Heat Stress and Seasonal Dissipation of Circulating Zonulin Levels Among Calves in Aydın Region

Zonulin, a well-recognized protein, is influencing the integrity of intercellular connections in the intestines. It has also been evidenced that heat stress (hS) might alter intestinal permeability. In the present retrospective field research the aim was to investigate the gastrointestinal permeability of calves exposed to hS (especially in summer) by determining serum zonulin levels and their relationship to seasonal dissipation among appearently healthy calves. As two different months represented 2 seasons, serum zonulin concentrations in January 2022 (at 20:00 pm 4°C and 08:00 am 10°C) and June 2022 (at 20:00 pm 19°C and 08:00 am 27°C) exhibited significant differences. Inter-group and intra-group comparison showed statistically significant differences (p=0.012) both in seasonal distribution and spatial distribution at different day/night times. When compared between the January and June groups, the mean zonulin levels (ng/mL) at 12 pm and 08:00 am in the January group were 28.04±12.49 vs. 11.55±8.45, respectively (p=0.012). On the other hand at June group the mean zonulin levels at 12 pm and 08.00 am were 58.54±19.16 vs 24.03±9.9, respectively (p=0.012). Obtained results should be cautiously subjected to interpretation, in which hS affect intestinal integrity and seasonal dissipation of circulating zonulin levels should be taken into consideration for intestinal health of calves.