Gut hormones act as appetite regulatory hormones in mammals. For example, the hunger hormone ghrelin, which is released from the stomach before food intake, stimulates appetite. In contrast, satiety hormones such as cholecystokinin, glucagon-like peptide-1, and peptide YY, which are released from the intestines after food intake, suppress appetite. The effects of these peptides on food intake have been shown to be similar in both mammals and fishes. However, evidence suggests that the physiological roles of these gut hormones may be different between birds and other vertebrates. This review summarizes the current information on the roles of gut hormones in the regulation of food intake in birds, especially in chickens.

The melanocortin 1 receptor (MC1R) gene is a candidate functional gene that controls the pigment production in melanocytes. The aim of this study was to identify polymorphisms and investigate the effect of the MC1R gene on plumage coloration in duck breeds, including Korean native ducks. Initially, 34 individuals from seven duck breeds were sequenced, obtaining 12 polymorphisms. Five single nucleotide polymorphisms (SNPs) in the coding region were non-synonymous, with mutations corresponding to amino acid changes. Among these, four SNPs were genotyped using polymerase chain reaction-restriction fragment length polymorphism method in 264 individuals from same seven duck breeds. Fisher’s exact test was conducted to identify possible relationships between the MC1R gene polymorphisms and plumage color variations. Four non-synonymous SNPs, c.52A>G (p.Lys18Glu), and c.376 A>G (p.Ile126Val), c.409G>A (p.Ala137Thr) and c.649C>T (p.Arg217Cys), were associated with the two deduced genotypes (i.e., E/E and e+/e+) based on plumage color phenotypes. In addition, we reconstructed MC1R gene haplotypes, where the haplotype AAGC showed its highest frequency in Nageswari duck breed, which presents an extended black phenotype. Our results indicate that the identified polymorphisms by this study can be used to explore associations with plumage color variations in Asian duck breeds.

We identified and evaluated differentially expressed genes (DEGs) by RNA-Sequencing (RNA-Seq) in the intestinal mucosa of two Fayoumi chicken lines, M5.1 and M15.2, that are affected by necrotic enteritis (NE); these chicken lines share the same genetic background but have different major histocompatibility complexes. RNA-Seq generated over 49 and 40 million reads for lines M5.1 and M15.2, respectively. The alignment of these sequences with the Gallus gallus genome database revealed the expression of more than 14,500 genes in two lines, among which 581, 1270, and 1140 DEGs were detected when lines M15.2 and M5.1 were compared with the control and compared between each other. The analysis of all DEGs using the gene ontology database revealed annotations for 111 biological processes, 32 cellular components, and 17 molecular functions, and KEEG pathway mapping indicated that the DEGs were primarily involved in immunity, responses to various stimuli, and signal transduction. In addition, we analyzed 183 innate immune genes that were differentially expressed in NE-induced chicken lines, including 46 CD molecular genes, 89 immune-related genes, and 13 β-defensin genes with 3 lineage-specific duplications. Taken together, the transcriptional profiles showed that line M5.1 was more resistant to NE than line M15.2 and that differential gene expression patterns were associated with host genetic differences in resistance to NE. qRT-PCR and RNA-Seq analyses showed that all the genes examined had similar responses to NE (correlation coefficient R＝0.84 to 0.88, p<0.01) in both lines. To the best of our knowledge, this is the first study that describes NE-induced DEGs using RNA-seq in two lines with different levels of susceptibility to NE. These results will lead to increased insights on NE disease resistance mechanisms and the role of host genes in the control of the host immune response.

This study was conducted to investigate the effects of Bacillus amyloliquefaciens (BA) and Saccharomyces cerevisiae (SC) as directed-fed microbials on performance, intestinal microflora, and intestinal morphology in broiler chickens. A total of four hundred one-day-old broiler chickens were randomly divided into 16 pens of 25 chickens each, and every treatment had 4 replicated pens with two pens of males and females respectively. A formulated corn-soybean meal based control diets and experimental diets, including 0.1% BA (1×10⁷ colony-forming units (CFU)/kg), the mixture of 0.05% BA (5×10⁶ CFU/kg) and 0.05% SC (5×10⁶ CFU/kg), and 10 ppm antibiotic (avilamycin), were fed for 5 weeks. The results showed no significant difference in the growth performance among all treatments. Supplementation of the mixture of BA and SC increased acetate and propionate and decreased the E. coli in ceca compared to control and antibiotic treatment. The treatments with antibiotic, BA, and the mixture of BA and SC compared to control treatment increased villus height / crypt depth ratio and decreased ammonia in excreta. In addition, supplementation of BA and the mixture of BA and SC compared to antibiotic treatment increased serum high-density lipoprotein, and decreased serum glutamic-oxaloacetic transaminase, respectively. In conclusion, supplementation of the mixture of BA and SC was better than added BA only, and the mixed probiotics product could potentially alter the use of avilamycin in broiler diets.

The present study investigated the effects of ethanol extracts of Allium hookeri (leaf, root, and fermented root) on parameters of innate immunity, tumour cell viability and antioxidant effect in vitro. Innate immunity was measured by spleen lymphocyte proliferation, nitric oxide production by chicken macrophage HD11 cells and suppressive effect on tumour cell viability was assessed using chicken RP9 cells. Free radical scavenging capacity as a measure of antioxidant capacity was determined by 0.15 mM of DPPH solution. In vitro culture of chicken spleen lymphocytes with ethanol extract of Allium hookeri (62.5-500 μg/mL) significantly induced higher proliferation compared with media control. Stimulation of macrophages with ethanol extract of Allium hookeri (62.5-500 μg/mL) showed increased Nitric oxide production. Tumor cells growth was significantly inhibited by extracts of Allium hookeri at 15.6-125 μg/mL compared with medium control and all extracts exhibited greater than 80% scavenging activity at 1000 μg/mL compared with ethanol vehicle control. Above all, fermented root extracts showed strongest effects on antioxidant activity compared to leaf and root extracts.

This study was conducted to evaluate the effects of xylanase and citric acid (CA) on growth, digesta pH, ileal populations of Clostridium perfringens and lactic acid bacteria, ileal nutrient digestibility, digestive enzyme activity, and mRNA expression of intestinal nutrient transporters in starter broilers challenged with C. perfringens. The experiment was conducted in a 2×2 factorial arrangement with two levels of CA (0 and 30 g/kg) and 2 levels of xylanase (0 and 200 mg/kg). Each of the four dietary treatments was fed to six replicate pens (15 birds/pen) between 0 and 21 d of age. Dietary CA significantly increased ADFI and ADG; meanwhile, xylanase addition led to a substantial reduction in FCR (P<0.05). No differences in digesta pH, C. perfringens counts, or quantity of lactic acid bacteria were found between the treatments. Xylanase supplementation increased AME values (P<0.01) and ileal digestibility of CP (P<0.05) in challenged birds. The inclusion of CA also increased the AME (P<0.01), and tended to increased ileal CP digestibility (P＝0.085). Xylanase supplementation increased α-amylase, trypsin, and sucrose activity in the jejunum (P<0.01). Dietary CA significantly increased (P<0.01) villi length as well as the villus length to crypt depth ratio in jejunum segments. The jejunal mRNA expression of sodium glucose co-transporter 1 (SGLT1) and H⁺-dependent peptide transporter 1 (PepT1) were upregulated by xylanase supplementation (P<0.01). The results suggest that dietary CA can promote growth as well as improve intestinal morphology and AME in birds challenged with necrotic enteritis. This study shows that xylanase supplementation improved FCR and AME in birds independent of C. perfringens infection; it also elevated the apparent ileal digestibility of CP, digestive enzyme activities, and mRNA expression of nutrient transporters in challenged birds.

The fruit Punica granatum L. has been used for years in traditional medicine owing to the presence of several phytobiotics with antimicrobial and immunomodulatory properties. This study investigated the effects of dietary supplementation with Punica granatum L. by-products (PGB) on performance, immunity, intestinal and excreta microflora, and odorous gas emissions from excreta of broiler chickens. Three experimental diets containing 0, 0.5 and 1.0% PGB were fed to 240 one-day-old broiler chicks until 35 days. Dietary PGB linearly reduced the average daily feed intake and feed conversion ratio of broilers. Supplementation with 1% PGB led to a linear increase in the relative weight of the spleen and bursa of Fabricius. The concentration of serum IgA and IgG increased linearly in response to dietary PGB. In the ileal digesta, the concentration of Saccharomyces cerevisiae increased linearly and quadratically in response to dietary PGB. Moreover, dietary PGB led to a linear decrease in Escherichia coli and Salmonella spp. alongside reducing the pH of the ileal digesta. In the cecal digesta, the concentration of Bacillus bacteria increased linearly in response to both levels of dietary PGB, while the concentrations of E. coli and Salmonella decreased when the diet was supplemented with 1% PGB, as did cecal pH. At 35 day, both levels of PGB increased the concentration of fecal Bacillus, whereas only 1% PGB increased the concentration of S. cerevisiae at 21 day. Increasing levels of PGB induce a linear reduction in fecal E. coli at 21 and 35 day, whereas Salmonella only at 21 day. Regarding the average of 48 h, dietary PGB effectively reduced the emissions of ammonia and methanethiol from broiler excreta. In conclusion, the results suggest that, dietary PGB improved immunity and the intestinal microbial ecosystem of broilers along with reduced odorous gas emissions from excreta.

Two experiments were conducted to evaluate the usefulness of urinary creatinine levels as a criterion for the estimation of protein and amino acid requirements in poultry. Here we studied the effects of dietary precursor levels of creatinine, methionine and arginine, on urinary creatinine excretion in experiments. Both experiments used 15 Chunky broilers chicks that were 8 days old. The chicks were assigned to three dietary groups, with five chicks each, and were fed an experimental diet for 7 days. The experimental diets mainly consisted of corn and soybean meal, and contained deficient, adequate, or excessive methionine and arginine levels in experiments 1 and 2, respectively. Excreta were collected for the last 3 days of the feeding trial, and chicks were terminated by dislocation of the neck at the end of the feeding trial to collect their livers. Creatinine concentration in the excreta and hepatic L-arginine-glycine amidinotransferase (AGAT) activities were determined.

Urinary creatinine levels increased with increasing both dietary methionine and arginine levels from deficient to adequate recommended by Japanese feeding standard (P<0.05), and then remained constant in experiments 1 and 2, respectively. The hepatic AGAT activity decreased when both dietary creatinine precursors levels were increased from deficient to adequate levels (p<0.05), and then remained constant.

These results suggested that creatinine excretion was changed with both increasing dietary methionine and arginine, dose-dependently.

This study examined the deposition of dietary bioactive fatty acids (FAs), including medium-chain and essential FAs, in tissues of broiler chickens. Six hundred newly hatched chicks were allotted to 4 treatments, 6 replicates of 25 chicks per treatment. The chicks were fed diets containing 0%, 1.6%, 4.0%, or 6.4% medium-chain triglycerides (MCTs) for 36 d. The abdominal fat deposition, fat content, and FA composition of breast meat, thigh meat, and abdominal fat were measured. The accumulation rate (AR) of bioactive FAs in the tissues was estimated as the slope of the linear regression between the FA composition of tissues and diets. Results showed that a diet containing 6.4% MCTs reduced the abdominal fat deposition and fat content of thigh meat (P<0.05). Essential FAs had higher AR than did medium-chain FAs. The AR of C10:0 was higher than that of C8:0. Moreover, C6:0 could not be detected in the tissues of broiler chickens. In conclusion, essential, but not medium-chain, FAs could efficiently deposit in tissues of broiler chickens.

The study was carried out in 48 poultry flocks to elucidate the roles of various complicating pathogens involved along with Newcastle disease (ND)/ low pathogenic avian influenza (LPAI) outbreaks. Necropsy was conducted and samples were collected for the isolation of Newcastle disease virus (NDV), Influenza A virus, infectious bronchitis virus (IBV), pathogenic bacteria; molecular detection of infectious laryngotracheitis virus (ILTV), fowl adeno virus (FAV), chicken anaemia virus (CAV), Mycoplasma synoviae (MS) and Mycoplasma gallisepticum (MG). The isolation results confirmed that 18/48 flocks (37%) were positive for the presence of hemagglutinating agents. Out of 18 hemagglutination (HA) positive flocks, 11 flocks (61%) were positive for both avian influenza virus (AIV) and NDV; 4 flocks (22%) were positive for NDV; and 3 flocks (17%) were positive for AIV. Sequence analysis of hemagglutinin and neuraminidase genes of AIV revealed that all were belonging to LPAI-H9N2 subtype. Sequence analysis of F gene of NDV revealed that they belong to virulent type. The PCR results confirmed the presence of three to seven etiological agents (CAV, FAV, ILTV, MG, MS and avian pathogenic E. coli along with LPAI/NDV from all the 18 HA-positive flocks. The detection rate of triple, quadruple, quintuple, sextuple and sevenfold infections was 17% (3 flocks), 28% (5 flocks), 11%, (2 flocks) 28% (5 flocks) and 17% (3 flocks), respectively. In conclusion, the disease complex involved more than one pathogen, primarily resulting from the interplay between LPAI-H9N2 and NDV; subsequently this could be exacerbated by co-infection with other agents which may cause exacerbated outbreaks that may otherwise go undetected in field.