Effects of the supplemental chromium form on performance and metabolic profile in laying hens exposed to heat stress.

This experiment was conducted to compare the effect of the supplemental chromium (Cr) form on performance, egg quality, and metabolic profile in laying hens exposed to heat stress (HS). Laying hens (n = 1800; 16-wk-old; Lohmann LSL-Lite) were kept in cages in temperature-controlled rooms at either 22 ± 2°C for 24 h/d (thermoneutral, TN) or 34 ± 2°C for 8 h/d, from 08:00 to 17:00 h, followed by 22°C for 16 h (HS) for 12 wks. Hens reared under both environmental conditions were fed 1 of 3 diets: a basal diet and the basal diet supplemented with either 1.600 mg of chromium-picolinate (CrPic, 12.43% Cr) or 0.788 mg of chromium-histidinate (CrHis, 25.22% Cr) per kg of diet, delivering 200 µg elemental Cr per kg diet. Data were analyzed by 2-way ANOVA. Exposure to HS caused decreases in feed intake (P < 0.0001), egg production (P < 0.0001), egg weight (P < 0.0001), eggshell weight (P < 0.0009), eggshell thickness (P < 0.0001), eggshell strength (P < 0.0001), and Haugh unit (P < 0.0001), deterioration in feed conversion ratio (P < 0.0001), increases in serum glucose and cholesterol concentrations (P < 0.0001 for both), decreases in serum and egg yolk Cr concentrations (P < 0.0001 for both), and decreases in serum Na (P < 0.002) and K (P < 0.01) concentrations. Both Cr sources were equally effective in alleviating performance variables under the HS condition. However, neither Cr sources alleviated deteriorations in egg quality parameters and serum electrolytes. Both Cr sources decreased serum glucose and cholesterol concentrations and increased serum and egg yolk Cr concentrations under the HS condition. In conclusion, HS adversely affected laying performance, egg quality, and metabolic profile. Both CrPic and CrHis partially alleviated the adverse effect of HS on these parameters. Inclusion of either Cr source could be a part of nutritional management strategies to overcome the adverse effects of HS performance and metabolic profile in laying hens.

Effects of the supplemental chromium form on performance and oxidative stress in broilers exposed to heat stress.

This experiment was conducted to investigate effects of the organic complex form of supplemental chromium (Cr) on performance, oxidative stress markers, and serum profile in broilers exposed to heat stress (HS). A total of 1,200 10-day-old boilers (Ross-308) was divided into one of the 6 treatments (2 environmental temperatures x 3 diets with different Cr forms). The birds were kept in temperature-controlled rooms at either 22 ± 2°C 24 h/d (thermoneutral, TN group) or 34 ± 2°C for 8 h/d, 08:00 to 17:00 h, followed by 22°C for 16 h (HS group) and fed either a basal diet (C) or the basal diet supplemented with Cr (200 µg/kg) through 1.600 mg of CrPic (12.43% Cr) and 0.788 mg of CrHis (25.22% Cr). Feed intake and body weight were recorded weekly. After cervical dislocation, liver samples were harvested to analyze Cr concentration and glucose transporter-2,4 (GLUT-2,4) expression. The breast meat also was sampled for the concentration of Cr and expressions of nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor kappa B (NF-κB). Data were analyzed by 2-way ANOVA. Heat stress caused depressions in feed intake (12.1%) and weight gain (21.1%) as well as elevations in feed conversion (11.2%) and abdominal fat (32.8%). It was also associated with depletion of Cr reserves and increases in serum concentrations of glucose, cholesterol, creatine, and enzymes. Exposure to HS was accompanied by suppression of the expressions of Nrf2 and GLUT-2 in muscle and GLUT-4 in the liver and amplification of the expression of NF-κB in muscle. Both Cr sources partially alleviated detrimental effects of HS on performance and metabolic profile. The efficacy of Cr as CrHis was more notable than Cr as CrPic, which could be attributed to higher bioavailability. In conclusion, CrHis can be added into the diet of broilers during hot seasons to overcome deteriorations in performance and wellbeing related to oxidative stress.

Chromium histidinate protects against heat stress by modulating the expression of hepatic nuclear transcription factors in quail.

1. This experiment was conducted to evaluate the effects of supplemental chromium histidinate (CrHis) on performance and expressions of hepatic nuclear factors kappaB, an enhancer (NF-κB) and an inhibitor (IκBα) of activated B cells in heat-stressed Japanese quail (Coturnix coturnix japonica). 2. A total of 180, 10-d-old Japanese quail were allocated randomly into 6 groups in a 2 × 3 factorial arrangement. Birds were reared either at 22°C for 24 h/d (thermoneutral, TN) or 34°C for 8 h/d (heat stress, HS) for 32 d and fed on one of three diets supplemented with 0, 400 or 800 µg of CrHis per kg of diet. Each group consisted of 10 cages, each containing three quail. Data (performance variables and hepatic NF-κB and IκBα) were analysed using 2-way ANOVA. 3. Heat stress caused reductions in cumulative feed intake (FI) by 5·7%, weight gain (WG) by 13·0%, final body weight (FBW) by 10·3%, carcase weight by 12·6% and carcase efficiency by 2·3% and an increase in feed conversion ratio (FCR, feed consumed, g:weight gained, g) by 8·4%. As supplemental CrHis level increased up to 800 µg/kg, there were linear increases in cumulative FI (from 602 to 609 g), WG (from 134 to 138 g), FBW (from 167 to 171 g), cold carcase weight (from 110 to 114 g) and cold carcase efficiency (from 65·5 to 66·4%) and a decrease in FE (from 4·51 to 4·42). The environmental temperature by CrHis level interaction effect on performance parameters was insignificant. Hepatic NF-κB p65 concentration was higher and hepatic IκBα concentration was lower in quail exposed to HS than in quail kept at TN temperature. Increasing supplemental CrHis level linearly inhibited hepatic NF-κB p65 expression from 134·4 to 105·3% and linearly enhanced hepatic IκBα expression from 73·4 to 99·6%. The decrease in hepatic NF-κB expression and the increase in hepatic IκB expression were more notable in the TN environment than in the HS environment. 4. In conclusion, heat stress depressed performance variables and augmented lipid peroxidation and supplemental CrHis alleviated oxidative stress through modulating expressions of stress-related hepatic nuclear transcription factors (NF-κB and IκBα).