Estrogen induction of VLDLy assembly in egg-laying hens

ELOVL5 and VLDLR synergistically affect n-3 PUFA deposition in eggs of different chicken breeds

There was no significant difference in the composition and content of fatty acids in eggs among different breeds initially, but following the supplementation of flaxseed oil, Dwarf Layer were observed to deposit more n-3 polyunsaturated fatty acid (PUFA) in eggs. Currently, there is limited research on the mechanisms underlying the differences in egg composition among different breeds. Therefore, in this study, 150 twenty-four-wk-old hens of each breed, including the Dwarf Layer and White Leghorn, were fed either a basal diet or a diet supplemented with 2.5% flaxseed oil. After 28 d, eggs and liver samples were collected to determine fatty acid composition, and serum, liver, intestine, and follicles were collected for subsequent biochemical, intestinal morphology, and lipid metabolism-related genes expression analysis. Duodenal contents were collected for microbial analysis. The results showed that there was no significant difference in the content and deposition efficiency of total n-3 PUFA in the liver of the 2 breeds, but the content and deposition efficiency of total n-3 PUFA in the egg of Dwarf Layer were significantly higher than those of White Leghorn after feeding flaxseed oil. Flaxseed oil and breeds did not have significant effects on cholesterol (CHO), free fatty acids (NEFA), low-density lipoprotein (LDL), and estrogen (E2) levels. After feeding with flaxseed oil, the villus height and the villus-to-crypt ratio in both breeds were increased and duodenal crypt depth was decreased. The villus-to-crypt ratio (4.78 vs. 3.60) in the duodenum of Dwarf Layer was significantly higher than that in White Leghorn after feeding with flaxseed oil. Flaxseed oil can impact the gut microbiota in the duodenum and reduce the microbiota associated with fatty acid breakdown, such as Romboutsia, Subdolibranulum, Lachnochlostridium, and Clostridium. This may mean that less ALA can be decomposed and more ALA can be absorbed into the body. Additionally, after feeding flaxseed oil, the mRNA levels of elongation enzymes 5 (ELOVL5), fatty acid desaturase 1 (FADS1), and fatty acid transporter 1 (FATP1) in the liver of Dwarf Layer were significantly higher than those in White Leghorn, while the mRNA levels of peroxisome proliferator-activated receptor alpha (PPAR), carnitine palmitoyl transferase 1 (CPT1), Acyl CoA oxidase 1 (ACOX1), and Acyl-CoA synthetase (ACSL) were significantly lower than those in White Leghorn. The mRNA level of FABP1 in the duodenum of Dwarf Layer was significantly higher than that of White Leghorn, while the mRNA level of FATP1 was significantly lower than that of White Leghorn. The protein levels of ELOVL5 in the liver of Dwarf Layer and very low-density lipoprotein receptor (VLDLR) in the follicles were significantly higher than those of White Leghorn. In summary, after feeding flaxseed oil, the higher ratio of villus height to crypt depth in Dwarf Layer allows more α-linolenic acid (ALA) to be absorbed into the body. The higher mRNA expression of FADS1, ELOVL5, and FATP1, as well as the higher protein expression of ELOVL5 in the liver of Dwarf Layer enhance the conversion of ALA into DHA. The higher protein expression of VLDLR in follicles of Dwarf Layer allows more n-3 PUFA to deposit in the follicles. These combined factors contribute to the Dwarf Layer's ability to deposit higher levels of n-3 PUFA in eggs, as well as improving the deposition efficiency of n-3 PUFA.

Fermented blueberry pomace supplementation improves egg quality, liver synthesis, and ovary antioxidant capacity of laying hens

The present study aimed to investigate the effects of dietary fermented blueberry pomace (FBP) supplementation on production performance, egg quality and nutritional value, plasma biochemical parameters, follicle number, reproductive hormones, lipid metabolism, and antioxidant capacity of laying hens during the late laying period. A total of 320 (345-d-old) Yukou Jingfen No. 8 laying hens were randomly divided into 4 groups, with eight replicates per group and 10 hens per replicate. The birds were fed a basal diet (control group) and a basal diet supplemented with 0.25, 0.5, and 1.0% FBP. The trial lasted 56 d. The results showed that FBP (0.25-1.0%) supplementation increased the egg albumen height and Haugh unit compared with the control group on d 14, while 0.5 to 1.0% FBP increased the eggshell thickness compared with the 0.25% FBP group on d 28 of the trial (P < 0.05). The methionine content in egg white was higher (P < 0.05) in the 1.0% FBP group compared with the 0.25% FBP group. The CAT activity in the ovary was increased (P < 0.05) in the FBP groups compared with the control group, while plasma GSH-PX activity was higher (P < 0.05) in the 1.0% FBP group compared with the 0.25% FBP and 0.5% FBP groups. Dietary FBP supplementation up-regulated (P < 0.05) gene expressions related to lipid metabolism in the liver (ACC, FAS, SCD1, and SREBP1) and yolk precursor synthesis (ESR2 and VTG II). Moreover, CYP11A1 expression in the ovary was up-regulated (P < 0.05) in the FBP groups compared with the control group, as well as in the 0.25% FBP group compared with the 1.0% FBP group. In summary, dietary FBP supplementation improved egg quality and nutritional value, ovarian antioxidant capacity, and yolk precursor synthesis, while 1.0% FBP had better effects than 0.25 and 0.5% doses.

Dietary silymarin improves performance by altering hepatic lipid metabolism and cecal microbiota function and its metabolites in late laying hens

BACKGROUND

Liver lipid dysregulation is one of the major factors in the decline of production performance in late-stage laying hens. Silymarin (SIL), a natural flavonolignan extracted from milk thistle, is known for its hepatoprotective and lipid-lowering properties in humans. This study evaluates whether SIL can provide similar benefits to late-stage laying hens. A total of 480 68-week-old Lohmann Pink laying hens were randomly assigned into 5 groups, each group consisting of 6 replicates with 16 hens each. The birds received a basal diet either without silymarin (control) or supplemented with silymarin at concentrations of 250, 500, 750, or 1,000 mg/kg (SIL250, SIL500, SIL750, SIL1000) over a 12-week period.

RESULTS

The CON group exhibited a significant decline in laying rates from weeks 9 to 12 compared to the initial 4 weeks (P = 0.042), while SIL supplementation maintained consistent laying rates throughout the study (P > 0.05). Notably, the SIL500 and SIL750 groups showed higher average egg weight than the CON group during weeks 5 to 8 (P = 0.049). The SIL750 group had a significantly higher average daily feed intake across the study period (P < 0.05), and the SIL500 group saw a marked decrease in the feed-to-egg ratio from weeks 5 to 8 (P = 0.003). Furthermore, the SIL500 group demonstrated significant reductions in serum ALT and AST levels (P < 0.05) and a significant decrease in serum triglycerides and total cholesterol at week 12 with increasing doses of SIL (P < 0.05). SIL also positively influenced liver enzyme expression (FASN, ACC, Apo-VLDL II, FXR, and CYP7A1; P < 0.05) and altered the cecal microbiota composition, enhancing species linked to secondary bile acid synthesis. Targeted metabolomics identified 9 metabolites predominantly involved in thiamin metabolism that were significantly different in the SIL groups (P < 0.05).

CONCLUSIONS

Our study demonstrated that dietary SIL supplementation could ameliorate egg production rate in late stage laying hens, mechanistically, this effect was via improving hepatic lipid metabolism and cecal microbiota function to achieve. Revealed the potentially of SIL as a feed supplementation to regulate hepatic lipid metabolism dysregulation. Overall, dietary 500 mg/kg SIL had the best effects.

Social Environment Alters the Duration of Rapid Yolk Deposition in Eggs of Domestic Hens

AbstractThe social environment can drive female birds to alter their investment in reproduction in the form of greater incubation behavior, more parental care, and greater allocation of physiological mediators to yolks. However, less is known about how social variables impact the speed at which females grow ovarian follicles in preparation for ovulation. We hypothesized that the social environment would influence how long ovarian follicles remain in rapid yolk deposition before reaching the size necessary for ovulation. For 8 d, we tested the effects of three types of social interactions: no social engagement (control), engagement with the same four females (social group 1), or engagement with the same four females plus six randomly selected roosters (social group 2). Starting on day 5 of engagement, we collected eggs and measured egg and yolk masses and yolk diameters. Then we stained the yolks with potassium dichromate to quantify the number of days the ovarian follicle spent accumulating yolk. We compared the results of the treatment groups with those of the control hens that were kept in individual laying cages throughout the study. The number of eggs laid, the yolk mass, and the yolk diameter did not differ among any of the three groups, but hens exposed to both females and males produced yolks with significantly more rings than hens in the other groups. Thus, the presence of males appeared to lengthen the time it took for ovarian follicles to reach the size needed for ovulation but did not result in larger or heavier yolks.

Fermented Aronia melanocarpa pomace improves the nutritive value of eggs, enhances ovarian function, and reshapes microbiota abundance in aged laying hens

Introduction

There is a decline in the quality and nutritive value of eggs in aged laying hens. Fruit pomaces with high nutritional and functional values have gained interest in poultry production to improve the performance.

Methods

The performance, egg nutritive value, lipid metabolism, ovarian health, and cecal microbiota abundance were evaluated in aged laying hens (320 laying hens, 345-day-old) fed on a basal diet (control), and a basal diet inclusion of 0.25%, 0.5%, or 1.0% fermented Aronia melanocarpa pomace (FAMP) for eight weeks.

Results

The results show that 0.5% FAMP reduced the saturated fatty acids (such as C16:0) and improved the healthy lipid indices in egg yolks by decreasing the atherogenicity index, thrombogenic index, and hypocholesterolemia/hypercholesterolemia ratio and increasing health promotion index and desirable fatty acids (P < 0.05). Additionally, FAMP supplementation (0.25%-1.0%) increased (P < 0.05) the ovarian follicle-stimulating hormone, luteinizing hormone, and estrogen 2 levels, while 1.0% FAMP upregulated the HSD3B1 expression. The expression of VTG II and ApoVLDL II in the 0.25% and 0.5% FAMP groups, APOB in the 0.5% FAMP group, and ESR2 in the 1% FAMP group were upregulated (P < 0.05) in the liver. The ovarian total antioxidant capacity was increased (P < 0.05) by supplementation with 0.25%-1.0% FAMP. Dietary 0.5% and 1.0% FAMP downregulated (P < 0.05) the Keap1 expression, while 1.0% FAMP upregulated (P < 0.05) the Nrf2 expression in the ovary. Furthermore, 1.0% FAMP increased cecal acetate, butyrate, and valerate concentrations and Firmicutes while decreasing Proteobacteria (P < 0.05).

Conclusion

Overall, FAMP improved the nutritive value of eggs in aged laying hens by improving the liver-blood-ovary function and cecal microbial and metabolite composition, which might help to enhance economic benefits.

Sex-specific effects of dietary restriction on physiological variables in Japanese quails

Nutritional limitation is a common phenomenon in nature that leads to trade-offs among processes competing for limited resources. These trade-offs are mediated by changes in physiological traits such as growth factors and circulating lipids. However, studies addressing the sex-specific effect of nutritional deficiency on these physiological variables are limited in birds. We used dietary restriction to mimic the depletion of resources to various degrees and investigated sex-specific effects on circulating levels of insulin-like growth factor 1 (IGF-1) and triglycerides in Japanese quails (Coturnix japonica) subjected to ad libitum, 20%, 30% or 40% restriction of their daily requirement, for 2 weeks. We also explored the association of both physiological variables with body mass and egg production. While dietary restriction showed no effects on circulating IGF-1, this hormone exhibited a marked sexual difference, with females having 64.7% higher IGF-1 levels than males. Dietary restriction significantly reduced plasma triglyceride levels in both sexes. Females showed more than six-fold higher triglyceride levels than males. Triglyceride levels were positively associated with body mass in females while showed not association in males. Overall, our findings revealed sex-specific expression of physiological variables under dietary restriction conditions, which coincide with body size.

High Dietary Folic Acid Supplementation Reduced the Composition of Fatty Acids and Amino Acids in Fortified Eggs

AIMS

The study aimed to evaluate the effects of dietary folic acid (FA) on the production performance of laying hens, egg quality, and the nutritional differences between eggs fortified with FA and ordinary eggs.

METHODS

A total of 288 26-week-old Hy-Line Brown laying hens (initial body weights 1.65 ± 0.10 kg) with a similar weight and genetic background were used. A completely randomized design divided the birds into a control group and three treatment groups. Each group consisted of six replicates, with twelve chickens per replicate. Initially, all birds were fed a basal diet for 1 week. Subsequently, they were fed a basal diet supplemented with 0, 5, 10, or 15 mg/kg FA in a premix for a duration of 6 weeks.

RESULTS

Supplementation of FA could significantly (p < 0.05) enhance the FA content in egg yolks, particularly when 10 mg/kg was used, as it had the most effective enrichment effect. Compared to the control group, the Glu content in the 10 and 15 mg/kg FA groups showed a significant (p < 0.05) decrease. Additionally, the contents of Asp, Ile, Tyr, Phe, Cys, and Met in the 15 mg/kg FA group were significantly (p < 0.05) lower compared to the other groups. Adding FA did not have significant effects on the levels of vitamin A and vitamin E in egg yolk, but the vitamin D content in the 5 and 10 mg/kg FA groups showed a significant (p < 0.05) increase. Furthermore, the addition of FA did not have a significant effect on the levels of Cu, Fe, Mn, Se, and Zn in egg yolk. The dietary FA did not have a significant effect on the total saturated fatty acids (SFA) and polyunsaturated fatty acid (PUFA) content in egg yolk. However, the total monounsaturated fatty acid (MUFA) content in the 5 and 10 mg/kg groups significantly (p < 0.05) increased. These changes in nutritional content might be attributed to the increased very low-density lipoprotein (VLDL) protein content. The significant decrease in solute carrier family 1 Member 1 (SLC1A1), solute carrier family 1 Member 2 (SLC1A2), and solute carrier family 1 Member 3 (SLC1A3) gene expression compared to the control group appeared to be the reason for the decrease in amino acid content in egg yolk within the dietary FA group.

CONCLUSION

The findings suggest that the appropriate addition of FA can enhance the levels of MUFA and vitamin D in egg yolks, thereby improving their nutritional value. Excessive intake of FA can decrease the effectiveness of enriching FA in egg yolk and impact the enrichment of certain amino acids. The yolk of eggs produced by adding 10 mg/kg of FA to the feed contains the optimal amount of nutrients. This study informs consumers purchasing FA-fortified eggs.

Attenuated AKT signaling by miR-146a-5p interferes with chicken granulosa cell proliferation, lipid deposition and progesterone biosynthesis

Steroid hormones play a crucial role in the growth and maturation of poultry ovarian follicles, with progesterone secretion by granulosa cells (GC) being essential. According to our previous transcriptome analysis, it apparented that miR-146a-5p expressions were upregulated in the follicles undergoing atresia. In this study, we delved the depth to explore the underlying mechanisms by miR-146a-5p in the regulation of follicle functions in chicken. The study demonstrated that miR-146a-5p suppressed cell growth, lipids accumulation, and progesterone biosynthesis in chicken GC. Through targeting association validations, we identified delta 4-desaturase, sphingolipid 1 (DEGS1) as capable of interacting with miR-146a-5p. Co-transfection experiments further confirmed that DEGS1 reversed the impairment of GC functions by miR-146a-5p. Moreover, we discovered that miR-146a-5p suppressed AKT phosphorylation, while DEGS1 enhanced AKT phosphorylation. Phosphatidylinositol-3 kinase (PI3K) inhibitor (LY294002) studies showed that miR-146a-5p would inhibit AKT phosphorylation by governing the DEGS1/AKT pathway, which in turn regulates GC function. In summary, the findings revealed that miR-146a-5p suppressed cell growth, lipid deposition, and progesterone biosynthesis via the DEGS1/AKT pathway. These results may further enrich our understandings of how non-coding RNA regulates productive performance in chickens.

Comparative analyses of laying performance and follicular development characteristics between fat and lean broiler lines

The deposition of high levels of fat in broiler breeder hens can have a profound impact on follicular development and laying performance. This study was formulated with the goal of comparing egg production and follicular development characteristics at different laying stages in the Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF). The egg production was analyzed using the birds from the 19th to 24th generations of NEAUHLF; the follicular development characteristics were analyzed by hematoxylin-eosin staining and quantitative real-time polymerase chain reaction using the birds from the 24th generation of NEAUHLF. The results showed that the age at first egg of lean hens was significantly earlier than that of fat hens in this study. While no significant differences in total egg output from the first egg to 50 wk of age were noted when comparing these 2 chicken lines, lean hens laid more eggs from the first egg to 35 wk of age relative to fat hens, whereas fat hens laid more eggs from wk 36 to 42 and 43 to 50 relative to their lean counterparts. No differences in ovarian morphology and small yellow follicle (SYF) histological characteristics were noted when comparing these 2 chicken lines at 27 wk of age. At 35 and 52 wk of age, however, lean hens exhibited significantly lower ovarian weight, ovarian proportion values, numbers of hierarchical follicles, hierarchical follicle weight, and SYF granulosa layer thickness as compared to fat hens, together with a significant increase in the number of prehierarchical follicles relative to those in fat hens. Gene expression analyses suggested that follicle selection was impaired in the fat hens in the early laying stage, whereas both follicle selection and maturation were impaired in the lean hens in the middle and late laying stages. Overall, these data highlight that fat deposition in broiler hens can have a range of effects on follicular development and egg production that are laying stage-dependent.

LncHLEF promotes hepatic lipid synthesis through miR-2188-3p/GATA6 axis and encoding peptides and enhances intramuscular fat deposition via exosome

Long noncoding RNAs (lncRNAs) have emergingly been implicated in mammalian lipid metabolism. However, their biological functions and regulatory mechanisms underlying adipogenesis remain largely elusive in chicken. Here, we systematically characterized the genome-wide full-length lncRNAs in the livers of pre- and peak-laying hens, and identified a novel intergenic lncRNA, lncHLEF, an RNA macromolecule with a calculated molecular weight of 433 kDa. lncHLEF was primarily distributed in cytoplasm of chicken hepatocyte and significantly up-regulated in livers of peak-laying hens. Functionally, lncHLEF could promote hepatocyte lipid droplet formation, triglycerides and total cholesterol contents. Mechanistically, lncHLEF could not only serve as a competitive endogenous RNA to modulate miR-2188-3p/GATA6 axis, but also encode three small functional polypeptides that directly interact with ACLY protein to enable its stabilization. Importantly, adeno-associated virus-mediated liver-specific lncHLEF overexpression resulted in increased hepatic lipid synthesis and intramuscular fat (IMF) deposition, but did not alter abdominal fat (AbF) deposition. Furthermore, hepatocyte lncHLEF could be delivered into intramuscular and abdominal preadipocytes via hepatocyte-secreted exosome to enhance intramuscular preadipocytes differentiation without altering abdominal preadipocytes differentiation. In conclusion, this study revealed that the lncHLEF could promote hepatic lipid synthesis through two independent regulatory mechanisms, and could enhance IMF deposition via hepatocyte-adipocyte communications mediated by exosome.

Effects of 3-Hydroxy-3-methylglutaryl-CoA Reductase Inhibitors on Cholesterol Metabolism in Laying Hens

This study aimed to investigate the effect of HMGCR inhibitors on egg yolk cholesterol content and its biological mechanisms. Four groups of 180-day-old laying hens (n = 8 cages/group, 6 laying hens/cage) were fed a corn/soybean-based diet (control) and the control diet supplemented with an HMGCR inhibitor at 60, 150, and 300 mg/kg for 4 weeks. The experimental results showed that adding HMGCR inhibitors of 150 mg/kg or more can significantly reduce the cholesterol content in the liver, yolk, serum, and pectoral muscles of laying hens. The RNA-seq results showed that compared with the control group, the addition of HMGCR inhibitors of 150 mg/kg or more to the diet significantly upregulated genes related to cholesterol synthesis in the liver, and the genes involved in steroid synthesis and metabolism, sterol synthesis and metabolism, and cholesterol synthesis and metabolism were all affected by the HMGCR inhibitors. In summary, adding HMGCR inhibitors of 150 mg/kg or more to the diet of hens can significantly reduce the cholesterol content in egg yolk. After the HMGCR inhibitors inhibited the activity of the liver HMGCR, they also altered the expression of genes related to cholesterol synthesis, bile acid synthesis, and cholesterol transport in the liver, and ultimately reduced cholesterol synthesis and cholesterol transport to the egg yolk.

The comparison of two different plumage-color lines of Japanese quail (Coturnix japonica) disclosed a significant effect in increasing abdominal fat contents with increasing age

This study aimed to investigate the characteristic differences between the white and brown-feathered Japanese quails, by evaluating the carcass traits and egg fat content, blood parameters, and intestinal histopathological features. A total of 1200 1-day-old Japanese quail chicks of two varieties (brown and white-feathered) were used in this study. Live body weight and feed intake were reordered every week. At the 4^th week of age, 80 birds from each variety were slaughtered and carcass quality measurements and histopathological changes were recorded. After 6 weeks of age, eggs were collected, and egg quality was assessed. The results revealed that white-feathered quails had significantly heavier body weights and higher growth rates. At 4 weeks of age, females of the white-feather quail had significantly heavier slaughter, after de-feathering, and carcass weights. Remarkable variations between the studied quail varieties, with significant dominance of females in both varieties, at the level of water holding capacity, pH, and meat tenderness ascertained an obvious superiority of white-feathered quails compared to brown ones and indicated the higher tendency of the white quails for meat production. These results were linked with significant changes in biochemical profiles including lipids biomarkers, total protein, and Ca and phosphorus levels along with variations in the intestinal morphometry. It can be concluded that white-feathered quails had, in general, higher values of productivity compared with the brown-feathered ones during growing and laying periods.

Low estradiol production of non-laying whooping cranes (Grus americana) is associated with the failure of small follicles to enter follicular hierarchy

For endangered species managed ex situ, production of offspring is a key factor to ensure healthy and self-sustaining populations. However, current breeding goals for the whooping crane (Grus americana) are impeded by poor reproduction. Our study sought to better understand mechanisms regulating ovarian function in ex situ managed whooping cranes and the regulatory function of the hypothalamic-pituitary-gonadal (HPG) axis in relation to follicle formation and egg laying. To characterize hormonal regulation of follicular development and ovulation, we collected weekly blood samples from six female whooping cranes during two breeding seasons, for a total of 11 reproductive cycles. The plasma samples were assessed for follicle stimulating hormone, luteinizing hormone, estradiol, and progesterone and the yolk precursors vitellogenin and very low-density lipoprotein. Ultrasonographic examination of the ovary was conducted at the time of blood collection. Preovulatory follicles (>12 mm) were present in laying cycles (n = 6) but absent in non-laying cycles (n = 5). The patterns of plasma hormone and yolk precursor concentrations corresponded to the stage of follicle development. Specifically, gonadotropin and yolk precursors concentrations increased as follicles transitioned from the non-yolky to yolky stage but did not increase further as the follicle advanced to preovulatory and ovulatory stages. Estrogen and progesterone concentrations increased as follicle size increased and reached peak concentrations (P < 0.05) when follicles developed to ovulatory and preovulatory stages, respectively. While overall mean circulating gonadotropin, progesterone, and yolk precursor concentrations did not differ for laying versus non-laying cycles, mean plasma estradiol in laying cycles was significantly higher than that in non-laying cycles. In summary, the findings suggested that disruption of mechanisms regulating follicle recruitment is likely responsible for the oviposition failure of the captive female whooping crane.

Influence of Improved Microclimate Conditions on Growth and Physiological Performance of Two Japanese Quail Lines

Microclimate parameters (ammonia, ambient temperature, heat index, and relative humidity) surrounding birds affect the production and health status of poultry. Therefore, this study aimed to evaluate the impact of adding natural zeolite to the litter of Japanese quail on improving microclimate parameters and its reflection in growth performance, blood gases, and blood biochemical parameters. A total of 1152 chicks were obtained from the same hatch at the 20th selection generation. Chicks were allocated into two groups based on the litter composition: Group 1: wheat straw as litter (untreated group); Group 2: 80% wheat straw + 20% zeolite (treated group). Each group consisted of 576 chicks: 410 selected line chicks and 166 control line chicks. Significant and favorable effects of the treatment on microclimate parameters during tested periods were found to favor the treated group. Either the treated group or the selected line had significantly better growth performance than the untreated group and control line. Zeolite-treated quails had significantly desirable blood gases and lower blood acidity and serum total iron binding capacity compared to the untreated group. Thus, adding natural zeolite to the litter enhanced the microclimate parameters that improved growth performance, blood gases, and blood biochemical parameters and reduced ammonia emission.

Egg Yolk Fat Deposition Is Regulated by Diacylglycerol and Ceramide Enriched by Adipocytokine Signaling Pathway in Laying Hens

The mechanism which regulates differential fat deposition in egg yolk from the indigenous breeds and commercial laying hens is still unclear. In this research, Chinese indigenous Huainan Partridge chickens and Nongda III commercial laying hens were used for egg collection and liver sampling. The weight of eggs and yolk were recorded. Yolk fatty acids were determined by gas chromatography-mass spectrometry. Lipid metabolites in the liver were detected by liquid chromatography-mass spectrometry. Yolk weight, yolk ratio and yolk fat ratio exhibited higher in the Huainan Partridge chicken than that of the Nongda III. Compared to the Nongda III, the content of total saturated fatty acid was lower, while the unsaturated fatty acid was higher in the yolk of the Huainan Partridge chicken. Metabolites of phosphatidylinositol and phosphatidylserine from glycerolphospholipids, and metabolites of diacylglycerol from glycerolipids showed higher enrichment in the Huainan Partridge chicken than that of the Nongda III, which promoted the activation of the adipocytokine signaling pathway. However, metabolites of phosphatidic acid, phosphatidylcholine, phosphatidylethanolamine and lysophosphatidylcholine from glycerol phospholipids, and metabolites of triacylglycerol from glycerolipids showed lower enrichment in the Huainan Partridge chicken than that of the Nongda III. The high level of yolk fat deposition in the Huainan Partridge chicken is regulated by the activation of the adipocytokine signaling pathway which can promote the accumulation of diacylglycerol and ceramide in the liver.

Dietary yolk supplementation decreases rates of yolk deposition in Japanese quail

Generation of egg yolk by birds requires the synthesis and deposition of large amounts of protein and lipid, and is often accompanied by the incorporation of additional physiological mediators. While there has been much work examining the relative quantities of yolk components, as well as potential adaptive patterns of their allocation, we still do not have a full understanding of what controls yolk formation and composition. Once ovarian follicles are recruited into the preovulatory hierarchy, the yolk is deposited in concentric rings, with one ring deposited per day. Previous studies have shown that there is substantial interspecific and intraspecific variation in the number of rings in yolks, and thus the number of days it took those yolks to grow. We hypothesized that the ability to grow follicles to maturity quickly is limited by the availability of materials to make yolk precursors in the female, either in body reserves or in dietary access. To test this, we supplemented the diets of Japanese quail with hard-boiled chicken yolk and examined the influences of treatment and female body condition on follicle growth rates. Contrary to predictions, females with higher body condition indices produced yolks that grew more slowly, and yolks from supplemented birds grew more slowly than controls. These results indicate that females can modulate the rate of yolk incorporation into developing follicles, and that an energy balance that is too high may not be optimal for the fast growth of developing ovarian follicles.

Effects of non-fasting molting on performance, oxidative stress, intestinal morphology, and liver health of laying hens

Animal welfare concerns in laying-hen production facilities have necessitated research on alternative strategies for improving egg production and hen health. At present, most laying-hen facilities in China use the fasting method, but with international emphasis on animal welfare, scholars have begun to find ways to improve production efficiency while ensuring animal welfare standards are adhered to. Therefore, this study investigated the effects of non-fasting molting on production performance, oxidative stress, intestinal morphology, and liver health of laying hens. A total of 180 healthy 90-week-old Dawu Jinfeng laying hens with similar body weights and laying rates (76 ± 2%) were randomly divided into three groups, with five replicates per group and 12 hens per replicate. The hens in the experimental group (NF) were molted using the non-fasting method, the negative control group (C) was not treated with centralized molting, and the positive control group (F) was molted using the fasting method. The results showed that: (1) During the molting period, the laying rate in the NF group (10.58%) decreased and was significantly lower than that in the other two groups (P < 0.05). During the secondary laying peak period, the laying rate in the NF group was highest (89.71%); significantly higher than that in the C group (P < 0.05). (2) During the molting period, compared to the C group, the NF group showed a significant decrease and increase in the total antioxidant capacity (T-AOC) and superoxide dismutase (T-SOD) activity, respectively (P < 0.05). During the secondary laying peak period, the T-SOD activity of the NF group was significantly lower than that of the C group (P < 0.05). (3) During the molting period, the villus height (VH) and the ratios of VH to crypt depth (V/C) of the duodenum, jejunum, and ileum in the NF group were significantly lower than those in the C group (P < 0.05). At the secondary laying peak period, the jejunum V/C was significantly higher than that in the C group (P < 0.05), whereas in the duodenum and ileum it increased but not significantly (P > 0.05). (4) During the molting period, serum glutathione transaminase (AST) and glutathione alanine transaminase (ALT) activities were significantly higher (P < 0.05), and very low-density lipoprotein (VLDL) content and liver weight were significantly lower (P < 0.05) in the non-fasted and fasted groups. However, there was a low degree of liver injury (cell boundary still visible) in the NF group. At the secondary laying peak period, there was no significant difference (P > 0.05) in the indices among the three groups and the liver returned to normal. In summary, non-fasting molting can improve the production performance of laying hens in the later stages, ensure the welfare and health of animals, and provide a theoretical basis for the efficient production of laying hens.

Feeding laying hens docosa hexaenoic acid-rich microalgae oil at 40 g/kg diet causes hypotriglyceridemia, depresses egg production, and attenuates expression of key genes affecting hepatic triglyceride synthesis and secretion, but is rescued by dietary co-supplementation of high-oleic sunflower oil

The primary goal of this study was to investigate the effect of feeding White Leghorn hens graded levels of a docosahexaenoic acid (DHA)-rich microalgae oil (MAO) on productive performance and enrichment of eggs with very long-chain (VLC) omega-3 (n-3) polyunsaturated fatty acids (PUFA). Forty-nine-week-old hens (8 per diet) were fed the following diets for 28 d: 1) A corn-soybean meal-based diet with no supplemental oil (CON); 2) CON + 10 g/kg MAO; 3) CON + 20 g/kg MAO; 4) CON + 30 g/kg MAO; 5) CON + 40 g/kg MAO; 6) CON + 40 g/kg MAO + 20 g/kg high-oleic sunflower oil (HOSO); and 7) CON + 40 g/kg MAO + 40 g/kg HOSO. Diets 6 and 7 were included because we previously reported that co-feeding high-oleic acid oils with n-3 PUFA-containing oils attenuated egg yolk n-3 PUFA contents vs. feeding hens the n-3 oils alone. All data were collected on an individual hen basis. Egg VLC n-3 PUFA enrichment plateaued, in terms of statistical significance, at the 30 g/kg MAO level (266 mg/yolk). Hens fed 40 g/kg MAO had greatly attenuated measures of hen performance, marked liver enlargement, an altered ovarian follicle hierarchy, greatly lowered circulating triglyceride levels, and depressed hepatic expression of key genes involved in triglyceride synthesis and secretion. As compared to hens fed 40 g/kg MAO alone, feeding hens 40 g/kg MAO co-supplemented with HOSO (Diets 6 and 7) restored egg production, ovarian morphology, and all other measures of hen productive performance to CON levels, elevated plasma triglyceride levels, prevented liver enlargement, and increased the hepatic expression of key genes involved in triglyceride synthesis and secretion. In conclusion, MAO can greatly enrich hens' eggs with VLC n-3 PUFA, but its recommended dietary inclusion should not exceed 20 g/kg. This would allow for near-maximal yolk VLC n-3 PUFA enrichment without impairing hen productive performance, altering the ovarian follicle hierarchy or, based on the work of others, presumably imparting off-flavors in the egg.

Flammulina velutipes stem regulates oxidative damage and synthesis of yolk precursors in aging laying hens by regulating the liver-blood-ovary axis

Egg production levels in late laying hens are negatively correlated with increasing age. Decreased liver and ovarian function in aging laying hens is accompanied by decreased antioxidant capacity, reproductive hormone levels, and follicular development, resulting in decreased synthesis of yolk precursors. The golden needle mushroom (Flammulina velutipes) has been reported to exhibit anti-inflammatory, antioxidant, and hypolipidemic properties. We aimed to reveal the therapeutic effects of F. velutipes stem (FVS) on liver-blood-ovary axis and investigate the underlying mechanisms. A total of 360 sixty-seven-wk-old laying hens were randomized into 4 treatment groups: 1) basal maize-soybean meal diet (CON); 2) basal maize + 20 g/kg FVS (2% FVS); 3) basal maize + 40 g/kg FVS (4% FVS); and 4) basal maize + 60 g/kg FVS (6% FVS). FVS groups demonstrated significantly increased egg production and ovarian development compared with the CON group. The addition of FVS increased the levels of antioxidant enzymes (GSH-Px, T-SOD, and T-AOC) in the liver, serum, and ovaries and decreased malondialdehyde levels by regulating the expression of proteins related to the Keap1-Nrf2/ARE signaling pathway. Additionally, FVS significantly decreased ovarian apoptosis by regulating Bax, Bcl-2, and caspase3 mRNA and protein expression levels. FVS significantly increased the expression levels of estradiol, progesterone, luteinizing hormone, and follicle stimulating hormone and their respective receptors. With increased levels of estradiol transported to the liver through the bloodstream, targeted binding to estrogen receptor (ER)-α and ER-β led to significant increases in ApoVLDL II, ApoB, and VTG II mRNA expression associated with yolk precursor synthesis. FVS decreased the levels of triglyceride and total cholesterol and significantly increased the expression of lipid metabolism, and transport-related mRNAs (FAS, PPAR-a/γ, and MTTP) in the liver. Therefore, the dietary supplementation of FVS can maintain the productive performance of aging laying hens by alleviating the degree of oxidative stress and regulating the transport of functional substances along the liver-blood-ovary axis, thereby improving the synthesis of yolk precursors.

Supplementation of Boswellia serrata and Salix alba Extracts during the Early Laying Phase: Effects on Serum and Albumen Proteins, Trace Elements, and Yolk Cholesterol

Extracts from Boswellia serrata (Bs) and Salix alba (Sa) are used as supplements in poultry feed. The aims of this research were to study the possible effects of dietary supplementation with Bs and Sa extracts on serum and albumen proteins, zinc and iron, and yolk cholesterol content in Leghorn hens during the critical phase of the onset of laying. A total of 120 pullets, 17 weeks of age, were assigned to two groups (control (C) and treated (T), n = 60 each). The T group received a supplement containing Bs (5%) and Sa (5%) for 12 weeks. The study lasted 19 weeks. Serum proteins were fractionated using agarose gel electrophoresis (AGE) and SDS–polyacrylamide gel electrophoresis (SDS–PAGE). Trace elements were determined in serum using atomic absorption spectrometry, and yolk cholesterol was determined using a colorimetric test. No significant differences were observed between control and supplemented hens for the analyzed biochemical indices. Moreover, the supplementation with phytoextracts did not negatively affect the physiological variations in serum proteins; therefore, it can be safely used as a treatment to prevent inflammatory states at onset and during the early laying phase.

The Diverse Roles of 17β-Estradiol in Non-Gonadal Tissues and Its Consequential Impact on Reproduction in Laying and Broiler Breeder Hens

Estradiol-17β (E2) has long been studied as the primary estrogen involved in sexual maturation of hens. Due to the oviparous nature of avian species, ovarian production of E2 has been indicated as the key steroid responsible for activating the formation of the eggshell and internal egg components in hens. This involves the integration and coordination between ovarian follicular development, liver metabolism and bone physiology to produce the follicle, yolk and albumen, and shell, respectively. However, the ability of E2 to be synthesized by non-gonadal tissues such as the skin, heart, muscle, liver, brain, adipose tissue, pancreas, and adrenal glands demonstrates the capability of this hormone to influence a variety of physiological processes. Thus, in this review, we intend to re-establish the role of E2 within these tissues and identify direct and indirect integration between the control of reproduction, metabolism, and bone physiology. Specifically, the sources of E2 and its activity in these tissues via the estrogen receptors (ERα, ERβ, GPR30) is described. This is followed by an update on the role of E2 during sexual differentiation of the embryo and maturation of the hen. We then also consider the implications of the recent discovery of additional E2 elevations during an extended laying cycle. Next, the specific roles of E2 in yolk formation and skeletal development are outlined. Finally, the consequences of altered E2 production in mature hens and the associated disorders are discussed. While these areas of study have been previously independently considered, this comprehensive review intends to highlight the critical roles played by E2 to alter and coordinate physiological processes in preparation for the laying cycle.

Choline diet improves serum lipid parameters and alters egg composition in breeder ducks

BACKGROUND

Choline is an important nutrient, playing key roles in numerous metabolic pathways relevant to animal health.

OBJECTIVES

The objective of this study was to evaluate the effect of dietary choline on the lipid parameters, cardiovascular health (CVH), and levels of egg trimethylamine (TMA) and cholesterol in breeder ducks during the late laying period.

METHODS

A total of 60 Jingjiang ducks were randomly separated into six replicates of 10 ducks each. After peak production until 65 weeks of age, the birds were fed a control basal diet. The same ducks served as the control group until 65 weeks of age, when the same ducks served as the choline-supplemented group, after 15 days of dietary choline supplementation at 2955 mg/kg choline above and over the basal diet initially provided. The 15 days of choline supplementation included an initial 5-day acclimatisation period.

RESULTS

Dietary choline supplementation increased serum TMA (p < 0.01), high-density lipoprotein cholesterol, very low-density lipoprotein, and triglyceride levels in older breeder ducks. However, it did not change the levels of trimethylamine N-oxide but decreased the atherosclerosis index compared with those of the control group (p < 0.01). Moreover, it increased (p < 0.01) the egg yolk TMA levels but did not change the concentrations of cholesterol in egg yolk.

CONCLUSIONS

Dietary choline supplementation had a beneficial effect on lipid parameters and CVH in older breeder ducks, although it increased the serum and egg yolk TMA levels.

Safety Evaluation of Porcine Bile Acids in Laying Hens: Effects on Laying Performance, Egg Quality, Blood Parameters, Organ Indexes, and Intestinal Development

Bile acids (BAs) have long been known to facilitate digestion, transport, and absorption of lipids in the small intestine as well as regulate host lipid metabolic homeostasis. However, excessive BAs may lead to long-term damage to tissue. Also, it is unknown whether different levels of porcine BAs supplementation could improve performance, host metabolism, intestinal functions in laying hens. Hence, this study was aimed to investigate the potential effects of BAs addition on laying performance, egg quality, blood parameters, organ indexes, and intestinal histopathology of hens in the late phase. A total of 300 58-week-old Hy-line Gray hens were randomly divided into five groups which fed a basal diet (control) or basal diets supplemented with 60, 300, 600, and 3,000 mg/kg BAs for 56 days. Compared with the control group, no significant differences (P > 0.05) were observed in egg production, egg weight, ADFI, and FCR of hens in 60, 300, 600, and 3,000 mg/kg BAs groups. Dietary 60 mg/kg BAs supplementation resulted in a significant increase (P < 0.05) in egg mass. Meanwhile, no significant differences were observed in egg quality, including eggshell strength, eggshell thickness, albumen height, and Haugh unit among any treatment groups (P > 0.05). Dramatically, dietary 3,000 mg/kg BAs supplement decreased yolk color (P < 0.05). There was no significant difference in the blood parameters such as WBC, RBC, HGB, HCT, and PLT among any treatments. However, in 3,000 mg/kg BAs group, ovary coefficient was lower than the control (P < 0.05), and serum urea and creatinine were higher than the control (P < 0.05). Also, kidney and oviduct injury appeared in 3,000 mg/kg BAs group. These results indicated that a porcine BAs concentration of 3,000 mg/kg may cause harmful effects while 600 mg/kg was non-deleterious to laying hens after a daily administration for 56 days, namely that dietary supplement of up to 10 times the recommended dose of BAs was safely tolerated by laying hens.

Impact of growth curve and dietary energy-to-protein ratio of broiler breeders on egg quality and egg composition

Egg characteristics have an impact on embryonic development and post-hatch performance of broilers. The impact of growth curve (GC) and dietary energy-to-protein ratio of broiler breeder hens on egg characteristics was investigated. At hatch, 1,536 pullets were randomly allotted to 24 pens in a 2 × 4 factorial dose-response design with 2 GC (standard growth curve = SGC or elevated growth curve = EGC (+ 15%)) and 4 diets, differing in energy-to-protein ratio (defined as 96%, 100%, 104% and 108% AME_n diet). Feed allocation per treatment was adapted weekly to achieve the targeted GC and to achieve pair-gain of breeders within each GC. Breeders on an EGC produced larger eggs (∆ = 2.3 g; P < 0.001) compared to breeders on a SGC. An exponential regression curve, with age (wk) of the breeders, was fitted to describe the impact of GC and dietary energy-to-protein ratio on egg composition. Yolk weight was 0.8 g higher for eggs from EGC breeders than from SGC breeders (a−108.1*0.907Age, where a was 22.1 and 22.9 for SGC and EGC, respectively; R² = 0.97; P<0.001). An interaction between GC and dietary energy-to-protein ratio on albumen weight was observed (P = 0.04). Dietary energy-to-protein ratio did not affect albumen weight in SGC breeders (42.7−56.2*0.934Age; R² = 0.89), but for EGC breeders, a higher dietary energy-to-protein ratio resulted in a 0.9 g lower albumen weight from 96% AME_n to 108% AME_n (a−62.9*0.926Age, where a was 43.4, 43.2, 42.8, and 42.5 for 96% AME_n, 100% AME_n, 104% AME_n, and 108% AME_n, respectively; R² = 0.86). Albumen DM content decreased linearly with an increased dietary energy-to-protein ratio, but this was more profound in EGC breeders (β = −0.03 %/% AME_n) than in SGC breeders (β = −0.01 %/% AME_n; P = 0.03). Overall, it can be concluded that an EGC for breeders led to larger eggs with a more yolk and albumen, whereas dietary energy-to-protein ratio had minor effects on egg composition.

Associations of the T329S Polymorphism in Flavin-Containing Monooxygenase 3 With Atherosclerosis and Fatty Liver Syndrome in 90-Week-Old Hens

This study aimed to evaluate the effects of the spontaneous genetic mutation T329S in flavin-containing monooxygenase 3 (FMO3) on atherosclerosis (AS), fatty liver syndrome (FLS), and adiposity in 90-week-old layers. At 90 weeks of age, 27 FMO3 genotyped Rhode Island White chickens (consisting of nine AA hens, nine AT hens, and nine TT hens) with normal laying performance were selected. The AS lesions, incidence of FLS, fat deposition, metabolic characteristics, and production performance of these egg-layers with different FMO3 genotypes were assessed. The T329S mutation in TT hens reduced the AS lesions (P < 0.01) and altered the plasma metabolic indices more than it did in the AA and AT hens. Furthermore, it reduced the incidence of FLS, hepatic triglyceride deposition (P < 0.05), liver indices (P < 0.05), and fat deposition (P < 0.05) in the subcutis and abdomen of TT hens compared to those of AA and AT hens. Moreover, as an effect of T329S, TT hens laid a higher than average number of eggs and maintained a higher egg-laying rate from 68 to 90 weeks than AA and AT hens. Our study confirmed that the T329S mutation in FMO3 could reduce the development of AS lesions, the incidence of FLS, and fat deposition, which are associated with changes in plasma and hepatic metabolic indices and improvements in the laying performance of older layers. Our results may provide a new strategy for using the T329S mutation to improve the health status and production performance of layers during the late laying period.

Expression of Oocyte Vitellogenesis Receptor Was Regulated by C/EBPα in Developing Follicle of Wanxi White Goose

Yolk precursor was synthesized under regulation of hormone secretion, while the mechanism of its incorporation into follicle is still unknown. The reproductive hormones, oocyte vitellogenesis receptor (OVR) expression at pre-, early-, peak- and ceased-laying period, and localization of Wanxi White goose were determined in this study. The results showed that the concentration of LH was lowest in serum at peak laying period compared to the other periods (p < 0.01). Moreover, the concentration of E2 was highest (p < 0.01) in serum at early laying period than that of other periods. Moreover, the gene expression level of OVR was highest at ceased laying period compared to other periods (p = 0.014) and was higher in developing follicles than other follicles (p < 0.01). The OVR was distributed in the granular cell layer and decreased with the maturation of follicles. Five transcription factors were predicted in the promoter of OVR, then were screened and verified by overexpression in granulosa cells. C/EBPα and MF3 significantly stimulated the expression of OVR. The combined overexpression of C/EBPα and OVR significantly stimulated the transportation of lipid from culture medium to cytoplasm. In conclusion, C/EBPα is the key transcription factor promoting OVR expression in goose follicle granulosa cells.

T329S Mutation in the FMO3 Gene Alleviates Lipid Metabolic Diseases in Chickens in the Late Laying Period

Simple Summary

The lipid deposition and health status of egg-laying hens is crucial to the development of the poultry industry. This study aimed to evaluate the effects of genetic variations in the flavin-containing monooxygenase 3 (FMO3) on the lipid metabolic diseases of laying hens during the late laying period. The results showed that the T329S mutation in FMO3 moderated the lipid parameters and decreased the atherosclerotic lesions and hepatic steatosis in laying hens with homozygous T329S mutation. In conclusion, the T329S mutation in FMO3 is closely associated with the improvement of lipid metabolic diseases in laying hens during the late laying period. The results of this study may contribute to overcoming the challenge of lipid metabolic diseases in laying hens during the late laying period.

Abstract

The T329S mutation in flavin-containing monooxygenase 3 (FMO3) impairs the trimethylamine (TMA) metabolism in laying hens. The TMA metabolic pathway is closely linked to lipid metabolic diseases, such as atherosclerosis and fatty liver disease. We aimed to evaluate the effects of the T329S mutation in FMO3 on lipid metabolism in chickens during the late laying period. We selected 18 FMO3 genotyped individuals (consisting of six AA, six AT, and six TT hens) with similar body weight and production performance. The lipid metabolism and deposition characteristics of the laying hens with different genotypes were compared. The T329S mutation moderated the serum-lipid parameters in TT hens compared to those in AA and AT hens from 49 to 62 weeks. Furthermore, it reduced the serum trimethylamine N-oxide concentrations and increased the serum total bile acid (p < 0.05) and related lipid transporter levels in TT hens. Moreover, it significantly (p < 0.01) decreased atherosclerotic lesions and hepatic steatosis in TT hens compared to those in the AA and AT hens. Our findings may help improve the health status in laying hens during the late laying period.

Roles of Estrogens in the Healthy and Diseased Oviparous Vertebrate Liver

The liver is a vital organ that sustains multiple functions beneficial for the whole organism. It is sexually dimorphic, presenting sex-biased gene expression with implications for the phenotypic differences between males and females. Estrogens are involved in this sex dimorphism and their actions in the liver of several reptiles, fishes, amphibians, and birds are discussed. The liver participates in reproduction by producing vitellogenins (yolk proteins) and eggshell proteins under the control of estrogens that act via two types of receptors active either mainly in the cell nucleus (ESR) or the cell membrane (GPER1). Estrogens also control hepatic lipid and lipoprotein metabolisms, with a triglyceride carrier role for VLDL from the liver to the ovaries during oogenesis. Moreover, the activation of the vitellogenin genes is used as a robust biomarker for exposure to xenoestrogens. In the context of liver diseases, high plasma estrogen levels are observed in fatty liver hemorrhagic syndrome (FLHS) in chicken implicating estrogens in the disease progression. Fishes are also used to investigate liver diseases, including models generated by mutation and transgenesis. In conclusion, studies on the roles of estrogens in the non-mammalian oviparous vertebrate liver have contributed enormously to unveil hormone-dependent physiological and physiopathological processes.

Global investigation of estrogen-responsive genes regulating lipid metabolism in the liver of laying hens

BACKGROUND

Estrogen plays an essential role in female development and reproductive function. In chickens, estrogen is critical for lipid metabolism in the liver. The regulatory molecular network of estrogen in chicken liver is poorly understood. To identify estrogen-responsive genes and estrogen functional sites on a genome-wide scale, we determined expression profiles of mRNAs, lncRNAs, and miRNAs in estrogen-treated ((17β-estradiol)) and control chicken livers using RNA-Sequencing (RNA-Seq) and studied the estrogen receptor α binding sites by ChIP-Sequencing (ChIP-Seq).

RESULTS

We identified a total of 990 estrogen-responsive genes, including 962 protein-coding genes, 11 miRNAs, and 17 lncRNAs. Functional enrichment analyses showed that the estrogen-responsive genes were highly enriched in lipid metabolism and biological processes. Integrated analysis of the data of RNA-Seq and ChIP-Seq, identified 191 genes directly targeted by estrogen, including 185 protein-coding genes, 4 miRNAs, and 2 lncRNAs. In vivo and in vitro experiments showed that estrogen decreased the mRNA expression of PPARGC1B, which had been reported to be linked with lipid metabolism, by directly increasing the expression of miR-144-3p.

CONCLUSIONS

These results increase our understanding of the functional network of estrogen in chicken liver and also reveal aspects of the molecular mechanism of estrogen-related lipid metabolism.

Serum Metabolomic Profiling to Reveal Potential Biomarkers for the Diagnosis of Fatty Liver Hemorrhagic Syndrome in Laying Hens

Fatty liver hemorrhage syndrome (FLHS), a nutritional and metabolic disease that frequently occurs in laying hens, causes serious losses to the poultry industry. Nowadays, the traditional clinical diagnosis of FLHS still has its limitations. Therefore, searching for some metabolic biomarkers and elucidating the metabolic pathway in vivo are useful for the diagnosis and prevention of FLHS. In the present study, a model of FLHS in laying hens induced by feeding a high-energy, low-protein diet was established. Gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) was used to analyze the metabolites in serum at days 40 and 80. The result showed that, in total, 40 differential metabolites closely related to the occurrence and development of FLHS were screened and identified, which were mainly associated with lipid metabolism, amino acid metabolism, and energy metabolism pathway disorders. Further investigation of differential metabolites showed 10 potential biomarkers such as 3-hydroxybutyric acid, oleic acid, palmitoleic acid, and glutamate were possessed of high diagnostic values by analyzing receiver operating characteristic (ROC) curves. In conclusion, this study showed that the metabolomic method based on GC-TOF-MS can be used in the clinical diagnosis of FLHS in laying hens and provide potential biomarkers for early risk evaluation of FLHS and further insights into FLHS development.

Slight Disruption in Intestinal Environment by Dextran Sodium Sulfate Reduces Egg Yolk Size Through Disfunction of Ovarian Follicle Growth

Intestinal environments such as microbiota, mucosal barrier function, and cytokine production affect egg production in laying hens. Dextran sodium sulfate (DSS) is an agent that disrupts the intestinal environment. Previously, we reported that the oral administration of dextran sodium sulfate (DSS: 0.9 g/kg BW) for 5 days caused severe intestinal inflammation in laying hens. However, the DSS concentration in the previous study was much higher to induce a milder disruption of the intestinal environment without heavy symptoms. Thus, the goal of this study was to determine the effects of a lower dose of DSS on the intestinal environment and egg production in laying hens. White Leghorn laying hens (330-day old) were oral administered with or without 0.225 g DSS/kg BW for 28 days (DSS and control group: n = 7 and 8, respectively). Weekly we collected all laid eggs and blood plasma samples. Intestinal tissues, liver, ovarian follicles, and the anterior pituitary gland were collected 1 day after the final treatment. Lower concentrations of orally administered DSS caused (1) a decrease in the ratio of villus height/crypt depth, occludin gene expressions in large intestine and cecal microbiota diversity, (2) a decrease in egg yolk weight, (3) an increase in VLDLy in blood plasma, (4), and enhanced the egg yolk precursor accumulation in the gene expression pattern in the follicular granulosa layer, (5) an increase in FSH and IL-1β gene expression in the pituitary gland, and (6) an increase in concentration of plasma lipopolysaccharide binding protein. These results suggested that the administration of the lower concentration of DSS caused a slight disruption in the intestinal environment. This disruption included poor intestinal morphology and decreased cecal microbiome diversity. The change in the intestinal environment decreases egg yolk size without decreasing the VLDLy supply from the liver. The decrease in egg yolk size is likely to be caused by the dysfunction of egg-yolk precursor uptake in ovarian follicles. In conclusion, the oral administration of a lower dose of DSS is an useful method to cause slight disruptions of intestinal environment, and the intestinal condition decreases egg yolk size through disfunction of ovarian follicle.

Sexual Maturity Promotes Yolk Precursor Synthesis and Follicle Development in Hens via Liver-Blood-Ovary Signal Axis

Several reproductive hormones were reported to be involved in regulating egg yolk precursor synthesis in chickens; however, the mechanism that shows how the liver-blood-ovary signal axis works in relation to age changes has not been reported yet. Therefore, in this study, we observe the morphology and histology of the liver and ovary and determine the serum biochemical parameters and the expression abundance of the critical genes from d90 to 153. Results show that the body weight and liver weight were significantly increased from d132, while the ovary weight increased from d139. Aside from the increase in weight, other distinct changes such as the liver color and an increased deposition of large amounts of yolk precursors into the ovarian follicles were observed. On d139, we observed small fatty vacuoles in the hepatocytes. The results of serum biochemical parameters showed a significant increase in the estradiol (E₂) level, first on d125, and then it reached its peak on d132. Meanwhile, the levels of follicle-stimulating hormone (FSH) increased initially and then remained at a high level from d146 to d153, while the levels of luteinizing hormone (LH) increased significantly on d132 and reached the top level on d153. Moreover, the levels of lecithin (LEC), vitellogenin (VTG), very low density lipoprotein y (VLDLy), triglyceride (TG), and total cholesterol (TC) were significantly increased at d125 and were close from d146 to d153. The mRNA and protein expression of estrogen receptor-alpha (ER-α) and E₂ levels in the liver and serum, respectively, showed similar changes. Moreover, with reference to an increase in serum E₂ level, the mRNA expression of genes related to yolk precursor synthesis (very low density apolipoprotein-II, ApoVLDL-II) and vitellogenin-II (VTG-II), lipogenesis (fatty acid synthase, FAS), and lipid transport (microsomal triglyceride transport protein, MTTP) in the liver showed up-regulation. These results suggest that the correlation between liver-blood-ovary alliances regulate the transport and exchange of synthetic substances to ensure synchronous development and functional coordination between the liver and ovary. We also found that E₂ is an activator that is regulated by FSH, which induces histological and functional changes in the hepatocytes through the ER-α pathway.

Expression characteristics and regulatory mechanism of Apela gene in liver of chicken (Gallus gallus)

Apela, a novel endogenous peptide ligand for the G-protein-coupled apelin receptor, was first discovered and identified in human embryonic stem cells in 2013. Apela has showed some biological functions in promoting angiogenesis and inducing vasodilatation of mammals by binding apelin receptor, but little is known about its expression characteristics and regulatory mechanism in chicken. In the present study, the coding sequences of Apela in chicken was cloned. The evolution history and potential function of Apela were analyzed. Subsequently, the spatiotemporal expression characteristics of chicken Apela were investigated. Furthermore, the regulatory mechanism of Apela mRNA responsing to estrogen was explored by in vitro and in vivo experiments. The results showed that the length of the CDs of Apela mRNA was 165 bp and encoded a protein consisting of 54 amino acids residues with a transmembrane domain in chicken. The Apela was derived from the same ancestor of Apelin, and abundantly expressed in liver, kidney and pancreas tissues. The expression levels of Apela in the liver of hens were significantly higher at the peak-laying stage than that at the pre-laying stage (p ≤ 0.05). The Apela mRNA levels were significantly up-regulated in primary hepatocytes treated with 17β-estradiol (p ≤ 0.05), and could be effectively inhibited by estrogen receptor antagonists MPP, ICI 182780 and tamoxifen. It indicated that chicken Apela expression was regulated by estrogen via estrogen receptor α (ERα). In individual levels, both the contents of TG, TC and VLDL-c in serum, and the expression of ApoVLDLII and Apela in liver markedly up-regulated by 17β-estradiol induction at 1mg/kg and 2mg/kg concentrations (p ≤ 0.05). This study lays a foundation for further research on Apela involving in hepatic lipid metabolism.

Comparative Analysis of Metabolites in the Liver of Muscovy Ducks at Different Egg-Laying Stages Using Nontargeted Ultra-High-Performance Liquid Chromatography-Electrospray Mass Spectrometry-Based Metabolomics

Liver plays an important physiological function in the synthesis of yolk materials during egg laying in birds. Liver metabolite profiles of Muscovy ducks at different egg-laying stages from the perspective of nontargeted metabolomics were analyzed in this study. Twelve Muscovy ducks were selected at pre-laying (22 weeks, TT group), laying (40 weeks, FT group), and post-laying (60 weeks, ST group) stages, resulting in 36 hepatic metabolite profiles by using ultra-high-performance liquid chromatography-electrospray mass spectrometry. A total of 324 differential metabolites (156 increased and 168 decreased) in FT as compared to the TT (FT/TT) group and 332 differential metabolites (120 increased and 212 decreased) in ST as compared to the FT (ST/FT) group were screened out. Metabolic pathways enriched in FT/TT and ST/FT groups were mainly amino acid metabolism, glycerophospholipid metabolism, nucleotide metabolism, and vitamin metabolism. The amino acid metabolism pathways were upregulated in the FT/TT group and downregulated in the ST/FT group (P < 0.05). The glutathione and ascorbic acid abundances were downregulated, and the choline abundance was upregulated during egg laying (P < 0.05). The liver provides amino acids, lipids, nucleotides, vitamins, and choline, and so on, which are essential materials for yolk precursor synthesis. The decrease in the abundance of glutathione and ascorbic acid indicates that Muscovy ducks might be in a relatively stable physiological state during egg laying.

Calcium and Cholecalciferol Levels in Late-Phase Laying Hens: Effects on Productive Traits, Egg Quality, Blood Biochemistry, and Immune Responses

Productive traits and immunity in laying hens decrease sharply during the late phase of laying due to aging, which negatively affects the metabolism and hormonal status of the animals. The influence of Ca levels (3.5, 4.0, and 4.5%) and/or cholecalciferol [Vitamin D₃ (VD₃)] supplementation (800-, 1,000-, and 1,200-IU/kg diet or as total of 3,800, 4,000, and 4,200 IC VD₃) on performance, egg quality, blood biochemistry, and immunity of brown egg layers was investigated. Three hundred and sixty H&N Brown egg layers (60 weeks old) were allocated at random into nine nutritional treatments of five replications (cages) of eight hens each. The control diet in this experiment contained a 3.5% Ca level with 800 IU VD₃. The addition of VD₃ at 1,000 and 1,200 IU to 3.5 and 4% Ca diets significantly (P ≤ 0.05) increased the rate of laying, egg mass, and feed conversion ratio (FCR) compared to the control diet on 3.5% and 800 U of VD₃. Besides this, the addition of VD₃ at 800 and 1,200 IU to 3.5% Ca level diets enhanced the Haugh unit score. Similar results were observed in eggshell quality measurements and tibia ash. Increasing the Ca concentration from 3.5 to 4 and 4.5% and increasing VD₃ levels from 800 to 1,000 or 1,200 IU significantly and similarly increased serum total protein and globulin. In addition, VD₃ at 1,000 IU increased serum albumin, compared to 800 IU. Increasing Ca level increased IgA, and 4 and 4.5% Ca levels similarly increased IgG and α-2 globulin compared to the 3.5% Ca diet. VD₃ addition at 1,200 IU to the 4% Ca diet significantly increased γ-globulin compared to 1,000 IU, but decreased β-globulin. Increasing the Ca level to 4% significantly reduced serum triglycerides, and the very low-density lipoprotein and the triglyceride/high-density lipoprotein ratio were both decreased with 4 and 4.5% Ca level diets. Increasing the Ca level caused a stepwise increase in catalase, which was markedly increased with VD₃ supplementation at 1,200 IU. Plasma estrogen was increased considerably with VD₃ supplementation at 3.5% Ca, but parathyroid hormone levels were not affected. In conclusion, increasing Ca levels in the diet of laying hens to 4% during the late production phase could be a useful tool to improve laying performance, eggshell quality, Haugh unit score, and physiological and immunological status. Besides, VD₃ at a 1,000 IU/kg diet to 3.5% Ca improved performance of hens fed 3.5% Ca, showing that the potential impact of VD₃ depends on Ca concentrations.

Should I Lay or Should I Grow: Photoperiodic Versus Metabolic Cues in Chickens

While photoperiod has been generally accepted as the primary if not the exclusive cue to stimulate reproduction in photoperiodic breeders such as the laying hen, current knowledge suggests that metabolism, and/or body composition can also play an influential role to control the hypothalamic-pituitary gonadal (HPG)-axis. This review thus intends to first describe how photoperiodic and metabolic cues can impact the HPG axis, then explore and propose potential common pathways and mechanisms through which both cues could be integrated. Photostimulation refers to a perceived increase in day-length resulting in the stimulation of the HPG. While photoreceptors are present in the retina of the eye and the pineal gland, it is the deep brain photoreceptors (DBPs) located in the hypothalamus that have been identified as the potential mediators of photostimulation, including melanopsin (OPN4), neuropsin (OPN5), and vertebrate-ancient opsin (VA-Opsin). Here, we present the current state of knowledge surrounding these DBPs, along with their individual and relative importance and, their possible downstream mechanisms of action to initiate the activation of the HPG axis. On the metabolic side, specific attention is placed on the hypothalamic integration of appetite control with the stimulatory (Gonadotropin Releasing Hormone; GnRH) and inhibitory (Gonadotropin Inhibitory Hormone; GnIH) neuropeptides involved in the control of the HPG axis. Specifically, the impact of orexigenic peptides agouti-related peptide (AgRP), and neuropeptide Y (NPY), as well as the anorexigenic peptides pro-opiomelanocortin (POMC), and cocaine-and amphetamine regulated transcript (CART) is reviewed. Furthermore, beyond hypothalamic control, several metabolic factors involved in the control of body weight and composition are also presented as possible modulators of reproduction at all three levels of the HPG axis. These include peroxisome proliferator-activated receptor gamma (PPAR-γ) for its impact in liver metabolism during the switch from growth to reproduction, adiponectin as a potential modulator of ovarian development and follicular maturation, as well as growth hormone (GH), and leptin (LEP).

Long Non-coding RNA and mRNA Profile of Liver Tissue During Four Developmental Stages in the Chicken

The liver is the major organ of lipid biosynthesis in the chicken. In laying hens, the liver synthesizes most of the yolk precursors and transports them to developing follicles to produce eggs. However, a systematic investigation of the long non-coding RNA (lncRNA) and mRNA transcriptome in liver across developmental stages is needed. Here, we constructed 12 RNA libraries from liver tissue during four developmental stages: juvenile (day 60), sexual maturity (day 133), peak laying (day 220), and broodiness (day 400). A total of 16,930 putative lncRNAs and 18,260 mRNAs were identified. More than half (53.70%) of the lncRNAs were intergenic lncRNAs. The temporal expression pattern showed that lncRNAs were more restricted than mRNAs. We identified numerous differentially expressed lncRNAs and mRNAs by pairwise comparison between the four developmental stages and found that VTG2, RBP, and a novel protein-coding gene were differentially expressed in all stages. Time-series analysis showed that the modules with upregulated genes were involved in lipid metabolism processes. Co-expression networks suggested functional relatedness between mRNAs and lncRNAs; the DE-lncRNAs were mainly involved in lipid biosynthesis and metabolism processes. We showed that the liver transcriptome varies across different developmental stages. Our results improve our understanding of the molecular mechanisms underlying liver development in chickens.

Identification of a Novel Lipid Metabolism-Associated Hepatic Gene Family Induced by Estrogen via ERα in Chicken (Gallus gallus)

Liver is the main organ of lipid metabolism in chicken, especially for laying hens. To explore the molecular mechanism of lipid metabolism in chicken, five novel genes discovered in chicken liver tissue were systematically studied. Bioinformatic analysis was used to analyze the gene characteristics. The expression patterns and regulatory molecular mechanism of the five genes were examined. Our results showed that all five novel genes contain a common NADP-binding site that belongs to the NADB-Rossmann superfamily, and the genes were designated NADB-LER1-5. Phylogenetic tree of the NADB-LERs gene family in different species suggested these five genes originated from the same ancestor. Tissue distributions showed that NADB-LER1-4 genes were highly expressed in lipid metabolism organs, including liver, kidney and duodenum, and that the NADB-LER5 gene was highly expressed in liver and kidney. The spatiotemporal expression indicated that the expression levels of NADB-LER1-5 genes in liver tissue were significantly greater in sexually mature hens than that of immature pullets (P-value ≤ 0.05). The expression levels of NADB-LER1-5 were significantly induced by 17β-estradiol in primary cultured chicken embryo hepatocytes (P-value ≤ 0.05), and 17β-estradiol regulated the expression of NADB-LER1-5 mediated by ERα. Individual assays verified that under induction of 17β-estradiol, the five novel genes were significantly upregulated, with subsequent alteration in serum TG, TC, and VLDLs in 10-week-old pullets. This study proved NADB-LERs family mainly expressed in liver, kidney, and duodenum tissues. 17β-estradiol induces the expression of NADB-LER1-5 genes predominantly mediated via ERα. They likely involved in lipid metabolism in the liver of chicken.

Dietary betaine improves egg-laying rate in hens through hypomethylation and glucocorticoid receptor-mediated activation of hepatic lipogenesis-related genes

In avian species, liver lipid metabolism plays an important role in egg laying performance. Previous studies indicate that betaine supplementation in laying hens improves egg production. However, it remains unclear if betaine improves laying performance by affecting hepatic lipid metabolism and what mechanisms are involved. We fed laying hens a 0.5% betaine-supplemented diet for 4 wks to investigate its effect on hepatic lipids metabolism in vivo and confirmed its mechanism via in vitro experiments using embryonic chicken hepatocytes. Results showed that betaine supplemented diet enhanced laying production by 4.3% compared with normal diet, accompanied with increased liver and plasma triacylglycerol concentrations (P < 0.05) in hens. Simultaneously, key genes involved in hepatic lipid synthesis, such as sterol regulatory element binding protein 1 (SREBP-1), fatty acid synthase, acetyl-CoA carboxylase, and stearoyl-CoA desaturase 1 (SCD1) were markedly upregulated at the mRNA level (P < 0.05). Western blot results showed that SREBP-1 and SCD1 protein levels were also increased (P < 0.05). Moreover, mRNA expression of main apolipoprotein components of yolk-targeted lipoproteins, apolipoprotein B (ApoB) and apolipoprotein-V1 (ApoV1), in addition to microsomal triglyceride transfer proteins, which is closely related to the synthesis and release of very-low density lipoprotein, were also markedly elevated (P < 0.05). Methylated DNA immunoprecipitation combined with PCR detects reduction of methylation levels in certain regions of the above gene promoters. Chromatin immunoprecipitation PCR assays showed increased binding of glucocorticoid receptor (GR) to SREBP1 and ApoB gene promoters. Similar results of ApoV1 gene expression were obtained from cultured hepatocytes treated with betaine. Additionally, betaine increased the expression of GR and some genes involved in methionine cycle in vitro. These results suggest that betaine supplementation could alter the expression of liver lipid synthesis and transport-related genes by modifying the methylation status and GR binding on their promoter and hence promote the synthesis and release of yolk precursor substances in the liver.

Estrogen Abolishes the Repression Role of gga-miR-221-5p Targeting ELOVL6 and SQLE to Promote Lipid Synthesis in Chicken Liver

Few studies have been conducted regarding the biological function and regulation role of gga-miR-221-5p in the liver. We compared the conservation of miR-221-5p among species and investigated the expression pattern of gga-miR-221-5p, validating the direct target genes of gga-miR-221-5p by dual luciferase reporter assay, the biological function of gga-miR-221-5p in the liver was studied by gga-miR-221-5p overexpression and inhibition. Furthermore, we explored the regulation of gga-miR-221-5p and its target genes by treatment with estrogen and estrogen antagonists in vivo and in vitro. The results showed that miR-221-5p was highly conserved among species, expressed in all tested tissues and significantly downregulated in peak-laying hen liver compared to pre-laying hen liver. Gga-miR-221-5p could directly target the expression of elongase of very long chain fatty acids 6 (ELOVL6) and squalene epoxidase (SQLE) genes to affect triglyceride and total cholesterol content in the liver. 17β-estradiol could significantly inhibit the expression of gga-miR-221-5p but promote the expression of ELOVL6 and SQLE genes. In conclusion, the highly conservative gga-miR-221-5p could directly target ELOVL6 and SQLE mRNAs to affect the level of intracellular triglyceride and total cholesterol. Meanwhile, 17β-estradiol could repress the expression of gga-miR-221-5p but increase the expression of ELOVL6 and SQLE, therefore promoting the synthesis of intracellular triglyceride and cholesterol levels in the liver of egg-laying chicken.

Green Tea Powder Decreased Egg Weight Through Increased Liver Lipoprotein Lipase and Decreased Plasma Total Cholesterol in an Indigenous Chicken Breed

Simple Summary

Tons of green tea powder (GTP) are produced and cast off during green tea processing. It is suggested that GTP could increase immunity and health, and so improve animal production performance. We demonstrated that one percent of GTP supplemented in the diet did not affect egg production. However, long time GTP inclusion resulted in decreased egg weight and increased feed-to-egg ratio. Combined with plasma lipid concentration, the decreased egg weight might be because of lower plasma lipid concentration, increased plasma orexin A, and liver lipoprotein lipase expression in chickens fed a diet containing GTP.

Abstract

Whether or not green tea promotes egg production is unclear. Huainan partridge chickens at 20 weeks of age were divided into two groups, with one group fed a basal diet (control) and one fed a basal diet plus 10 g/kg green tea powder (GTP) for 12 weeks. Egg production (EP) and feed intake (FI) were recorded daily. Plasma lipid parameters, and apolipoprotein-B (Apo-B), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), and lipoprotein lipase (LPL) expression were determined every four weeks. Egg production and FI showed no significant difference between the two groups (p > 0.05). Egg weight was 47.58 g in the control group, which was higher than that of the GTP group, and the feed-to-egg ratio (FCR) was 4.62 in the control group, which was lower than that of the GTP group after 12 weeks feeding. Compared with the control group, plasma orexin A (p < 0.05), high-density lipoprotein (HDL), apolipoprotein A (Apo A), and very high-density lipoprotein (VHDL) (p < 0.01, respectively) were increased. Plasma glucose (Glu), free fatty acid (FFA), apolipoprotein B (Apo B), triglyceride (TG), total cholesterol (TC) (p < 0.01, respectively), and low density lipoprotein (LDL) (p < 0.05) were decreased in the GTP group after 8 weeks feeding. The LPL expression in the liver was increased in the GTP group after 8 to 12 weeks feeding when compared to the control group (p < 0.05). Chickens fed GTP did not affect EP, but decreased egg weight, which might be because of lower plasma lipid concentration, increased plasma Orexin A, and liver LPL expression.

Intestinal inflammation induced by dextran sodium sulphate causes liver inflammation and lipid metabolism disfunction in laying hens

Gut inflammation caused by various factors including microbial infection leads to disorder of absorption of dietary nutrients and decrease in egg production in laying hens. We hypothesized that intestinal inflammation may affect egg production in laying hens through its impact on liver function. Dextran sodium sulphate (DSS) is known to induce intestinal inflammation in mammals, but whether it also induces inflammation in laying hens is not known. The goal of this study was to assess whether oral administration of DSS is a useful model of intestinal inflammation in laying hens and to characterize the effects of intestinal inflammation on egg production using this model. White Leghorn hens (350-day old) were administrated with or without 0.9 g of DSS/kg BW in drinking water for 5 D (n = 8, each). All laid eggs were collected, and their whole and eggshell weights were recorded. Blood was collected every day and used for biochemical analysis. Liver and intestinal tissues (duodenum, jejunum, ileum, cecum, cecal-tonsil, and colon) were collected 1 D after the final treatment. These tissue samples were used for histological analysis and PCR analysis. Oral administration of DSS in laying hens caused 1) histological disintegration of the cecal mucosal epithelium and increased monocyte/macrophage infiltration and IL-1β, IL-6, CXCLi2, IL-10, and TGFβ-4 gene expression; 2) decreased egg production; 3) increased leukocyte infiltration and IL-1β, CXCLi2, and IL-10 expression in association with a high frequency of lipopolysaccharide-positive cells in the liver; and 4) decreased expression of genes related to lipid synthesis, lipoprotein uptake, and yolk precursor production. These results suggested that oral administration of DSS is a useful method for inducing intestinal inflammation in laying hens, and intestinal inflammation may reduce egg production by disrupting egg yolk precursor production in association with liver inflammation.

Effects of dietary lysine on productivity, reproductive performance, protein and lipid metabolism-related gene expression in laying duck breeders

This study investigated whether dietary lysine (Lys) affects productive performance and expression of genes related to protein and lipid metabolism in laying duck breeders. Longyan duck breeders (n = 540, 19 wk of age) were randomly assigned to 6 groups with 6 replicates of 15 birds each. Breeders were fed diets with 6 total Lys levels (6.4, 7.2, 8.0, 8.8, 9.6, and 10.4 g/kg) for 26 wk duration. Egg production, egg weight, egg mass, feed conversion ratio, hatchability, hatchling weight, albumen weight, eggshell weight, yolk weight, and yolk proportion increased with dietary Lys levels (P < 0.05). Dietary Lys level had a linear (P < 0.05) and quadratic (P < 0.05) effects on maternal hepatic expression of mechanistic target of rapamycin, eukaryotic translation initiation factor 4E binding protein 1, ubiquitin conjugating enzyme E2K (UBE2K), cathepsin B (CTSB), and quadratically (P < 0.05) increased the concentrations of plasma Lys, leucine, threonine, and tryptophan in duck breeders. In contrast, maternal dietary Lys suppressed expression of proteasome 26S subunit, UBE2K, and CTSB in the liver of hatchlings. Moreover, relative expression of peroxisome proliferator-activated receptors alpha, carnitine palmitoyltransferase 1A, and very low density apolipoprotein-II increased linearly (P < 0.05) and quadratically (P < 0.05), and that of VLDL receptor (VLDLR) decreased quadratically (P < 0.05) in the liver of duck breeders with increasing dietary Lys levels; hepatic triglyceride and cholesterol contents were reduced. Maternal dietary Lys suppressed hepatic expression of VLDLR in the hatchlings. A diet containing 8.6 g Lys/kg promoted protein turnover and lipid metabolism in laying duck breeders, which positively reflected in the productivity and reproductive performance.

Unravelling fatty liver haemorrhagic syndrome: 1. Oestrogen and inflammation

Previous studies have implicated oestrogen as a factor in the induction of fatty liver haemorrhagic syndrome (FLHS). In this study, a refined laying hen model was employed to permit further investigations. Intramuscular (i.m.) injections of exogenous oestrogen as β-estradiol-17-dipropionate (E₂) (5 mg/kg BW) were given every 4 days for 20 days to 30-week-old hens fed either ad libitum or with restricted feed intake. Elevated (P < 0.01) plasma oestrogen concentrations produced significant macroscopic and microscopic hepatic alterations. Hens in the E₂-treated ad libitum fed (EAL) group experienced a higher incidence of FLHS than hens in the E₂-treated restricted feed intake group, showing that birds with a higher feed intake are more at risk of developing FLHS. Histological examination of livers revealed that hens in the E₂-treated ad libitum fed group had consistent and severe fat infiltration in the liver, and fat vacuolization within hepatocytes. Fat accumulation and fat droplets were found not only in the cytoplasm of hepatocytes but also in liver sinusoids. White blood cell counts and fibrinogen concentrations were altered (P < 0.01) in hens treated with E₂ when compared with controls. Plasma fibrinogen concentrations were altered over time, and correlated with white blood cell counts (Pearson's correlation r = 0.96; P = 0.001). Hens treated with E₂ had increased (P < 0.01) levels of cholesterol and triglycerides, confirming that E₂ induced hypercholesterolaemia and hypertriglyceridaemia. It was concluded that E₂ successfully induced FLHS in hens, with typical systemic and hepatic events resulting from a disturbance in lipid metabolism and chronic low-grade inflammation.

miR-34a-5p Increases Hepatic Triglycerides and Total Cholesterol Levels by Regulating ACSL1 Protein Expression in Laying Hens

Accumulating evidence has shown that miR-34a serves as a posttranscriptional regulatory molecule of lipid metabolism in mammals. However, little studies about miR-34a on lipid metabolism in poultry have been reported until now. To gain insight into the biological functions and action mechanisms of miR-34a on hepatic lipid metabolism in poultry, we firstly investigated the expression pattern of miR-34a-5p, a member of miR-34a family, in liver of chicken, and determined its function in hepatocyte lipid metabolism by miR-34a-5p overexpression and inhibition, respectively. We then validated the interaction between miR-34a-5p and its target using dual-luciferase reporter assay, and explored the action mechanism of miR-34a-5p on its target by qPCR and Western blotting. Additionally, we looked into the function of the target gene on hepatocyte lipid metabolism by gain- and loss-of-function experiments. Our results indicated that miR-34a-5p showed a significantly higher expression level in livers in peak-laying hens than that in pre-laying hens. miR-34a-5p could increase the intracellular levels of triglycerides and total cholesterol in hepatocyte. Furthermore, miR-34a-5p functioned by inhibiting the translation of its target gene, long-chain acyl-CoA synthetase 1 (ACSL1), which negatively regulates hepatocyte lipid content. In conclusion, miR-34a-5p could increase intracellular lipid content by reducing the protein level, without influencing mRNA stability of the ACSL1 gene in chickens.