Dynamics of oxidative stress and immune responses in neonatal calves during diarrhea

Oxidative stress is the imbalanced redox status between oxidants production and their scavengers leading to intestinal physiological dysfunction. However, the role of systemic and local oxidative status during neonatal calf diarrhea is not known. This study assessed systemic (serum) and local (fecal) oxidative status when calves either naturally developed diarrhea or naturally recovered. Healthy calves were enrolled in the study at age of d 18 and their health status were monitored from the enrollment. Based on their enteric health status on D21 and D28, calves were grouped as continuous diarrhea from D21 to D28 (DD group, n = 14), diarrhea at D21 but recovered at D28 (DH group, n = 19), healthy at D21 but developed diarrhea at D28 (HD group, n = 15), and healthy throughout the study (HH group, n = 16). Serum and fecal samples were collected at D21 and D28 from all calves in the morning 2 h after feeding. Dynamics of oxidative stress indicators including reactive oxygen species (ROS), malondialdehyde (MDA), H2O2, 8-hydroxylated deoxyguanosine (8-OHDG), glutathione peroxidase (GPX), superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC) and inflammatory indicators TNF-α, IL-1β, IL-4, IL-6, IL-10 and IFN-γ were evaluated using serum samples. In addition, fecal oxidative stress indicators ROS and MDA were measured. Serum ROS, MDA, 8-OHDG, as well as fecal ROS and MDA were higher, while serum CAT and H2O2 were lower in diarrheic calves than those of healthy calves. Serum ROS, MDA, and 8OHDG and fecal ROS and MDA increased in HD group from D21 to D28 as they developed diarrhea. In contrast, all these oxidative stress markers decreased inDH group from D21 to D28 as they recovered. However, serum H2O2 had opposite changing trend, which became lower in HD group and higher in DH group at D28. In conclusion, both systemic and local oxidative stress markers and cytokine profiles altered as calves move from healthy to diarrhea or vice versa. Serum ROS, MDA and 8-OHDG can be used to develop biomarkers to screen calves prone to enteric infections during pre-weaning period.