Raman spectroscopy has been widely applied in the analysis of biological tissues. In this study, beak cuticle was studied to investigate its compositional and secondary structural changes during the laying period and aging of laying hens. The analysis revealed markedly increased contents of amide I and amino acids (phenylalanine and tyrosine) within the beak during the intense laying period from 17 to 20 weeks. In addition, α-helical protein was also gradually synthesized in this period. The relative area ratio of 1003/1448 cm⁻¹ (assigned to the vibrations of phenylalanine and organic C-H respectively) was confirmed as an excellent indicator for estimating the start of the laying period. This ratio increased from 0.36 to 0.42 from 17 to 20 weeks. The Raman peak at 1156 cm⁻¹ was assigned to carotenoids in the beak. The intensities of the 1156 cm⁻¹ peak significantly decreased during aging. The area ratio of 1156/1448 cm⁻¹ was successfully applied to estimate ages (still within the laying period) of laying hens. This study shows the potential of using Raman spectroscopy to quantify ages and laying period of birds.

In the present study, quantitative trait loci (QTLs) analysis was performed to identify the chromosomal positions of growth and carcass-related trait QTLs using 319 F₂ chickens obtained from intercrosses of an Oh-Shamo male and four White Plymouth Rock females. Body weight was measured weekly until the birds were 7 weeks old. Carcass-related traits were also measured at this timepoint. A genetic linkage map was constructed using 545 single nucleotide polymorphism (SNP) markers that were developed using a restriction-site associated DNA sequencing method. The linkage map included the 23 autosomes and the Z chromosome. Using simple interval QTL mapping, we were able to identify 10 significant and suggestive main-effect QTLs for growth and carcass-related traits present on chromosomes 1, 2, 3, 5, 8, 19, 24, and Z. These loci explained 5.60–16.52% of the phenotypic variances. The chromosomal positions of the 10 QTLs overlapped with those of previously reported QTLs, whereas the targeted traits varied. Our QTLs will aid future breeding programs in improving growth and meat yield of chickens (e.g., via marker-assisted selection), particularly in the Japanese brand chicken industry.

The effects of insulin-like growth factor binding protein 2 (IGFBP2) on the expression of fatty acid synthesis regulators and triglyceride production were investigated in primary cultured chicken hepatocytes. The full-length chicken IGFBP2 coding region was synthesized by overlap extension PCR and cloned into the pcDNA3.1 vector. An in situ digestion method was used to prepare the chicken hepatocytes. Primary chicken hepatocytes were maintained in monolayer culture. Real-time PCR was used to detect changes in the expression of IGFBP2, PPARG, IGF1, IGF1R, APOAI, and LFABP, after the overexpression of IGFBP2 in chicken hepatocytes. Triglyceride production and glucose content were also evaluated using triglyceride and glucose analysis methods. The expression level of IGFBP2 increased after transfection of the IGFBP2-containing vector. The expression levels of PPARG, IGF1, and IGF1R also increased in cultured chicken hepatocytes after the overexpression of IGFBP2, whereas the expression of LFABP and APOAI decreased. Triglyceride production in primary cultured chicken hepatocytes increased after the overexpression of IGFBP2. These results suggest that IGFBP2 is involved in lipogenesis, increasing both the expression of fatty acid synthesis regulators, and triglyceride production in primary cultured chicken hepatocytes.

The effects of dietary palygorskite (Pal) supplementation on growth performance, oxidative status, and intestinal barrier function in ducks were investigated. In total, 720 one-day-old Cherry Valley ducks were categorized into 4 treatments comprising 6 replicates with 30 ducks each. Ducks were fed a basal diet supplemented with 0, 5, 10, or 20 g/kg Pal for 42 days. Twenty-four ducks (1 male/replicate) were slaughtered at 14 and 42 days and samples were collected for analysis. Pal supplementation quadratically increased weight gain and linearly and quadratically increased feed intake (P<0.05) during the starter period. Pal enhanced serum glutathione peroxidase activity (GSHPx) at 14 (linear and quadratic, P<0.05) and 42 days (linear, P<0.001), and lowered serum malondialdehyde (MDA) content at 14 and 42 days (quadratic, P<0.05). It enhanced 42-day liver superoxide dismutase activity (linear, P=0.003) and GSH-Px activity at 14 (quadratic, P=0.044) and 42 days (linear and quadratic, P<0.001), but decreased 14-day liver MDA content (quadratic, P=0.003). Pal reduced 42-day serum diamine oxidase activity (linear and quadratic, P<0.05) and serum endotoxin content at 14 (linear and quadratic, P<0.05) and 42 days (quadratic, P=0.017). It linearly and quadratically increased jejunal mucosal immunoglobulin (Ig) M at 42 days and IgG at 14 and 42 days, and 42-day ileal mucosal IgG and secretory IgA (P<0.05). Ileal mucosal IgM content was quadratically increased at 14 and 42 days (P<0.05) by Pal. Moreover, Pal enhanced the mRNA expression of 14-day occludin in the jejunal mucosa (quadratic, P=0.033) and that of 42-day zonula occludens-1 in the ileal mucosa (linear, P=0.027). Thus, dietary Pal supplementation exerts beneficial effects through improving growth performance, antioxidant capacity, and intestinal barrier function of ducks.

In this study, we investigated the effect of methionine isomers (D- and L-methionine) on growth performance, blood metabolite levels, nutrient digestibility, intestinal morphology, and foot pad dermatitis in broilers challenged with acute heat stress. In total, 240 broilers were randomly allocated in a 2×2 factorial arrangement consisting of two dietary treatments (D- vs. L-methionine) and two thermal environmental conditions (thermo-neutral vs. acute heat stress). Methionine isomers were added to the diet as an ingredient according to the diet formulation. The broilers were exposed to acute heat stress at 33°C for 5 h on day 14. The average daily gain and feed conversion ratio of birds fed L-methionine were higher than those fed D-methionine (P<0.05) from the time of hatching till 21 days. Induced acute heat stress impaired (P<0.05) the daily gain and feed intake of the broilers on day 21. Furthermore, the blood urea nitrogen levels of birds subjected to acute heat stress on days 14 and 21 were higher (P<0.05) than those of their counterparts. Longer villi (P<0.05) were observed in broilers fed L-methionine-supplemented diet than in those fed D-methionine-supplemented diet on day 14, irrespective of thermal environmental conditions. Heat stress reduced (P<0.01) nutrient digestibility of the broilers on days 14 and 21. Higher incidence and severity of foot pad dermatitis were observed (P<0.05) in broilers fed diet containing D-methionine than in those fed L-methionine-supplemented diet. In conclusion, L-methionine-supplemented diet improved growth performance, overcame growth depression, and reduced the incidence of foot pad dermatitis when broilers were exposed to acute heat stress in the starter period.

Here, we investigated whether the optimal threonine (Thr) to lysine (Lys) ratio in high Lys diet improves the growth performance of modern broiler chickens at finisher period and determined the possible mechanism underlying improvement in the growth performance of chickens fed with high Lys or Lys + Thr diet using metabolome analyses. Eighteen 21-day-old chickens housed in individual cages were randomly divided into three groups of six chickens fed with different diets as follows: control diet, high Lys diet (150% Lys content of National Research Council requirement), and high Lys + Thr diet (0.68 of Thr/Lys in high Lys diet). Body weight gain (BWG) increased in chickens receiving high Lys diet as compared with those fed with the control diet (P<0.05); no significant difference was observed in BWG of chickens from high Lys + Thr and high Lys groups. Feed conversion ratio (FCR) was lower in chickens fed with high Lys or high Lys + Thr diet than in those on the control diet. Serotonin concentration increased in the plasma of chickens fed with high Lys diet as compared to those fed with other diets. A negative correlation was observed between plasma serotonin concentration and FCR. These results provide the first evidence on the use of high Lys in broiler diets to reduce FCR during finisher period, which may be associated with change in plasma serotonin concentration. These findings suggest that high Lys content in finisher diet, but not high Thr + Lys diet, may affect the peripheral serotonergic metabolism and improve FCR. Thus, plasma serotonin may serve as a biomarker of FCR in broilers.

The aim of this study was to investigate the effects of tea tree oil (TTO) supplementation on the growth performance, cecal microflora composition, immunity, and antioxidant status of Partridge Shank chickens. A total of 144 one-day-old chicks were allocated into three treatments with six replicates of eight chicks each and fed with a basal diet supplemented with 0 (Control group), 500, and 1000 mg/kg TTO for 50 days. Compared with the control group, the broilers fed with the basal diet supplemented with 1000 mg/kg TTO exhibited an increase in average daily gain from 22 to 50 days (P=0.035) and in both relative thymus weight (P<0.001) and Lactobacillus colonies in the cecal contents (P=0.045) at 50 days of age, but a reduction in the feed/gain ratio during 1 to 50 days (P=0.048). Additionally, dietary TTO supplementation, irrespective of dosage, increased the relative spleen weight (P=0.003) and total antioxidant capacity in the jejunum (P=0.049) and ileum (P=0.001) at 21 days, but decreased the malondialdehyde content in the ileum at both 21 (P=0.003) and 50 days (P<0.001) and in the jejunum at 50 days (P=0.012). The results suggested that TTO supplementation could improve the growth performance, cecal microflora composition, immunity, and antioxidant capacity of Partridge Shank chickens.

This study was conducted to investigate the influence of in ovo vitamin D₃ (Vit D₃) administration on growth of broiler chickens when Vit D₃ was dissolved in soybean oil. Sixty Ross broiler eggs were incubated at 37.8°C and >60% relative humidity. Distilled water, soybean oil, or Vit D₃ (60 IU / 0.5 mL) dissolved in soybean oil, was administered in ovo on Day 18 of incubation. Seven days after hatching, chicks were sexed, and 12 birds (six female and six male) close to the average body weight (BW) of each treatment were selected and their BW continuously recorded until 28 days of age, then sacrificed. Liver and pectoral muscle were collected to determine the mRNA expression of IGF-1 and IGF-1 receptor, and the length of tibia was measured. There were no significant differences in BW, liver weight, or pectoral muscle weight between the groups. However, an interaction was observed between treatments and sexes in the tibia length. In comparison among only males, tibia length in the Vit D₃ with oil group was longer than that of the control, but not different from that of the oil group. The same tendency was observed in the hepatic IGF-1 mRNA expression in chicks of either sex, with this effect only being observed after the treatments and not in the control. On the other hand, there was an interaction between treatments and sexes in the mRNA expression of IGF-1 receptor, which was highest in the Vit D₃ with oil group in females, but not in males. These results indicated that the in ovo administration of Vit D₃ affected IGF-1 receptor mRNA expression without growth.

Skeletal muscle mass is an important trait in poultry meat production. In mammals, myostatin, a negative regulator of skeletal muscle growth, activates Smad transcription factors and induces the expression of atrogin-1 by regulating the Akt/FOXO pathway. Although the amino acid sequence of chicken myostatin is known to be completely identical to its mammalian counterpart, previous studies in chicken skeletal muscles have implied that the physiological roles of chicken myostatin are different from those of mammals. Furthermore, it remains to be elucidated whether myostatin affects cellular signaling factors and atrogin-1 expression. In this study, using chick embryonic myotubes, we found that myostatin significantly increased the phosphorylation rate of Smad2 and mRNA levels of atrogin-1. No significant change was observed in the phosphorylation of Akt and FOXO1. These in vitro results suggest that the molecular mechanisms underlying myostatin-induced expression of atrogin-1 might be different between chickens and mammals.

Descriptive sensory characteristics of eggs produced by conventional corn-based feeding and unhulled whole rice grain-feeding were compared in two cooking procedures using a trained panel. Rice-feeding significantly decreased brothy and roasted odor in eggs cooked into half-cooked egg yolks, and decreased the creamy odor, smoothness and moisture of eggs cooked into custard puddings. However, a statistical interaction between rice-feeding and production farm was not observed in every sensory attribute. These findings indicated that replacing corn with unhulled whole rice grain in diets for laying hens alters the sensory attributes of eggs.