Sex-based responses of heat stress and subsequent recovery on the growth performance, metabolic changes, and redox status of broilers at market age.

This experiment investigated the sex responses of heat stress (HS) and subsequent recovery on growth performance, serum metabolic parameters, and redox status. Two hundred 38-day-old broilers were arranged in a completely randomized design with a 2 × 2 (temperatures and sexes) factorial arrangement in five replicates. Broilers were raised at 24 ± 1 °C or 32 ± 1 °C for 3 days and returned to 24 °C for 2 days. The study showed that HS decreased both average daily feed intake (ADFI), average daily gain (ADG), serum total glutathione peroxidase (GPx), and superoxide dismutase (T-SOD). However, it increased feed conversion ratio (FCR), rectal temperature (RT), respiratory rate (RR), serum glucose, blood urea nitrogen (BUN), low-density lipoprotein cholesterol, and the protein carbonyl group (PCG). Male broilers had higher ADFI, ADG, lactic acid (LA), high-density lipoprotein cholesterol (HDL-C), and PCG, but lower FCR, albumin, total antioxidant capacity, T-SOD, and GPx. Temperature and sex significantly interacted with ADFI, ADG, LA, and HDL-C. The effects of HS on RR, RT, glucose, albumin, BUN, PCG, T-SOD, and GPx recovered after 2 days. These results indicate that HS and subsequent recovery affect growth performance, which is accompanied by disturbances in serum nutrient metabolism and abnormalities in redox function and manifested by temporal and gender differences.

Effects of betaine on viability, apoptosis, function protein expression and oxidative status in heat-stressed IEC-6 cells.

Intestinal epithelial dysfunction is one of the key factors in the pathogenesis of heat stress-induced disease. The purpose of this experiment was to investigate whether betaine protects IEC-6 cells from dysfunction induced by heat stress (HS) through antioxidative mechanism. The IEC-6 cells were divided into four groups: control group incubated at 37 °C, while those in heat treated groups (41 °C for 24 h) were pretreated with 0, 0.5 and 1 mmol/L betaine, respectively. Cell viability, apoptosis, barrier function protein and oxidative status were analyzed. Compared to control group, the rate of apoptosis and the Bax and caspase-3 expressions significantly increased in HS group (P < 0.05), however, cell activity, total antioxidative capacity (T-AOC), activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and the expression of Bcl-2, claudin-1 and occludin decreased significantly (P < 0.05). Betaine (0.5 mmol/L) can significantly enhance IEC-6 cell viability, while significantly reduce the apoptosis rate of cell during HS (P < 0.05). Meanwhile, the expression of Bcl-2, claudin-1 and occludin proteins were also significantly upregulated (P < 0.05) when compared to HS group. HS had a negative impact on IEC-6 cells, while betaine protected from damage caused by HS via increasing the antioxidative capacity. This suggested that betaine might be an effective dietary additive to protect animals from detrimental intestinal reactions caused by HS.