Assessment of Serum Malondialdehyde (MDA), Reduced Glutathione (GSH) and Thiol–Disulfide Homeostasis in Neonatal Calves Diagnosed with Cryptosporidiosis

Cryptosporidiosis is an important cause of neonatal calf diarrhea and may contribute to systemic oxidative and redox imbalance through intestinal epithelial injury, inflammation, and antioxidant consumption. Although malondialdehyde (MDA) and reduced glutathione (GSH) are commonly used indicators of lipid peroxidation and antioxidant defense, respectively, dynamic thiol–disulfide homeostasis (TDH) may provide complementary information on the circulating thiol pool and protein-based redox buffering capacity. However, data evaluating conventional oxidative stress biomarkers together with TDH parameters in neonatal calves with naturally occurring cryptosporidiosis remain limited. Therefore, this study aimed to assess serum MDA, GSH, and TDH parameters in neonatal calves diagnosed with cryptosporidiosis and to determine whether TDH components provide additional insight into cryptosporidiosis-associated redox alterations. The study was conducted on 40 calves aged 0–28 days, including 30 calves with cryptosporidiosis and 10 healthy controls. Diagnosis was established using an immunochromatographic test on fresh fecal samples, and only calves that tested negative for other enteric agents in the same panel were included. Serum MDA levels were measured using the thiobarbituric acid reactive substances (TBARS) method, GSH levels using the Beutler method, and total thiol (TT) and native thiol (NT) levels using the Erel–Neşelioğlu method; disulfide (Ds) levels and related ratios were calculated. In calves with cryptosporidiosis, serum GSH, TT, and NT levels were significantly lower than those in healthy controls (p=0.010, p=0.010, and p=0.030, respectively). Although MDA levels were numerically higher in the diseased group, the difference was not statistically significant (p=0.150). No significant differences were detected between groups for Ds levels or TDH-derived ratios (Ds/TT, Ds/NT, and NT/TT). These findings suggest that neonatal calf cryptosporidiosis may be associated mainly with depletion of antioxidant and thiol pools rather than a marked systemic lipid peroxidation response. In this context, TT and NT may represent supportive redox indicators for the evaluation of cryptosporidiosis-associated neonatal diarrhea.