The shifts in colostrum and milk secretion dynamics concerning immunoglobulins, TDS, glucose and pH values are presented in (Table 1). In addition, the physiological, hematological and biochemical profiles of representing the systemic physiological baseline are presented in (Fig 1) and (Table 2-3).
Monitoring immunoglobulins, TDS, glucose and pH of colostrum and milk
Immunoglobulins, TDS, glucose and pH values exhibited distinct patterns as the secretion transitioned from colostrum to mature milk. The dynamics of colostrum and milk secretion over the first four days postpartum were characterized by a sharp decline in immunoglobulins, TDS and glucose levels (P<0.001). Immunoglobulins concentrations decreased from a peak of 20.50% on day 1 to 8.0% by day 4, TDS values decreased from a peak of 23.40% on day 1 to 11.70% by day 4 and glucose levels dropped from 40.0 mg/dl to 22.0 mg/dl over the same period. On the other hand, the pH values showed a progressive increase over the four-days. On day 1, the colostrum was slightly acidic (6.80). Thereafter, the pH values increased to reach 7.10 by day 2 and 7.20 by day 4.
Physiological Profiles mares and foals
The physiological profiles including rectal temperature (°C), pulse rate (beats/min.) and oxygen saturation (%) in presented in Fig (1). The results indicated 38.6°C rectal temperature, 99.0 beats/min. and 94.0% SpO
2 of foals compared to 38.2°C rectal temperature, 60.0 beats/min. and 96.0% SpO
2 of mares.
Hematological Profiles of none pregnant Arabian mares in Al-Ahsa region
The hematological profiles of none pregnant Arabian mares in Al-Ahsa is presented in Table (2). The average RBCs count was 8.29±0.27×10
12/L, supported by a mean hemoglobin (Hb) concentration of 11.92 g/dL and a packed cell volume (PCV) of 35.6%. While these averages are within expected limits, the minimum values for Hb (8.4 g/dL) and PCV (26.4%) suggest that certain individuals in the cohort may be experiencing borderline anemia. The red cell indices, including a mean corpuscular volume (MCV) of 43.13 fl and a mean corpuscular hemoglobin concentration (MCHC) of 33.35 g/dL, indicate that the circulating erythrocytes are generally normocytic and normochromic. The leukocyte parameters indicate a stable immune status with most values falling within the standard equine reference ranges. The average total white blood cells (WBCs) count was 8.18±0.43×10
9/L. This total is comprised of a mean granulocyte count of 5.17±0.31×10
3/µl and an agranulocyte count of 3.00±0.26×10
3/µl. The average platelet count (PLT) was 168.21±12.91×10
3/µl, which is adequate for normal hemostasis, although the minimum recorded value of 119 sits near the lower threshold for the species. The mean platelet volume (MPV) remained very consistent with a narrow range (average 6.3 fl).
Biochemical profile of none pregnant Arabian mares in Al-Ahsa region
The biochemical profiles of none pregnant Arabian mares in Al-Ahsa is presented in (Table 3). Total protein value averaged 5.58 g/dl, supported by an albumin mean of 3.53 g/dl, resulting in a healthy albumin/globulin (A/G) ratio of 1.85. Kidney function appeared robust, as evidenced by a mean creatinine of 0.75 mg/dL and blood urea nitrogen (BUN) of 10.42 mg/dL. The average glucose value (96.33 mg/dL) was within normal limit.
Aspartate Aminotransferase (AST) levels averaged 310.12 U/L, with individual maximums reaching 393 U/L, which sits at the upper threshold of the equine reference range. This finding is paired with a significantly elevated total bilirubin average of 2.57 mg/dL (peaking at 4.8 mg/dL). Since the gamma-glutamyl transferase (GGT) remained low and stable at an average of 18.87 U/L, the data suggests that the elevated bilirubin and AST are more likely indicative of hepatocellular strain or mild hemolysis rather than an obstructive biliary condition.
Electrolyte balance and acid-base indicators reveal a systemic trend toward metabolic alkalosis and specific mineral fluctuations within the cohort. The total CO
2 (TCO
2) averaged 32.45 mmol/L, which is consistently high and suggests a compensatory metabolic or respiratory shift. While the average potassium (4.13 mmol/L) were within normal limits, the potassium data showed extreme variability with a maximum of 8.3 mmol/L, signaling individual cases of critical hyperkalemia. Furthermore, the mildly low sodium (133.41 mmol/L) and slightly elevated calcium (11.50 mg/dL) highlight a complex electrolyte profile likely influenced by the specific environmental or physiological conditions of the mares.
The current investigation tracked the specific shifts in colostrum and milk secretion dynamics, with a particular focus on immunoglobulin, TDS, glucose and pH fluctuations (Table 1). In addition, the current study determined the physiological, hematological and biochemical profiles defining the systemic baseline as illustrated in (Fig 1) and (Table 2-3). The blood circulation and its profiles including blood cells and plasma components represents one of the most critical aspects of body health and physiology. Diagnosis of complete blood picture and plasma biochemistry profiles are the most frequent tests used for investigation of suboptimal performances or diseases (
Maśko et al., 2021). Complete blood picture (CBCs) and plasma biochemistry profiles provide insights into organ functions, oxygen transport and fluid, acid–base balance and electrolyte (
Mohammed, 2018).
Immunoglobulins, TDS, glucose and pH in colostrum and milk
The highest concentration of immunoglobulins was recorded on day 1 (20.50%), followed by a significant reduction to 11.80% on day 2 and 8.00% by day 4 (P< 0.001). The obtained results of day 1 is lower than that obtained by
Storme et al. (2020) (27.9%). This could be attributed to genetic and environmental factors (
Alkhalifah and Mohammed, 2026;
Alhamd and Mohammed 2026). Unlike primates or rodents, the epitheliochorial placenta of the mare prevents the transfer of maternal antibodies to the fetus in utero. Consequently, the foal is born agammaglobulinemic and relies entirely on the ingestion of high-quality colostrum for passive transfer of immunity (
Turini et al., 2024). The drop observed between day 1 and day 4 is primarily attributed to the cessation of the selective transport of IgG from the maternal serum into the mammary gland and the dilution caused by the rapid increase in milk volume as lactation is established
(Aoki et al., 2020).
The TDS value for colostrum at day 1 showed a mean of 23.50%% with sharp decline from day 2 (15.50%) to day 4 (11.70%). The concentration of total dissolved solids (TDS) in equine mammary secretions serves as a vital physiological marker for the transition from colostrogenesis to mature lactation. In Arabian mares, the highest TDS levels were observed immediately postpartum, typically ranging from 20% to 25%, driven primarily by the dense accumulation of immunoglobulins, specifically IgG and essential macro-minerals
(Hachana et al., 2022; Rivero et al., 2024). This high initial density is critical for providing the neonate with passive immunity and the caloric energy required for early thermoregulation. Following parturition, the TDS levels undergo a rapid decline, often dropping to approximately 13-15% by the second day and stabilizing near 10-12% by the fourth day as the gland increases water and lactose production (
Gálik et al., 2012). Research indicates that monitoring these fluctuations via Brix refractometry or digital conductivity meters allows for the efficient assessment of colostrum quality, where a TDS value above 23% is widely considered the gold standard for ensuring adequate passive transfer of immunity in foals (
Gálik et al., 2012).
Glucose levels exhibited a similar falling from 40.00 mg/dl on day 1 to 22.00 mg/dl on day 4. In the early equine postpartum phase, glucose is highly available in the colostrum and the majority of available glucose is diverted toward the synthesis of lactose as mature milk production begins
(Lin et al., 2016). Therefore, the deceases of glucose values is typically met by increases in lactose values as the milk matures to meet the foal’s growing energy requirements for growth rather than just immediate survival
(Barreto et al., 2020).
The colostrum pH on day 1 was slightly acidic (6.80) and increased reaching 7.10 by day 2 to 7.20 on day 4. The pH of equine mammary secretions undergoes a significant physiological transition during the early postpartum period, shifting from a slightly acidic state in colostrum to a more neutral or slightly alkaline state in mature milk. At the onset of parturition, mare colostrum typically exhibits a pH ranging from 6.2 to 6.8, a characteristic that is frequently utilized as a clinical predictor for foaling, where a drop below 6.4 often indicates imminent delivery within 24 hours (
Ellerbrock and Canisso 2016). This relative acidity in colostrum is attributed to the high concentration of proteins, specifically caseins and immunoglobulins, as well as dissolved carbon dioxide and organic acids (
Csapó-Kiss et al., 1995;
Gálik et al., 2012). As lactation progresses into the fourth day and beyond, the pH consistently rises, stabilizing between 7.0 and 7.2 in mature milk; this increase corresponds with the decline in protein density and a shift in mineral balance, particularly the reduction of dihydrogen phosphate
(Kossaliyeva et al., 2025; Pânzaru et al., 2026). Monitoring these pH fluctuations is essential, as deviations from this expected upward trend can serve as early indicators of subclinical mastitis or systemic maternal stress.
Physiological parameters of mares and foals
The observed vital signs for the Arabian foals and mares comprising a rectal temperature of 38.6 and 38.2°C, a pulse rate of 99 and 60 beats/min and peripheral oxygen saturation (SpO2) of 94.0 and 96.0%, respectively (Fig 1). The recorded parameters fall within the established physiological reference ranges for healthy foals and mare at rest. The physiological monitoring of Arabian mares and their neonates during the early postpartum period is essential for verifying successful transition and neonatal stability (
Magdesian, 2013). Rectal temperature serves as a critical indicator of thermoregulation. Foals generally exhibit a slightly higher range of RT (38.6°C) compared to mares (38.2°C) due to the high caloric density of colostrum (
Hines, 2018;
Stachurska et al., 2023). This suggests the absence of systemic inflammation or pyrexia during the study period. In foals, the resting pulse rate was 99 BPM while the mares maintain a much lower baseline of 60 BPM (
Evans, 2007;
Madigan, 2013). Furthermore, the foals provides 94.0% SpO
2 versus 96.0% for mares. The SpO
2 values below 90% may signal respiratory distress or neonatal maladjustment syndrome (
van Handel et al., 2007;
Rossi et al., 2025). Collectively, these results confirm that the foals and mares remained in a state of physiological homeostasis.
Hematological profile of none pregnant Arabian mares in Al-ahsa region
The hematological profiles of none pregnant Arabian mares is presented in Table 2. The mean red blood cellc count of 8.29×10
6/µl and hemoglobin concentration of 11.92 g/dl align with established norms for Arabian horses, a breed known for high hematological efficiency compared to heavier breeds
(Sawesi et al., 2023). The packed cell volume averaged 35.6%, which is within the healthy resting range of 32%-46%. Interestingly, the minimum Hb value of 8.4 g/dl and PCV of 26.4% suggest that some individuals may experience borderline physiological anemia or significant hemodilution. This could be attributed to the high ambient temperatures of Al-Ahsa leading to increased plasma volume as a thermoregulatory mechanism
(Mecocci et al., 2026). The mean corpuscular volume of 43.13 fl and MCHC of 33.35 g/dl indicate a normocytic normochromic erythrocyte population, suggesting that the mares were nutritionally stable and free from iron-deficiency markers. The white blood cells count averaged 8.×10
3/µl, falling within the standard equine range of 5.4-14.3×10
3/µl
(Lumsden et al., 1980). The distribution of granulocytes (5.17×10
3/µl) and agranulocytes (3.00×10
3/µl) indicates a balanced immune profile. These results suggest that the mares were not experiencing acute systemic inflammation or significant chronic stress at the time of sampling (
Honstein and Monty 1977;
Ayala et al., 2012). The average platelet count was 168.21×10
3/µl, which sits within the typical range for mares (100-350×10
3/µl). The mean platelet volume of 6.3 fl remained remarkably stable, indicating consistent thrombopoiesis. Platelet stability is a vital indicator of normal hemostatic function, particularly important in mares residing in regions where seasonal environmental shifts might otherwise affect blood viscosity and coagulation dynamics. These values provide a critical local reference for clinicians and researchers working with Arabian horses in the Eastern Province of Saudi Arabia.
Biochemical profile of none pregnant Arabian mares in Al-ahsa region
The biochemical profiles of none pregnant Arabian mares is presented in Table 3. These data indicate a high degree of metabolic adaptation to the local environment, with most parameters reflecting healthy organ function and homeostatic balance. The average total protein (5.58 g/dl) and albumin (3.53 g/dl) levels in this study are slightly on the lower end of the global equine reference range (typically 5.5-7.5 g/dl). This might be attributed to the high ambient temperatures of Al-Ahsa. The heat-adapted horses often exhibit expanded plasma volume to facilitate thermoregulation
(Cifuentes et al., 2026). The albumin/globulin ratio of 1.85 suggests a healthy immune status, as a low A/G ratio is typically an indicator of chronic inflammation or infection. Liver-associated enzymes, including GGT (18.87 U/L) and AST (310.12 U/L), fall within the normal limits for the breed (GGT: 4-44 U/L; AST: 226-466 U/L). Interestingly, the total bilirubin (2.57 mg/dL) shows a relatively high maximum of 4.8 mg/dL. While high bilirubin in other species suggests pathology, in horses, mild unconjugated hyperbilirubinemia is frequently a normal physiological response to short-term fasting or environmental stress (
Engelking, 1993). The creatine phosphokinase average of 176.38 U/L is within the normal resting range (typically <400 U/L), indicating no significant muscle damage or exertional rhabdomyolysis. The glucose levels (96.33 mg/dl) reflect stable glycemic control, consistent with the metabolic profile of the Arabian equine breeds
(Johnson et al., 2012). Renal health is confirmed by creatinine (0.75 mg/dL) and BUN (10.42 mg/dl) levels, which are within standard equine reference values (creatinine: 0.8-1.8 mg/dL; BUN: 10-24 mg/dl). The total CO
2 (32.45 mmol/L) indicates a healthy acid-base balance, crucial for mares in hot climates where respiratory rates may increase to dissipate heat. Electrolyte concentrations for calcium (11.50 mg/dl) and sodium (133.41 mmol/L) remained stable. However, the wide range in potassium (2.5-8.3 mmol/L) is notable. The higher maximum might be a result of slight hemolysis during sampling or dietary intake variations in the Al-Ahsa region
(Pires et al., 2025).
Limitations should be considered when interpreting the findings of this study. First, the relatively small sample size may have limited the statistical power to detect weaker associations and may reduce the generalizability of the results. Second, the study population was drawn from a single geographic region, which may not fully represent mares and foals managed under different environmental, nutritional, or husbandry conditions. Finally, direct measurement of colostral immunoglobulin G (IgG) concentration was not performed, limiting the ability to validate the assessed indicators against the gold-standard measure of colostrum quality.
