The effects of dietary supplementation of different organic chromium forms on glucose transporters and heat shock proteins in the ovary of laying hens

Heat stress is one of the important environmental factors that reduce productivity in poultry. Earlier studies report that chromium picolinate (CrPic) and chromium histidinate (CrHis) increase egg yield. The effects of various organic chromium sources supplemented to the diets of laying hens were investigated on ovarian orexin (hypocretin), glucose transporters (GLUTs), heat shock proteins (HSPs) and nuclear factor kappaB (NF-κB) levels in this study. 16-weeks-old; Lohmann LSL-Lite, 1800 laying hens were allocated to 6 random groups according to a 2 × 3 factorial trial scheme with two different environmental temperatures [Thermoneutral (TN groups; at either 22±2 °C 24 h/d) and Heat Stress (HS groups; at 34±2 °C for 8 h/d, 08:00 to 17:00 h, followed by 22°C enviromental temperature for 16 h for a period of 12 weeks)]. The hens that reared under both environments were fed either a basal diet or the basal diet supplemented with 0, 1.600 mg of CrPic (12.43% Cr) and 0.788 mg of CrHis (25.22% Cr) per kg of diet (elemental Cr 200 μg / kg). In the heat stress groups, it was found that GLUT1, GLUT4 and orexin protein levels decreased (P <0.0001), while NF-κB, HSP60, HSP70 and HSP90 protein levels (P <0.0001) were increased, compared to the thermoneutral groups. Dietary chromium supplementation (CrPic-CrHis) increased orexin and GLUT levels whereas NF-κB and HSP levels were decreased in comparison to thermoneutral groups (P <0.0001). Chromium supplements treatment on heat stressed laying hens, is able to increase orexin and GLUTs levels and decrease NF-κB and HSPs. As a result, CrPic and CrHis have been found to have beneficial effects in alleviation of negative effects and treatment of stress complications, and CrHis is determined to be more effective than CrPic.