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Modeling the performance of broilers under heat stress.

ABSTRACT: A meta-analysis was developed to model performance depression in heat stress (HS), to analyze the influence of HS type (cyclic or constant), and to assess the correlation between dietary electrolyte balance (DEB) and HS in broilers. Two databases (Dat) with performance and temperature were constructed (initial phase - up to 21 d of age - 14 articles, 7,667 animals, average replicate number treatment-ARN/T, 5 and growing phase - over 21 d of age - 74 articles and 25,145 broilers, ARN/T, 7). The criteria for article selection were (1) experiments using at least 2 temperatures (thermoneutral and high temperature); (2) results of ADFI and ADG; (3) feed and water ad libitum during the experiment. Each treatment was classified as cyclic or constant HS and the HS group response was calculated relative to the thermoneutral group. Performance was evaluated as raw data or as relativized information (indicated as "HS effect or ≠"), expressed as a percentage of the difference between results. The models to predict "HS effect" showed that for the initial phase, only ADG was influenced by HS, while for the grower phase, prediction equations were created for ADFI and ADG. Considering the simplest models, there was a reduction of 1.4% in ADFI and 2.1% in ADG for each unit (°C) above the upper critical temperature for broilers older than 21 d. Feed conversion (FC) was not affected by HS in any of the studied phases. Constant HS proved to be more negative than cyclic HS to broiler performance after 21 d of age. The relation between DEB and performance of broilers under HS was analyzed considering broilers over 21 d of age, and very weak correlations were observed. It was concluded that HS affects broilers over 21 d more, although FC is not affected. ADFI is the most important variable affected by HS and the relation between the DEB of the diet and HS is very weak. The empirical models generated in this study accurately predicted ADG and ADFI of broilers exposed to HS and can be used to minimize those effects on poultry production.

SUBMITTER: Andretta I

PROVIDER: S-EPMC8350525 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundGlobal warming leading to heat stress (HS) is becoming a major challenge for broiler production. This study aimed to explore the protective effects of seaweed (Enteromorpha prolifera) polysaccharides (EPS) on the intestinal barrier function, microbial ecology, and performance of broilers under HS. A total of 144 yellow-feathered broilers (male, 56 days old) with 682.59 ± 7.38 g were randomly assigned to 3 groups: 1) TN (thermal neutral zone, 23.6 ± 1.8 °C), 2) HS (heat stress, 33.2 ± 1.5 °C for 10 h/d), and 3) HSE (HS + 0.1% EPS). Each group contained 6 replicates with 8 broilers per replicate. The study was conducted for 4 weeks; feed intake and body weights were measured at the end of weeks 2 and 4. At the end of the feeding trial, small intestine samples were collected for histomorphology, antioxidant, secretory immunoglobulin A (sIgA) content, apoptosis, gene and protein expression analysis; cecal contents were also collected for microbiota analysis based on 16S rDNA sequencing.ResultsDietary EPS promoted the average daily gain (ADG) of broilers during 3-4 weeks of HS (P < 0.05). At the end of HS on broilers, the activity of total superoxide dismutase (T-SOD), glutathione S-transferase (GST), and the content of sIgA in jejunum were improved by EPS supplementation (P < 0.05). Besides, dietary EPS reduced the epithelial cell apoptosis of jejunum and ileum in heat-stressed broilers (P < 0.05). Addition of EPS in HS group broilers' diet upregulated the relative mRNA expression of Occludin, ZO-1, γ-GCLc and IL-10 of the jejunum (P < 0.05), whereas downregulated the relative mRNA expression of NF-κB p65, TNF-α and IL-1β of the jejunum (P < 0.05). Dietary EPS increased the protein expression of Occludin and ZO-1, whereas it reduced the protein expression of NF-κB p65 and MLCK (P < 0.01) and tended to decrease the protein expression of TNF-α (P = 0.094) in heat-stressed broilers. Furthermore, the proportions of Bacteroides and Oscillospira among the three groups were positively associated with jejunal apoptosis and pro-inflammatory cytokine expression (P < 0.05) and negatively correlated with jejunal Occludin level (P < 0.05). However, the proportions of Lactobacillus, Barnesiella, Subdoligranulum, Megasphaera, Collinsella, and Blautia among the three groups were positively related to ADG (P < 0.05).ConclusionsEPS can be used as a feed additive in yellow-feathered broilers. It effectively improves growth performance and alleviates HS-induced intestinal injury by relieving inflammatory damage and improving the tight junction proteins expression. These beneficial effects may be related to inhibiting NF-κB/MLCK signaling pathway activation and regulation of cecal microbiota.

Project description:Heat stress (HS) adversely affects several physiological responses in organisms, but the underlying molecular mechanisms involved are yet to be fully understood. L-Citrulline (L-Cit) is a nutraceutical amino acid that is gaining research interest for its role in body temperature regulation and nitric oxide synthesis. This study investigated whether dietary supplementation with L-Cit (1% of basal diet) could ameliorate the effects of acute HS on thermotolerance, redox balance, and inflammatory responses of broilers. Ross 308 broilers (288 chicks) were subjected to two environments; thermoneutral at 24°C (TNZ) or HS at 35°C for 5 h, and fed two diets; control or L-Cit. The results showed that HS increased the ear, rectal (RT), and core body (CBT) temperatures of broilers, along with higher respiratory rate. The RT and CBT readings were intermittently affected with time effect, whereas, L-Cit supplementation lowered the mean CBT than the control diet. Antioxidant assays showed that superoxide dismutase was increased during HS, while, catalase was promoted by L-Cit supplementation. In addition, L-Cit induced glutathione peroxidase activity compared to the control diet during HS. Hypothalamic heat shock protein (HSP)-90 was upregulated by HS, but L-Cit downregulated heat shock factor (HSF)-1, and HSP 60 mRNA expressions. HSF 3 mRNA expression was downregulated by L-Cit under TNZ condition. More so, HS increased the plasma nitric oxide (NO) concentration but lowered the total NO synthase (tNOS) activity. In contrast, L-Cit supplementation limited NO production but increased the tNOS activity. Arginase activity was increased in the control fed group during HS but L-Cit supplementation lowered this effect. The NOS-COX pathway was significantly affected under TNZ condition, since L-Cit supplementation downregulated the mRNA expression of iNOS-COX2 in the hypothalamus, and further reduced the serum PGE2 concentration. Together, these data indicates that L-Cit influenced the antioxidant defense, heat shock response and nitric oxide regeneration both under thermoneutral and HS conditions; and that L-Cit may be directly and/or indirectly involved in the central regulation of body temperature.

Project description:Resveratrol (RSV) is a natural polyphenolic compound with potent antioxidant and anti-inflammatory properties. This study aimed to investigate the protective effects of RSV supplementation on the inflammatory responses of broilers during heat stress. A total of 432 28-d-old white-feathered broilers (817 crossbred chicken) with an average weight of 549 ± 4 g were randomly allotted to 4 equal groups (Half male and half female, 6 replicates/group, 18 chickens/replicate), including normal temperature (NT) group (24 ± 2°C for 24 h/d, basal diet), NT+RSV group (24 ± 2°C for 24 h/d, basal diet + RSV), heat stress (HT) group (37 ± 2°C for 8 h/d, basal diet), and HT+RSV group (37 ± 2°C for 8 h/d, basal diet + RSV). Serum samples were collected on d 7 and 14 of heat stress, and thymus, spleen, jejunum, and bursa of Fabricius samples were collected and analyzed on d14. RSV treatment decreased the feed conversion ratio, partially reversed the negative alternations in body weight, average daily gain, and average daily feed intake caused by heat stress. RSV treatment also decreased the elevated levels of corticosterone on d 14, adrenocorticotropic hormone, and triiodothyronine in serum on d 7 caused by heat stress, and significantly increased the villus height to crypt depth ratio in the jejunum on d 14. Dietary RSV also reduced heat stress-induced splenic pro-inflammatory cytokine concentrations. TUNEL assay showed that RSV significantly reduced heat stress-induced the number of apoptotic cells. Remarkably, RSV down-regulated some splenic related genes for apoptosis genes, including BCL-2, Apaf-1, and MDM2 mRNA levels induced by heat stress. According to GO and KEGG enrichment analyses, the differential genes between HT and HT + RSV groups were mainly associated with immune system process, hematopoietic or lymphoid organ development, and toll-like receptor signaling pathway. The relative mRNA expression of NF-κB, heat shock protein 70 (HSP70), and p38 MAPK were markedly decreased by the combination of RSV and heat stress. These findings showed that RSV might reduce the splenic inflammatory response in heat-stressed white-feather broilers by inhibiting heat stress-induced activation of NF-B, MAPK, and HSP70, as well as inhibiting the activation of mitochondrial apoptotic pathways.

Project description:Global warming and climate changes have a detrimental impact on poultry production, causing substantial economic losses. This study investigated the effects of incorporating dietary betaine (BT) and organic minerals (OMs) on broilers' performance as well as their potential to mitigate the negative impacts of heat stress (HS). Six hundred 1-day-old Ross 308 chicks were randomly allocated to 12 experimental treatments with 5 replicates of 10 birds each (5 male + 5 female). The birds were provided with diets containing BT (0 and 2,000 ppm) and OMs (0, 250, and 500 ppm), either individually or in combination, under both thermoneutral and HS-inducing temperatures. The HS conditions involved exposing the birds to cyclic periods of elevated temperature (35°C ± 2°C) for 6 h daily, from 10:00 am to 4:00 pm, starting from d 10 and continuing until d 35. The exposure to HS deteriorated birds' growth performance; however, dietary BT and OMs inclusion improved the growth performance parameters bringing them close to normal levels. Carcass traits were not affected by dietary supplementation of BT, OMs, HS, or their interaction. Interestingly, while HS led to increased (P < 0.05) levels of total cholesterol, LDL-cholesterol, and hepatic malondialdehyde (MDA), these adverse effects were mitigated (P < 0.05) by the addition of BT and OMs. Moreover, dietary BT supplementation led to elevated serum total protein and globulin concentrations. Cyclic HS did not alter Mn, Zn, and Cu contents in the pectoral muscle. However, the incorporation of OMs at both levels increased concentrations of these minerals. Notably, the combination of 500 ppm OMs and 2,000 ppm BT improved Mn, Zn, Cu, and Fe digestibility, which has been compromised under HS conditions. Cyclic HS upregulated gene expression of interleukin-1β, heat shock protein 70, and Toll-like receptor-4 while downregulated the expression of claudin-1, uncoupling protein, growth hormone receptor, superoxide dismutase 1, glutathione peroxidase 1 and insulin-like growth factor 1. The aforementioned gene expressions were reversed by the combination of higher dietary levels of BT and OMs. In conclusion, the dietary supplementation of 500 ppm OMs along with 2,000 ppm BT yielded significant improvements in growth performance and mineral digestibility among broiler chickens, regardless of thermal conditions. Moreover, this combination effectively restored the expression of growth-related genes even under heat-stress conditions.

Project description:BackgroundModern fast-growing broilers are susceptible to heart failure under heat stress because their relatively small hearts cannot meet increased need of blood pumping. To improve the cardiac tolerance to heat stress in modern broilers through breeding, we need to find the important genes and pathways that contribute to imbalanced cardiac development and frequent occurrence of heat-related heart dysfunction. Two broiler lines - Ross 708 and Illinois - were included in this study as a fast-growing model and a slow-growing model respectively. Each broiler line was separated to two groups at 21 days posthatch. One group was subjected to heat stress treatment in the range of 35-37 °C for 8 h per day, and the other was kept in thermoneutral condition. Body and heart weights were measured at 42 days posthatch, and gene expression in left ventricles were compared between treatments and broiler lines through RNA-seq analysis.ResultsBody weight and normalized heart weight were significantly reduced by heat stress only in Ross broilers. RNA-seq results of 44 genes were validated using Biomark assay. A total of 325 differentially expressed (DE) genes were detected between heat stress and thermoneutral in Ross 708 birds, but only 3 in Illinois broilers. Ingenuity pathway analysis (IPA) predicted dramatic changes in multiple cellular activities especially downregulation of cell cycle. Comparison between two lines showed that cell cycle activity is higher in Ross than Illinois in thermoneutral condition but is decreased under heat stress. Among the significant pathways (P < 0.01) listed for different comparisons, "Mitotic Roles of Polo-like Kinases" is always ranked first.ConclusionsThe increased susceptibility of modern broilers to cardiac dysfunction under heat stress compared to slow-growing broilers could be due to diminished heart capacity related to reduction in relative heart size. The smaller relative heart size in Ross heat stress group than in Ross thermoneutral group is suggested by the transcriptome analysis to be caused by decreased cell cycle activity and increased apoptosis. The DE genes in RNA-seq analysis and significant pathways in IPA provides potential targets for breeding of heat-tolerant broilers with optimized heart function.

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Modeling the performance of broilers under heat stress.

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