Dietary betaine improves meat quality and oxidative status of broilers under heat stress

Nano-Se exhibits limited protective effect against heat stress induced poor breast muscle meat quality of broilers compared with other selenium sources

BACKGROUND

At present, heat stress (HS) has become a key factor that impairs broiler breeding industry, which causes growth restriction and poor meat quality of broilers. Selenium (Se) is an excellent antioxidant and plays a unique role in meat quality improvement. Recent years, nano-selenium (NanoSe) has received tremendous attention in livestock production, due to its characteristic and good antibacterial performance in vitro. Here, we developed the heat stressed-broiler model to investigate the protective effects of NanoSe on growth performance and meat quality of broilers and compare whether there are differences with that of other Se sources (Sodium selenite, SS; Selenoyeast, SeY; Selenomethionine, SeMet).

RESULTS

HS jeopardized the growth performance and caused poor meat quality of breast muscle in broilers, which were accompanied by lowered antioxidant capacity, increased glycolysis, increased anaerobic metabolism of pyruvate, mitochondrial stress and abnormal mitochondrial tricarboxylic acid (TCA) cycle. All Se sources supplementation exhibited protective effects, which increased the Se concentration and promoted the expression of selenoproteins, improved the mitochondrial homeostasis and the antioxidant capacity, and promoted the TCA cycle and the aerobic metabolism of pyruvate, thus improved the breast muscle meat quality of broilers exposed to HS. However, unlike the other three Se sources, the protective effect of NanoSe on meat quality of heat stressed-broilers was not ideal, which exhibited limited impact on the pH value, drip loss and cooking loss of the breast muscle. Compared with the other Se sources, broilers received NanoSe showed the lowest levels of slow MyHC, the highest levels of fast MyHC and glycogen, the highest mRNA levels of glycolysis-related genes (PFKM and PKM), the highest protein expression of HSP60 and CLPP, and the lowest enzyme activities of GSH-Px, citroyl synthetase (CS) and isocitrate dehydrogenase (ICD) in breast muscle. Consistent with the SS, the Se deposition in breast muscle of broilers received NanoSe was lower than that of broilers received SeY or SeMet. Besides, the regulatory efficiency of NanoSe on the expression of key selenoproteins (such as SELENOS) in breast muscle of heat stressed-broilers was also worse than that of other Se sources.

CONCLUSION

Through comparing the meat quality, Se deposition, muscle fiber type conversion, glycolysis, mitochondrial homeostasis, and mitochondrial TCA cycle-related indicators of breast muscle in heat stressed broilers, we found that the protective effects of organic Se (SeY and SeMet) are better than that of inorganic Se (SS) and NanoSe. As a new Se source, though NanoSe showed some protective effect on breast muscle meat quality of heat stressed broilers, the protective effect of NanoSe is not ideal, compared with other Se sources.

Effects of intermittent cold stimulation on growth performance, meat quality, antioxidant capacity and liver lipid metabolism in broiler chickens

Intermittent cold stimulation (ICS) enhances broilers' resistance to cold stress. Nonetheless, further research is needed to investigate the underlying mechanisms that enhance cold stress resistance. A total of 160 one-day-old male Ross 308 broilers were randomly divided into 2 groups (CC and CS5), with the CC group managing temperature according to the standard for broiler growth stages, while the CS5 group were subjected to cold stimulation at a temperature 3℃ lower than the CC group for 5 h, every 2 d from 15 to 35 d. Sampling was conducted at 36 d (36D), 50 d (50D) and after acute cold stress for 24 h (Y24). First, we examined the effects of ICS on broiler growth performance, meat quality, antioxidant capacity, and lipid metabolism. The results demonstrated that ICS enhanced the performance of broilers to a certain degree. Specifically, the average weight gain in the CS5 group was significantly higher than that of the CC group, and the feed conversion ratio significantly decreased compared to CC at 4 W and 6 W (P ≤ 0.05). Compared with the CC group, cold stimulation significantly reduced drip loss, shearing force, and yellowness (a* value) of chicken meat, while significantly increased redness (b* value) (P ≤ 0.05). At Y24, the levels of T-AOC and GSH-PX in the serum of the CS5 group were significantly higher than those of the CC group, while the level of MDA was significantly lower (P ≤ 0.05). The content of TG, FFA, and VLDL in the serum of the CS5 group was significantly elevated, whereas the level of TC and HDL was significantly lower (P ≤ 0.05). In addition, we further explored whether AMPK-mTOR pathway is involved in the regulation of changes in lipid metabolism and the possible regulatory mechanisms downstream of the signaling pathway. The results showed that ICS significantly upregulated the expression levels of AMPK mRNA and protein in the liver of the CS5 group at 36D and Y24, while significantly down-regulating mTOR (P ≤ 0.05). Compared with the CC group, ICS significantly down-regulated the mRNA expression levels of lipid synthesis and endoplasmic reticulum stress-related genes (SREBP1c, FAS, SCD, ACC, GRP78 and PERK) at 36D and Y24, while significantly up-regulating the mRNA expression levels of lipid decomposition and autophagy-related genes (PPAR and LC3) (P ≤ 0.05). In addition, at Y24, the protein expression levels of endoplasmic reticulum stress-related genes (GRP78) in the CS5 group were significantly lower, while autophagy-related genes (LC3 and ATG7) were significantly higher (P ≤ 0.05). ICS can affect meat quality and lipid metabolism in broilers, and when broilers are subjected to acute cold stress, broilers trained with cold stimulation have stronger lipid metabolism capacity.

Selenomethionine alleviates chronic heat stress-induced breast muscle injury and poor meat quality in broilers via relieving mitochondrial dysfunction and endoplasmic reticulum stress

In the present study, the chronic heat stress (CHS) broiler model was developed to investigate the potential protection mechanism of organic selenium (selenomethionine, SeMet) on CHS-induced skeletal muscle growth retardation and poor meat quality. Four hundred Arbor Acres male broilers (680 ± 70 g, 21 d old) were grouped into 5 treatments with 8 replicates of 10 broilers per replicate. Broilers in the control group were raised in a thermoneutral environment (22 ± 2 °C) and fed with a basal diet. The other four treatments were exposed to hyperthermic conditions (33 ± 2 °C, 24 h in each day) and fed on the basal diet supplied with SeMet at 0.0, 0.2, 0.4, and 0.6 mg Se/kg, respectively, for 21 d. Results showed that CHS reduced (P < 0.05) the growth performance, decreased (P < 0.05) the breast muscle weight and impaired the meat quality of breast muscle in broilers. CHS induced protein metabolic disorder in breast muscle, which increased (P < 0.05) the expression of caspase 3, caspase 8, caspase 9 and ubiquitin proteasome system related genes, while decreased the protein expression of P-4EBP1. CHS also decreased the antioxidant capacity and induced mitochondrial stress and endoplasmic reticulum (ER) stress in breast muscle, which increased (P < 0.05) the ROS levels, decreased the concentration of ATP, increased the protein expression of HSP60 and CLPX, and increased (P < 0.05) the expression of ER stress biomarkers. Dietary SeMet supplementation linearly increased (P < 0.05) breast muscle Se concentration and exhibited protective effects via up-regulating the expression of the selenotranscriptome and several key selenoproteins, which increased (P < 0.05) body weight, improved meat quality, enhanced antioxidant capacity and mitigated mitochondrial stress and ER stress. What's more, SeMet suppressed protein degradation and improved protein biosynthesis though inhibiting the caspase and ubiquitin proteasome system and promoting the mTOR-4EBP1 pathway. In conclusion, dietary SeMet supplementation increases the expression of several key selenoproteins, alleviates mitochondrial dysfunction and ER stress, improves protein biosynthesis, suppresses protein degradation, thus increases the body weight and improves meat quality of broilers exposed to CHS.

Protective influence of supplementary betaine against heat stress by regulating intestinal oxidative status and microbiota composition in broiler chickens

To assess the impact of supplementing betaine (BT) under heat stress (HS) conditions on broiler performance and intestinal health from 21 to 42 days of age, a total of 150 male Ross 308 broilers were indiscriminately allotted to 3 treatments with 10 replications of 5 birds each. The control (CON) group was given a basal ration and accommodated at a thermoneutral condition (22 ± 1 °C), whereas the HS and HS + BT groups were raised under cyclic HS (33 ± 1 °C for 8 h and 22 ± 1 °C for 16 h per day) and received the basal ration without or with 1000 mg/kg BT, respectively. The HS reduced average daily gain (ADG); average daily feed intake; villus height (VH); VH to crypt depth (CD) ratio (VCR); activities of trypsin, lipase, glutathione peroxidase (GPX), and catalase; and enumeration of Lactobacillus and Bifidobacterium (P < 0.05) and augmented feed conversion ratio (FCR), CD, malondialdehyde (MDA) accumulation, and enumeration of Escherichia coli, Clostridium, and coliforms (P < 0.05). Conversely, BT supplementation heightened ADG, VH, VCR, trypsin activity, GPX activity, and populations of Lactobacillus and Bifidobacterium (P < 0.05) and lowered FCR, MDA accumulation, and Clostridium population (P < 0.05). Furthermore, the FCR value, trypsin and GPX activities, MDA content, and Bifidobacterium and Clostridium populations in the HS + BT group were nearly equivalent to those in the CON group. To conclude, feeding BT under HS conditions could improve broiler performance through improving intestinal health by specifically mitigating oxidative damage and enhancing the colonization of beneficial bacteria.

Improving quality of poultry and its meat products with probiotics, prebiotics, and phytoextracts

Remarkable changes have occurred in poultry farming and meat processing in recent years, driven by advancements in breeding technology, feed processing technology, farming conditions, and management practices. The incorporation of probiotics, prebiotics, and phytoextracts has made significant contributions to the development of poultry meat products that promote both health and functionality throughout the growth phase and during meat processing. Poultry fed with these substances improve meat quality, while incorporating probiotics, prebiotics, and phytoextracts in poultry processing, as additives or supplements, inhibits pathogens and offers health benefits to consumers. However, it is vital to assess the safety of functional fermented meat products containing these compounds and their potential effects on consumer health. Currently, there's still uncertainty in these aspects. Additionally, research on utilizing next-generation probiotic strains and synergistic combinations of probiotics and prebiotics in poultry meat products is in its early stages. Therefore, further investigation is required to gain a comprehensive understanding of the beneficial effects and safety considerations of these substances in poultry meat products in the future. This review offered a comprehensive overview of the applications of probiotics and prebiotics in poultry farming, focusing on their effects on nutrient utilization, growth efficiency, and gut health. Furthermore, potential of probiotics, prebiotics, and phytoextracts in enhancing poultry meat production was explored for improved health benefits and functionality, and possible issues associated with the use of these substances were discussed. Moreover, the conclusions drawn from this review and potential future perspectives in this field are presented.

The role of phytogenic feed additives in stress mitigation in broiler chickens

The increase in global temperature and consumers' welfare has increased the use of phytogenic feed additives (PFA) to mitigate the negative effects of heat stress on chickens in recent years. Various bioactive compounds capable of improving the thermotolerance of broiler chickens during exposure to thermal challenges have been identified in different plant species and parts. This review is an overview of the roles of bioactive compounds of different PFA, such as polyphenols and flavonoids, antioxidants, growth-promoting and immune-modulating agents, in heat stress management in broiler chickens. Common PFA in use, particularly in tropical environments, are also discussed. An understanding of the roles of the PFA in chickens' thermotolerance could further stimulate interest in their use, thereby improving the birds' productivity and addressing consumers' concerns. This review collates the existing data on the roles of herbs in mitigating heat stress on chickens and highlights future research perspectives.

Biogenic Selenium Nanoparticles Synthesized Using Alginate Oligosaccharides Attenuate Heat Stress-Induced Impairment of Breast Meat Quality via Regulating Oxidative Stress, Metabolome and Ferroptosis in Broilers

Selenium (Se) is an indispensable trace element with versatile functions in antioxidant defense in poultry. In our previous study, we synthesized a novel type of biogenic selenium nanoparticle based on alginate oligosaccharides (SeNPs-AOS), and found that the particles are sized around 80 nm with an 8% Se content, and the dietary addition of 5 mg/kg of SeNPs-AOS could effectively alleviate the deleterious effects of heat stress (HS) in broilers, but it is still unclear whether SeNPs-AOS can improve the meat quality. Therefore, the aim of this study was to evaluate the protective effects of SeNPs-AOS on breast meat quality in heat-stressed broilers, and explore the relevant mechanisms. Birds at the age of 21 days were randomly divided into four groups with six replicates per group (eight broilers per replicate) according to a 2 × 2 experimental design, using HS (33 ± 2 °C, 10 h/day vs. thermoneutral, TN, under 23 ± 1.5 °C) and SeNPs-AOS (5 mg/kg feed vs. no inclusion) as variables. The results showed that dietary SeNPs-AOS decreased the cooking loss (p < 0.05), freezing loss (p < 0.001), and shear force (p < 0.01) of breast muscle in heat-stressed broilers. The non-targeted metabolomics analysis of the breast muscle identified 78 differential metabolites between the HS and HS + SeNPs-AOS groups, mainly enriched in the arginine and proline metabolism, β-alanine metabolism, D-arginine and D-ornithine metabolism, pantothenate, and CoA biosynthesis pathways (p < 0.05). Meanwhile, supplementation with SeNPs-AOS increased the levels of the total antioxidant capacity (T-AOC), the activities of catalase (CAT) and glutathione peroxidase (GSH-Px), and decreased the content of malondialdehyde (MDA) in the breast muscle (p < 0.05) in broilers under HS exposure. Additionally, SeNPs-AOS upregulated the mRNA expression of CAT, GPX1, GPX3, heme oxygenase-1 (HO-1), masculoaponeurotic fibrosarcoma G (MafG), MafK, selenoprotein W (SELENOW), SELENOK, ferritin heavy polypeptide-1 (FTH1), Ferroportin 1 (Fpn1), and nuclear factor erythroid 2-related factor 2 (Nrf2) (p < 0.05), while it downregulated Kelch-like ECH-associated pro-36 tein 1 (Keap1) and prostaglandin-endoperoxide Synthase 2 (PTGS2) expression (p < 0.05) in broilers under HS. These findings demonstrated that the dietary addition of SeNPs-AOS mitigated HS-induced oxidative damage and metabolite changes in the breast muscle of broilers, which may be related to the regulation of the Nrf2 signaling pathway and selenoprotein synthesis. In addition, SeNPs-AOS upregulated the breast muscle gene expression of anti-ferroptosis-related molecules in broilers under HS, suggesting that SeNPs-AOS can be used as novel Se supplements against HS in broilers.

Effects of Dietary Betaine on the Laying Performance, Antioxidant Capacity, and Uterus and Ovary Function of Laying Hens at the Late Stage of Production

Betaine has been found to alleviate oxidative stress, inflammation, and apoptosis. However, whether dietary betaine can protect late-laying hens against these adverse effects is unknown. Here, 270 65-week-old Jinghong-1 laying hens were randomly divided into the Control, 0.1% Betaine, and 0.5% Betaine groups and fed a basal diet, 0.1%, and 0.5% betaine supplemented diet, respectively. The trial lasted for seven weeks. Birds that consumed 0.5% betaine laid more eggs with thicker eggshells. Accordingly, uterine reduced glutathione (GSH), glutathione peroxidase (GSH-PX), and ovarian superoxide dismutase (SOD) contents were increased. The uterine calcium ion content and the mRNA expression of ovalbumin, ovotransferrin, and carbonic anhydrase two were increased. Moreover, ovarian IL-1β, Caspase-1, Caspase-8, and Caspase-9 mRNA expressions were decreased; luteinising hormone receptor (LHR) and follicle-stimulating hormone receptor mRNA expressions were increased. Furthermore, dietary betaine decreased the ovaries' mRNA expression of DNA methyltransferase 1 (DNMT)1, DNMT3a, and DNMT3b. The methylation level at the promoter region of ovarian LHR decreased. These results indicated that dietary betaine consumption with a concentration of 0.5% could increase the laying rate and the eggshell thickness during the late-laying period. The underlying mechanism may include antioxidative, anti-apoptosis, and hormone-sensitivity-enhancing properties.

Effect of individual or combination of dietary betaine and glycine on productive performance, stress response, liver health, and intestinal barrier function in broiler chickens raised under heat stress conditions

The current experiment was conducted to investigate the effect of individual or combination of dietary betaine (Bet) and glycine (Gly) on productive performance, stress response, liver health, and intestinal barrier function in broiler chickens raised under heat stress (HS) conditions. A total of four hundred twenty 21-d-old Ross 308 broiler chickens were randomly allotted to 1 of 5 dietary treatments with 7 replicates. Birds in treatment 1 were raised under the thermoneutral condition (TN; 23 ± 0.6°C). Birds in other 4 treatment groups were subjected to a cyclic HS by exposing them to 32 ± 0.9°C for 8 h/d (from 09:00 to 17:00 h) and 28 ± 1.2°C for the remaining time for 14 d. Birds were fed a basal diet in TN condition (TN-C) and one group in HS conditions (HS-C), whereas other birds raised under HS conditions were fed the basal diet supplemented with 0.20% Bet (HS-Bet), 0.79% Gly (HS-Gly), or their combination (0.20% Bet + 0.79% Gly; HS-Bet+Gly). Results indicated that birds in HS-Bet, HS-Gly, or HS-Bet+Gly treatment had higher (P < 0.05) final BW and BW gain, but lower (P < 0.05) feed conversion ratio (FCR) than those in HS-C treatment. However, values for improved final BW, BW gain, and FCR by dietary treatments were lower (P < 0.05) than those measured in TN-C treatment. Under HS conditions, birds in HS-Bet, HS-Gly, or HS-Bet+Gly treatment had lower (P < 0.05) heterophil to lymphocyte ratio than those in HS-C treatment. Birds in HS-Gly or HS-Bet+Gly treatment had higher (P < 0.05) villus height and goblet cell number than birds in HS-C treatment. Intestinal permeability was higher (P < 0.05) in all HS-treatment groups than in TN-C treatment, but it was not affected by dietary treatment. In conclusion, individual supplementation of 0.20% Bet or 0.79% Gly in diets alleviates the negative effect of HS in broiler chickens. However, the synergistic effect of the combination of 0.20% Bet and 0.79% Gly in broiler diets seems lower than expected.

Muscle quality traits and oxidative status of Iberian pigs supplemented with zinc and betaine under heat stress

The study analyzed the effect of supplemental zinc and betaine on meat quality and redox status of muscles (longissimus lumborum and gluteus medius) from heat- stressed pigs. Twenty-four pure Iberian pigs were assigned to one of three treatments (n = 8): control diet, Zn supplemented diet (120 mg/kg) and betaine supplemented diet (5 g/kg) that were all exposed to 30 °C during 28 days. No significant differences were observed in chemical composition and fatty acid profile of the muscles. The Zn diet improved the water retention capacity of longissimus, increased the antioxidant properties (ABTS and FRAP) and the glutathione peroxidase activity, and reduced the level of MDA. No significant effects associated to the betaine diet were observed in quality traits and antioxidant markers of muscles. These findings suggest that Zn supplementation may be used as a nutritional strategy to improve the antioxidant properties of meat of Iberian pigs subjected to heat stress conditions.

An evaluation of the thermoregulatory potential of in ovo delivered bioactive substances (probiotic, folic acid, and essential oil) in broiler chickens

Mitigating the negative effects of heat stress (HS) is a critical challenge for the global poultry industry. This study evaluated the thermoregulatory potential of 3 in ovo delivered bioactive substances using selected gut health parameters. Eggs were incubated and allotted to 5 groups, and respective bioactive substances delivered. These groups included-the noninjected, in ovo saline, in ovo folic acid (FA), in ovo probiotics (P), and in ovo essential oil (EO). At hatch, chicks were assigned to 5 new posthatch treatment combinations, including A) Negative control (NC)-noninjected eggs offered a basal corn-wheat-soybean diet, B) Antibiotics-NC + 0.05% bacitracin methylene disalicylate, C) In ovo FA-eggs injected with FA + NC diet, D) In ovo probiotics-eggs injected with probiotics + NC diet, E) In ovo + in-water EO-eggs injected with EO and supplied EO via drinking water + NC diet. Birds were raised for 28 d in 8 replicate cages/treatment (6 birds/cage) and exposed to either a thermoneutral (24°C ± 0.2) or HS challenge (31°C) condition from d 21 to d 28. The in ovo delivered FA and EO treatments reduced (P < 0.001) hatchability by at least 26% compared to NC. Induced HS reduced (P < 0.001) total plasma protein, total antioxidant capacity, and villus width in the duodenum and jejunum. Independent of HS and compared to NC, the in ovo + in-water EO treatment resulted in (P < 0.05) at least a 15% increase in villus height: crypt depth across the 3 gut sections. The in ovo + in-water EO treatment also increased the relative mRNA expression of intestinal barrier-related genes (Claudin1,3,4, Occludin, Zona occludens-2, and Mucin 2). Under HS, the in ovo + in-water EO treatment recorded a 3.5-fold upregulation of amino acid transporter gene (SLC1A1), compared to NC. Subject to further hatchability optimization, the in ovo + in-water delivery of EO show potential to afford broiler chicken thermotolerance.

Comparative Analysis of the Temporal Impacts of Corticosterone and Simulated Production Stressors on the Metabolome of Broiler Chickens

The impact of physiological stress on the metabolome of breast muscle, liver, kidney, and hippocampus was investigated in Ross 308 broiler chicks. Simulated on-farm stressors were compared to a corticosterone model of physiological stress. The three different stressors investigated were: (i) corticosterone at a dose of 15 mg/kg of feed; (ii) heat treatment of 36 °C and 40% RH for 8 h per day; and (iii) isolation for 1 h per day. Liver, kidney, breast muscle, and hippocampus samples were taken after 2, 4, 6, and 8 days of stress treatment, and subjected to untargeted ¹H-nuclear magnetic resonance (NMR) spectroscopy-based metabolomic analysis to provide insights on how stress can modulate metabolite profiles and biomarker discovery. Many of the metabolites that were significantly altered in tissues were amino acids, with glycine and alanine showing promise as candidate biomarkers of stress. Corticosterone was shown to significantly alter alanine, aspartate, and glutamate metabolism in the liver, breast, and hippocampus, while isolation altered the same pathways, but only in the kidneys and hippocampus. Isolation also significantly altered the glycine, serine, and threonine metabolism pathway in the liver and breast, while the same pathway was significantly altered by heat in the liver, kidneys, and hippocampus. The study's findings support corticosterone as a model of stress. Moreover, a number of potential metabolite biomarkers were identified in chicken tissues, which may allow producers to effectively monitor stress and to objectively develop and evaluate on-farm mitigations, including practices that reduce stress and enhance bird health.

Evaluation of modified dried vinasse as an alternative dietary protein source for broilers

The increase in poultry production and the high cost of soybean led to the search for alternative protein sources. One of these sources is vinasse, a by-product of the baker's yeast industry. Modified dried vinasse (MDV) can be produced for use in poultry nutrition by making some improvements in vinasse. Therefore, the present study aimed to examine the effect of the usage of MDV in broiler diets. A total of 192 daily male Ross 308 chicks were randomly assigned to four groups. MDV was included at the levels of 0%, 2%, 4%, and 6% in the diets for 42-day trial. Linear significant improvements in the final weight, body weight gain, feed efficiency, and digestibility were seen with increasing MDV levels. The use of MDV caused a significant reduction in feed consumption. The relative weight percentages of abdominal fat and serum cholesterol concentration were reduced linearly with increases in MDV levels. MDV inclusion linearly decreased the malondialdehyde concentration, but increased 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity in breast meat significantly. The protein content in breast meat was increased with MDV. Cecal beneficial microorganisms and serum IgG levels were increased linearly with MDV. In conclusion, results suggested that MDV could be a feasible option for alternative protein sources for broilers.

Effects of Heat Stress on Production Performance, Redox Status, Intestinal Morphology and Barrier-Related Gene Expression, Cecal Microbiome, and Metabolome in Indigenous Broiler Chickens

This study was done to evaluate the effects of heat stress (HS) on production performance, redox status, small intestinal barrier-related parameters, cecal microbiota, and metabolome of indigenous broilers. A total of forty female indigenous broilers (56-day-old) were randomly and equally divided into normal treatment group (NT group, 21.3 ± 1.2°C, 24 h/day) and HS group (32.5 ± 1.4°C, 8 h/day) with five replicates of each for 4 weeks feeding trial. The results showed that the body weight gain (BWG) of broilers in HS group was lower than those in NT group during 3–4 weeks and 1–4 weeks (p &lt; 0.05). The HS exposure increased the abdominal fat rate (p &lt; 0.05) but decreased the thigh muscle rate (p &lt; 0.01). Besides, broilers in HS group had higher drip loss of breast muscle than NT group (p &lt; 0.01). Broilers exposed to HS had lower total antioxidant capacity (T-AOC) in serum and jejunum, activities of total superoxide dismutase (T-SOD) in the jejunum, glutathione peroxidase (GSH-Px) in the thigh muscle, duodenum, and jejunum; and catalase (CAT) in breast muscle, duodenum, and jejunum (p &lt; 0.05). Whereas the malondialdehyde (MDA) contents in breast muscle, duodenum, and jejunum was elevated by HS exposure (p &lt; 0.05). Moreover, the relative mRNA expression of Occludin and ZO-1 in the duodenum, Occludin, Claudin-1, Claudin-4, ZO-1, Mucin-2 in the jejunum, and the Claudin-4 and Mucin-2 in the ileum was down-regulated by HS exposure (p &lt; 0.05). The 16S rRNA sequencing results showed that the HS group increased the relative abundance of Anaerovorax in the cecum at the genus level (p &lt; 0.05). Cecal metabolomics analysis indicated 19 differential metabolites between the two groups (p &lt; 0.10, VIP &gt;1). The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the differential metabolites mainly enriched in 10 signaling pathways such as the Citrate cycle (TCA cycle) (p &lt; 0.01). In summary, chronic HS exposure caused a decline of production performance, reduced antioxidant capacity, disrupted intestinal barrier function, and negatively affected cecal microbiota and metabolome in indigenous broilers.

Betaine Regulates the Production of Reactive Oxygen Species Through Wnt10b Signaling in the Liver of Zebrafish

When fish are under oxidative stress, levels of reactive oxygen species (ROS) are chronically elevated, which play a crucial role in fish innate immunity. In the present study, the mechanism by which betaine regulates ROS production via Wnt10b/β-catenin signaling was investigated in zebrafish liver. Our results showed that betaine enrichment of diet at 0.1, 0.2 and 0.4 g/kg induced Wnt10b and β-catenin gene expression, but suppressed GSK-3β expression in zebrafish liver. In addition, the content of superoxide anion (O₂^·−), hydrogen peroxide (H₂O₂) and hydroxyl radical (·OH) was decreased by all of the experimental betaine treatments. However, betaine enrichment of diet at 0.1, 0.2 and 0.4 g/kg enhanced gene expression and activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and catalase (CAT) in zebrafish liver. In addition, Wnt10b RNA was further interfered in zebrafish, and the results of Wnt10b RNAi indicated that Wnt10b plays a key role in regulating ROS production and antioxidant enzyme activity. In conclusion, betaine can inhibit ROS production in zebrafish liver through the Wnt10b/β-catenin signaling pathway.

Functional roles of taurine, L-theanine, L-citrulline, and betaine during heat stress in poultry

Heat stress (HS) is an important environmental stress factor affecting poultry production on a global scale. With the rise in ambient temperature and increasing effects of global warming, it becomes pertinent to understand the effects of HS on poultry production and the strategies that can be adopted to mitigate its detrimental impacts on the performance, health, welfare, immunity, and survival of birds. Amino acids (AAs) have been increasingly adopted as nutritional modifiers in animals to ameliorate the adverse effects of HS. They are essential for protein synthesis, growth, maintenance, reproduction, immunity, stress response, and whole-body homeostasis. However, HS tends to adversely affect the availability, transport, absorption, and utilization of these AAs. Studies have investigated the provision of these AAs to poultry during HS conditions, and variable findings have been reported. Taurine, L-theanine, and L-citrulline are non-essential amino acids that are increasingly gaining attention as nutritional supplements in HS animals. Similarly, betaine is an amino acid derivative that possesses favorable biological properties which contributes to its role as a functional additive during HS. Of particular note, taurine is negligible in plants, while betaine, L-theanine, and L-citrulline can be found in selected plants. These nutrients are barely found in feed ingredients, but their supply has been shown to elicit important physiological roles including anti-stress effects, anti-oxidative, anti-inflammatory, gut promoting, and immunomodulatory functions. The present review provides information on the use of these nutritionally and physiologically beneficial nutrients as functional additives to poultry diets during HS conditions. Presently, although several studies have reported on the positive effects of these additives in human and murine studies, however, there is limited information regarding their utilization during heat stress in poultry nutrition. Therefore, this review aims to expound on the functional properties of these nutrients, their potentials for HS alleviation, and to stimulate further researches on their biological roles in poultry nutrition.

Dietary lycopene supplementation improves meat quality, antioxidant capacity and skeletal muscle fiber type transformation in finishing pigs

This study aimed to investigate effects of dietary lycopene supplementation on meat quality, antioxidant ability and muscle fiber type transformation in finishing pigs. In a 70-day experiment, 18 Duroc × Landrace × Yorkshire barrows were randomly allocated to 3 dietary treatments including a basal diet supplemented with 0, 100 and 200 mg/kg lycopene, respectively. Each dietary treatment had 6 replicates with one pig each. Results showed that dietary 200 mg/kg lycopene supplementation increased muscle redness a∗ value, intramuscular fat and crude protein contents, and decreased muscle lightness L∗ and yellowness b∗ values (P < 0.05), suggesting that addition of 200 mg/kg lycopene to the diet of finishing pigs improved color, nutritional value and juiciness of pork after slaughter. Results also showed that dietary lycopene supplementation enhanced antioxidant capacity of finishing pigs (P < 0.05). Moreover, dietary supplementation of 200 mg/kg lycopene significantly increased slow myosin heavy chain (MyHC) protein level and slow-twitch fiber percentage, and decreased fast MyHC protein level and fast-twitch fiber percentage (P < 0.05), suggesting that the addition of 200 mg/kg lycopene to the diet of finishing pigs promoted muscle fiber type conversion from fast-twitch to slow-twitch. Together, we provide the first evidence that dietary 200 mg/kg lycopene supplementation improves meat quality, enhances antioxidant capacity and promotes muscle fiber type transformation from fast-twitch to slow-twitch in finishing pigs.

Effects of dietary betaine supplementation on growth performance, meat quality, muscle fatty acid composition and antioxidant ability in slow-growing broiler chickens

1. This study investigated the effects of dietary betaine supplementation on growth performance, meat quality, muscle fatty acid composition and antioxidant ability in slow-growing broiler chickens.2. In total, 400, one-day-old female Xueshan broiler chicks were randomly divided into five groups with eight replicates of ten chickens each for 102 d. Broilers were fed a basal diet supplemented with 0, 125, 250, 500 or 1,000 mg/kg betaine.3. Broilers fed betaine had better feed conversion efficiency and weight gain (P < 0.05) and increased meat redness and yellowness 24 h after slaughter. Supplementation linearly decreased cooking loss and drip loss from breast muscle (P < 0.05). Muscular resilience was improved and tenderness increased (P < 0.05). Intra-muscular saturated fatty acids decreased, while total monounsaturated fatty acids and polyunsaturated fatty acids increased (P < 0.05). Betaine increased activities of glutathione peroxidase (GPx) and total superoxide dismutase (SOD), glutathione (GSH) level, ratio of reduced glutathione/oxidised glutathione, and activity of scavenging hydroxyl radicals. It increased the activity of total antioxidant capacity (T-AOC) in the breast muscle (P < 0.05). Moreover, supplementation up-regulated (P < 0.05) mRNA expression levels of blood and antioxidant markers.4. In conclusion, 1000 mg/kg betaine can be recommended as a supplement for slow-growing, Xueshan chicken.

Meta-analysis to predict the effects of temperature stress on meat quality of poultry

Temperature stress (TS) is a significant issue in poultry production, which has implications for animal health and welfare, productivity, and industry profitability. Temperature stress, including both hot (heat stress) and cold conditions (cold stress), is associated with increased incidence of meat quality defects such as pale, soft, and exudative (PSE) and dark, firm, and dry (DFD) meat costing poultry industries millions of dollars annually. A meta-analysis was conducted to determine the effect of ambient TS on meat quality parameters of poultry. Forty-eight publications which met specific criteria for inclusion were identified through a systematic literature review. Temperature stress was defined by extracting 2 descriptors for each treatment mean from the chosen studies: (1) temperature imposed for the experimental treatments (°C) and duration of temperature exposure. Treatment duration was categorized for analysis into acute (≤24 h) or chronic (>24 h) treatments. Meat quality parameters considered were color (L*-a*-b* scheme), pH (initial and ultimate), drip loss, cooking loss, and shear force. Linear mixed model analysis, including study as a random effect, was used to determine the effect of treatment temperature and duration on meat quality. Model evaluation was conducted by performing a k-fold cross-validation to estimate test error, and via assessment of the root mean square prediction error (RMSPE), and concordance correlation coefficient (CCC). Across both acute and chronic durations, treatment temperature was found to have a significant effect on all studied meat quality parameters. As treatment temperature increased, meat demonstrated characteristics of PSE meat and, as temperature decreased, meat demonstrated characteristics of DFD meat. The interaction between treatment temperature and duration was significant for most traits, however, the relative impact of treatment duration on the studied traits was inconsistent. Acute TS had a larger effect than chronic TS on ultimate pH, and chronic stress had a more considerable impact on color traits (L* and a*). This meta-analysis quantifies the effect of ambient TS on poultry meat quality. However, quantitative effects were generally small, and therefore may or may not be of practical significance from a processing perspective.

Betaine improves growth performance, liver health, antioxidant status, breast meat yield, and quality in broilers fed a mold-contaminated corn-based diet

Betaine has been demonstrated to improve growth performance and antioxidant status of animals under various stress conditions. However, there is no literature on the effects of betaine in animals exposed to mycotoxins, which are among the most prevalent contaminants in feed. Therefore, this study was conducted to evaluate the influence of dietary betaine on broilers fed a diet based on mold-contaminated corn (MCC). A total of 192 Ross 308 male broiler chicks at 1 d of age were randomly divided into 4 groups with 6 replicates and fed an MCC-based diet supplemented with 0, 250, 500, and 1,000 mg/kg betaine, respectively. Betaine increased average daily gain (linear, P = 0.030) and decreased feed conversion ratio (linear, P = 0.027) of broilers during d 1 – 21, and decreased feed conversion ratio during d 22 – 42 (linear, P = 0.012; quadratic, P < 0.001) and d 1 – 42 (linear, P = 0.003; quadratic, P = 0.004), whereas feed intake was not affected. Total cholesterol (linear, P = 0.024), alanine aminotransferase (quadratic, P < 0.001) and alkaline phosphatase (linear, P = 0.007; quadratic, P = 0.025) activities in serum were decreased by betaine. Betaine linearly increased breast muscle yield (P = 0.003) and pH_24 h (P = 0.008), and decreased drip loss (P = 0.022). Betaine increased (linear, P = 0.025; quadratic, P = 0.016) total superoxide dismutase activity in breast muscle and reduced malondialdehyde content in serum (linear, P = 0.006), liver (quadratic, P = 0.006) and breast muscle (linear, P = 0.003). Moreover, the zearalenone concentrations in breast muscle were linearly decreased by betaine (P = 0.006). It was concluded that betaine could improve growth performance, liver health, antioxidant status, and breast meat yield and quality, and reduce zearalenone residue in broilers fed the MCC-based diet, especially at 500 or 1,000 mg/kg.

Effects of guanidinoacetic acid and complex antioxidant supplementation on growth performance, meat quality, and antioxidant function of broiler chickens

BACKGROUND

This study was conducted to evaluate the effects of adding guanidinoacetic acid (GAA), or complex antioxidant (CA), or their combination, in diets on the growth performance, carcass traits, meat quality, and antioxidant capacity of broilers. A total of 192 25-day-old broilers were assigned to a 2 × 2 factorial design including two dietary supplements at two different levels, in which the main effects were the addition of GAA (0 or 600 mg kg^-1 ) and CA (0 or 150 mg kg^-1 ). This trial lasted for 18 days.

RESULTS

Compared with the control group, the GAA group, CA group, and GAA + CA group, decreased feed conversion ratio by 7.02%, 6.58%, and 11.40%, respectively. Guanidinoacetic supplementation increased eviscerated yield, pH_24h (P < 0.05). Complex antioxidant supplementation increased the a* values (P < 0.05). The combination of GAA and CA did not affect the carcass traits and meat quality. Guanidinoacetic acid alone and CA alone and combined with GAA and CA decreased the reactive oxygen species (ROS) level and malonaldehyde (MDA) content (P < 0.05), and the GAA + CA group had the lowest ROS level and MDA content of broilers.

CONCLUSION

Dietary supplementation of GAA, CA or their combination had beneficial effects on growth performance and breast antioxidant capacity, and the combination of GAA and CA could exert a synergistic effect in improving antioxidant capacity. © 2020 Society of Chemical Industry.

Effects of Nano Emulsified Vegetable Oil and Betaine on Growth Traits and Meat Characteristics of Broiler Chickens Reared under Cyclic Heat Stress

The effects of nano-emulsified vegetable oil (NEVO) and betaine (BET) supplements on growth performance and meat qualities of broilers reared under cyclic heat stress (HS) were investigated. Two hundred and eighty-eight mixed-sex broilers at 21 d were randomly distributed to a 2 × 3 factorial arrangement of treatments formed by two environmental temperatures (thermoneutral (TN; 24 ± 1 °C) and cyclic high-temperature (HT; 35 ± 1 °C)) and three dietary treatments (control (CON), NEVO, and BET). The cumulative performance (21-35 d) revealed a reduction in average daily gain (ADG) (p < 0.05) in the CON compared to NEVO. NEVO and BET groups had a better feed conversion ratio (FCR) and performance efficiency factor (PEF) compared with the CON (p < 0.001, p < 0.01, respectively). The environmental temperature affected daily feed intake (DFI), ADG, FCR, and PEF. The addition of BET improved breast fillets yield, temperature, pH_15min, and pH_24hr (p < 0.05) in comparison with the CON. Moreover, the TN group had lower fillet temperature and higher pH_15min compared to the HT. Moreover, HT increased shear force (SF), hardness, springiness, cohesiveness, and chewiness of the fillets compared to TN. In conclusion, dietary supplementation with BET and NEVO could effectively improve performance parameters and meat characteristics under HS conditions.

Protective effects of dietary synbiotic supplementation on meat quality and oxidative status in broilers under heat stress

This study evaluated protective effects of synbiotic on meat quality and oxidative status of breast muscle in heat-stressed broilers. Twenty 2-day-old broilers were allocated in a 2×2 factorial design, and the main factors consisted of synbiotic level (0 (basal diet) or 1.5 g/kg synbiotic) and temperature (thermoneutral or high temperature), resulting in 4 treatments. From 22 to 42 days, chickens were raised at thermoneutral temperature (22 °C) or subjected to cyclic high temperature (heat stress, HS) by keeping them at 32-33 °C for 8 h and 22 °C for rest 16 h daily. Cyclic HS decreased relative weight, redness (45 min), and pH values (45 min and 24 h) but increased contents of moisture and ether extract, lightness (45 min and 24 h), drip loss (24 h and 48 h), and cooking loss in breast muscle of broilers compared with those under thermoneutral temperature. It also increased malondialdehyde content and mRNA abundances of heat shock protein 70 (HSP70) and HSP90 but decreased glutathione (GSH) concentration and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), as well as mRNA abundances of nuclear factor (erythroid 2)-like 2 (Nrf2), NAD(P)H quinone dehydrogenase 1 (NQO1), GSH-Px, and copper and zinc superoxide dismutase in breast muscle in broilers. Dietary synbiotic supplementation was effective in increasing weight and reducing lightness (45 min), drip loss (24 h and 48 h) and cooking loss of breast muscle in heat-stressed broilers compared with those fed the basal diet. It also reduced malondialdehyde content and HSP70 mRNA abundance and increased GSH-Px activity, GSH content, and mRNA abundances of Nrf2, NQO1 and GSH-Px in breast muscle of heat-stressed broilers. These results suggested that synbiotic supplementation at a level of 1.5 g/kg could ameliorate compromised meat quality and oxidative status in broilers under cyclic HS.

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.

Impact of Dietary Betaine and Metabolizable Energy Levels on Profiles of Proteins and Lipids, Bioenergetics, Peroxidation and Quality of Meat in Japanese Quail

Three different diets were formulated with three levels of metabolizable energy (ME) (optimum; 2900, restricted; 2800 and low; 2700 kcal ME/kg diet) without or with (0 and 0.15%) betaine supplementation in 2 × 3 factorial design to evaluate the effect of six experimental diets on performance, proteins and lipids profiles, bioenergetics, peroxidation and meat quality of Japanese quail. Therefore, 360 quails allocated into six groups in a 23-day experiment. Dietary betaine and ME levels did not affect the performance, meat energy indices (ATP and AMP) and malondialdehyde (MDA) levels of Japanese quail meat. Dietary betaine and/or ME levels induced significant changes in serum triacylglycerol (TAG), total cholesterols (TC), low-density lipoprotein cholesterol (LDL-c), very low-density lipoprotein cholesterol (VLDL-c), meat total lipids and cholesterol of Japanese quail. Optimum and restricted ME levels reduced total volatile basic nitrogen (TVBN) whereas dietary betaine increased ecosapentaenoic (EPA), docosahexaenoic acids (DHA) and glutamine concentrations in breast meat of Japanese quail. Dietary betaine and low energy diet improved cooking loss, thawing loss (ThL) and water holding capacity (WHC) in breast meat of Japanese quail. Conclusively, dietary betaine improved meat quality of Japanese quail fed diets containing either restricted or low ME by enrichments the meat with omega-3 fatty acids and reduction of lipids levels.

Radical Response: Effects of Heat Stress-Induced Oxidative Stress on Lipid Metabolism in the Avian Liver

Lipid metabolism in avian species places unique demands on the liver in comparison to most mammals. The avian liver synthesizes the vast majority of fatty acids that provide energy and support cell membrane synthesis throughout the bird. Egg production intensifies demands to the liver as hepatic lipids are needed to create the yolk. The enzymatic reactions that underlie de novo lipogenesis are energetically demanding and require a precise balance of vitamins and cofactors to proceed efficiently. External stressors such as overnutrition or nutrient deficiency can disrupt this balance and compromise the liver’s ability to support metabolic needs. Heat stress is an increasingly prevalent environmental factor that impairs lipid metabolism in the avian liver. The effects of heat stress-induced oxidative stress on hepatic lipid metabolism are of particular concern in modern commercial chickens due to the threat to global poultry production. Chickens are highly vulnerable to heat stress because of their limited capacity to dissipate heat, high metabolic activity, high internal body temperature, and narrow zone of thermal tolerance. Modern lines of both broiler (meat-type) and layer (egg-type) chickens are especially sensitive to heat stress because of the high rates of mitochondrial metabolism. While this oxidative metabolism supports growth and egg production, it also yields oxidative stress that can damage mitochondria, cellular membranes and proteins, making the birds more vulnerable to other stressors in the environment. Studies to date indicate that oxidative and heat stress interact to disrupt hepatic lipid metabolism and compromise performance and well-being in both broilers and layers. The purpose of this review is to summarize the impact of heat stress-induced oxidative stress on lipid metabolism in the avian liver. Recent advances that shed light on molecular mechanisms and potential nutritional/managerial strategies to counteract the negative effects of heat stress-induced oxidative stress to the avian liver are also integrated.

Effects of supplementation of DL-methionine on tissue and plasma antioxidant status during heat-induced oxidative stress in broilers

Exposure to high ambient temperature has been shown to impair growth performance and to cause oxidative stress in broilers. This study investigated the hypothesis that supplementation with methionine (Met) as DL-Met (DLM) more than the National Research Council recommendations improves growth performance and alleviates oxidative stress in broilers exposed to high ambient temperature. One-day-old male Cobb-500 broilers (n = 68) were allotted to 4 groups and phase-fed 3 basal diets during days 1 to 10, 11 to 21, and 22 to 35. One group was kept under thermoneutral temperature conditions and received the basal diets with Met + cysteine (Cys) concentrations according to recommendations of NRC. The other 3 groups were kept in a room with an increased ambient temperature from week 3 to 5 and were fed either the basal diet or the basal diets supplemented with 2 levels of DLM in which Met + Cys concentrations exceeded NRC recommendations by around 20% (group DLM1) and 40% (group DLM2), respectively. As expected, the broilers exposed to high ambient temperature showed a lower feed intake, lower body weight gains, a higher feed:gain ratio, and biochemical indications of oxidative stress in comparison to broilers kept under thermoneutral temperature conditions. Supplementation of DLM did not improve the growth performance in broilers exposed to high ambient temperature. However, the broilers supplemented with DLM had increased concentrations of glutathione in liver and breast muscle (groups DLM1 and DLM2), increased concentrations of tocopherols in the liver (group DLM2), and reduced concentrations of 7α-hydroxycholesterol and 7-ketocholesterol in heat-processed thigh muscle (groups DLM1 and DLM2) in comparison to the control group exposed to high ambient temperature. Concentrations of thiobarbituric acid-reactive substances and vitamin C in plasma, liver, and muscle were not different between the 3 groups exposed to heat stress. Nevertheless, the study shows that supplementation of DLM in slight excess of the Met concentration required for maximum growth performance improved the antioxidant status in tissues and reduced the susceptibility of muscle toward oxidation in heat-stressed broilers.

Dietary betaine supplementation improves meat quality of transported broilers through altering muscle anaerobic glycolysis and antioxidant capacity

BACKGROUND

To investigate the effect of dietary betaine supplementation on growth performance, meat quality, muscle anaerobic glycolysis and antioxidant capacity of transported broilers, 1-day-old partridge-shank-broiler-chickens (n = 192) were randomly divided into three groups for a 50-day feeding trial. The broilers in the control group were fed a basal diet, and experienced 0.75-h transport before slaughter. The broilers in the other three groups were fed a basal diet supplemented with 0, 500 or 1000 mg kg^-1 betaine, respectively, and experienced 3-h transport before slaughter (T, T + BET₅₀₀ or T + BET₁₀₀₀ groups).

RESULTS

Dietary betaine supplementation increased (P < 0.05) average daily gain of broilers, and feed conversion ratio was also improved (P < 0.05) by 500 mg kg^-1 betaine supplementation. Compared with the control group, 3-h transport increased (P < 0.05) live weight loss, serum corticosterone and cortisol concentrations, as well as muscle lactate and malondialdehyde (MDA) contents, and decreased (P < 0.05) muscle pH_24h , glycogen content and total superoxide dismutase activity. Compared with the T group, betaine supplementation decreased (P < 0.05) serum corticosterone and cortisol concentrations and muscle MDA content, and increased (P < 0.05) muscle a*_24 h . In addition, 1000 mg kg^-1 betaine supplementation further decreased (P < 0.05) muscle drip loss, lactate content and lactate dehydrogenase activity, and increased (P < 0.05) muscle glutathione content and glutathione peroxidase activity.

CONCLUSION

Betaine supplementation not only improved growth performance of broilers, but also alleviated meat quality deterioration of transported broilers through altering muscle anaerobic glycolysis and antioxidant capacity. © 2020 Society of Chemical Industry.

Effects of nicotinamide and sodium butyrate on meat quality and muscle ubiquitination degradation genes in broilers reared at a high stocking density

This study was conducted to investigate the effects of supplementation with nicotinamide (NAM) and sodium butyrate (BA) on meat quality and expression of muscle development genes in broilers reared at a high stocking density. A total of 567, 21-day-old AA broilers were randomly assigned to 5 treatment groups and 2 control groups, with 7 replicates of each group. The control groups included a low stocking density (LD; 12.9 birds/m²) and were fed a basal diet. The treatment groups were kept at a high stocking density (HD; 18.6 birds/m²) and received either a low dose of NAM (50 mg/kg; treatment LN), a high dose of NAM (100 mg/kg; treatment HN), a low dose of BA (500 mg/kg; treatment LB), a high dose of BA (1,000 mg/kg; treatment HB), or a compound supplement (50 mg/kg NAM+500 mg/kg BA; treatment COMB); broilers were reared till 42 D of age. The control groups were kept at HD or at LD (12.9 birds/m²) and were fed a basal diet. The heterophil-to-lymphocyte ratio was significantly higher in the HD control group than that in the LD group; this ratio was significantly lower in treatments LN, HN, HB, and COMB than that in the HD control group. The lightness of breast muscles at 45 min and 24 h after slaughter was significantly higher in the HD group than that in the LD group, and the HD group showed the highest drip loss at 24 h and 48 h. Lightness and drip loss were lower in the HN, LB, and COMB treatments than those in the HD group. HD rearing significantly reduced gene expression of myogenic regulatory factor 5 (MYF5) while significantly increased expression of the protein ubiquitin degradation genes FBXO9, FBXO22, and FBXO32. All treatments significantly reduced FBXO9 and FBXO32 expression. Our results suggest dietary supplementation with NAM and BA can improve meat quality of broilers under high stocking density by upregulating the expression of myogenic genes, and inhibiting protein ubiquitination.

Betaine protects against heat exposure-induced oxidative stress and apoptosis in bovine mammary epithelial cells via regulation of ROS production

Heat stress is one of the wide varieties of factors which cause oxidative stress in vivo; elevated temperature can lead to oxidative stress of dairy cows that affects milk production. The aim of this study was to determine the capacity of the betaine to act as an antioxidant against oxidative stress induced by heat exposure and apoptosis in mammary epithelial cells (mammary alveolar cells, MAC-T). The MAC-T were divided into four treatment groups: control (37 °C), heat stress (HS, 42 °C), betaine (37 °C), and HS + betaine. MAC-T under heat stress (HS) showed increased ROS accumulation, malondialdehyde (MDA) content, superoxide dismutase (SOD) concentration, and catalase (CAT) activity. During heat stress, betaine decreased the mRNA expression level of HSP70 and HSP27 in MAC-T. Bax/Bcl-2 ratio and caspase-3, the markers of apoptosis, were also elevated in MAC-T under heat stress. The markers of oxidative stress Nrf-2/HO-1 genes were also elevated in MAC-T under heat stress. Pretreatment of betaine reversed the heat-induced depletion in total antioxidant status, ROS accumulation, and SOD and CAT contents in MAC-T. Bax/Bcl-2 ratio and Nrf-2/HO-1 expression of heat-exposed MAC-T were also reduced with betaine supplementation. In conclusion, betaine alleviated oxidative stress and apoptosis of MAC-T by inhibiting ROS accumulation.