Effect of alpha-lipoic acid on relieving ammonia stress and hepatic proteomic analyses of broilers.

Ammonia in poultry houses not only affects worker health but also induces a variety of poultry diseases. Alpha-lipoic acid (LA) is an effective antioxidant that protects cells against oxidative injury during various toxic and pathological processes. This study was designed to evaluate the mitigating effects of LA supplementation on ammonia stress and hepatic proteome changes in broilers. Male broilers (22 d old) were allocated to 3 groups: (1) a control group without ammonia stress (CTRL); (2) exposure to 70 ppm ammonia (AM); and (3) exposure to 70 ppm ammonia and dietary administration of 300 mg/kg LA (AM+LA). Ammonia exposure significantly decreased broiler growth performance and plasma glutathione peroxidase activity (P < 0.05), and increased plasma malondialdehyde content and glutamic-pyruvic transaminase activity (P < 0.05). These negative effects were eliminated by LA supplementation. Comparative proteomic analyses revealed 291 differentially expressed proteins in the AM group compared to the CTRL and AM+LA groups. A total of 30 proteins were differentially expressed between the AM/CTRL and (AM+LA)/AM groups. The addition of LA restored 24 of these proteins to control levels; these proteins were mainly related to transcription regulation, detoxification, protein translation and degradation, and immune and stress responses. The differentially expressed proteins included the high mobility group box (HMGB) and glutathione S-transferase (GST), which is closely related to immune response and oxidative stress, and collagens, which are implicated in liver injury. The addition of LA to broiler diet may reduce ammonia toxicity by maintaining the antioxidant system, xenobiotic metabolism, and metabolic pathways.

Antioxidant capacity and meat quality of broilers exposed to different ambient humidity and ammonia concentrations.

To investigate the effect of humidity and ammonia on the antioxidative capacities and meat qualities of broilers, 192 broilers were divided into 2 groups: high (H, 70 ppm) and low (L, 30 ppm) ammonia concentration. These groups were divided into 30% (Treatment humidity, T) and 60% (Control humidity, C) humidity, giving 4 treatments: C+L, C+H, T+L, and T+H. Blood and muscle antioxidative capacities and meat quality were measured. In the H group, body weight (BW), average daily feed intake (ADFI), average daily weight gain (ADG), blood and muscle antioxidative capacities, and postmortem pectoral muscle a* of broilers were significantly decreased (P < 0.05), and pectoral muscle thiobarbituric acid reactive substance (TBARS) contents and drip losses, postmortem pectoral muscle b* (P < 0.05) and L* (P = 0.054), and pectoral muscle shear forces (P = 0.075) increased. In the T condition, BW, ADFI, pectoral muscle superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities, and pectoral muscle L* decreased (P = 0.053), and pectoral muscle shear forces and TBARS contents increased (P < 0.05). In the T+H group, BW, ADFI, ADG, blood antioxidative capacities, pectoral muscle SOD and GSH-Px activities, and postmortem pectoral muscle a* were significantly lower than those of the C+L group, but postmortem pectoral muscle TBARS contents and pectoral muscle drip losses and shear forces significantly increased (P < 0.05). These results revealed that T+H could significantly reduce growth performance, antioxidative capacities, and meat quality of broilers; T intensified these negative effects.