Effects of Dietary Supplementation with Epigallocatechin Gallate on Meat Quality and Muscle Antioxidant Capacity of Broilers Subjected to Acute Heat Stress

This study evaluated epigallocatechin gallate’s (EGCG’s, 400 mg/kg) effect on meat quality and muscle antioxidant status of broilers under acute heat stress (AHS). A total of 144 21-day-old male Huainan partridge chickens were randomly allocated to the EGCG-free group (12 replicates) and the EGCG group (6 replicates). On day 94, the EGCG-free group was divided into the control group (CON) and the AHS group, and then AHS group and EGCG group (identified as AHS + EGCG group) were treated with AHS (33 ± 1 °C for 12 h). AHS increased (p < 0.05) L*24h, drip loss, muscle lactic acid, malondialdehyde (MDA) contents, and kelch-like ECH-associated protein 1 (Keap1) mRNA level, and decreased (p < 0.05) eviscerated percentage, pH24h, a*, muscle total superoxide dismutase (T-SOD) activity, the ratio of T-SOD/MDA and glutathione peroxidase /MDA, glycogen content, and nuclear factor erythroid 2-related 2 (Nrf2), catalase (CAT), NAD(P)H/quinone dehydrogenase 1 (NQO1) mRNA levels. The AHS + EGCG group exhibited lower (p < 0.05) L*24h, drip loss, muscle lactic acid, MDA contents and Keap1 mRNA level, and greater (p < 0.05) eviscerated percentage, pH24h, a*, muscle T-SOD activity, the ratio of T-SOD/MDA, Nrf2, and NQO1 mRNA levels compared with the AHS group. In conclusion, EGCG protects against AHS-impaired meat quality by improving muscle antioxidant capacity, which seems to be associated with the activation of the Nrf2 signaling pathway.

Perspective Chapter: Using Feed Additives to Eliminate Harmful Effects of Heat Stress in Broiler Nutrition

Global warming is one of the major challenges for mankind, with animal breeding one of the most affected sectors in the agricultural industry. High ambient temperatures negatively affect all domestic animals. While it is true that pork and dairy production suffer the consequences of heat waves, it is actually the poultry industry which is hit the hardest by the heat stress poultry must endure due to hotter weather. Consequently, we have a fundamental interest in reducing and/or eliminating the negative effects of climate change, i.e. prolonged high ambient temperatures. The aim of this chapter is to present the adverse effects of heat stress on energy metabolism, anti- and pro-oxidant capacity and production in birds. A further goal is to show how various feed additives (e.g. vitamin A, C and E, selenium, zinc, betaine, plant extract, and probiotics) can reduce the negative effects of heat stress. Based on the large number of recent scientific findings, the following conclusions were drawn: Using fat in the diet (up to 5%) can reduce heat production in livestock. Vitamins (e.g. A, E and C) are capable of reacting with free radicals. Vitamin E and Vitamin C, Zn, and Se supplementation improved antioxidant parameters. Antioxidant potential of vitamins and micro minerals is more efficient in combination under heat stress in poultry nutrition. Plant extracts (e.g. oregano) could decrease the negative effects of heat stress on antioxidant enzyme activity due to its antioxidant constituents. Betaine reduces heat production in animals at high ambient temperatures. While acute heat stress induces a drop in feed intake, with the resulting increased nutrient demand leading to weight loss, if heat stress is prolonged, adaptation will occur. Probiotics and vitamins (C and E) seem to be the most effective means to reduce the negative effects of heat stress.

De Novo Transcriptome Analysis Reveals Potential Thermal Adaptation Mechanisms in the Cicada Hyalessa fuscata

In metropolitan Seoul, populations of the cicada Hyalessa fuscata in hotter urban heat islands (“high UHIs”) exhibit higher thermal tolerance than those in cooler UHIs (“low UHIs”). We hypothesized that heat stress may activate the expression of genes that facilitate greater thermal tolerance in high-UHI cicadas than in those from cooler areas. Differences in the transcriptomes of adult female cicadas from high-UHI, low-UHI, and suburban areas were analyzed at the unheated level, after acute heat stress, and after heat torpor. No noticeable differences in unheated gene expression patterns were observed. After 10 min of acute heat stress, however, low-UHI and suburban cicadas expressed more heat shock protein genes than high-UHI counterparts. More specifically, remarkable changes in the gene expression of cicadas across areas were observed after heat torpor stimulus, as represented by a large number of up- and downregulated genes in the heat torpor groups compared with the 10 min acute heat stress and control groups. High-UHI cicadas expressed the most differentially expressed genes, followed by the low-UHI and suburban cicadas. There was a notable increase in the expression of heat shock, metabolism, and detoxification genes; meanwhile, immune-related, signal transduction, and protein turnover genes were downregulated in high-UHI cicadas versus the other cicada groups. These results suggested that under heat stress, cicadas inhabiting high-UHIs could rapidly express genes related to heat shock, energy metabolism, and detoxification to protect cells from stress-induced damage and to increase their thermal tolerance toward heat stress. The downregulation of apoptosis mechanisms in high-UHI cicadas suggested that there was less cellular damage, which likely contributed to their high tolerance of heat stress.