Riboflavin is an essential micronutrient and a precursor of flavin mononucleotide and flavin adenine dinucleotide for maintaining cell homeostasis. Riboflavin deficiency (RD) induces cell apoptosis. Endoplasmic reticulum (ER) stress is considered to induce apoptosis, and C/EBP homologous protein (CHOP) is a key pathway involved in this process. However, whether RD-induced apoptosis is mediated by ER stress and the CHOP pathway remains unclear and needs further investigation. Therefore, the current study presents the effect of RD on ER stress and apoptosis in the human hepatoma cell line (HepG2). Firstly, cells were cultured in a RD medium (4.55 nM riboflavin) and a control (CON) medium (1005 nM riboflavin). We conducted an observation of cell microstructure characterization and determining apoptosis. Subsequently, 4-phenyl butyric acid (4-PBA), an ER stress inhibitor, was used in HepG2 cells to investigate the role of ER stress in RD-induced apoptosis. Finally, CHOP siRNA was transfected into HepG2 cells to validate whether RD triggered ER stress-mediated apoptosis by the CHOP pathway. The results show that RD inhibited cell proliferation and caused ER stress, as well as increased the expression of ER stress markers (CHOP, 78 kDa glucose-regulated protein, activating transcription factor 6) (p < 0.05). Furthermore, RD increased the cell apoptosis rate, enhanced the expression of proapoptotic markers (B-cell lymphoma 2-associated X, Caspase 3), and decreased the expression of the antiapoptotic marker (B-cell lymphoma 2) (p < 0.05). The 4-PBA treatment and CHOP knockdown markedly alleviated RD-induced cell apoptosis. These results demonstrate that RD induces cell apoptosis by triggering ER stress and the CHOP pathway.

Background: Although methionine (Met), the first-limiting dietary amino acid, has crucial roles in growth and regulation of lipid metabolism in ducks, mechanisms underlying are not well understood. Therefore, the objective was to use dietary Met deficiency to investigate the involvement of Met in lipid metabolism and fat accumulation of Pekin ducks. Methods: A total of 150 male Pekin ducks (15-d-old, 558.5 ± 4.4 g) were allocated into 5 groups (6 replicates with 5 birds each) and fed corn and soybean meal-based diets containing 0.28%, 0.35%, 0.43%, 0.50%, and 0.58% Met, respectively, for 4 weeks. Met-deficient (Met-D, 0.28% Met) and Met-adequate (Met-A, 0.43% Met) groups were selected for subsequent molecular studies. Serum, liver, and abdominal fat samples were collected to assess the genes and proteins involved in lipid metabolism of Pekin ducks and hepatocytes were cultured in vivo for verification. Results: Dietary Met deficiency caused growth depression and excess fat deposition that were ameliorated by feeding diets with adequate Met. Serum triglyceride and non-esterified fatty acid concentrations increased (P < 0.05), whereas serum concentrations of total cholesterol, low density lipoprotein cholesterol, total protein, and albumin decreased (P < 0.05) in Met-D ducks compared to those in Met-A ducks. Based on hepatic proteomics analyses, dietary Met deficiency suppressed expression of key proteins related to fatty acid transport, fatty acid oxidation, tricarboxylic acid cycle, glycolysis/gluconeogenesis, ketogenesis, and electron transport chain; selected key proteins had similar expression patterns verified by qRT-PCR and Western blotting, which indicated these processes were likely impaired. In vitro verification with hepatocyte models confirmed albumin expression was diminished by Met deficiency. Additionally, in abdominal fat, dietary Met deficiency increased adipocyte diameter and area (P < 0.05), and down-regulated (P < 0.05) of lipolytic genes and proteins, suggesting Met deficiency may suppress lipolysis in adipocyte. Conclusion: Taken together, these data demonstrated that dietary Met deficiency in Pekin ducks resulted in stunted growth and excess fat deposition, which may be related to suppression of fatty acids transportation and hepatic catabolism.

This study aimed to investigate the effects of dietary riboflavin levels on the reproductive performance of pigeon breeders and the growth performance and carcass traits of offspring squabs to estimate the riboflavin requirement of pigeon breeders. The natural riboflavin content in the basic diet of corn–peas–soybean–wheat–sorghum–corn gluten is 1.20 mg/kg. Different doses of riboflavin (0, 2.5, 5, 10, and 15 mg/kg) were supplemented with the basal diet to produce five dietary treatments with total riboflavin levels of 1.20, 3.70, 6.20, 10.20, and 16.20 mg/kg. A total of 120 pairs of White King pigeons, aged 60 wks, were randomly allocated into five treatment groups, each consisting of 24 pairs. Each pair was individually raised for 8 wks. After the experiment, an assessment was conducted to evaluate the reproductive performance of the pigeon breeders, as well as the growth and carcass traits of offspring squabs at 28 days of age. The results showed that the dietary riboflavin levels had no significant effect on body weight, feed intake, egg weight, egg production, and egg fertility (p > 0.05). However, pigeons fed a diet without riboflavin had the lowest egg hatchability, egg yolk color, carcass trait, and riboflavin status, while exhibiting higher liver weight and liver index (p < 0.05). Moreover, the indices above showed increased or decreased linearly as the level of riboflavin was increased in the diet. Based on the broken-line regression model, pigeon breeders were determined to require a dietary riboflavin content of 11.4, 13.6, 13.4, 6.60, 4.28, 4.47, 4.67, 6.69, and 6.82 mg/kg to optimize hatchability, eviscerated weight, half-eviscerated weight, breast muscle weight, breast muscle percentage, liver weight, liver index, egg yolk riboflavin, and squab plasma riboflavin, respectively. In conclusion, the optimal supplemental dosage of riboflavin in the diets of pigeon breeders is 13.6 mg/kg.

This study aimed to evaluate the effects of different dietary pantothenic acid levels on growth performance, carcass traits, and plasma biochemical parameters of starter Pekin ducks from 1 to 21 days of age, as well as the pantothenic acid requirement of starter ducks. A total of 384 one-day-old male white Pekin ducklings were assigned randomly into 6 dietary treatments, each with 8 replicate pens of 8 ducks. Ducks were fed conventional basal corn–soybean diets containing 8.5, 10.5, 12.5, 14.5, 16.5, and 18.5 mg/kg pantothenic acid for 21 days. Growth depression, poor pantothenic acid status, fasting hypoglycemia, and elevated plasma uric acid (UA) content were observed in the ducks fed the pantothenic acid-deficient basal diet (p < 0.05), and these adverse effects were ameliorated by pantothenic acid supplementation. Among all ducks, the birds fed the basal diet with no supplementation of pantothenic acid had the lowest body weight, average daily weight gain (ADG), average daily feed intake (ADFI), breast meat yield, and plasma pantothenic acid and glucose contents (p < 0.05), and the greatest plasma UA content (p < 0.05). In addition, all these parameters showed a linear or quadratic response as dietary pantothenic acid levels increased (p < 0.05). According to broken-line regression, the pantothenic acid requirements of starter male white Pekin ducks for body weight, ADG, and plasma pantothenic acid content were 13.36, 13.29, and 15.0 mg/kg, respectively. The data potentially provides theoretical support for the utilization of pantothenic acid in duck production.

We aimed to explore the effects of two different doses of Zn on the fecal microbiota in pigeons and the correlation between these effects and intestinal immune status. Zn doses affected pigeon growth performance, and pigeons in the T60 (60 mg/kg Zn) and T90 (90 mg/kg Zn) groups exhibited higher villus height and crypt depth in duodenum and ileum compared to the control group, respectively. Supplementation with Zn increased the expression of the IL8, CD798, TJP and NKTR genes (p < 0.05), while enhancing serum immunoglobulin (Ig) G, IgM, and IgA concentrations compared to the control pigeons (p < 0.05). T60 treatment reduced relative Actinobacteriota abundance, while Lactobacillus spp. abundance was highest in the T90 group compared to the two other groups. The core functional genera significantly associated with immune indices in these pigeons were Rhodococcus erythropolis and Lactobacillus ponti. Our findings will help facilitate the application of dietary Zn intake in pig production.

Manganese (Mn) is indispensable for skeletal development in poultry, yet its dietary requirement for meat pigeons has never been established. This study fed 120 pairs of White King pigeon breeders diets containing 28.43, 63.43, 98.43, 133.43, or 168.43 mg/kg total Mn (0, 35, 70, 105, or 140 mg/kg supplemental Mn) for 53 days to assess effects on reproductive performance, squab tibia development, and epiphyseal cartilage gene expression. Egg hatchability responded quadratically (p = 0.006), peaking at 97.9% in the 98.43 mg/kg group and falling to 83.3% at 168.43 mg/kg. Mn concentration in squab crop contents increased linearly with increasing dietary Mn levels provided to breeders (p = 0.009), indicating greater Mn exposure in the sampled offspring. However, this measurement does not directly quantify Mn transfer through pure crop milk. In 28-day-old squabs, serum alkaline phosphatase (ALP) activity was affected by dietary Mn level (overall treatment effect, p = 0.010) and showed a quadratic response (p = 0.003), with the highest activity observed in the 98.43 mg/kg total dietary Mn group. Tibial strength and maximum deflection did not differ among dietary treatments (p > 0.05). Tibial ash percentage showed a significant treatment effect (p = 0.001) and a linear response to dietary Mn level (p = 0.021), although the difference between the basal and highest-Mn groups was relatively modest (49.9% vs. 46.9%). These findings do not provide sufficient evidence of severe impairment of tibial mineralization at the highest dietary Mn level. In tibial epiphyseal cartilage, fibroblast growth factor 23 (FGF23) mRNA expression at 63.43 mg/kg total dietary Mn was approximately 3.85 times that in the basal group, whereas expression at 98.43~168.43 mg/kg did not differ significantly from the basal group. ETS-related gene (ERG) mRNA expression was approximately 5.63~5.85 times that in the basal group at 63.43~133.43 mg/kg, but expression at 168.43 mg/kg was lower than in these intermediate-dose groups and did not differ significantly from the basal group. Quadratic regression analyses based on replicate-level observations revealed significant relationships between dietary total Mn levels and egg hatchability (R² = 0.931, p = 0.0155) and relative ERG expression (R² = 0.783, p = 0.0368). The estimated optimal dietary total Mn levels were 92.63 and 95.34 mg/kg based on egg hatchability and ERG expression, respectively. These findings suggest a preliminary optimal dietary total Mn range of 92.63~95.34 mg/kg for meat pigeons under the conditions of this study, which requires further validation.