Effects of Gaba on the Thymus Cytokines of Wenchang Chickens Submitted to Heat Stress

Maternal Dietary Supplementation with γ-Aminobutyric Acid Alleviated Oxidative Stress in Gestating Sows and Their Offspring by Regulating GABRP

Sows usually suffer oxidative stress during gestation, and this limits the growth of fetuses via placenta. Gamma-aminobutyric acid (GABA) is a functional nonessential amino acid engaged in regulating the physiological status of animals. However, the effects of GABA on the oxidative homeostasis of sows and their offspring remain unclear. Eighteen late gestating sows (85 d) were divided into the CON and GABA groups and fed the basal diet and the GABA diet (200 mg/kg GABA), respectively, until farrowing. At parturition, the sows’ litter characteristics, the plasma antioxidant parameters of sows, and their offspring were evaluated. The results showed that GABA supplementation had no marked effect on the reproductive performance of sows (p > 0.10) but had a trend of reducing the amount of intrauterine growth restriction (IUGR) in piglets (0.05 < p < 0.10). At the same time, the addition of GABA elevated the plasma superoxide dismutase (SOD) level of sows and enhanced the glutathione peroxidase (GSH-Px) activity of newborn piglets (p < 0.05). Based on the H2O2-induced oxidative stress in pTr-2 cells, GABA elevated intracellular GSH-Px, SOD, catalase (CAT), and total antioxidant capacity (T-AOC, p < 0.01) and upregulated the gene expressions of CAT, gamma-aminobutyric acid receptor (GABRP), and nuclear factor-erythroid 2-related factor-2 (Nrf2) in H2O2-treated pTr-2 cells (p < 0.05). Taken together, GABA improved the antioxidant capacity of sows and alleviated the placental oxidative stress by upregulating the GABRP and Nrf2 genes, which have the potential to promote oxidative homeostasis in newborn piglets.

The effect of gamma-aminobutyric acid supplementation on growth performances, immune responses, and blood parameters of chickens reared under stressful environment: a meta-analysis

Gamma-aminobutyric acid (GABA) is a well-known feed supplement for its capability of reducing the adverse effect of stress in chickens. Several studies using GABA supplementation as a mitigatory measure have been published. However, it remains difficult to draw a general conclusion since these studies have been done under different experimental conditions. Therefore, the objective of this study was to quantify the response (growth performances, immune responses, and blood biochemical parameters) of chickens to GABA supplementation under various stressful conditions through a meta-analysis approach. A total of 19 articles published from 2011 to 2020, including 30 treatments, were used. A mixed-model ANOVA was used to assess how the growth parameters varied based on the GABA mode of supplementation. Linear mixed models and general linear models were used to evaluate the effects of the GABA doses and the duration of the supplementation on the growth performances and the immune parameters. Results indicated that supplementation of GABA via drinking water was more effective than dietary supplementation for reducing the feed conversion ratio in heat-stressed birds (P < 0.01). In addition, an increase in the GABA doses resulted in an augmentation (P < 0.01) of the body weight gain while a longer duration of supplementation resulted in increasing (P<0.01) the feed intake. Furthermore, increasing the duration of the supplementation reduced the immunoglobulin (P < 0.0001) and bursa's relative weight (P < 0.0001), while increasing blood CD8+ count (P < 0.001) and spleen's relative weight (P < 0.0001). Finally, blood total protein content was increased (P < 0.0001) by a longer duration of supplementation. This study showed that the doses and the duration of the GABA supplementation can affect the growth performances of chickens under stressful conditions. However, the effect of GABA on immune responses and blood parameters is perceived with a relatively longer supplementation duration.

Effect of Acute Heat Stress on the mRNA Levels of Cytokines in Broiler Chickens Subjected to Embryonic Thermal Manipulation

Simple Summary

Heat stress affects animal husbandry by impeding the health and production of livestock and leads to commercial losses during the hot summer season. The broiler chicken is one variety of poultry that is bred and reared for commercial meat production, but exposing this breed to high environmental temperatures causes immunosuppression. To improve heat stress tolerance in broilers, thermal manipulation (TM), a process which involves timed changes in incubation temperature during embryonic development, has been suggested as a way to enhance thermotolerance acquisition and immune response. Cytokines are small extracellular signaling peptides with critical roles in immunity by enabling cell communication during immunological development and an immune response. The objective of the current study was to investigate the effects of TM during broiler chicken embryonic development on splenic mRNA levels of the Interferon-α (IFN-α), Interferon- β (IFN-β), Interferon- γ (IFN-γ), Interleukin-4 (IL-4), Interleukin-8 (IL-8), Interleukin-15 (IL-15), Interleukin-16 (IL-16), Interleukin-17 (IL-17), and Interleukin-18 (IL-18) genes during acute heat stress (AHS). Our findings suggest that TM has a long-term effect on cytokine expression dynamics during AHS. Consequently, TM may improve heat tolerance acquisition by increasing the expression of signaling proteins important to tissue stability as well as to repair mechanisms that are employed during and/or after heat stress recovery.

Abstract

Heat stress significantly impacts the immunity and cytokine expression of chickens. However, the effects of embryonic thermal manipulation (TM) on cytokine expression in broiler chickens (broilers) is unclear. The objective of the current study was to evaluate the effects of TM on the splenic mRNA expression dynamics of certain cytokines—namely, IFN-α, IFN-β, IFN-γ, IL-4, IL-8, IL-15, IL-16, IL-17, and IL-18—in broilers during subsequent exposure to acute heat stress (AHS). TM was performed by elevating the incubation temperature to 39 °C at 65% relative humidity (RH) for 18 h daily during embryonic days (ED) 10–18. On post-hatch day 28, AHS was carried out for 7 h at 40 °C. At 0 h and after 1, 3, 5, and 7 h of AHS, splenic tissues were collected from all study groups to evaluate mRNA expression by relative-quantitative real-time (RT)-PCR. Plasma was collected to measure IL-4, IL-8, and IFN-γ levels. At 0 h, TM significantly reduced the basal mRNA level of IFN-β and the plasma level of IFN-γ and IL-8. Moreover, AHS significantly decreased IFN-β in control chicks, decreased IL-4 in both TM and control chicks, and increased IFN-γ and IL-16 in TM chicks. IFN-α, IL-8, IL-15, IL-17, and IL-18 expression all significantly increased during AHS in both TM and control chicks, but expression dynamics were improved in TM chicks for all cytokines (except IL-17). AHS resulted in increased plasma IFN-γ levels in TM chicks only, and increased IL-8 levels at 3 and 5 h of AHS in TM chicks, but at 7 h in control chicks. Lastly, 3 h of AHS increased IL-4 plasma levels in control chicks. The results of this study may indicate that TM has a long-term effect on cytokine expression dynamics of broilers, especially during AHS. Therefore, TM may improve heat tolerance acquisition by increasing the expression of signaling proteins important to tissue stability and to repair mechanisms that are employed during and/or after heat stress recovery.