Dietary taurine supplementation ameliorates muscle loss in chronic heat stressed broilers via suppressing the perk signaling and reversing endoplasmic reticulum-stress-induced apoptosis.

BACKGROUND: Heat stress seriously affects animal health and induces enormous financial losses in poultry production. Exploring the appropriate means for ameliorating unfavorable effects caused by heat stress is essential. We investigated whether taurine supplementation could attenuate breast muscle loss in chronic heat-stressed broilers, as well as its mechanism. We designed three groups: a normal control group (22 °C), a heat stress group (32 °C) and a taurine treatment group (32 °C, basal diet + 5 g·kg-1 taurine). RESULTS: We found that taurine significantly moderated the decreases of breast muscle mass and yield, as well as the increases of serum aspartate aminotransferase activity and serum urine acid level in chronic heat-stressed broilers. Additionally, supplementary taurine significantly alleviated elevations of the cytoplasm Ca2+ concentration, protein expressions of GRP78 and p-PERK, mRNA expressions of Ca2+ channels (RyR1, IP3R3) and endoplasmic reticulum (ER) stress factors (GRP78, GRP94, PERK, EIF2α, ATF4, IRE1, XBP1, ATF6 and CHOP), apoptosis (Caspase-3 and TUNEL), protein catabolism, and the reduction of taurine transporter (TauT) mRNA expression in the breast muscle induced by chronic heat stress. CONCLUSION: Supplementary taurine could attenuate chronic heat stress-induced breast muscle loss via reversing ER stress-induced apoptosis and suppressing protein catabolism. © 2020 Society of Chemical Industry.

Dietary taurine supplementation decreases fat synthesis by suppressing the liver X receptor α pathway and alleviates lipid accumulation in the liver of chronic heat-stressed broilers.

BACKGROUND: Chronic heat stress can enhance fat synthesis and result in lipid accumulation in the liver of broilers. To investigate the effects and molecular mechanisms of dietary taurine supplementation on fat synthesis and lipid accumulation in the liver of chronic heat-stressed broilers, 144 28 day-old chickens (Arbor Acres) were randomly distributed to normal control (NC, 22 °C, basal diet), heat stress (HS, consistent 32 °C, basal diet), or heat stress plus taurine (HS + T, consistent 32 °C, basal diet +5.00 g kg-1 taurine) groups for a 14-day feeding trial. RESULTS: Compared with those of the HS group, dietary taurine supplementation significantly decreased the level of very-low-density lipoprotein and the activity of aspartate aminotransferase in plasma and the relative weight of liver in the HS + T group. In addition, dietary taurine supplementation also significantly decreased the levels of triglyceride, acyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), and suppressed the mRNA expression levels of liver X receptor α (LXRα), sterol response element-binding protein 1c, ACC and FAS in the liver of chronic heat-stressed broilers. Meanwhile, dietary taurine supplementation effectively alleviated lipid accumulation in the liver of broilers exposed to chronic heat stress. CONCLUSION: Chronic heat stress significantly increased fat synthesis and resulted in excess lipid deposition in the liver of broilers. Dietary taurine supplementation can effectively decrease fat synthesis by suppressing the LXRα pathway and alleviate lipid accumulation in the liver of chronic heat-stressed broilers. © 2019 Society of Chemical Industry.

Chronic heat stress alters hypothalamus integrity, the serum indexes and attenuates expressions of hypothalamic appetite genes in broilers.

The hypothalamus is crucial to ensure the functionality of the entire organisms, such as body temperature, feed intake and energy regulation. Exposing broilers to high ambient temperature usually induces lower feed intake and energy imbalance. We investigated the molecular mechanisms by which heat stress impairs the appetite via dysfunction in hypothalamus of the broilers. Broilers were allocated to three groups: the normal control (NC) group, and fed ad libitum; heat-stress (HS) group, and fed ad libitum; pair-fed (PF) group, which received the feed intake equal to HS group. Experiment lasted from the age of 28 to 42 d. The results showed that HS increased the head surface temperature of broiler and changed hypothalamic ultrastructure. HS treatment also increased the serum corticosterone in the broilers after 7 days of heat stress, elevated the FT4 and FT3 after 14 days of heat stress. Heat stress of 14 days showed a tendency to increase the leptin. However, the serum corticosterone in the HS group had no significant difference after 14 days of heat stress. In addition, HS treatment decreased the expression of orexigenic gene neuropeptide Y (NPY) after 14 days of heat stress, while HS treatment had no effect on the reactive oxygen species (ROS), as well as the gene expression of AMPKα1 and LKB1 in the hypothalamus. In conclusion, HS increased the surface temperature of head in broiler, and then altered the integrity of hypothalamus. Meanwhile, HS increased the serum corticosterone which may ascribe to the activation of HPA axis in the broilers. In addition, chronic heat stress decreased the expression of orexigenic gene NPY, which may cause the broiler to reduce feed intake.

Effects of dietary taurine supplementation on growth performance, jejunal morphology, appetite-related hormones, and genes expression in broilers subjected to chronic heat stress.

This study was aimed to elucidate effects of taurine supplementation on growth performance, jejunal histology, and appetite-related genes expressions of broilers under heat stress. A total of 144 broilers on 28 d were allocated to three groups with 6 cages each group, 8 broilers per cage. The experiment period is from 28 to 42 d of age. In normal control (NC) group, chickens were held at 22°C ambient temperature (thermoneutral) and fed a basal diet. In the heat stress (HS) group, chickens were raised to constant HS at 32°C and received a basal diet. In the HS+ taurine group, chickens were fed a basal diet with 5 g/kg taurine supplementation. The results showed that HS group had lower average daily feed intake, average daily gain, higher feed/gain ratio compared with the NC group (P < 0.05), while taurine addition did not ameliorate the lowered growth performance. Cloacal temperatures and respiration rates in the HS and heat taurine group were higher (P < 0.05) than in the NC group. Heat stress treatment elevated (P < 0.05) the concentrations of ghrelin and cholecystokinin (CCK) in serum and intestine, together with peptide YY and somatostatin (SS) in the intestine after 7 or 14 d of heat exposure. In addition, HS damaged the jejunal morphology by shortening villus height and deepening crypt depth (P < 0.05), upregulated (P < 0.05) the mRNA expression of taste receptor type 1 member 1 (T1R1), taste receptor type 1 member 3 (T1R3), CCK and ghrelin in the intestine. Taurine supplementation significantly mitigated the impairment of jejunal morphology, decreased the concentrations of serum ghrelin, increased the concentrations of somatostatin and peptide YY in the duodenum, elevated the mRNA expression levels of CCK in the jejunum compared with the HS group. In conclusion, taurine exerted no positive effects on the growth performance, while mitigated the impairment of jejunal morphology, increased some anorexic hormones secretion and mRNA expression of appetite-related genes in the intestine of broilers subjected to HS.

Dietary taurine supplementation improves breast meat quality in chronic heat-stressed broilers via activating the Nrf2 pathway and protecting mitochondria from oxidative attack.

BACKGROUND: Chronic heat stress can induce oxidative impairment and decrease breast meat quality in broilers. Taurine is a ß-amino acid with antioxidant properties. To investigate the alleviative effects and molecular mechanisms of taurine supplementation on breast meat quality in broilers exposed to chronic heat stress, 144 28-day-old chickens (Arbor Acres) were randomly distributed to thermoneutral (TN, 22 °C, basal diet), heat stress (HS, consistent 32 °C, basal diet), or heat stress plus taurine (HS + T, consistent 32 °C, basal diet + 5.00 g kg-1 taurine) groups for a 14-day trial. RESULTS: Chronic heat stress did not affect the contents of moisture, crude protein and crude fat in breast muscle, but impaired breast meat quality in broilers. Taurine supplementation significantly alleviated the increase in lightness and drip loss and the decrease in pH45 min and shear force of breast meat in chronic heat-stressed broilers. Compared with the HS group, taurine supplementation significantly decreased the levels of reactive oxygen species and malonaldehyde and increased the messenger RNA expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), NAD(P)H quinone dehydrogenase 1 and heme oxygenase 1 in the HS + T group. Meanwhile, taurine supplementation effectively alleviated mitochondrial damage caused by chronic heat exposure. CONCLUSION: Dietary taurine supplementation can effectively improve the quality of breast meat in chronic heat-stressed broilers via activating the Nrf2 pathway and protecting mitochondria from oxidative attack. © 2018 Society of Chemical Industry.