Because the evidence on existence of the genuine avian leptin gene has been revealed in several birds, debate about the existence of avian leptin will finally stop. Over the past 15 years, many researchers struggled to find avian leptin as well as to determine physiological roles of leptin in birds. During these processes, orthologue of leptin receptor (LEPR) has been identified in several birds and of which function was also deeply investigated.
This review summarizes over a decade of research on avian leptin to integrate knowledge toward future advance of this field after finding the authentic leptin in bird.

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Avian embryos have reproductive organs with unique characteristics. In female, the gonads develop asymmetrically: the left gonad generates a functional ovary, whereas the right gonad and associated embryonic oviduct (Müllerian duct) regress. In males, however, both left and right gonads develop into testes. Recent evidence, however, revealed that left-right asymmetry can be detected in both sexes. Even male embryos have a greater number of germ cells in the left gonad. Moreover, pluripotency-associated markers, as well as SSEA1, the surface antigen that is strongly expressed in chick embryonic stem cells, also show asymmetric expression in both sexes both in germ cells and in stromal cells of the gonad. This review provides an update of the state of the field.

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This study was aimed to evaluate the genetic diversity of Egyptian native chickens by using mtDNA sequence polymorphism. A 546-bp fragment of the mtDNA D-loop region was sequenced for a total of 36 Egyptian native chickens with 14 reference sequences from DNA databank. Of the Egyptian chickens 5 haplotypes were identified. Haplotype diversity and nucleotide diversity of the Egyptian native chickens were 0.5635±0.0845 and 0.00123±0.00108, respectively. The Egyptian native chickens were distributed within one clade, which were closed to the haplotypes from Indian subcontinent and Southeast Asia. Most of Egyptian native chickens were classified into the haplotype E1, which contains 63.9% of individuals followed by E4 (16.6%), E5 (11.1%), E2 (5.5%) and E3 (2.7%), respectively. These findings indicate that the maternal lineages was involved in the origin of domestic chicken in Egypt may have roots in Indian subcontinent and other Southeast Asia. The genetic information from this study will probably pave the way to further studies for evaluation, preservation and improvement of Egyptian native chickens as genetic resources in the future.

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The objective of the present study was to investigate the relationship between the g.2582481G>A, g.2583935G>A and g.2584057C>T single nucleotide polymorphisms (SNPs) within the lactate dehydrogenase A gene (LDHA) coding for lactate dehydrogenase isoform A and the racing performance of homing pigeons. As a measure of racing performance, we used the mean values of ace points won by individual birds during the whole season. The estimated heritability of the racing performance of pigeons was relatively low (h²＝0.0596; SE＝0.0249). The analysis performed for all race reports together showed that the factors such as gender, weather conditions at the start and at the end of the race affect the analyzed trait. Of the 3 single nucleotide polymorphisms, only the effect of the g.2582481G>A genotype on the performance of racing pigeons was significant. Statistical analysis indicated the difference in the value of ace points between the animals of GG and GA genotypes for the g.2582481G>A SNP. The study showed that the genotype homozygous for g.2582481A is linked to the highest mean value of ace points. Consequently, the relationship between the genotype for g.2582481G>A and the racing performance was shown.

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In the present study, we have explored the genetic relationships between red junglefowls and domestic chickens in Southeast Asia by using single nucleotide polymorphism (SNP) markers. We genotyped 475 individuals from 17 populations of red junglefowls (4 subspecies, n＝39), native chickens (10 populations, n＝346) and commercial breeds (3 breeds, n＝90) using PCR-RFLP for the 98 autosomal SNP markers. The genotyping results showed that average heterozygosity was 0.225±0.077 for red junglefowl, 0.272±0.009 for native chickens, and 0.211±0.037 for commercial breeds of chickens. The resultant neighbor-joining (NJ) tree with three distinct clusters corresponds to red junglefowls, native chickens and commercial breeds. The subspecies of red junglefowl was clustered into one clade and more closely related to native chickens than the commercial lines. Furthermore, the results of the population structure analysis suggested that the 17 populations appear to be derived from 11 genetic populations (K＝11). Among the domestic chickens, the NJ tree and genetic structure analysis revealed that Thailand native chickens was the most ancestral group of all chickens. These findings provide molecular evidence supporting the theory that the original domestication event occurred in Thailand. They also provide additional clustering information to classify red junglefowls and domestic chickens.

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Quantitative trait loci (QTLs) analyses for internal egg quality of chickens were performed with 143 microsatellite markers on 27 linkage groups in 371 F₂ hens obtained from an intercross between Japanese Large Game (Oh-Shamo) and White Leghorn breeds. Internal egg traits, such as weight and size of the albumen, weight and size of the yolk, and yolk colors, were measured in three different egg laying stages (early, middle, and late stages). We detected 11 significant and four suggestive QTLs with main effects on 27 internal egg traits in the three stages. Albumen weight and size QTLs were identified on chromosomes 1, 2, 4, 5, 6, 8, 9, 27, and Z. Yolk weight and size QTLs were discovered on chromosomes 4, 7, 8, 15, and Z, whereas yolk color QTLs were detected on chromosomes 1, 3, 4, 8, 9, and 27. Moreover, we revealed four significant and two suggestive QTLs with epistatic interaction effects on three internal egg traits in the late stage. This is the first report of epistatic QTLs for internal egg traits in chickens. The four significant loci were on chromosomes 1, 2, 8, and 17 and affected yolk size and yolk color, whereas the two suggestive loci were located on chromosomes 2 and 10 and affected albumen height. Among these epistatic QTLs, the two QTLs detected on chromosomes 1 and 8 were found at the regions of main-effect QTLs. The present main and epistatic QTLs accounted for 3.61-18.46% of the phenotypic variances. The chromosomes 1 and 8 QTLs with main effects on internal egg traits exerted their effects throughout all three stages, whereas the other QTLs with main- or epistatic-effects were detected in one or two stages. These results demonstrated that age-related changes of QTLs will make the genetic features of quantitative traits more complex.

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One of the breeds of native Japanese chickens is the Ryujin-Jidori (RJ) from Tanabe City (formerly Ryujin Village), Wakayama Prefecture, Japan. To estimate the genetic diversity of RJ, 29 microsatellite loci were analyzed with 68 RJ adult birds (all possible sires and dams) reared by five breeders (four and one breeders in Wakayama and Nara Prefectures, respectively) in April, 2012. Among the 29 loci, 14 to 20 loci were monomorphic depending on populations (breeders). Genetic diversity indices in RJ were also low in mean number of alleles (1.34 to 1.55) and expected heterozygosity (0.140 to 0.174). There was no reduction of genetic diversity in the RJ breed reared in Wakayama and Nara Prefectures in 2012, as compared with the RJ population in 2007 reported elsewhere. In the phylogenetic tree analysis, the birds from the Wakayama populations and the Nara population were separated. The pairwise F_ST values and genetic structure analysis also supported the genetic uniqueness of the Nara population. Also, significant and positive F_IS value was estimated in the Nara population. The low genetic diversity and inbred condition observed in the RJ breed in 2012 indicated the necessity to promote the conservation of this breed immediately. For the conservation of the RJ breed, it might be better to maintain the Nara population and four Wakayama populations separately because of the significant F_ST value observed between them. However, integration of the Nara population to the Wakayama populations might become necessary in the near future because of the possibility that the Nara population can become extinct through inbred deficiency. The primary and immediate concern should be increasing the number of RJ individuals and avoiding inbreeding as far as possible with the cooperation of public institutions and private breeders.

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The effects of dietary calcium (Ca) concentration on the digestion of Ca, phosphorus (P), nitrogen (N), fat and starch along the intestinal tract of broilers were assessed. Three-week old broilers were fed maize-soy diets containing 6, 9 or 12 g/kg of Ca (Ca: total P ratios of 1:1, 1.4:1 and 2:1, respectively) for six days and digesta were collected from the duodenum, jejunum, upper ileum and lower ileum. Apparent digestibility coefficients of P, Ca, N, fat and starch in different intestinal segments were calculated based on indigestible marker ratios in the diet and digesta. Apparent digestibility coefficients of P and Ca were determined to be negative in the duodenum. Apparent P digestibility was reduced (P<0.05) by increasing dietary Ca concentrations, but there was a Ca x intestinal site interaction (P<0.05). Jejunum was the major site of P absorption in birds fed the low Ca and normal Ca diets, but both the jejunum and upper ileum were involved in birds fed high Ca diets. Dietary Ca concentration had no effect (P>0.05) on apparent Ca digestibility. Calcium was absorbed predominantly in the jejunum. Digestibility of N and fat was reduced (P<0.05) by increasing dietary Ca concentrations. A significant (P<0.05) dietary Ca x intestinal site interaction was observed for N. In birds fed low Ca and normal Ca diets, N was primarily digested by the end of jejunum, but in birds fed high Ca diet both jejunum and upper ileum were involved. At all dietary Ca concentrations, fat was digested mainly in the jejunum and upper ileum, but digestion continued in the lower ileum. Apparent starch digestibility and AME were unaffected (P>0.05) by dietary Ca concentrations. Most of the starch digestion was completed by the end of the jejunum. The present data suggest that the site of digestion of P and N shifts depending on dietary Ca concentrations. Increasing dietary Ca concentrations negatively influenced the digestion of P, N and fat, but had no effect on those of Ca and starch.

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The effect of 3 multi-enzyme mixtures (MEM), A, B and C, having equivalent phytase activities but with different activities of carbohydrases (except invertase) and protease on growth performance and nutrient utilization in broiler chickens fed diets containing different types of cereals and industrial by-products was investigated. Day-old broiler chicks (N＝400) were distributed in a completely randomized design, with 8 treatments of 10 replicates each. Two control diets, one consisted of wheat, corn, soybean meal, canola meal and wheat-corn distillers dried grains with solubles (WCS), and one with sorghum, cottonseed meal, sunflower meal and brewer’s dried grains (SCS) were formulated and fed to birds without or with one of the 3 MEM. Feed intake (FI) and body weight gain (BWG) were determined weekly. On day 20 excreta samples were collected for determination of total tract apparent retention (TTAR) of nutrients and nitrogen corrected apparent metabolizable energy (AME_n). On day 22, eight birds per treatment were killed by cervical dislocation to collect jejunal and ileal digesta for determination of viscosity and apparent ileal digestibility (AID) of nutrients, respectively. Diet and enzyme interactions were only detected for overall feed conversion ratio (FCR, P<0.001) with MEM B and MEM C shown to reduce overall FCR in birds offered SCS and WCS diets, respectively. Most observed differences were due to diet type showing that birds offered WCS diets had higher FI (P<0.0001) and BWG (P<0.0001) throughout the experiment, higher wk 1 FCR (P<0.0001), higher AME_n (P<0.0001) and TTAR of P (P<0.0001) and NDF (P<0.0001) compared with SCS diets. In conclusion, the MEM did not affect growth performance and nutrient utilization though MEM B and MEM C acted differently to reduce overall FCR in birds offered SCS and WCS diets, respectively.

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The present study was performed to measure the chemical composition and in vitro digestibilities of heads and hulls in three different species of the edible shrimp, and discussed their nutritional quality from the view point of practical use of shrimp meal (SM). Heads and hulls of black tiger (Penaeus monodon) (BT), white leg (Litopenaeus vannamei) (WL) and argentine red (Pleoticus muelleri) (AR) shrimps were prepared: 2 sizes of specimen were used in BT. Their inedible parts, such as heads and abdominal exoskeleton with tails (hulls) were removed, dried at 55°C and ground to pass through 1.0 mm aperture and then used as SM. Compared with hulls, heads were significantly rich in crude protein (CP) and ether extract (EE), and poor in crude fibre (CF), crude ash (CA) and chitin. Among head groups, CP level was the greatest in WL, EE level in AR, CF level in large and small BT, CA level in 3 species other than WL, chitin level in large BT. Among hull groups, CP level was the greatest in WL, CF level in large and small BT and chitin level in large BT: EE level in hulls were extremely low in all group. Overall, in vitro dry matter (DM) and CP digestibilities were significantly greater in heads than in hulls, which is reasonable because the level of chitin, non-digestible amino polysaccharide, was greater in hulls than heads in all species. There is no great difference in parameters measured between heads and heads+hulls. The results obtained here suggest that the heads of WL can be a more nutritious source of SM in poultry diets.

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A series of experiments was conducted to elucidate the factor(s) involved in the spontaneous gonadal germ cells (GGCs) discharge from chick embryonic gonads. The developing gonads recovered from 7-day-old White Leghorn (WL) embryos were incubated for 1 h in Dulbecco’s phosphate-buffered saline (PBS) supplemented with Ca²⁺ and/or Mg²⁺ at temperatures of 4-42°C. The number of GGCs spontaneously discharged from gonads into PBS was negatively correlated with Ca²⁺ concentration and positively correlated with incubation temperature (P<0.05). Effects of Mg²⁺ on spontaneous GGCs discharge into PBS[-] was observed to be minimal (P>0.05). Gonadal germ cells discharged into PBS was observed when divalent cations in the medium were chelated using EDTA. In conclusion, it was revealed that spontaneous discharge of GGCs from gonad of 7-day-old chick embryo into PBS was primarily affected by Ca²⁺ concentration and incubation temperature.

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Salmonella infection is one of the major constraints in poultry farming that has hindered its development in Bangladesh. Salmonella serotypes with multidrug resistant phenotypes are a threat to the poultry of Bangladesh. This study focused on genotypic characterization of Salmonella spp. isolated previously from 5 different poultry farms of Savar, Bangladesh. Among the 67 Salmonella isolates, 12 were found to be plasmid-free and showed resistance to as high as 7 groups of antibiotics. PCR using Salmonella specific primers ascertained that all 67 isolates were invA gene positive, 17 were sefA gene positive and 4 were fliC gene positive. Genotyping using Random Amplified Polymorphic DNA (RAPD) and Amplified Ribosomal DNA Restriction Analysis (ARDRA) differentiated three distinct genetic variants circulating in five poultry farms indicating no single source of infection. Sequencing of representatives from each genotype detected close similarity to S. Enteritidis, S. Typhimurium and S. Heidelberg within the poultry samples indicating significant zoonotic hazard. S. Enteritidis was highly prevalent, accounting for 88% (59 out of 67) of the poultry isolates. Contaminations or prevalence of such multidrug resistant zoonotic Salmonella indicates an unhygienic practice of poultry farming in Bangladesh which is becoming a potential threat to public health.

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The purpose of this study was to investigate the immune status or infection rates for primary egg-transmitted bacterial diseases such as pullorum disease-fowl typhoid (PD-FT), Mycoplasma gallisepticum (MG) infection, and Mycoplasma synoviae (MS) infection among 70 broiler breeder flocks throughout Korea between July 2011 and August 2011. The sero-prevalence of flocks and individual chickens for PD-FT was 50.0% and 9.7%, respectively. The prevalence of PD-FT sero-positivity increased over time from rearing to advanced age period. The sero-positive rate of flocks and individual chickens for Salmonella Gallinarum 9R (SG 9R) was 95.7% and 83.6%, respectively. Only two flocks in the brooding period and one flock in the laying period out of all flocks tested were sero-negative for SG 9R. When evaluating MG infection rates, 63 flocks were sero-positive. This excluded two flocks in the brooding period, one flock in the rearing period, and four flocks in the laying period. The sero-prevalence of individual chickens was as high as 66.1% and 67.8% in the rearing and laying periods, respectively. Additionally, birds that were an advanced age period had a high sero-prevalence rate of 86.6%. The rates of sero-positivity for MS infection among flocks and individual chickens were 88.6% and 64.2%, respectively. Data from the present investigation confirmed that the sero-prevalence of PD-FT, MG infection, and MS infection among broiler breeder flocks in Korea is very high. Consequently, we recommend that a national intervention strategy should be established in the near future to eradicate these diseases from broiler breeder flocks.

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A pyrolysis/ashing process for poultry manure with the aim of recovering both the potential energy and the plant nutrients is proposed. Volatile compounds derived from the pyrolysis process were subsequently decomposed using a catalyst to produce light fuel gases, while the solid residues (char or ash) were applied to plant cultivation to examine their usefulness as fertilizers. During the poultry manure pyrolysis, the evolution of volatiles was found to occur at temperatures below 500°C and the volatiles thus derived were effectively converted into light fuel gases by employing a commercial Ni/Al₂O₃ catalyst. Steam addition promoted the water-gas-shift reaction and resulted in high yields of hydrogen. The plant nutrients nitrogen, phosphorus, and potassium were concentrated in the poultry manure char. Komatsuna cultivation tests demonstrated that this char represented a source of highly available nutrients and produced higher crop yields than conventional fertilizers. The porous structure of the poultry manure char was considered to be an important factor in terms of its function as a fertilizer.

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