%) and Montbeliarde (20.63%).Only one farm was sampled per region. The number of cows included in this study was 60 in Oran, 127 in Tipaza, 644 in Mila, 32 in M’sila, 42 in Setif, 208 in Medea, and 42 cows in Ghardaia.

2.2. Diagnosis of postpartum health problems 
Cows were examined for the following postpartum disorders: Uterine prolapsed (UP), retained placenta (RP), milk fever (MF), acute metritis (AM), delayed uterine involution (DUI), chronic endometritis (CE), MAS, lameness (LAM) and abortion (ABO). All these postpartum disorders were confirmed in conjunction with the herd’s veterinarians.
Cows with no health problems were considered healthy, while those with at least one health problem were considered unhealthy.
Cows classified as INF (infectious disorders) have at least one of the following conditions: UP, RP, AM, DUI, CE and MAS. Cows classified as metabolic disorders (MET) have at least one of the following conditions: LAM or MF. 

2.3. Data analyses
For statistical analysis, the chi-square test and ANOVA were used with significance level of P<0.05. Data analysis was conducted using R i386 3.0.2 program with a Windows GUI front-end. 
A directed acyclic graph (DAG) provides a conceptual framework for understanding how various factors contribute to postpartum health disorders in dairy cows.
A bubble diagram was made to show the importance of each postpartum disorder. The most important factors represent large bubbles. Those with little relative weight, on the other hand, have small bubbles. 

3. Results
The health status of cows (healthy, one disorder, or ≥2 disorders) and the type of disorder (inflammatory or metabolic) varied significantly across the different regions (P<0.0001) (Table 1).

Notably, Setif exhibited an extremely high proportion of inflammatory disorders (69.05%) and cows with ≥2 disorders (52.38%). Conversely, M’sila showed a proportion of healthy cows (62.50%) well above the overall average (37.38%). The highest prevalence of MET was observed in Setif (69.05%) and Medea (55.77%) (P<0.0001) (Table 1).
Overall, cows with a single postpartum disorder (37.21%) and those classified as having inflammatory disorder (31.66%) were significantly more frequent than cows with ≥2 postpartum disorders (25.59%) and those with a metabolic disorder (24.89%), respectively (P<0.001) (Table 1).
The DAG (Figure 2) illustrates causal relationships between various factors influencing postpartum health disorders in dairy cows.

Exogenous variables (circles), such as breed, parity, and calving ease, as well as ancestor variables (rectangles), such as number of lactations, AM, or placental retention (PR), represented by postpartum health disorders (blue circle), interact directly or indirectly to affect the final outcome. The arrows indicate causal influences, highlighting complex causal chains, such as the impact of the number of lactations via parity, or indirect effects via intermediate variables such as the DUI. Postpartum pathologies vary according to the number of lactations, particularly for MF and LAM (P<0.001). Inflammatory disorders (AM, DUI) decrease as the number of lactations increases. LAM is particularly frequent from the third lactation onward (>30%) (P<0.001) (Table 2).

Holstein and Montbeliarde breeds show differences in metabolic and inflammatory disorders (P<0.001). Holstein cows were more prone to inflammatory disorders such as MAS (17.98%) and DUI (6.07%), while Montbeliarde cows exhibit a high prevalence of LAM (52.61%) (P<0.001) (Table 2).
Cows that experienced dystocic calving show a higher prevalence of inflammatory and MET compared to those with normal calving (P<0.001). Dystocia significantly increases the risk of DUI (8.82%) and LAM (25.74%) (P<0.001) (Table 2).
Multiparous cows exhibit higher rates of metabolic and inflammatory disorders (P<0.001) (Table 2).
Overall, the most frequent postpartum disorders were AM and LAM, followed by RP and MAS (P<0.01) (Table 2). Bubble diagram analysis results showed that LAM and AM are the most important factors (with large bubbles at the top). However, UP and ABO are factors with little relative weight (small bubbles at the bottom) (Figure 3).

The principal component analysis (PCA) (Figure 3) of the prevalences of various postpartum disorders based on the studied factors reveals the existence of strong positive correlations between UP, LAM, CE, RP and DUI. MAS is opposed to these disorders. Some pathologies, such as MF and ABO, have moderate contributions and are partially independent of other pathologies (Figure 4).

4. Discussion
To the best of our knowledge, this study represents the first comprehensive investigation carried out in Algeria that specifically addresses the prevalence and risk factors (parity, lactation number, breed, calving ease, and region) associated with postpartum health disorders in dairy cattle farms. This research fills a critical gap in the existing literature and provides valuable insights into the challenges faced by the dairy industry. 
Changes in feed intake in dairy cows during the periparturient period must be monitored, as inadequate feed intake is associated with numerous postpartum inflammatory and MET [8]. In our study, Setif has an extremely high proportion of inflammatory disorders (69.05%) and cows with ≥2 postpartum disorders (52.38%), indicating particularly unfavorable breeding conditions in this region. However, M’sila shows a proportion of healthy cows (62.50%) well above the overall average (37.38%) suggests favorable management practices or local conditions. The postpartum period in dairy cows is characterized by a correlation between reduced feed consumption and MET [8]. Therefore, the high prevalence of MET observed in our survey in Medea (55.77%) could be linked to nutritional factors or suboptimal peripartum management.
Cows with two or more postpartum health disorders had lower milk production, decreased reproductive performance, increased risk of culling and death compared to cows with only one postpartum health disorder or to healthy cows [9]. However, in our study, healthy cows (37.38%) or with one postpartum disorder (37.21%) were significantly more frequent than cows with ≥2 postpartum disorders (25.59%) which aligns with the findings of Macmillan et al. [9] in Canada. 
The proportion of cows diagnosed with one postpartum health disorder ranged from 21.88% to 46.15%, which similar to the findings of Ribeiro et al. [10] in Florida but lower than those reported by Macmillan et al. [9] in Canada.
Multi-part cows have an increased risk of MAS [11] and MF [12], but a lower risk of metritis [13], which is consistent with our study. The overall prevalence of clinical MAS (17.26%), MF (hypocalcemia) (1.47%), RP (16.91%), and AM (23.94%) was comparable to the findings of Macmillan et al. [9], Rodríguez et al. [12] and Koeck et al. [14].
Regarding MF, the prevalence in our study was 1.47%, ranging from 0.84% in primiparous cows to 1.83% in multiparous cows. Our results are similar to those reported by Macmillan et al. [9] (0.9%), but lower than those reported by Rodríguez et al. [12] (4%).
For clinical MAS in primiparous cows, our findings (7.3%) are comparable to Macmillan et al. [9] (7.6%), but lower than Hocine et al. [15] (9.80%). 
These differences may be explained by geographical, environmental, and agro-ecological variations, as well as differences in farm management, husbandry systems, production methods, study protocols, or instruments used by researchers [16]. An increasing prevalence of MAS was also observed with parity in our study: 7.30%, 20.54%, 26.02%, 19.54%, 26.56%, and 38.89% for first, second, third, fourth, fifth, and more than six lactations, respectively. This trend is consistent with findings reported by Bitew et al. [17]. Additionally, Jha et al. [18] highlighted the role of enhanced diapedesis and more active mononuclear leukocyte function in primiparous cows compared to multiparous cows. Furthermore, milk production declines with increasing parity and age, making cows more susceptible to infections. Older cows have been associated with an increased risk of MAS [11], MF [12], and a lower risk of metritis [13]. Assisted calving has been linked to an elevated risk of postpartum health disorders, notably RP and uterine diseases [1, 10]. This association underscores the importance of closely monitoring cows that require assistance during calving for potential postpartum complications. Dystocia is closely associated with increased uterine bacterial contamination, trauma, and heightened risks of RP and metritis [19]. It is important to recognize that while RP, metritis, and purulent vaginitis may be interconnected, the presence of one condition does not necessarily lead to the development of the others [20]. This nuanced understanding is critical for effective management and treatment strategies in dairy herd health. 
LAM in dairy cows is considered the main cause of pain and discomfort, with direct repercussions on animal welfare, leading to considerable economic losses [21] due to the premature elimination of the most productive animals, decreased milk production, treatment costs and lower fertility rates [21]. Despite the importance of this problem, no information is available on LAM in the Algeria, which prevents a proper understanding of the scale of the problem and its associated factors. In North America, LAM prevalence ranges from 20% and 55% of dairy cows [22].
In a literature review, an analysis of worldwide data over a 30-year period (1989-2020) revealed an average prevalence of LAM of 22.8% [23] which aligns with our findings (24.72%). Koeck et al. [14] reported a lower prevalence 12.1% [14].
The overall incidence of postpartum endometritis revealed herein was 8.95%, significantly lower than the 36.6% reported by Kim and Kang [24]. Variations in incidence rates can be attributed to differences in diagnostic methods, timing of endometritis detection, cow characteristics, or variations in herd management practices [25]. In our survey, RP, UP, and DUI were associated with increased odds of developing metritis, consistent with previous studies [20]. This is explained by the fact that dystocia interventions were generally associated with an increased risk of contamination of the uterus and vagina, due to the large amount of necrotic tissue present, delayed expulsion of lochia, and potential uterine lesions caused by manual extraction [19, 20].
Globally, the most common postpartum disorders observed in this study were AM and LAM, followed by RP and MAS. Similar findings have been reported in other studies [9].
It can be concluded that 37.21% of cows were diagnosed with 1 postpartum disorder, while 25.59% of cows had ≥2 postpartum disorders. Inflammatory disorders (31.66%) were more frequent than MET (24.89%). The most frequent postpartum disorders were AM and LAM, followed by RP and MAS. Inflammatory disorders (metritis, DUI) decreased with increasing lactation number. Cows that experienced dystocic calving show a higher prevalence of inflammatory and MET compared to those with normal calving. Multiparous cows exhibit higher rates of metabolic and inflammatory disorders. 

5. Conclusion 
The study highlights the importance of close monitoring postpartum health, especially on farms at higher risk, suggesting that optimized reproductive and nutritional management could help reduce these disorders. Further research into management practices is needed to improve prevention and treatment strategies.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of the University of Blida 1, Ouled Yaïch, Algeria (Code: UB-115/2024).

Data availability
All data analyzed during this study are included in this article. 

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Authors' contributions
Conceptualization, study design, experiments, review and editing: Radhia Dahmani, Nassim Ouchene, and Nadjet Amina Khelifi Touhami; Data analysis and interpretation: Seddik Kebbal, Mustapha Nabi, Amar Kalem, Omar Salhi, Nassim Ouchene, and Nadjet Amina Khelifi Touhami; Writing the original draft: Nadjet Amina Khelifi Touhami.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgements
We would like to extend our heartfelt gratitude to all the veterinarians, breeders, and farm owners who generously contributed their time and expertise to provide the essential information for this study.

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