Heat stress is a non-specific physiological response of the body when exposed to high ambient temperatures, which can break the balance of body redox and result in oxidative stress that affects growth performance as well as the health of poultry species. Polyphenols have attracted much attention in recent years due to their antioxidant ability and thus, can be an effective attenuator of heat stress. In this paper, the potential mechanisms underlying the inhibitory effect of polyphenols on heat stress in poultry has been reviewed to provide a reference and ideas for future studies related to polyphenols and poultry production.

Ruminant production, especially in the tropics and developing countries suffers a setback when compared with the temperate and developed countries, which is attributable to the kinds of available feed resources in the region of production. In the tropics, ruminants are restricted to grazing on low-quality forages, crop residues and agro-industrial by-products with very little or no concentrate diets, which adversely affect the animals in exhibiting their full production potential. Considering this fact, there is an increasing interest in improving the digestibility of these feed resources. In recent years, researchers have explored several methods to enhance the functions of rumen microflora, improve digestion and fermentation processes, as well as increase bioavailability and utilization of nutrients through feed supplementation. This review aims to explore the positive effects of supplementation of ruminant diets with probiotics or botanical extracts and their metabolites on the productivity of the animals. Moreover, the functions of these non-pathogenic and non-toxic live microorganisms (probiotics) and plant biologically active compounds (botanical extract) are explored because of the ban on non-therapeutic use of antibiotics as growth promoters coupled with the critical preference of consumers to high quality and safe animal products. It has been reported that these alternative supplemental products have a beneficial impact on both animal health and productivity, which is affecting stabilization of rumen environment, inhibition of pathogenic bacteria proliferation in gastro-intestinal tract, modulation of immune response, increase in fibre degradation and fermentation, nutrients availability and utilization, animal growth performance and milk production, among others. However, long-term in vivo studies are still required to determine the synergetic effects of these 2 safe supplemental products.

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The present study was conducted to investigate the effects of dietary Achyranthes bidentata polysaccharide (ABPS) supplementation on performance, immune response, intestinal mucosal morphology, and gut microbiome in yellow-feathered broilers challenged with Escherichia coli K88. A 2 × 2 factorial design was used for the trial. Two hundred and forty one-day-old female broilers were randomly assigned to four treatments: (1) negative-control broilers were fed by a basal diet and saline (NG); (2) positive-control broilers were fed by a basal diet and orally challenged with 108 CFU E. coli K88 (CNG); (3) ABP group broilers were fed by a basal diet containing ABPS (500 mg/kg of feed) and saline; (4) CABP group broilers were fed by a basal diet containing ABPS (500 mg/kg of feed) and orally challenged with 108 CFU E. coli K88. Growth performance, serum biochemical indexes, immune responses, intestinal mucosal morphology, and cecal microbial community structure were evaluated. The ABP group had greatest body weight (BW), average daily body weight gain (ADG), and intestinal villus height compared to other treatments (p < 0.05). The CABP group had a higher villus height/crypt depth ratio (V/C) compared with other treatments (p < 0.05). The expression levels of NF-κB were lower in the ABP group. The CNG group had higher Escherichia coli and Enterococcus contents in cecal samples compared to other treatments (p < 0.05). Serum glucose, uric acid, TNF-α, and Secretory Immunoglobulin A (S-IgA) levels were higher in broilers challenged with E. coli (p < 0.001) than that with saline. Broilers challenged with E. coli had reduced taxa richness in the cecal samples. Sequencing of 16S rRNA genes in cecal samples revealed that a lower proportion of Firmicutes and a higher proportion of Proteobacteria were detected in the broilers challenged with E. coli. Compared with the controls, dietary ABPS supplementation increased serum total protein, albumin, and S-IgA levels, but decreased serum glucose, uric acid, and TNF-α levels in broilers (p < 0.05). Diet supplemented with ABPS increased the Firmicutes/Bacteroidetes ratio and the abundance of Ruminococcaceae and Lachnospiraceae, and altered cecal microbiota community structure. These results suggest that ABPS can promote growth performance and improve intestinal morphology and microbiota community structure in broilers challenged with E. coli K88.

This study investigated the effect of dietary resveratrol supplementation on growth performance, rectal temperature, and serum parameters of yellow‐feather broilers under heat stress. A total of 480 yellow‐feather broilers (28‐day‐old) were randomly allotted to five groups with six replicates. A thermoneutral group (TN) (24 ± 2°C) received a basal diet and another four heat‐stressed groups (37 ± 2°C for 8 hr/day and 24 ± 2°C for the remaining time) were fed the basal diet or basal diet with 200, 350, and 500 mg/kg resveratrol for 14 consecutive days. The results revealed that resveratrol supplementation improved average daily gain (p = 0.001), and decreased (p < 0.05) rectal temperature from d 3 when compared with heat‐stressed group without resveratrol. In addition, supplementation with resveratrol at 350 or 500 mg/kg lowered (p < 0.05) the contents of corticosterone, adrenocorticotropic hormone, cholesterol, triglycerides, uric acid, malonaldehyde, and activities of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase, increased (p < 0.05) the levels of triiodothyronine, the ratio of triiodothyronine to thyroxine, total protein, glutathione, and activities of alkaline phosphatase, total superoxide dismutase, catalase, and glutathione peroxidase, though with few fluctuation. In conclusion, supplementation with resveratrol can improve the growth performance by positively regulating serum metabolic parameters and alleviating tissue oxidant damage of broilers under heat stress.