The sustainability of cattle herds within breeding enterprises depends on the success of healthy calf breeding programs. The most crucial period for calf care and breeding is the first 24 hours after birth(Gundelach et al., 2009). Immaturity of the immune system of newborn calves leads to the highest mortality rates during the initial 7 days of the postpartum period. With an immature immune system, the transition from a functionally monogastric to ruminant status involves several metabolic, physiological, and nutritional changes(Rajaei-Sharifabadi et al., 2024).

Various risk factors are directly associated with herd management, such as group housing and immunoglobulin deficiency resulting from inadequate colostrum intake, which contribute to calf mortality(Barry et al., 2019);(Olson et al., 1999);(Svensson et al., 2003). With excellent care and feeding practices, mortality rates can be at or below 5%(Wynn et al., 2009). Consequently, colostrum has emerged as a unique food source for minimizing health problems. Newborn calves lack developed defense mechanisms against diseases; however, colostrum feeding provides passive protection by supplying immunoglobulins (IgG) that are actively absorbed by the small intestine(Korhonen et al., 2000);(Salles et al., 2025);(Uyama et al., 2022).

Trace minerals are important micronutrients that play various roles in physiological processes, including oxidative metabolism and optimal cellular function(Ogilvie et al., 2023). Trace minerals such as selenium, chromium, and zinc are critical for immune function and overall metabolism(Arthington et al., 2014);(Shambhvi et al., 2023);(Willmore et al., 2021). Insufficient intake of these essential trace minerals can lead to clinical or subclinical symptoms, depending on the degree of deficiency. The optimal quantity of trace minerals included in diets depends on their bioavailability and the presence of antagonistic substances that may decrease their bioavailability(Byrne & Murphy, 2022). Despite being present in low concentrations within an organism, trace minerals play crucial roles in numerous physiological processes, including vitamin synthesis, hormone production, enzyme activity, regulation of cell osmotic pressure, collagen formation, tissue synthesis, oxygen transport, energy production, growth, fertility, and overall health. Failure to meet these needs can result in severe economic losses for animal producers owing to their animals’ decreased health and productivity. Inorganic salts (oxides, sulfates, and carbonates) are commonly used to meet the trace mineral needs of animals; however, products of organic origin have also been used in recent years(Harvey et al., 2021);(Mousavi-Haghshenas et al., 2022). Organic minerals are formed by combining trace minerals in an organic matrix, such as amino acids or polysaccharides, through covalent bonds(Harvey et al., 2021);(Ram et al., 2021).

At an early age, calves have limited prenatal trace mineral reserves, an immature immune system, and low endogenous antioxidant capacity, and they exhibit rapid metabolic adaptation, leading to distinct oxidative and physiological stress, which renders them highly dependent on postnatal mineral supply. Selenium and zinc are critical for antioxidant defense and immune maturation, whereas the stress response is mediated by chromium through the modulation of cortisol secretion and immune function, collectively justifying targeted trace mineral supplementation in early-age calves(Ghorbani et al., 2012);(Teixeira et al., 2014). Newborn calves fed adequately with colostrum supplemented with an organic source of trace minerals can show improved health and metabolic status. To our knowledge, no study has been conducted to evaluate the effects of organic minerals on immunoglobulin G, cortisol as a stress biomarker, and blood metabolites in newborn calves, and comparing Holstein and Simmental breeds. This limits our understanding of how breed-specific responses to organic minerals may influence early life immune competence and stress resilience. Therefore, the objective of this study was to analyze and compare the effects of organic mineral mixtures containing selenium, chromium, and zinc on the levels of immunoglobulin G, cortisol, and blood metabolites in newborn Holstein and Simmental calves.

All experimental protocols used in this experiment were approved by the Animal Ethics Committee of Afyon Kocatepe University, Afyonkarahisar, Turkey (01-120420).

The composition of Holstein colostrum, Simmental colostrum, and tank milk differed (Table 1). Colostrum fat, protein, lactose, and somatic cell count (SCC) were higher in the colostrum of Simmental cows than in that of Holstein cows; the lowest values of fat, protein, lactose, and SCC were observed in tank milk samples (p<0.001).

The effects of organic minerals on the blood metabolites of Holstein and Simmental calves were compared (Table 2). When comparing blood biochemical variables within the group over time, no differences were observed in serum urea, uric acid, triglyceride, or total protein levels (p>0.05). However, time-dependent changes were observed in AST, ALT, GGT, LDL, HDL, cholesterol, and glucose levels (p<0.05). Among the various treatment groups, differences were observed in AST, ALT, GGT, LDL, HDL, and cholesterol levels on various days (p<0.05). However, organic mineral supplementation had no effect on serum urea, uric acid, glucose, triglyceride, or total protein concentrations (p>0.05). Serum AST levels in Holstein calves at birth and during the first 9 days after birth were lower than those in Simmental calves (p<0.05), irrespective of mineral supplementation (p>0.05). Similarly, serum ALT levels were lower in Holstein calves than in Simmental calves on days 0 and 3 after birth (p<0.05). Serum ALT levels remained higher in all groups until day 3 (p<0.05) and did not change afterwards (p>0.05). Serum GGT levels remained higher on various days postpartum (p>0.05). Serum LDL levels were lower in Holstein calves than in Simmental calves on day 0 (p<0.05). Serum cholesterol, HDL, and LDL levels increased during the first 21 days after birth in both Simmental and Holstein calves (p<0.05). Serum glucose levels decreased gradually during the first 21 days after birth (p<0.05).

Serum cortisol levels changed in a time-dependent manner in all calves () (Table 4). Serum cortisol levels decreased with increasing days of age in both Holstein and Simmental calves (p<0.05). Although no effect of organic mineral supplementation was observed early postpartum, serum cortisol decreased significantly from days 15 to 21 in calves supplemented with organic minerals (p<0.05). From 28 days of age, serum cortisol levels increased until 42 days postpartum and decreased afterwards (p<0.05). However, no differences were observed in cortisol levels with regard to breed or mineral supplementation (p>0.05).

Serum IgG concentrations were similar in Holstein and Simmental calves, irrespective of organic mineral supplementation (; p<0.05). However, serum IgG concentrations decreased with increasing age in all calves (p<0.05).

Serum levels of AST, ALT, and GGT provide indications of liver function. These three liver enzymes typically increase in the case of acute or chronic liver disease(Stojević et al., 2005). Serum AST and GGT levels are increased in adult cows with subclinical diseases such as fatty liver syndrome and ketosis(Pinedo & Melendez, 2022);(Steen, 2001). The AST activity in newborn calves ranges from 5 to 40 IU/L in the first few days after birth(Quezada-Tristán et al., 2014). ALT and AST activities ranged from 1 to 5 IU/L and from 19 to 31 IU/L, respectively, in calves aged 7–27 days, with both levels increasing with age(Kaneko et al., 2008). According to previous studies, serum ALT levels decreased in calves given zinc and methionine for 8 weeks after birth, but serum AST levels did not change(Ülger & Küçük, 2011). In other animal species, the addition of zinc to rations or an increase in zinc in the serum increases ALT and AST activity(Liu et al., 2023);(Wei et al., 2019).

Serum total protein, urea, and uric acid levels in calves provide information on metabolic and growth-related activities. Pekcan et al. (2023)(Pekcan et al., 2023) reported that liver diseases and conditions associated with infections, such as diarrhea and arthritis in newborn calves, did not change the blood total protein and uric acid levels, whereas urea levels may increase more than two-fold. According to their findings, the serum urea level in healthy calves was 17.73 ± 2.80 mg/dL, whereas in animals with arthritis and diarrhea, it increased to 41.54 ± 5.29 mg/dL.

Based on the results of our study, the mixture of organic zinc, chromium, and selenium added to colostrum and milk from birth to weaning in both Holstein and Simmental calves did not alter the blood total protein, urea, or uric acid concentrations. Furthermore, urea nitrogen levels in the calves did not exceed 26.96 mg/dL throughout the study period. These results are similar to those previously reported for healthy calves(Pekcan et al., 2023). Furthermore, according to the literature, organic zinc and methionine were given to newborn calves for 8 weeks, which did not affect the serum total protein level, consistent with the findings of our study(Ülger & Küçük, 2011).

Total cholesterol, triglyceride, HDL, and LDL concentrations in serum are important variables that provide information about metabolism in newborn calves. Additionally, the fact that serum lipid and lipoprotein levels were within normal limits in farm animals indicates that the animals were in a healthy and normal physiological state(Motta et al., 2023);(Żarczyńska et al., 2021). Piccione et al. (2010)(Piccione et al., 2010) found that the serum total cholesterol levels of calves nearly doubled in the first 5 days after birth and increased to approximately four times the level seen at birth by 30 days of age. However, triglyceride levels did not change despite an increase during the first 30 days. Pekcan et al. (2023)(Pekcan et al., 2023) reported that while the serum cholesterol level was 112.57 ± 11.88 mg/dL in healthy calves, this level decreased to 57.33 ± 4.61 mg/dL in animals with arthritis and diarrhea. In the present study, cholesterol, HDL, and LDL levels increased during the first 21 days after birth in both Simmental and Holstein calves, with no changes thereafter. Similarly, serum triglyceride levels did not change from birth until weaning, which is consistent with the findings of Piccione et al. (2010)(Piccione et al., 2010). The total cholesterol levels observed in the present study increased with time, in parallel with the levels specified for healthy calves close to the weaning period, and approached the blood cholesterol level of adult cattle. This outcome is consistent with the cholesterol levels documented for calves(Pekcan et al., 2023) and for adult cattle(Alameen & Abdelatif, 2012) in previous studies. Likewise, the addition of organic zinc to calves’ diet for 8 weeks from birth did not change the blood cholesterol and triglyceride(Ülger & Küçük, 2011) the calves’ blood cholesterol and triglyceride levels reported previously were similar to those observed in the current study. These findings are consistent with those of previous studies that demonstrated the beneficial effects of dietary modifications in managing lipid profiles in hyperlipidemic models(Iqbal et al., 2024). Although concrete data on neonatal calves are limited, enhanced metabolic responses to organic minerals may be associated with changes in biochemical parameters, including lipids and liver enzyme stability, suggesting enhanced hepatic function. Additionally, an enhanced metabolic status with organic trace mineral sources has been linked with improved overall biochemical profiles, which could plausibly reflect triglyceride, LDL, HDL, and cholesterol dynamics in neonatal calves receiving such supplementation. Moreover, the interplay between inflammation and lipid metabolism is evident in various studies, highlighting the importance of considering both metabolic and inflammatory pathways when investigating lipid-lowering interventions(Wang et al., 2022).

Studies have demonstrated the effectiveness of organic salts and hyperosmotic sodium bicarbonate in correcting metabolic acidosis in neonatal calves, providing insights into how metabolic balance and correction can be restored through targeted interventions, thereby aiding overall health improvements(Humayun et al., 2022). Blood glucose levels are one of the most important variables of metabolic health and facilitate the determination of rumen development in calves and the level of absorption from the rumen wall, especially regarding volatile fatty acid production in the rumen. Calves are born monogastric, and their rumen develops over time as they transition into multistomached ruminants. After this stage, blood glucose levels are determined by the digestion of nutrients in the rumen, the synthesis of essential fatty acids, and their utilization in glucogenesis in the liver. One of the minerals used in this study is organic chromium. Chromium positively affects glucose utilization primarily by enhancing the effect of insulin as a glucose tolerance factor(Khare et al., 2023). Blood glucose levels do not change significantly within the first 30 days after birth(Piccione et al., 2010). However, a different study argued that as calves are born functionally monogastric, their blood glucose levels tend to decrease(Wenker et al., 2022). The findings obtained in the present study showed a decrease in blood glucose levels in calves, especially in the first 21 days after birth, which is in agreement with previous reports(Piccione et al., 2010), regardless of whether they were Holstein or Simmental. Similarly, supplementation of calves with organic zinc did not affect their blood glucose levels(Ülger & Küçük, 2011).

Blood cortisol levels increase because of the organism’s reaction to various internal and external factors that cause stress(Kim et al., 2022). Several studies have reported that blood cortisol levels increase with stress and gradually decrease with the disappearance of stress(Kim et al., 2011);(Kovács et al., 2021);(Slayi & Jaja, 2025). For example, blood cortisol levels increase significantly in sheep because of stress during shearing(Kotianová et al., 2025). In the present study, blood cortisol levels, which were very high at birth, decreased in the first 21 days in all groups, regardless of the breed. However, they increased on the days when weaning was initiated (after the 42nd day of the study) and decreased again after weaning. Breed-related differences in serum IgG levels between Holstein and Simmental calves likely reflect the inherent variation in colostrum quality and the efficiency with which immunoglobulins are absorbed at birth, as breed has been identified as a major factor influencing colostrum IgG concentrations and passive transfer to neonates. Genetic selection pressures and metabolic specialization also differ between these breeds, with Holsteins being intensely selected for high milk yield and Simmentals having a more dual-purpose background, potentially shaping early immune and metabolic trajectories and baseline IgG status in neonatal calves(Cavirani et al., 2024). Breed differences in stress physiology may exhibit variations in the hypothalamic–pituitary–adrenal axis activity. Because cortisol interacts closely with immune modulation and inflammatory adaptation in early life, such differences in cortisol dynamics may contribute to the divergent IgG and cortisol responses observed in calves supplemented with organic minerals(Sgorlon et al., 2015). The observed differences in serum cortisol and IgG levels have important implications for early calf growth. Higher serum IgG levels in newborn calves have been reported to be associated with better passive immunity and a higher average daily gain at an early age, indicating that calves with better immunity grow faster in early life(Elsohaby et al., 2019). Conversely, higher cortisol levels are indicative of higher stress levels and can suppress immune function and appetite, with potential adverse effects on average daily gain and overall growth(Hulbert & Moisá, 2016). Therefore, breed-specific differences in stress responses and immune status, as well as the potential benefits of organic mineral supplementation on physiological markers, may translate into meaningful variations in the growth of neonatal calves.

Almost all factors that contribute to immunity in newborn calves are acquired via the colostrum(Lopez & Heinrichs, 2022). A vital proportion (80%) of the antibodies contained in the colostrum is constituted by IgG(Johnson et al., 2007). Therefore, IgG levels in calf blood in the first few weeks after birth provide essential information regarding passive immunization, which is the primary defense against infections in calves(Rocha et al., 2012). Previous studies have shown that organic mineral supplementation has a positive effect on immunity levels in farm animals(Zhang et al., 2021). Adding organic or inorganic chromium to the diets of calves increases blood IgG levels(Kumar et al., 2023). The findings of the current study indicate that the level of maternal antibodies acquired at birth decreases over time, regardless of breed. Additionally, organic mineral supplementation did not have a significant positive or negative effect on this decline. However, its effects may become apparent when active immunity develops, subsequently affecting the immune system. This study emphasizes the importance of passive immunization in calves from the beginning to the end of oral administration.