Factors affecting adipose tissue development in chickens: A review

Epigallocatechin gallate improves oleic acid-induced hepatic steatosis in laying hen hepatocytes via the MAPK pathway

Fatty liver disease in laying hens, characterized by excessive lipid accumulation in hepatocytes, poses significant challenges to poultry health and production efficiency. In this study, we investigated the therapeutic potential of epigallocatechin gallate (EGCG), a bioactive compound found in green tea, in mitigating oleic acid (OA)-induced hepatic steatosis in primary chicken hepatocytes. Treatment with EGCG effectively attenuated lipid deposition by downregulating lipid synthesis-related genes. Moreover, EGCG mitigated oxidative stress, inflammation, DNA damage, and apoptosis induced by OA, thereby preserving hepatocyte viability. Mechanistically, EGCG exerted its protective effects by modulating the p38 MAPK signaling pathway. Our findings suggest that EGCG holds promise as a therapeutic agent for managing fatty liver disease in poultry, offering insights into novel strategies for improving poultry health and production outcomes.

Research Note: Sexual dimorphic effect of myostatin mutation on fat accumulation in Japanese quail

As an anti-myogenic factor, the myostatin (MSTN) gene was mainly considered as a genetic marker to improve meat production. Moreover, an additional effect of the MSTN mutation on reducing fat deposition in various farm animals suggested a potential application of the MSTN gene on regulating fat deposition in poultry species. Although increase in muscle mass resulted from muscle hyperplasia in the MSTN mutant quail, cellular mechanism behind the decrease in fat deposition was not investigated in the quail model. In the current study, to investigate sexual dimorphic association between fat deposition and Mstn mutation in quail, leg and abdominal fat pads from 4-month-old male and female quail were histologically analyzed. Interestingly, abdominal and leg fat pad weights were significantly decreased by the MSTN mutation only in female quail, but not in male quail, showing sexual dimorphism in regulating fat deposition by the MSTN mutation in quail. Histological analysis also revealed that fat cell sizes of leg and abdominal fats were significantly reduced only in female groups aligning with the decreased fat pad weights. Sexual dimorphic effect of the MSTN mutation on fat cell hypotrophy and reduced fat pad weights in quail provided an important scientific finding to be considered on the usage of the MSTN gene as a genetic marker to reduce fat deposition in poultry species.

Effect of dietary supplementation with sanguinarine on meat quality and lipid metabolism of broilers

Dietary Macleaya cordata extract (MCE) can improve the meat quality of poultry. However, the specific mechanism by which MCE regulates the meat quality has not been clarified yet. Sanguinarine (SAN) is one of the important natural active components in MCE. Our study aims to explore the regulatory mechanism of dietary SAN supplementation on meat quality through transcriptomic and gut microbiome analysis, thereby providing a basis for regularing meat quality with MCE. 240 1-day-old broilers were divided into 4 groups according to different doses of SAN (0, 0.225, 0.75, and 2.25 mg/kg). The results indicated that SAN significantly improve the physicochemical quality indicators of breast and thigh muscle in broilers, improved the serum biochemical indexes. Through transcriptome sequencing analysis of the liver and ileum tissues of broilers, we found that the differentially expressed genes induced by SAN were mainly enriched in lipid metabolism, which were related to the peroxisome proliferator-activated receptor (PPAR) pathway. It reconfirmed that SAN can regulate lipid metabolism in the body by promoting the expression of genes related to cholesterol metabolism, fatty acid transport and oxidation by RT-PCR, this ultimately affects the physicochemical quality of muscle. Additionally, through 16S rRNA sequencing analysis, we found that dietary addition of SAN increased the relative abundance of Bacteroides, Lactobacillus and unclassified_f_Lachnospiraceae, while decreased the relative abundance of Alistipes in ceca. To further investigate the impact of gut microbiota on lipid metabolism, we conducted a correlation analysis of PPAR pathway factor expression in cecum tissue and microflora structure. The results showed that Bacteroides exhibited a positive correlation with the expression of most genes in the PPAR signaling pathway. Unclassified_f__Lachnospiraceae is positively correlated with PPARγ, Cytochrome P450 family 7 subfamily A member 1 (CYP7A1) and Acyl-CoA synthetase long-chain family member 5 (ACSL5). In conclusion, dietary addition of SAN can promote the genes expression of the PPAR pathway, target the regulation of intestinal microflora structure and abundance and regulate lipid metabolism, thereby improving meat quality of broilers.

Effect of energy level of pullet diet and age on laying performance and expression of hypothalamus-pituitary-gonadal related genes in laying hens

Dietary energy density influences feed intake (FI) and development of layer-type pullets. A total of 384 nine-wk-old Hy-Line Brown pullets were randomly assigned to one of 3 dietary treatments: fed a diet with 2,600, 2,750, and 2,900 Kcal metabolizable energy/kg (ME/kg) from 10 to 21 wk of age. The results showed that the 2,900 and 2,600 ME groups had lower feed and ME intake (P < 0.01) from 10 to 21 wk of age. The 2,600 ME pullets had heavier body weight (BW) and longer shank length (P < 0.05) at 21 wk of age than the 2,750 ME group. The eggshell percentage was increased by the 2,600 and 2,900 kcal/kg treatments (P = 0.002). Serum concentration of 17-β-estradiol (E2), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) decreased at 70 wk of age (P < 0.05). Pullet diet and its interaction with age had a significant influence (P < 0.001) on the expression of gonadotropin-releasing hormone 1 (GnRH-1) and gonadotropin-inhibitory hormone (GnIH) in the hypothalamus and of gonadotropin releasing hormone 1 receptor (GnRH-1R) and gonadotropin-inhibitory hormone receptor (GnIHR) in the pituitary. In the hypothalamus, GnRH-1 expression increased from 9 to 40 wk of age and then decreased; however, GnIH expression was highest at 70 wk of age. Follicle-stimulating hormone receptor (FSHR) expression increased (P < 0.001) at wk 40 and decreased at wk 70 compared to wk 21 at various follicular stages. In conclusion, the energy level of pullet diet had no unfavorable influence on feed intake, laying rate, egg mass, and FCR, whereas change egg weight and mortality during the laying period from 21 to 70 wk of age. during the laying period. These results suggest that pullet dietary energy can activate the expression of genes related to reproduction in the hypothalamus, whereas it plays a minor role in the regulation of genes in the pituitary and ovary. Age-induced gene expression in the hypothalamus-pituitary-gonadal (HPG) axis is associated with laying performance in hens.

Integrated Lipidomics and Transcriptomics Analyses Reveal Key Regulators of Fat Deposition in Different Adipose Tissues of Geese (Anser cygnoides)

The fat deposition of different adipose tissues is widely recognized as correlated, with distinct effects on meat quality traits and reproductive performance in poultry. In this study, we utilized lipidomics and transcriptomics analyses to investigate the heterogeneity and regulators of intramuscular fat (IMF), abdominal fat (AF), and subcutaneous fat (SF) in geese. Lipidomic profiling revealed 165, 129, and 77 differential lipid molecules (DLMs) between AF vs. IMF, SF vs. IMF, and SF vs. AF, respectively, with 47 common DLMs identified between AF vs. IMF and SF vs. IMF. Transcriptomic analysis identified 3369, 5758, and 131 differentially expressed genes (DEGs) between AF vs. IMF, SF vs. IMF, and SF vs. AF, respectively, with 2510 common DEGs identified between AF vs. IMF and SF vs. IMF. The KEGG results indicate that DLMs were predominantly enriched in glycerophospholipid and glycerolipid metabolism pathways, while DEGs were primarily enriched in metabolic pathways. Pearson correlation analysis identified FABP4, LPL, PLCB1, DSE, and PDE5A as potential factors influencing fat deposition. This study elucidates the heterogeneity and regulatory factors of different adipose tissues in geese, offering new insights for targeted improvements in goose meat quality and production efficiency.

Glucagon-like peptide-1 analog liraglutide reduces fat deposition in chicken adipocytes

Previously, we reported that glucagon-like peptide-1 (GLP-1) and its analog liraglutide could inhibit fat de novo synthesis in the liver and reduce abdominal fat accumulation in broiler chickens. Nevertheless, the impact of GLP-1 on adipocyte fat deposition remains enigmatic. This study aimed to investigate the effects of GLP-1, via its analog liraglutide, on chicken chicken adipocytes in vitro. Chemical assays, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot were employed to assess the proliferation, differentiation, and fat deposition of chicken adipocytes. Our findings indicated that liraglutide significantly suppressed cell proliferation and promoted preadipocyte differentiation in comparison to the control group. This was evidenced by elevated triglyceride (TG) content and upregulated mRNA expression of lipogenesis-related enzymes, such as acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), as well as regulators including peroxisome proliferator-activated receptor γ (PPARγ), sterol regulatory element binding protein-1 (SREBP1) and CCAAT/enhancer binding protein α (CEBPα). In mature adipocytes, liraglutide attenuated fat deposition by inhibiting fat de novo synthesis, evidenced by decreased mRNA expression of ACC, FAS, PPARγ, C/EBPα, and SREBP1, and concurrent upregulation of phosphorylated AMP-activated protein kinase (p-AMPK) and phosphorylated ACC (p-ACC). This resulted in reduced accumulation of lipid droplets and TG content in mature adipocytes. Collectively, our findings indicate that liraglutide suppresses the proliferation of preadipocytes, enhances their differentiation, and concurrently inhibits de novo lipogenesis in mature adipocytes. This observation offers profound insights into the mechanisms that underlie liraglutide's anti-adipogenic effects, which could have significant implications for the treatment of obesity in broiler chickens.

Effects of finisher diet nutrients density and slaughter age on energy and protein efficiency, productive and economic performance and meat quality of broilers

BACKGROUND

The current broilers have been greatly optimized for weight gain and breast yield, which necessitates the provision of nutrients-dense diets for maximum potential.

OBJECTIVES

The current study aimed to evaluate the effect of finisher diet nutrients density (ND) on energy and protein efficiency, productive and economic performance and breast meat quality of broilers raised until different slaughter age.

METHODS

A total of 600 23-day-old broiler male chicks (Cobb-500) were assigned to 10 treatments with six replicates and 10 birds each. Experimental treatments were included factorial arrangement of five increment (2.5%) levels of finisher diet ND (92.5%, 95%, 97.5%, 100% and 102.5% as strain recommendation) and slaughtered at 38 or 46 days of age. The relative difference in the energy level of experimental diets was used to increase ND levels at the same ratio.

RESULTS

Feed intake (FI) and breast meat quality traits exception water holding capacity (WHC) were not affected by finisher diet ND. In response to increasing finisher diet ND, energy and protein efficiency, productive traits, bio-economic index (BEI) and breast relative weight (BRW) linearly improved. However, residual feed intake and breast meat WHC improved with a quadratic trend. By using broken-line regression analysis, the optimum dietary ND was obtained at 97.5%-102% of strain recommendation. Energy and protein efficiency, feed conversion ratio and BEI deteriorated by prolonging rearing period. The BRW, meat lightness (L*), redness (a*), hue angle (h*) and WHC values for the birds slaughtered at 46 days of age were significantly higher, and cooking loss was lower than those slaughtered at 38 days old.

CONCLUSIONS

Broilers during the finisher period are not able to regulate their FIs with diet ND. The energy and protein efficiency, productive and economic performance were reduced when broilers were fed diluted diet or the rearing period was prolonged.

Functional oil in the feeding of heat-stressed Japanese quail

The objective of the present study was to evaluate a blend of functional oils (FO) composed of copaiba and garlic essential oils, pepper oleoresin and cashew nut liquid to mitigate the effects of heat stress on productivity, egg quality, organ morphology of the gastrointestinal tract, serum biochemical profile, nutrient metabolism and body temperature of Japanese quail. A completely randomized design was used in a 3 × 2 factorial scheme (without additive; 300 and 500 mg FO/kg of feed x birds raised in a thermal comfort (TC) and heat stress (HS) environment), with 6 replicates of 8 birds per plot. The birds under HS had lower feed intake (P = 0.0000), egg mass (P = 0.0000), laying rate (P = 0.0000) and higher percentage of infertile non-commercial eggs (P = 0.0004), lower head temperature amplitude (P = 0.0000) and higher average of body temperature (P = 0.0312). HS worsened the external and internal quality of the eggs. Birds kept in HS showed higher values of cholesterol (P = 0.0000) and glutamic-pyruvic transaminase (P = 0.0272). The use of 300 and 500 g FO/ton of feed improved the feed conversion (P = 0.0000) and egg mass (P = 0.0000) of the quail bred under HS, respectively, by 8.4 and 7.2% and increased the relative weight of liver (P = 0.0064) and pancreas (P = 0.0492). The use of such additives also provided a higher % of yolk (P = 0.0018) and reduced the percentage of albumen (P = 0.0029) of the eggs produced in TC, in addition to reducing the amplitude of head temperature (P = 0.0484) of birds bred under HS. The breeding of Japanese quail under HS results in negative impacts on the production, physiological and qualitative aspects of the eggs. The use of 300 g/ton of FO in the diet of Japanese quail leads to improvements in feed conversion, increased liver capacity in nutritional metabolism and results in eggs with a higher proportion of yolks, being, therefore, an alternative for feeding quail in a hot climate.

Antioxidant and antihyperlipidemic effects of hawthorn extract (Crataegus oxyacantha) in broiler chickens

BACKGROUND

One of the main problems in the poultry industry is excess body fat, and the anti-fat effect of Cratagus extract has been confirmed in several studies.

OBJECTIVES

The present study was carried out to investigate the effects of hawthorn extract (Crataegus oxyacantha) on growth performance, haematological variables and hepatic gene expression in broiler chickens reared at high altitude (2100 m).

METHODS

A total of 225-day-old chicks (Ross 308) were randomly distributed into three treatments. Experimental treatments were prepared by adding 0.0, 0.2 and 0.4 mL of hawthorn extract per litre of consumption of water.

RESULTS

The results showed that weight gain and feed conversion ratio were significantly improved and abdominal fat decreased by consumption of two levels of Crateagus extract when compared to the control (p < 0.05). Consumption of hawthorn extract decreased circulatory levels of malondialdehyde, triacylglycerol, total cholesterol and low-density lipoproteins cholesterol but increased ferric reducing antioxidant power and high-density lipoproteins cholesterol (p < 0.05). Hawthorn extract caused an up-regulation of catalase, superoxide dismutase1, glutathione peroxidase1 and peroxisome proliferator-activated receptor alpha but reduced the expression of key lipogenic enzymes (p < 0.05).

CONCLUSIONS

Overall, consumption of 0.4 mL hawthorn extract per litre of drinking water, improved growth performance, suppressed lipogenesis and enhanced antioxidant response.

Identification of key differentially methylated genes in regulating muscle development and intramuscular fat deposition in chickens

Muscle development and intramuscular fat (IMF) deposition are intricate physiological processes characterized by multiple gene expressions and interactions. In this research, the phenotypic variations in the breast muscle of Jingyuan chickens were examined at three different time points: 42, 126, and 180 days old. Differential expression analysis and weighted gene co-expression network analysis (WGCNA) were performed to identify differentially methylated genes (DMGs) responsible for regulating muscle development and IMF deposition. The findings indicate a significant increase in breast muscle weight (BMW), myofiber diameter, and cross-sectional area, as well as IMF content, in correlation with the progressive number of growing days in Jingyuan chickens. The findings also revealed that 380 hypo-methylated and 253 hyper-methylated DMGs were identified between the three groups of breast muscle. Module gene and DMG association analysis identified m6A methylation-mediated multiple DMGs associated with muscle development and fat metabolism. In vitro cell modeling analysis reveals stage-specific differences in the expression of CUBN, MEGF10, BOP1, and BMPR2 during the differentiation of myoblasts and intramuscular preadipocytes. Cycloleucine treatment significantly inhibited the expression levels of CUBN, BOP1, and BMPR2, and promoted the expression of MEGF10. These results suggest that m6A methylation-mediated CUBN, MEGF10, BOP1, and BMPR2 can serve as potential candidate genes for regulating muscle development and IMF deposition, and provide an important theoretical basis for further investigation of the functional mechanism of m6A modification involved in adipogenesis.

Transcriptional regulatory mechanism of NR2F2 and ZNF423 in avian preadipocyte differentiation

In the poultry industry, excessive abdominal fat deposition is not conducive to meat quality. Therefore, selection for optimal fat content levels in poultry has become a major breeding goal. We previously constructed NR2F2 overexpression (NR2F2OE) and knockout (NR2F2Δ/Δ/83-125aa) cell lines using Piggybac and CRISPR/Cas9 techniques, and confirmed that the transcription factor NR2F2 can significantly inhibit the differentiation of avian preadipocytes. In this study, we identified a downstream gene ZNF423 regulated by NR2F2, which is also involved in regulating avian fat deposition. First, we performed transcriptome analysis of the NR2F2-edited lines, which has been proven to be an inhibitor of avian fat deposition in our previous studies. Our findings revealed that NR2F2 affects a series of candidate regulators related to adipogenesis. Among these, we focused on ZNF423, which was significantly down-regulated in the NR2F2OE cell line and up-regulated in the NR2F2Δ/Δ/83-125aa cell line. Next, dual luciferase reporter assay results showed that the DNA-binding domain (DBDΔ72-143aa) of transcription factor NR2F2 may negatively affect the expression of downstream target gene ZNF423 by binding to its distal promoter region (-2356 to -2346). Moreover, we constructed a function analytical model and found that overexpression of ZNF423 significantly facilitated the differentiation of adipocytes in immortalized chicken preadipocytes (ICP1). Consistent with these findings, global transcriptome analysis of the ZNF423-overexpressed cell line (ZNF423OE) further demonstrated that the process of adipogenesis was significantly enriched. These results indicate that ZNF423 is a positive regulator of avian adipocyte differentiation. Overexpression of ZNF423 in the NR2F2OE cell line compensated for the inhibition of fat deposition phenotype, further suggesting that ZNF423 is a downstream target gene of NR2F2. These findings uncover a novel function of ZNF423 in avian adipocyte differentiation and analyzed the transcriptional regulation by its upstream transcription factor NR2F2. Additionally, we identified a list of functional candidate genes, providing important insights for further research on the mechanism of avian fat deposition.

Fecal microbiota transplantation revealed the function of folic acid on reducing abdominal fat deposition in broiler chickens mediated by gut microbiota

Excess abdominal fat reduces carcass yield and feed conversion ratio, thereby resulting in significant economic losses in the poultry industry. Our previous study demonstrated that dietary addition of folic acid reduced fat deposition and changed gut microbiota and short-chain fatty acid. However, whether folic acid regulating abdominal fat deposition was mediated by gut microbiota was unclear. A total of 210 one-day-old broiler chickens were divided into 3 groups including the control (CON), folic acid (FA), and fecal microbiota transplantation (FMT) groups. From 14th day, broiler chickens in CON and FA groups were given perfusion administration with 1 mL diluent daily, while 1 mL fecal microbiota transplantation suspension from FA group prepared before was perfusion in FMT group receiving control diets. The result showed that abdominal fat percentage was significantly lower in FA and FMT groups when compared with CON group (P < 0.05). Morphology analysis revealed that the villus height of jejunum and ileum were significantly higher in FMT group (P < 0.05), and the villus height of jejunum was also significantly higher in FA group (P < 0.05), while the diameter and cross-sectional area (CSA) of adipocytes were significantly decreased in FA and FMT groups when compared with CON group (P < 0.05). Western blot results indicated that the expression levels of FOXO1 and PLIN1 in FMT group were significantly increased (P < 0.05), whereas the expression levels of PPARγ, C/EBPα, and FABP4 were significantly decreased (P < 0.05). Additionally, the Chao1, Observed-species, Shannon and Simpson indexes in FA and FMT groups were significantly higher (P < 0.05), but the microbiota were similar between FMT and FA groups (P < 0.05). LEfSe analysis determined that Lactobacillus, Clostridium and Dehalobacterium were found to be predominant in FA group, while Oscillospira, Shigella, and Streptococcus were the dominant microflora in FMT group. Furthermore, these cecal microbiota were mostly involved in infectious disease, cellular community prokaryotes, cell motility and signal transduction in FA group (P < 0.05), whereas functional capacities involved in signal transduction, cell motility, infectious disease and environment adaptation were enriched significantly of cecal microbiota in FMT group (P < 0.05). In summary, both fecal microbiota transplantation from the broiler chickens of dietary added folic acid and dietary folic acid addition effectively reduced abdominal fat deposition, indicating that the regulatory effect of folic acid on abdominal fat deposition was mediated partly by gut microbiota in broiler chickens.

Performance, fatty acid composition, and liver fatty acid metabolism markers of broilers fed genetically modified soybean DP-3Ø5423-1

Several genetically modified (GM) plants have been produced and approved by regulatory agencies worldwide for cultivation and commercialization. Soybean and its by-products are major components of poultry diets and approximately 74% of world production is obtained from GM soybean events. The aim of this study was to evaluate the nutrient composition of DP-3Ø5423-1 extruded full-fat soybean meal (FFSBM) and near isoline non-GM control FFSBM included in broiler diets. Also assessed were their effects on bird performance, body composition, intestinal morphology, tissue fatty acid profile, and mRNA abundance of fatty acid metabolism markers. A total of 480 Ross 308 d of hatch birds were randomly allocated to 24 floor pens in a 2 × 2 factorial arrangement with diet and gender as main factors. Birds were fed diets containing 20% of either DP-3Ø5423-1 or control FFSBM for 35 d. Data were subjected to a 2-way ANOVA using the GLM procedure of JMP (Pro13). No significant interaction (P > 0.05) was observed between treatment groups in terms of performance and carcass composition. Morphological measurements of the jejunum and ileum were not influenced by the SBM treatments. Dietary addition of the DP-3Ø5423-1 FFSBM resulted in higher monounsaturated fatty acid composition of the thigh muscle and abdominal fat. Moreover, dietary treatment had no significant impact on the mRNA abundance of metabolic markers ACCα, FAS, MTTP, SREBP1, PPARα, PPARγ, AMPK-α1, SOD, CAT, and GPx in the liver. In conclusion, our results showed that DP-3Ø5423-1 extruded FFSBM is nutritionally equivalent to non-GM near-isoline counterpart with a comparable genetic background as evidenced by feed analyses except for fatty acid composition. Furthermore, the findings of this study clearly indicate that the examined DP-3Ø5423-1 FFSBM yields similar bird performance as conventional FFSBM.

RNA sequencing identifies key genes involved in intramuscular fat deposition in chickens at different developmental stages

BACKGROUND

Intramuscular fat (IMF) is an important factor in meat quality, and triglyceride (TG) and Phospholipids (PLIP), as the main components of IMF, are of great significance to the improvement of meat quality.

RESULTS

In this study, we used 30 RNA sequences generated from the transcriptome of chicken breast muscle tissues at different developmental stages to construct a gene expression matrix to map RNA sequence reads to the chicken genome and identify the transcript of origin. We used weighted gene co-expression network analysis (WGCNA) and identified 27 co-expression modules, 10 of which were related to TG and PLIP. We identified 150 highly-connected hub genes related to TG and PLIP, respectively, which were found to be mainly enriched in the adipocytokine signaling pathway, MAPK signaling pathway, mTOR signaling pathway, FoxO signaling pathway, and TGF-beta signaling pathway. Additionally, using the BioMart database, we identified 134 and 145 candidate genes related to fat development in the TG-related module and PLIP-related module, respectively. Among them, RPS6KB1, BRCA1, CDK1, RPS3, PPARGC1A, ACSL1, NDUFAB1, NDUFA9, ATP5B and PRKAG2 were identified as candidate genes related to fat development and highly-connected hub genes in the module, suggesting that these ten genes may be important candidate genes affecting IMF deposition.

CONCLUSIONS

RPS6KB1, BRCA1, CDK1, RPS3, PPARGC1A, ACSL1, NDUFAB1, NDUFA9, ATP5B and PRKAG2 may be important candidate genes affecting IMF deposition. The purpose of this study was to identify the co-expressed gene modules related to chicken IMF deposition using WGCNA and determine key genes related to IMF deposition, so as to lay a foundation for further research on the molecular regulation mechanism underlying chicken fat deposition.

NOTCH1 as a Negative Regulator of Avian Adipocyte Differentiation: Implications for Fat Deposition

The NOTCH signaling pathway plays a pivotal role in diverse developmental processes, including cell proliferation and differentiation. In this study, we investigated whether this signaling molecules also contribute to avian adipogenesis. Using previous mRNA-seq datasets, we examined the expression of 11 signaling members during avian adipocyte differentiation. We found most members are down-regulated throughout differentiation (p < 0.05). As a representative, NOTCH1 was decreased in cultured chicken abdominal adipocytes during adipogenesis at mRNA and protein levels (p < 0.05). Moreover, using an overexpression plasmid for NOTCH1's intracellular domain (NICD1), as well as siRNA and DAPT to activate or deplete NOTCH1 in cells, we investigated the role of NOTCH1 in avian adipogenesis. Our findings illuminate that NOTCH1 activates the expression of HES1 and SOCS3 while it decreases NR2F2 and NUMB (p < 0.05), as well as inhibits oleic acid-induced adipocyte differentiation (p < 0.01). We further demonstrate that HES1, a downstream transcription factor activated by NOTCH1, also significantly inhibits adipogenesis by suppressing PPARγ and C/EBPα (p < 0.01). Collectively, these findings establish NOTCH1 as a negative regulator of avian adipocyte differentiation, unveiling NOTCH signaling as a potential target for regulating avian fat deposition.

Stress-Related Gene Expression in Liver Tissues from Laying Hens Housed in Conventional Cage and Cage-Free Systems in the Tropics

Global egg production is mainly based on cage systems, which have been associated with negative effects on the welfare of birds. Stress factors in restrictive production systems can lead to changes in gene transcription and protein synthesis, ultimately impacting the quality of poultry products. The liver serves various metabolic functions, such as glycogen storage, and plays a crucial role in animals' adaptation to environmental changes. Consequently, both internal and external conditions can influence liver functions. The aim of this study was to evaluate the gene expression of AGP, CRP, NOX4, SOD1, CAT, GPX1, SREBF1, and FXR in the liver of laying hens under two different production systems. Liver tissues from Hy-Line Brown hens housed in conventional cage and cage-free egg production systems at 60 and 80 weeks of production were used. mRNA transcript levels were determined by qPCR using the relative quantification method and ACTB as the reference gene. AGP, SOD1, and SREBF1 gene expressions were significantly higher in the conventional cage group at the 60 weeks of production. Furthermore, the mRNA levels of transcripts related to oxidative stress and lipid metabolism were higher in the group of laying hens housed in conventional cages compared to those in cage-free systems. These results suggest differential gene expression of genes related to oxidative stress in liver tissues from hens housed in conventional cages compared to cage-free systems. The conditions of the egg production system can impact the gene expression of oxidative stress and lipid synthesis genes, potentially leading to changes in the metabolism and performance of hens, including egg quality.

The effect of diet density on allometry in pullet growth and early egg production

Understanding the effect of nutrition on pullet growth curves and body composition may help to design new feeding strategies that influence body composition and (long-term) laying performance. Therefore, this study examined the effect of nutrient density (low, medium or high metabolizable energy and essential amino acids), fed in the rearing phase until 17 wk of age, on Hy-Line white W80 pullet growth, body composition development and egg production performance until wk 35. Data were subjected to mixed model analyses. To determine a multiphasic allometric relationship between body components, an overall growth curve was established and inflection points were determined. The linear higher BW at the end of the rearing phase, due to increased diet density, was maintained during the peak production phase until wk 35. Egg production parameters were not affected by rearing diet density. Breast and body crude protein percentages were not influenced by dietary treatments, whereas body crude fat and abdominal fat pad percentages were linearly increased with diet density from early age onward. Body crude protein was initially deposited at the same rate as body dry matter. In a second phase of growth from wk 12 onward, crude protein deposition was lower than body dry matter deposition, but was not influenced by rearing diet. Body crude fat, on the other hand, initially grew at a lower rate than body dry matter, but increased in deposition rate during a second phase of growth starting at wk 2 to 5. Pullets fed the high density diet showed higher deposition of crude fat vs. dry matter as compared to pullets fed the medium density diets in the first phase until wk 2, but exhibited lower crude fat deposition in the second phase until wk 8. These results indicate that until approximately wk 12, crude protein deposition was mainly driving growth and was not influenced by diet density. From wk 5 to 6 onward, crude fat deposition relative to protein deposition increased and this was influenced by diet density from an early age.

Investigation of seasonal changes in lipid synthesis and metabolism-related genes in the oviduct of Chinese brown frog (<em>Rana dybowskii</em>)

A peculiar physiological characteristic of the Chinese brown frog (Rana dybowskii) is that its oviduct dilates during pre-brumation rather than during the breeding season. This research aimed to examine the expression of genes connected with lipid synthesis and metabolism in the oviduct of R. dybowskii during both the breeding season and pre-brumation. We observed significant changes in the weight and size of the oviduct between the breeding season and pre-brumation. Furthermore, compared to the breeding season, pre-brumation exhibited significantly lower triglyceride content and a marked increase in free fatty acid content. Immunohistochemical results revealed the spatial distribution of triglyceride synthase (Dgat1), triglyceride hydrolase (Lpl and Hsl), fatty acid synthase (Fasn), and fatty acid oxidases (Cpt1a, Acadl, and Hadh) in oviductal glandular cells and epithelial cells during both the breeding season and pre-brumation. While the mRNA levels of triglycerides and free fatty acid synthesis genes (dgat1 and fasn) did not show a significant difference between the breeding season and pre-brumation, the mRNA levels of genes involved in triglycerides and free fatty acid metabolism (lpl, cpt1a, acadl, acox and hadh) were considerably higher during pre-brumation. Furthermore, the R. dybowskii oviduct's transcriptomic and metabolomic data confirmed differential expression of genes and metabolites enriched in lipid metabolism signaling pathways during both the breeding season and pre-brumation. Overall, these results suggest that alterations in lipid synthesis and metabolism during pre-brumation may potentially influence the expanding size of the oviduct, contributing to the successful overwintering of R. dybowskii.

Age-Related Changes in Hepatic Lipid Metabolism and Abdominal Adipose Deposition in Yellow-Feathered Broilers Aged from 1 to 56 Days

The objective of this study was to evaluate the age-related changes in hepatic lipid metabolism, adipocyte hyperplasia, hypertrophy, and lipid metabolism in the abdominal adipose tissue of yellow-feathered broilers. Blood, liver, and abdominal adipose samples were collected on days 1, 7, 14, 21, 28, 35, 42, 49, and 56. Body, liver, and abdominal weight increased (p < 0.05) with age-related changes. The triacylglycerol content peaked on day 14, and total cholesterol content peaked on day 56. The adipocyte diameter and area peaked on day 56, and total DNA content peaked on day 7. The age-related changes in hepatic lipogenesis-related gene (ChREBP, SREBP-1c, ACC, FAS, SCD1) expression mainly occurred during days 1 to 21, hepatic lipolysis-related gene (CPT1, LPL, ApoB) expression mainly occurred during days 1 to 14, and abdominal adipose-deposition-related gene (PPARα, CPT1, LPL, PPARγ, C/EBPβ) expression occurred during days 1 to 14. These results demonstrated a dynamic pattern of hepatic lipid metabolism and abdominal adipose deposition in yellow-feathered broilers, which provides practical strategies to regulate hepatic lipid metabolism and reduce abdominal adipose deposition in yellow-feathered broilers.

Genomic Insights into Molecular Regulation Mechanisms of Intramuscular Fat Deposition in Chicken

Intramuscular fat (IMF) plays an important role in the tenderness, water-holding capacity, and flavor of chicken meat, which directly affect meat quality. In recent years, regulatory mechanisms underlying IMF deposition and the development of effective molecular markers have been hot topics in poultry genetic breeding. Therefore, this review focuses on the current understanding of regulatory mechanisms underlying IMF deposition in chickens, which were identified by multiple genomic approaches, including genome-wide association studies, whole transcriptome sequencing, proteome sequencing, single-cell RNA sequencing (scRNA-seq), high-throughput chromosome conformation capture (HiC), DNA methylation sequencing, and m6A methylation sequencing. This review comprehensively and systematically describes genetic and epigenetic factors associated with IMF deposition, which provides a fundamental resource for biomarkers of IMF deposition and provides promising applications for genetic improvement of meat quality in chicken.

Effect of dietary betaine supplementation on the liver transcriptome profile in broiler chickens under heat stress conditions

OBJECTIVE

The objective of the present study was to investigate the effect of dietary betaine (BT) supplementation on the hepatic transcriptome profiles in broiler chickens raised under heat stress (HS) conditions.

METHODS

A total of 180 (21-d-old) Ross 308 male broiler chicks were allotted to 1 of 3 treatment groups with 6 replicated cages in a completely randomized design. One group was kept under thermoneutral conditions at all times and was fed a basal diet (PC). Other 2 groups were exposed to a cyclic heat stress condition. One of the 2 groups under heat stress conditions was fed the basal diet as a negative control (NC), whereas the other group was fed the basal diet supplemented with 0.2% BT. All chickens were provided with diets and water ad libitum for 21 d. Following the experiment, the liver samples were collected for RNA sequencing analysis.

RESULTS

Broiler chickens in NC and BT group had decreased (p<0.05) growth performance. In the transcriptome analysis, the number of differentially expressed genes were identified in the liver by HS conditions and dietary BT supplementation. In the comparison between NC and PC treatments, genes related to energy and nucleic acid metabolism, amino acid metabolism, and immune system were altered by HS, which support the reason why heat-stressed poultry had decreased growth performance. In the comparison between NC and BT treatments, genes related to lipid metabolism, carbohydrate metabolism, and immune system were differently expressed under HS conditions.

CONCLUSION

HS negatively impacts various physiological processes, including DNA replication, metabolism of amino acids, lipids, and carbohydrates, and cell cycle progression in broiler chickens. Dietary BT supplementation, however, offers potential counteractive effects by modulating liver function, facilitating gluconeogenesis, and enhancing immune systems. These findings provide a basis for understanding molecular responses by HS and the possible benefits of dietary BT supplementation in broiler chickens exposed to HS.

Comparative effects of medium-chain fatty acids or phytobiotics-based feed additives on performance, caecum microbiota, volatile fatty acid production and intestinal morphology of broilers

Antibiotic growth promoters have been utilized in broiler nutrition to alleviate the negative effects of the pathogenic microbes to promote performance. However, after the prohibition of antibiotics because of the increasing disclosure related to public health issues, various products have been developed as alternatives. This study was carried out to determine the effects of medium-chain fatty acids (MCFAs) or phytobiotics (essential oils [EOs] and alkaloids [ALKs]), blended feed additives on the growth performance, jejunum histomorphology, and cecal microbiota of broiler chickens. A total of 765 male Ross 308 chicks were randomly distributed into 5 experimental groups, each having 9 replicates with 17 chicks. The experimental procedures were as follows: a control group without supplementation (T1); control group+ MCFAs and EOs blend (T2); control group+ different EOs blend (T3); control group+ ALK sanguinarine (T4); and control group+ EOs and ALK piperine mixture (T5). The results showed that, broilers fed with MCFAs blended with EOs had significantly greater body weight gain during overall period in comparision to the control and T3 groups. Further, only MCFAs blended with EOs group significantly improved jejnum morphology in comparison with the control group (p ≤ 0.05). Besides, the MCFAs blended with EOs group significantly elevated propionate, acetate and butyrate concentration, and decreased the concentration of branch chain fatty acids in caecum (p ≤ 0.05). The results indicated that, the combination of MCFAs and EOs seems to have improvement effects and could be preferred as an efficient feed additive in broiler production.

Age-associated changes in the growth development of abdominal fat and their correlations with cecal gut microbiota in broiler chickens

Excess abdominal fat is a common phenomenon in broiler chickens. Gut microbiota could regulate lipid metabolism through their effects on short-chain fatty acids (SCFAs) production. This study was conducted to investigate the potential relationship between abdominal fat development and cecal microorganism populations. Abdominal fat and cecum contents were collected at 3, 7, 14, 21, 28, 35, and 42 d of age. The results showed that abdominal fat weight increased with age. The abdominal fat percentage was higher between 7 and 21 d of age than at 3 d (P < 0.05), and it increased again at 28 to 42 d (P < 0.05). Morphological analysis showed that adipocyte diameter and cross-sectional area (CSA) increased significantly after 14 d of age (P < 0.05). Moreover, gut microbiota analysis indicated that the Chao1 and Shannon indices were higher between 14 and 28 d than at 3 d of age (P < 0.05). Furthermore, LEfse analysis revealed that Faecalibacterium, Anaerotruncus, Anaeroplasma, Subdoligranulum, and Clostridium emerged to become dominant at 14 d. A greater abundance of Bacteroides, Ruminococcus, Dehalobacterium, and Lactobacillus were determined at 28 d when compared with 14 d of age. Parabacteroides, Ochrobactrum, Lactobacillus, Blautia, Alistipes, Dehalobacterium, Odoribacter, and Suuterella were found to be predominant at 42 d. PICRUSt analysis revealed that amino acid metabolism, lipid metabolism, and terpenoids and polyketides metabolism were elevated at 14 d; the immune and digestive systems were significantly developed at 28 d. In addition, cecum propionic acid and butyric acid contents gradually increased (P < 0.05), while the isobutyric acid contents gradually decreased with advancing age (P < 0.05). Correlation analysis among SCFAs, differential genera and abdominal fat suggested that Coprobacillus, Shigella, and Butyricicoccus had negative correlations with propionic acid, butyric acid, and abdominal fat weight, but positive correlations with isobutyric acid. Isobutyric acid was identified as being negatively associated with abdominal fat weight, while the reverse was found for propionic acid and butyric acid. In conclusion, abdominal fat development is correlated with the emergence of specific microbes and d 14 may be a pivotal age for establishing this relationship.

Transcriptome analysis reveals FABP5 as a key player in the development of chicken abdominal fat, regulated by miR-122-5p targeting

BACKGROUND

The development of abdominal fat and meat quality are closely related and can impact economic efficiency. In this study, we conducted transcriptome sequencing of the abdominal fat tissue of Gushi chickens at 6, 14, 22, and 30 weeks, and selected key miRNA-mRNA regulatory networks related to abdominal fat development through correlation analysis.

RESULTS

A total of 1893 differentially expressed genes were identified. Time series analysis indicated that at around 6 weeks, the development of chicken abdominal fat was extensively regulated by the TGF-β signaling pathway, Wnt signaling pathway, and PPAR signaling pathway. However, at 30 weeks of age, the apoptosis signaling pathway was the most significant, and correlation analysis revealed several genes highly correlated with abdominal fat development, including Fatty Acid Binding Protein 5 (FABP5). Based on miRNA transcriptome data, it was discovered that miR-122-5p is a potential target miRNA for FABP5. Cell experiments showed that miR-122-5p can directly target FABP5 to promote the differentiation of preadipocytes.

CONCLUSION

The present study confirms that the key gene FABP5 and its target gene miR-122-5p are critical regulatory factors in the development of chicken abdominal fat. These results provide new insights into the molecular regulatory mechanisms associated with the development of abdomen-al fat in chickens.

An atlas of regulatory elements in chicken: A resource for chicken genetics and genomics

A comprehensive characterization of regulatory elements in the chicken genome across tissues will have substantial impacts on both fundamental and applied research. Here, we systematically identified and characterized regulatory elements in the chicken genome by integrating 377 genome-wide sequencing datasets from 23 adult tissues. In total, we annotated 1.57 million regulatory elements, representing 15 distinct chromatin states, and predicted about 1.2 million enhancer-gene pairs and 7662 super-enhancers. This functional annotation of the chicken genome should have wide utility on identifying regulatory elements accounting for gene regulation underlying domestication, selection, and complex trait regulation, which we explored. In short, this comprehensive atlas of regulatory elements provides the scientific community with a valuable resource for chicken genetics and genomics.

PNX14 but not PNX20 as a novel regulator of preadipocyte differentiation via activating Epac-ERK signaling pathway in Gallus gallus

Small integral membrane protein 20 (SMIM20) could generate two main peptides, PNX14 and PNX20, which participate in multiple biological roles such as reproduction, inflammation and energy metabolism in mammals. However, little is known about their physiological functions in non-mammalian vertebrates. Using chicken (c-) as an animal model, we found cSMIM20 was moderately expressed in adipose tissues, and its expression was gradually increased during the differentiation of chicken preadipocytes, suggesting that it may play an important role in chicken adipogenesis. Further research showed cPNX14 could facilitate the differentiation of chicken preadipocytes into mature adipocytes by enhancing expression of adipogenic genes including PPARγ, CEBPα and FABP4, and promoting the formation of lipid droplets. This pro-adipogenic effect of cPNX14 was completely attenuated by Epac-specific and ERK inhibitor. Interestingly, cPNX20 failed to regulate the adipogenic genes and lipid droplet content. Collectively, our findings reveal that cPNX14 but not cPNX20 can serve as a novel adipogenesis mediator by activating the Epac-ERK signaling pathway in chickens.

In ovo corticosterone exposure does not influence yolk steroid hormone relative abundance or skeletal muscle development in the embryonic chicken

In ovo corticosterone (CORT) exposure reportedly reduces growth and alters body composition traits in meat-type chickens. However, the mechanisms governing alterations in growth and body composition remain unclear but could involve myogenic stem cell commitment, and/or the presence of yolk steroid hormones. This study investigated whether in ovo CORT exposure influenced yolk steroid hormone content, as well as embryonic myogenic development in meat-type chickens. Fertile eggs were randomly divided at embryonic day (ED) 11 and administered either a control (CON; 100 µL of 10 mM PBS) or CORT solution (100 µL of 10 mM PBS containing 1 µg CORT) into the chorioallantoic membrane. Yolk samples were collected at ED 0 and ED 5. At ED 15 and hatch, embryos were humanely killed, and yolk and breast muscle (BM) samples were collected. The relative abundance of 15 steroid hormones, along with total lipid content was measured in yolk samples collected at ED 0, ED 5, ED 15, and ED 21. Muscle fiber number, cross-sectional area, and fascicle area occupied by muscle fibers were measured in BM samples collected at hatch. Relative expression of MyoD, MyoG, Pax7, PPARγ, and CEBP/β, and the sex steroid receptors were measured in BM samples collected at hatch. The administration of CORT had a limited effect on yolk steroid hormones. In ovo CORT significantly reduced fascicle area occupied by muscle fibers and CEBP/β expression was increased in CORT exposed birds at hatch. In addition, the quantity of yolk lipid was significantly reduced in CORT-treated birds. In conclusion, in ovo exposure to CORT does not appear to influence early muscle development through yolk steroid hormones in embryonic meat-type chickens however, the results provide a comprehensive analysis of the composition of yolk steroid hormones in ovo at different developmental time points. The findings may suggest increased mesenchymal stem cell commitment to the adipogenic lineage during differentiation and requires further investigation.

Dietary folic acid addition reduces abdominal fat deposition mediated by alterations in gut microbiota and SCFA production in broilers

Intensive selective breeding for high growth rate and body weight cause excess abdominal fat in broilers. Gut microbiota and folic acid were reported to regulate lipid metabolism. A total of 210 one-day-old broilers were divided into the control (folic acid at 1.3 mg/kg) and folic acid groups (folic acid at 13 mg/kg) to illustrate the effects of folic acid on growth performance, abdominal fat deposition, and gut microbiota, and the experiment lasted 28 d. Results revealed that dietary folic acid addition decreased abdominal fat percentage (P < 0.05) and down-regulated genes expression related to cell proliferation and differentiation in abdominal fat including IGF1, EGF, C/EBPα, PPARγ, PLIN1, FABP4 and PCNA (P < 0.05). Folic acid addition decreased caecal Firmicutes-to-Bacteroidetes ratio (P < 0.01) and increased the proportions of Alistipes, Oscillospira, Ruminococcus, Clostridium, Dehalobacterium and Parabacteroides (P < 0.05). Caecal acetic acid, and propionic acid contents were found to be higher under folic acid treatment (P < 0.05), which were negatively related to genes expression associated with adipocyte proliferation and differentiation (P < 0.05). Ruminococcus was positively correlated with caecal acetic acid content, and the same phenomenon was detected between propionic acid and Oscillospira and Ruminococcus (P < 0.05). Acetic acid and Oscillospira were identified to be negatively associated with abdominal fat percentage (P < 0.05). In conclusion, our data demonstrated that dietary supplementation of folic acid reduced fat deposition in broilers by inhibiting abdominal adipocyte proliferation and differentiation, which might be mediated by changes in gut microbiota and short chain fatty acid production.

Effect of in ovo feeding of γ-aminobutyric acid combined with embryonic thermal manipulation on hatchability, growth, and hepatic gene expression in broilers

OBJECTIVE

This study investigated the effects of in ovo feeding of γ-aminobutyric acid (GABA) and embryonic thermal manipulation (ETM) on growth performance, organ indices, plasma biochemical parameters, hepatic antioxidant levels, and expression of lipid metabolism-related genes in broilers.

METHODS

Two hundred and fifty eggs were assigned to one of four treatments: control eggs incubated under standard conditions (CON); eggs that received an in ovo injection of 10% GABA on day 17.5 of incubation (G10); thermally manipulated eggs between days 10 and 18 of incubation at 39.6°C for 6 h daily (TM); and eggs that received both treatments during incubation (G10+TM). After 28 days of rearing, five birds per treatment were selected for blood and organ sampling.

RESULTS

No differences were found in hatchability or growth parameters among different treatment groups. Hepatic gene expression of catalase (CAT) and glutathione peroxidase 1 (GPx1) was upregulated (p = 0.046 and p = 0.006, respectively) in the G10+TM group, while that of nuclear factor erythroid 2-related factor 2 (NRF2) was upregulated (p = 0.039) in the G10 group. In addition, the relative gene expression of NADPH oxidase 1 (NOX1) was significantly lower (p = 0.007) in all treatment groups than that in the CON group. Hepatic fatty acid synthase (FAS) levels and average daily feed intake (ADFI) of last week showed a positive correlation (r = 0.50, p = 0.038). In contrast, the relative gene expression of the extracellular fatty acid-binding protein (EXFAB) and peroxisome proliferator-activated receptor-γ (PPAR-γ) were positively correlated (r = 0.48, p = 0.042 and r = 0.50, p = 0.031) with the overall ADFI of birds.

CONCLUSION

Taken together, the results of this study suggest that the combination of in ovo feeding of GABA and ETM can enhance hepatic antioxidant function in broilers.

Genome analysis reveals hepatic transcriptional reprogramming changes mediated by enhancers during chick embryonic development

The liver undergoes a slow process for lipid deposition during chick embryonic period. However, the underlying physiological and molecular mechanisms are still unclear. Therefore, the aim of the current study was to reveal the epigenetic mechanism of hepatic transcriptional reprogramming changes based on the integration analysis of RNA-seq and H3K27ac labeled CUT&Tag. Results showed that lipid contents increased gradually with the embryonic age (E) 11, E15, and E19 based on morphological analysis of Hematoxylin-eosin and Oil Red O staining as well as total triglyceride and cholesterol detection. The hepatic protein level of SREBP-1c was higher in E19 when compared with that in E11 and E15, while H3K27ac and H3K4me2 levels declined from E11 to E19. Differential expression genes (DEGs) among these 3 embryonic ages were determined by transcriptome analysis. A total of 107 and 46 genes were gradually upregulated and downregulated respectively with the embryonic age. Meanwhile, differential H3K27ac occupancy in chromatin was investigated. But the integration analysis of RNA-seq and CUT&Tag data showed that the overlap genes were less between DEGs and target genes of differential peaks in the promoter regions. Further, some KEGG pathways enriched from target genes of typical enhancer were overlapped with those from DEGs in transcriptome analysis such as insulin, FoxO, MAPK signaling pathways which were related to lipid metabolism. DNA motif analysis identify 8 and 10 transcription factors (TFs) based on up and down differential peaks individually among E11, E15, and E19 stages where 7 TFs were overlapped including COUP-TFII, FOXM1, FOXA1, HNF4A, RXR, ERRA, FOXA2. These results indicated that H3K27ac histone modification is involved in the transcriptional reprogramming regulation during embryonic development, which could recruit TFs binding to mediate differential enhancer activation. Differential activated enhancer impels dynamic transcriptional reprogramming towards lipid metabolism to promote the occurrence of special phenotype of hepatic lipid deposition.

Effects and potential mechanism of dietary vitamin C supplementation on hepatic lipid metabolism in growing laying hens under chronic heat stress

The adverse effects of chronic heat stress (CHS)-induced fatty liver syndrome on laying hens during the egg-producing stages have been wildly documented. However, until nowadays, the CHS responses of growing laying hens as well as its alleviating effects of vitamin C are rarely reported. In this study, 12-wk-old laying hens were subjected to CHS at 36 °C for 10 h/d for 3 wk with or without dietary supplementation of 300 mg/kg vitamin C. Results showed that CHS significantly impaired the growth performances and the liver functions of birds, as characterized by reduced feed intake and body weight, increased hepatic lipid accumulation and serum concentrations of TG, ALT, and AST, as well as the abnormal expression patterns of the lipid metabolism-related genes. Vitamin C supplementation successfully mitigated the lipid accumulation, while showing no alleviating effect on the serum contents of ALT or AST, which are two key indicators of liver functions. Metabolomic analysis based on UPLC-Q-TOF/MS identified 173 differential metabolites from the HS and HSV group samples, and they are mainly enriched in the pathways related to the cellular components, vitamin and amino acid metabolism and energy substance metabolism. The results indicate that CHS-induced hepatic lipid deposition in growing laying hens is effectively alleviated by dietary supplementation of vitamin C, which is probably resulted from the alterations of hepatocellular metabolic patterns.

Oxidized corn oil changes the liver lipid metabolism of broilers by upregulating peroxisome proliferators activate receptor-α

The objective of the following study was to investigate the effects of naturally oxidized corn oil on the antioxidant capacity and lipid metabolism of broilers. A total of 450, 1-day-old Arbor Acres male broilers were randomly divided into 5 treatments with 6 replicate cages and 15 birds/cage. The dietary treatment array consisted of ratios of naturally oxidized corn oil to non-oxidized corn oil from 0:100, 25:75, 50:50, 75:25, and 100:0, respectively. Serum, liver, and abdominal fat samples were taken at 42 d. The results showed that the liver organ index, liver catalase (CAT) activity, malondialdehyde (MDA) content, and the serum aspartate aminotransferase (AST) content had significant quadratic relationships with the ratio of naturally oxidized corn oil (P < 0.05). Inflammatory infiltrating cells appeared in the liver of the 50% and 75% oxidized corn oil group. The percentage of abdominal fat, and serum free fatty acids (FFA) content increased linearly with the increased proportion of oxidized corn oil (P < 0.05). The mRNA expression of NADH quinone oxidoreductase 1 (NQO-1), nuclear factor kappa B (NF-κB), toll-like receptor-4 (TLR-4), peroxisome proliferators activate receptor-α (PPARα), carnitine acyltransferase (CPT1), and acyl-coenzyme oxidase (ACO) of the liver increased linearly while oxidized corn oil increased in the diet (P < 0.05). Diets containing 100% oxidized corn oil significantly changed the mRNA expression of liver Caveolin compared with other treatment groups (P < 0.05). Taken together, this study demonstrated that naturally oxidized corn oil could change liver lipid metabolism and accelerate lipid deposition of broilers by upregulating PPARα.

m6A demethylase FTO regulate CTNNB1 to promote adipogenesis of chicken preadipocyte

BACKGROUND

N6-methyladenosine (m⁶A) is an abundant post-transcriptional RNA modification that affects various biological processes. The fat mass and obesity-associated (FTO) protein, a demethylase encoded by the FTO gene, has been found to regulate adipocyte development in an m⁶A-dependent manner in multiple species. However, the effects of the m⁶A methylation and FTO demethylation functions on chicken adipogenesis remain unclear. This study aims to explore the association between m⁶A modification and chicken adipogenesis and the underlying mechanism by which FTO affects chicken preadipocyte development.

RESULTS

The association between m⁶A modification and chicken lipogenesis was assessed by treating chicken preadipocytes with different doses of methyl donor betaine and methylation inhibitor cycloleucine. The results showed that betaine significantly increased methylation levels and inhibited lipogenesis, and the inverse effect was found in preadipocytes after cycloleucine treatment. Overexpression of FTO significantly inhibited m⁶A levels and promoted proliferation and differentiation of chicken preadipocytes. Silencing FTO showed opposite results. Mechanistically, FTO overexpression increased the expression of catenin beta 1 (CTNNB1) by improving RNA stability in an m⁶A-dependent manner, and we proved that FTO could directly target CTNNB1. Furthermore, CTNNB1 may be a positive regulator of adipogenesis in chicken preadipocytes.

CONCLUSIONS

m⁶A methylation of RNA was negatively associated with adipogenesis of chicken preadipocytes. FTO could regulate CTNNB1 expression in a demethylation manner to promote lipogenesis.

The landscape of the long non-coding RNAs and circular RNAs of the abdominal fat tissues in the chicken lines divergently selected for fatness

BACKGROUND

Excessive deposition of abdominal fat poses serious problems in broilers owing to rapid growth. Recently, the evolution of the existing knowledge on long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) have established their indispensable roles in multiple physiological metabolic processes, including adipogenesis and fat deposition. However, not much has been explored on their profiles in the abdominal fat tissues of broilers to date. In the study, we aimed to characterize the vital candidates of lncRNAs and circRNAs and their underlying regulations for abdominal fat deposition in broilers.

RESULTS

The present study sequenced the lncRNAs and circRNAs expression profiles in the abdominal fat tissues isolated from 7-week-old broilers, who were divergently selected for their fatness. It identified a total of 3359 lncRNAs and 176 circRNAs, demonstrating differential expressed (DE) 30 lncRNAs and 17 circRNAs between the fat- and lean-line broilers (|log2FC| ≥ 1, P < 0.05). Subsequently, the 20 cis-targets and 48 trans-targets of the candidate DE lncRNAs were identified for depositing abdominal fat by adjacent gene analysis and co-expression analysis, respectively. In addition, the functional enrichment analysis showed the DE lncRNAs targets and DE circRNAs host genes to be mainly involved in the cellular processes, amino/fatty acid metabolism, and immune inflammation-related pathways and GO terms. Finally, the vital 16 DE lncRNAs located in cytoplasm and specifically expressed in fat/lean line and their targets were used to construct the lncRNA-miRNA-mRNA competing endogenous RNA (ceRNA) regulatory network, comprising 7 DE lncRNAs, 28 miRNAs, 11 DE mRNAs. Notably, three lncRNAs including XR_001468036.2, XR_003077610.1 and XR_001466431.2 with the most connected degrees might play hub regulatory roles in abdominal fat deposition of broilers.

CONCLUSIONS

This study characterized the whole expression difference of lncRNAs and circRNAs between the two lines broilers with divergently ability of abdominal fat. The vital candidate DE lncRNAs/circRNAs and ceRNA regulations were identified related to the deposition of abdominal fat in chicken. These results might further improve our understanding of regulating the non-coding RNAs in obesity.

Knockout and Restoration Reveal Differential Functional Roles of PPARγ1 and PPARγ2 in Chicken Adipogenesis

Peroxisome proliferator-activated receptor γ (PPARγ) is the master regulator of adipogenesis and is expressed as two isoforms, PPARγ1 and PPARγ2. Our previous lentiviral overexpression study showed that PPARγ1 and PPARγ2 differentially regulated proliferation, differentiation, and apoptosis of the immortalized chicken preadipocyte cell line (ICP2). However, we cannot rule out the possibility that the endogenous expression of PPARγ isoforms may compromise our findings. In this study, using the dual sgRNA-directed CRISPR/Cas9 system, we generated PPARγ (PPARγ^-/-) and PPARγ2-specific knockout (PPARγ2^-/-) ICP2 cell lines and investigated the differences in proliferation and differentiation among PPARγ^-/-, PPARγ2^-/-, and wild-type ICP2 cells. EdU proliferation assay showed that both PPARγ2-specific and PPARγ knockouts significantly increased the proliferation rates. Consistently, real-time RT-PCR analysis showed that both PPARγ2-specific and PPARγ knockouts significantly upregulated the expression of proliferation marker genes PCNA and cyclinD1. FACS analysis revealed that PPARγ knockout significantly increased the number of cells accumulating in the S phase and decreased the number of cells accumulating in the G₁/G₀ phase. Oil Red O staining and gene expression analysis showed both PPARγ2-specific and PPARγ knockouts dramatically reduced capacity for adipogenic differentiation. To corroborate our previous findings, PPARγ1 and PPARγ2 expression were restored in PPARγ^-/- cells by using the lentiviruses expressing chicken PPARγ1 (LV-PPARγ1) and PPARγ2 (LV-PPARγ2), respectively. Subsequent assays showed that restoration of expression of either PPARγ1 or PPARγ2 suppressed proliferation and stimulated differentiation of the PPARγ^-/- cells. By comparison, PPARγ2 had stronger anti-proliferative and pro-adipogenic effects than PPARγ1. To understand the molecular mechanism underlying their differential effects on differentiation of the PPARγ^-/- cells, we performed RNA-seq in the PPARγ^-/- cells in which individual PPARγ isoform expression was restored at 72 h of differentiation. Transcriptomic analysis revealed that restoring PPARγ1 expression caused far more differentially expressed genes (DEGs) than restoring PPARγ2 expression. GO and KEGG pathway enrichment analyses indicated that PPARγ1 and PPARγ2 had distinct and overlapping functions in adipogenesis. Taken together, our results clearly indicate that PPARγ1 and PPARγ2 differentially impact chicken adipogenesis.

iPSC Technology: An Innovative Tool for Developing Clean Meat, Livestock, and Frozen Ark

Induced pluripotent stem cell (iPSC) technology is an emerging technique to reprogram somatic cells into iPSCs that have revolutionary benefits in the fields of drug discovery, cellular therapy, and personalized medicine. However, these applications are just the tip of an iceberg. Recently, iPSC technology has been shown to be useful in not only conserving the endangered species, but also the revival of extinct species. With increasing consumer reliance on animal products, combined with an ever-growing population, there is a necessity to develop alternative approaches to conventional farming practices. One such approach involves the development of domestic farm animal iPSCs. This approach provides several benefits in the form of reduced animal death, pasture degradation, water consumption, and greenhouse gas emissions. Hence, it is essentially an environmentally-friendly alternative to conventional farming. Additionally, this approach ensures decreased zoonotic outbreaks and a constant food supply. Here, we discuss the iPSC technology in the form of a "Frozen Ark", along with its potential impact on spreading awareness of factory farming, foodborne disease, and the ecological footprint of the meat industry.

Alterations in hepatic mitotic and cell cycle transcriptional networks during the metabolic switch in broiler chicks

During embryonic life, chicks mainly derive energy from hepatic oxidation of yolk lipids. After hatch, chicks must rely on carbohydrate-rich feed to obtain energy. This requires an abrupt and intensive switch of metabolic processes, particularly in the liver. We recently identified a number of transcriptional and post-transcriptional regulatory networks that work concordantly to tune metabolic processes during the metabolic switch. Here, we used delayed feeding post-hatch (48 h) to impede the metabolic switch in broilers. We used RNA-seq to identify hepatic transcriptome differences between late stage embryos (E18) and two-day-old chicks (D2), which were either fed-from-hatch (FED) or not fed (DLY). Between FED and E18, 2,430 genes were differentially expressed (fold-change≥ 2; FDR p-value 0.05), of these 1,237 were downregulated in FED birds and 1,193 were upregulated. Between DLY and E18, 1979 genes were differentially expressed, of these 1,043 were downregulated and 936 were upregulated in DLY birds. Between DLY and FED, 880 genes were differentially expressed, of these 543 were downregulated and 337 were upregulated in DLY birds. We found that in addition to disturbances in a number of metabolic pathways, unfed chicks had a widespread suppression of gene networks associated with cell proliferation, cell cycle progression and mitosis. Expression patterns suggest that hepatocytes of delayed-fed birds have abnormal mitosis and increased polyploidization. This suggests that post-hatch feed consumption maintains the rate and integrity of liver growth immediately, which in turn, likely helps facilitate the appropriate programming of hepatic metabolic networks.

Sclerocarya birrea caffra nut meal as a substitute to soyabean meal: Effects on growth performance, feed intake and utilisation and viscera macromorphometry of blue-helmeted guinea fowl

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Marula nut meal can be used as a replacer of soyabean meal in guinea fowl feeds.

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Use of other tree seeds as dietary protein sources in poultry feeds needs further exploitation.

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Marula nut meal does not affect the viscera macromorphometry and feed utilisation in guinea fowl.

Imported soyabean meal (SBM) is the major dietary protein (DP) source for the sub-Saharan African poultry industry making poultry production costly. Therefore, alternative locally available DP sources are required. We evaluated the potential of locally available Marula nut meal (MNM) to substitute SBM in Guinea fowl (GF) diets by determining its effects on growth, feed intake (FI) and utilisation and viscera macromorphometry. Five grower diets wherein, on a CP basis, MNM substituted SBM at 0, 25, 50, 75 and 100% were formulated. Thirty-eight 4-week-old keets (n = 7 – 8), each individually housed in a cage, were randomly assigned to grower diets, and fed for 5 weeks and then transferred to corresponding finisher diets and fed for 3 weeks. Induction and weekly body mass, daily FI, and terminal body mass (TBM), body mass gain (BMG), average daily gain (ADG) and feed conversion ratio (FCR) were determined. On slaughter, viscera masses, small and large intestines lengths, tibiae and femora indices were determined. In week 2 of the grower phase GF fed diet 3 (50% MNM CP) had the highest weekly BMG and ADG (P < 0.05) and in week 5 GF fed diet 5 (100% MNM CP) had the highest FI (P < 0.05). Dietary MNM did not affect the GF's BMG, ADG, FI and FCR during weeks 1, 3 and 4 of the grower phase. In week 3 of the finisher phase GF fed diet 3 (50% MNM CP) had the highest (P < 0.05) FCR. Dietary MNM had no effect (P > 0.05) on the trial BMG, ADG and FI of the GF but GF reared on grower and finisher diets 3 (50% substitution of SBM CP) had the highest (P < 0.05) FCR. MNM had no effect on tibiae and femora masses, lengths, and mass: length ratios and viscera macromorphometry of the GF. We conclude that MNM can, on a CP basis, substitute SBM, in GF grower and finisher diets at 25%, 75% and 100% without compromising growth, FI and utilization and viscera of GF.

Effects of Fatty-Type and Lean-Type on Growth Performance and Lipid Droplet Metabolism in Pekin Ducks

Simple Summary

Lipid deposition in animals is closely related to lipid anabolism. In order to further explore how differences in different metabolic types regulate lipid deposition, we compared the growth performance and lipid droplet metabolism of fatty-type ducks and lean-type ducks. The results showed that fatty-type ducks showed a faster growth rate and more fat deposition in the early growth stage after feeding the same diet, and produced more lipoproteins in serum and deposited in adipose tissue. However, fewer triglycerides accumulated in the liver. We believe that this performance of fatty-type ducks is caused by the increased expression level of lipid droplet-related genes.

Abstract

The reasons for differences in lipid depositions between fatty-type (F-T) and lean-type (L-T) ducks remain unknown. The present study aimed to compare the growth performance, lipid deposition, and gene expression related to lipid droplet formation in F-T and L-T Pekin ducks. One-day-old, 140 each L-T and F-T male ducks were selected and distributed separately into 20 replicate cages. All ducks were fed commercial diets up to 35 d of age. F-T ducks had a higher average daily gain from 21 to 28 d of age. On 35-day-old, F-T ducks had higher serum levels of high- and low-density lipoprotein cholesterol, cholesterol, albumin, and hydroxybutyrate dehydrogenase activity than L-T ducks. F-T ducks had higher abdominal fat and subcutaneous fat percentages than those in L-T ducks. Liver histological examination showed that L-T ducks contained more lipid droplets in the liver, which gradually decreased with increasing age. The average adipocyte area and diameter of abdominal fat and subcutaneous fat in the F-T and L-T ducks increased with age and were higher in F-T ducks than those in L-T ducks. Furthermore, the gene expression of perilipin 1, perilipin 2, angiopoietin-like protein 4, adipose triglyceride lipase, alpha/beta-hydrolase domain-containing protein 5 (ABHD5), and serine/threonine kinase 17a in the liver, abdominal fat, and subcutaneous fat of F-T ducks was higher than that in L-T ducks, and it increased with age. Compared to L-T ducks, F-T ducks had higher expression of ABHD5 in the abdominal fat and subcutaneous fat and lower expression in the liver. Thus, F-T ducks displayed lower hepatic lipid deposition and a higher percentage of abdominal fat and subcutaneous fat, suggesting that F-T ducks had higher lipid storage capacity due to increased gene expression related to lipid droplets.

Chicken Protein S Gene Regulates Adipogenesis and Affects Abdominal Fat Deposition

Simple Summary

Low-fat meat is increasingly desired by the public due to the growing popularity of healthy diets, and the excessive accumulation of abdominal fat increases costs in the broiler breeding industry, all of which have encouraged breeding changes in the broiler industry. Investigating fat accumulation at a cellular level from a genetic perspective will help us understand gene-mediated abdominal fat accumulation in chickens. This study aimed to explore the role of the PROS1 gene in adipose cells and its application prospect in broiler breeding. Based on our findings, we found that the PROS1 gene can contribute to adipose cell proliferation and can reduce fat deposits at the cellular level, and its mutations are highly correlated with chicken fat traits.

Abstract

(1) Background: Excessive abdominal fat deposition in broilers not only causes feed waste but also leads to a series of metabolic diseases. It has gradually become a new breeding goal of the broiler industry to improve growth rates and to reduce abdominal fat rates. In a previous study, PROS1 was highly expressed in low-abdominal fat broilers, suggesting a potential role in broilers adipogenesis. However, the function of PROS1 in preadipocytes and its association with abdominal fat traits need to be characterized. (2) Methods: qRT-PCR and Western Blot were used to quantify gene expression at the RNA and protein levels; flow cytometry and EdU were carried out to detect cell proliferation; and a GLM analysis was used to determine the association between PROS1 SNPs and carcass traits. (3) Results: PROS1 was downregulated in high-abdominal fat chicken; PROS1 contributed preadipocyte proliferation but suppressed preadipocyte differentiation; and the SNPs in the PROS1 5′ flank were significantly associated with the abdominal fat weight rate. (4) Conclusions: Chicken PROS1 is able to suppress adipogenesis, and its polymorphisms are associated with the abdominal fat weight rate, which can be considered the molecular markers for chicken breeding, indicating that PROS1 is an effective potential gene in regulating abdominal fat deposition.

Identifying the shortfalls of crude protein-reduced, wheat-based broiler diets

The objective of this review is to identify the shortfalls of wheat-based, crude protein (CP)-reduced diets for broiler chickens as wheat is inferior to maize in this context but to inconsistent extents. Inherent factors in wheat may be compromising gut integrity; these include soluble non-starch polysaccharides (NSP), amylase trypsin inhibitors (ATI) and gluten. Soluble NSP in wheat induce increased gut viscosities, which can lead to compromised gut integrity, which is not entirely ameliorated by NSP-degrading feed enzymes. Wheat ATI probably compromise gut integrity and may also have the capacity to increase endogenous amino acid flows and decrease apparent starch and protein digestibilities. Gluten inclusions of 20 g/kg in a maize-soy diet depressed weight gain and feed intake and higher gluten inclusions have been shown to activate inflammatory cytokine-related genes in broiler chickens. Further research is required, perhaps particularly in relation to wheat ATI. The protein content of wheat is typically higher than maize; importantly, this results in higher inclusions of non-bound amino acids in CP-reduced broiler diets. These higher inclusions could trigger post-enteral amino acid imbalances, leading to the deamination of surplus amino acids and the generation of ammonia (NH₃) which, if not adequately detoxified, results in compromised growth performance from NH₃ overload. Thus, alternatives to non-bound amino acids to meet amino acid requirements in birds offered CP-reduced, wheat-based diets merit evaluation. The digestion of wheat starch is more rapid than that of maize starch which may be a disadvantage as the provision of some slowly digestible starch in broiler diets may enhance performance. Alternatively, slowly digestible starch may result in more de novo lipogenesis. Therefore, it may prove instructive to evaluate CP-reduced diets based on maize-wheat and/or sorghum–wheat blends rather than entirely wheat. This would reduce non-bound amino acid inclusions by lowering dietary CP derived from feed grains and may enhance starch digestive dynamics by retarding starch digestion rates. Also, the use of biomarkers to monitor gut integrity in broiler chickens is examined where calprotectin, ovotransferrin and possibly citrulline appear to hold promise, but their validation requires further research.

Whole transcriptome RNA Sequencing Reveals the Global Molecular Responses and circRNA/lncRNA-miRNA-mRNA ceRNA Regulatory Network in Chicken Fat Deposition

Fat deposition is a vital factor affecting the economics of poultry production. Numerous studies on fat deposition have been done. However, the molecular regulatory mechanism is still unclear. In the present study, the whole-transcriptome RNA sequencing in abdominal fat, back skin, and liver both high- and low-abdominal fat groups was used to uncover the competitive endogenous RNA (ceRNA) regulation network related to chicken fat deposition. The results showed that differentially expressed (DE) genes in abdominal fat, back skin, liver were 1207(784 mRNAs, 330 lncRNAs, 41 circRNAs, 52 miRNAs), 860 (607 mRNAs, 166 lncRNAs, 26 circRNAs, 61 miRNAs), and 923 (501 mRNAs, 262 lncRNAs, 15 circRNAs, 145 miRNAs), respectively. The ceRNA regulatory network analysis indicated that the fatty acid metabolic process, monocarboxylic acid metabolic process, carboxylic acid metabolic process, glycerolipid metabolism, fatty acid metabolism, and peroxisome proliferator-activated receptor (PPAR) signaling pathway took part in chicken fat deposition. Meanwhile, we scan the important genes, FADS2, HSD17B12, ELOVL5, AKR1E2, DGKQ, GPAM, PLIN2, which were regulated by gga-miR-460b-5p, gga-miR-199-5p, gga-miR-7470-3p, gga-miR-6595-5p, gga-miR-101-2-5p. While these miRNAs were competitive combined by lncRNAs including MSTRG.18043, MSTRG.7738, MSTRG.21310, MSTRG.19577, and circRNAs including novel_circ_PTPN2, novel_circ_CTNNA1, novel_circ_PTPRD. This finding provides new insights into the regulatory mechanism of mRNA, miRNA, lncRNA, and circRNA in chicken fat deposition.

Dietary crude protein concentrations, feed grains and whey protein interactively influence apparent digestibility coefficients of amino acids, protein, starch and performance of broiler chickens

The present study was designed to investigate the impacts of dietary crude protein (CP) concentrations (220 and 180 g/kg) in either maize- or wheat-based diets, without or with 25 g/kg inclusions of whey powder (WP) concentrate on performance parameters and apparent amino acid digestibility coefficients in broiler chickens. The maize and wheat used in this study had CP levels of 84 and 119 g/kg, respectively. The 2 × 2 × 2 factorial array of 8 dietary treatments was offered to a total of 336 off-sex, male Ross 308 chicks from 7 to 35 d post-hatch with 7 replicate cages (6 birds per cage) per treatment. A treatment interaction (P = 0.016) between dietary CP and feed grains was detected for weight gains, where birds offered 180 g/kg maize-based diets displayed a weight gain advantage of 6.74% (2,628 vs. 2,462 g/bird) compared to their wheat-based counterparts. An interaction (P = 0.022) between feed grains and whey protein was observed for FCR as the addition of WP to maize-based diets improved FCR by 3.45% (1.314 vs. 1.361), but compromised FCR in wheat-based diets by 2.98% (1.415 vs. 1.374). A treatment interaction (P = 0.038) between dietary CP and feed grains was recorded for relative abdominal fat-pad weights weight gains as birds offered 180 g/kg CP maize-based diets had 43.4% (11.17 vs. 7.79 g/kg) heavier fat-pads than their wheat-based counterparts. Following the reduction in dietary-CP, apparent amino acid digestibility coefficients were depressed to greater extents in wheat-based diets. However, significant interactions between CP and feed grains were found in 14 of the 16 amino acids assessed and significant interactions between CP and WP were observed for 15 amino acids. Maize was the more suitable feed grain in terms of weight gain and FCR in 180 g/kg CP diets despite causing greater fat deposition. The inclusion of WP in reduced-CP diets did not enhance bird performance. Data generated indicate concentrations of microbial amino acids in distal ileal digesta were depressing apparent amino acid digestibility coefficients, which was more evident in wheat-based diets. Higher gut viscosities in birds offered wheat-based diets may have facilitated the proliferation of microbiota along the small intestine.

Effects of Dietary Inclusion of β-Hydroxy-β-Methylbutyrate on Growth Performance, Fat Deposition, Bile Acid Metabolism, and Gut Microbiota Function in High-Fat and High-Cholesterol Diet-Challenged Layer Chickens

Excessive lipid deposition in layer chickens due to inappropriate feeding adversely affects egg production; however, nutritional manipulation methods to deal with this issue are still limited. β-hydroxy-β-methylbutyrate (HMB), a metabolite of L-leucine, was recently reported as a lipid-lowering nutrient in mice and pigs, although its role in layers had not been investigated. Here, we employed high-fat and high-cholesterol diet (HFHCD)−challenged growing layers as an obese model to explore HMB function in the regulation of lipid metabolism and the potential mechanisms involved. We found that dietary supplementation with (0.05% or 0.10%) HMB significantly reduced HFHCD−induced bodyweight growth in layers, mainly due to reduction in abdominal fat deposition. Mechanistically, HMB supplementation enhanced hepatic bile acid synthesis from cholesterol through elevating expression of Cyp7a1, a gene coding a key enzyme in bile acid synthesis. Furthermore, 16S rRNA gene sequencing revealed that HMB supplementation remodeled the diversity and composition of the layers’ cecal microbiota, and the abundance of Bacteroidetes at the phylum level were especially affected. Correlation analysis further indicated a strong negative association between Bacteroidetes abundance and lipid metabolism−related parameters. Taken together, these data suggest that dietary HMB supplementation could improve abdominal fat deposition in layers, probably through modulating hepatic bile acid synthesis and gut microbiota function.

Comparative Transcriptome Analysis Provides Novel Insights into the Effect of Lipid Metabolism on Laying of Geese

Simple Summary

The importance of lipid metabolism in the egg production of poultry has been widely reported. Meanwhile, geese have lower egg production and unique lipid metabolism patterns compared with chicken and duck. It is of great significance to further improve egg laying performance to explore the differences of fat metabolism and the molecular mechanisms in geese with different egg laying performance. This study compared the phenotypic differences of liver and abdominal fat, as well as the transcriptome level differences of liver, abdominal fat, and ovarian stroma among high-, low-, and no-egg production groups. The results reveal that lipid metabolism regulated by the circadian rhythm of the liver may directly or indirectly affect ovarian function through the inflammation and hormone secretion of abdominal fat.

Abstract

The lower egg production of geese (20~60 eggs per year) compared with chicken and duck limits the development of the industry, while the yolk weight and fatty liver susceptibility of geese was higher than that of other poultry. Therefore, the relationship between lipid metabolism and the laying performance of geese remains to be explored. Phenotypically, we observed that the liver fat content of the high-, low-, and no-egg production groups decreased in turn, while the abdominal fat weight increased in turn. For transcriptional regulation, the KEGG pathways related to lipid metabolism were enriched in all pairwise comparisons of abdominal fat and liver through functional analysis. However, some KEGG pathways related to inflammation and the circadian rhythm pathway were enriched by DEGs only in abdominal fat and the liver, respectively. The DEGs in ovarian stroma among different groups enriched some KEGG pathways related to ovarian steroidogenesis and cell adhesion. Our research reveals that lipid metabolism regulated by the circadian rhythm of the liver may directly or indirectly affect ovarian function through the inflammation and hormone secretion of abdominal fat. These results offer new insights into the regulation mechanisms of goose reproductive traits.

Transcriptomics-Based Study of Differentially Expressed Genes Related to Fat Deposition in Tibetan and Yorkshire Pigs

Fat deposition traits are one of the key factors in pig production and breeding. The fat deposition capacity of pigs mainly affects the quality of pork and pig productivity. The aim of this study was to analyze the differential expression of mRNA levels in dorsal adipose tissue of Tibetan and York pigs at different growth stages using transcriptomic data to estimate key genes that regulate fat deposition in pigs. The results showed that a total of 32,747 positively expressed genes were present in the dorsal adipose tissue of the two breeds. Differentially expressed gene (DEG) screening of multiple combinations between the two breeds yielded 324 DEGS. Gene ontology (GO) biofunctional enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that these DEGS were mainly involved in lipid metabolic pathways, steroid biosynthetic pathways and lipid biosynthetic processes, sterol biosynthetic processes, brown adipocyte differentiation, and other pathways related to lipid deposition and metabolism. The results showed that ACACA, SLC2A4 and THRSP genes positively regulated the lipid deposition ability and CHPT1 gene negatively regulated the lipid deposition ability in pigs. The results of this experiment suggest a theoretical basis for further studies on the regulatory mechanisms of fat deposition in pigs.

Breast Meat Fatty Acid Profiling and Proteomic Analysis of Beijing-You Chicken During the Laying Period

The disparity in fatty acids (FA) composition exhibits a significant impact on meat quality, however, the molecular regulatory mechanisms underlying this trait in chicken are far from clear. In this study, a total of 45 female Beijing-You chicken (BYC) hens, fed on the same diet, were collected at the slaughter age of 150, 300, or 450 days (D150, D300, and D450) from sexual maturation stage to culling stage (15 birds per age). Gas chromatography-mass spectrometry (GC-MS) and tandem mass tag labeling technology based on liquid chromatography mass spectrometry (TMT-LC-MS/MS) analysis strategies were applied to profile FA compositions and to compare differential expressed proteins (DEPs) between these different slaughter ages, respectively. The FA profiling showed that increasing hen ages resulted in increased contents of both saturated and unsaturated fatty acids. Proteomic analyses showed a total of 4,935 proteins in chicken breast muscle with the false discovery rate (FDR) < 1% and 664 of them were differentially expressed (fold change > 1.50 or < 0.67 and P < 0.01). There were 410 up- and 116 down-regulated proteins in D150 vs. D300 group, 32 up- and 20 down-regulated in D150 vs. D450 group, and 72 up- and 241 down-regulated in D300 vs. D450 group. A total of 57 DEPs related to FA/lipid-related metabolisms were obtained according to the enrichment analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). These DEPs were involved in 21 significantly enriched (P < 0.05) pathways, including well-known pathways for FA synthesis (metabolism, desaturation, and elongation) and the signaling pathways for lipid metabolism (PPAR, adipocytokine, calcium, VEGF, MAPK, and Wnt). In addition, there existed several representative DEPs (FABP, FABP3, apoA-I, apoA-IV, apoC-III, apoB, VTG1, and VTG2) involved in the regulation of FA/lipid transportation. The construction of the interaction networks indicated that HADH, ACAA2, HADHA, ACSL1, CD36, CPT1A, PPP3R1, and SPHK1 were the key core nodes. Finally, eight DEPs were quantified using parallel reaction monitoring (PRM) to validate the results from TMT analysis. These results expanded our understanding of how the laying age affects the FA compositions and metabolism in hen breast meat.

Long-Lasting Effects of Incubation Temperature During Fetal Development on Subcutaneous Adipose Tissue of Broilers

Increasing evidence indicates that fetal programming may cause permanent effects on offspring adipose tissue and body composition. Previous study showed reduction in newly-hatched broiler chick adiposity by manipulating incubation temperature during fetal development. The present study examined whether incubation temperature during fetal development has long-term effects on post-hatching fat deposition in broilers. Broiler breeder eggs (Cobb-500^®) were incubated under constant low (36°C, LT), control (37.5°C, CT) or high (39°C, HT) temperature from day 13 onward, giving to eggshell temperature of 37.3 ± 0.08°C, 37.8 ± 0.2°C, and 38.8 ± 0.3°C, respectively. Male chicks were reared under recommended temperatures until 42 days old. LT 21 days old broilers exhibited higher blood cholesterol than CT broilers, and higher triglycerids, VLDL, and LDL, and lower HDL than CT and HT broilers. LT broilers presented higher liver cholesterol than CT broilers and lower ether extract percentage than CT broilers. Adipocyte count was lower in the abdomen than in the thigh. Until day 21 of age, feed intake was higher in LT than in HT broilers. At day 42 of age, blood cholesterol and LDL were higher in HT broilers than in CT and LT broilers. Liver cholesterol was higher in LT than in HT broilers. LT treatment reduced neck and increased thigh adipocyte size compared to CT treatment, while the HT treatment reduced abdomen and neck adipocyte size compared to other two treatments and in the thigh compared to LT treatment. In CT broilers, thigh adipocytes were smaller than abdomen and neck adipocytes. HT treatment increased adipocyte number per area in the neck compared to LT and CT treatment, and LT and HT treatments reduced adipocyte count in the thigh compared to CT treatment. CT broilers presented higher adipocyte count in the thigh than the abdomen and neck, while HT broilers presented higher adipocyte count in the neck than the abdomen and thigh. Cell proliferation was lower in the abdomen than in the thigh. The results show incubation temperature manipulation during fetal development has long-term and distinct effects on regional adiposity, and can be used to modulate broiler fat deposition.