Chickens display a wide spectrum of phenotypic variations in quantitative traits such as egg-related traits. Quantitative trait locus (QTL) analysis is a statistical method used to understand the relationship between phenotypic (trait measurements) and genotypic data (molecular markers). We have performed QTL analyses for egg-related traits using an original resource population based on the Japanese Large Game (Oh-Shamo) and the White Leghorn breeds of chickens. In this article, we summarize the results of our extensive QTL analyses for 11 and 66 traits for egg production and egg quality, respectively. We reveal that at least 30 QTL regions on 17 different chromosomes affect phenotypic variation in egg-related traits. Each locus had an age-specific effect on traits, and a variety in effects was also apparent, such as additive, dominance, and epistatic-interaction effects. Although genome-wide association study (GWAS) is suitable for gene-level resolution mapping of GWAS loci with additive effects, QTL mapping studies enable us to comprehensively understand genetic control, such as chromosomal regions, genetic contribution to phenotypic variance, mode of inheritance, and age-specificity of both common and rare alleles. QTL analyses also describe the relationship between genotypes and phenotypes in experimental populations. Accumulation of QTL information, including GWAS loci, is also useful for studies of population genomics approached without phenotypic data in order to validate the identified genomic signatures of positive selection. The combination of QTL studies and next-generation sequencing techniques with uncharacterized genetic resources will enhance current understanding of the relationship between genotypes and phenotypes in livestock animals.
Dopamine inhibited prolactin secretion via dopamine D2 receptor (DRD2) at the pituitary level, but its effects on reproduction in pigeons are unclear. In this study, Single Nucleotide Polymorphisms (SNPs) in the exons of DRD2 gene were identified and analyzed by using DNA sequencing methods in 60 female domestic pigeons (Columba livia), and the association between DRD2 polymorphisms and reproduction traits was also analyzed. Sequencing results showed that 7 nucleotide mutations were detected in the exon 1, 4, and 6 regions of DRD2 gene. The analysis revealed three genotypes (AA, AB, and BB) in exon 4 and two genotypes (AA, AB) in exon 6, in which the AA genotype was consistently dominant, and the A allele showed a dominant advantage. The C4532T genotypes located in exon 6 of DRD2 gene were significantly (P<0.05) associated with reproductive traits of pigeon. Moreover, the individuals with AB genotype had significantly higher fertility rate and total hatching number within 500 days of age than those with AA genotype (P<0.05). These findings suggested that the DRD2 gene should be included in future genetic studies of pigeon reproduction and the SNP of C4532T might be a potential candidate genetic marker for Marker-aid breeding in pigeon.
Genetic polymorphisms of 19 microsatellites were investigated in nine local chicken breeds collected from low, middle and high altitudes areas in China (total number was 256) and their population genetic diversity and population structure were analyzed. All breeds were assigned into three groups, including the high (Tibetan chicken (T) and Grey chicken (G), their altitudes were above 1000 m); middle (Chengkou mountainous chicken (CK), Jiuyuan chicken (JY) and Pengxian yellow chicken (PY), their altitudes were between 500 and 1000 m), and low groups (Da ninghe chicken (DH), Tassel first chicken (TF), Gushi chicken (GS) and Wenchang chicken (WC), their altitudes were below 500 m). We found 780 genotypes and 324 alleles via the 19 microsatellites primers, and the results showed that the mean number of alleles (Na) was 17.05; the average polymorphism information content (PIC) was 0.767; the mean expected heterozygosity (He) was 0.662; as for observed heterozygosity (Ho), it was 0.647. The AMOVA results indicated the genetic variation mainly existed within individuals among populations (80%). There was no genetic variation among the three altitude groups (0%). The mean inbreeding coefficient among individuals within population (FIS) was 0.031 and the mean gene flow (Nm) was 1.790. The mean inbreeding coefficient among populations within a group (FST) was 0.157. All loci deviated Hardy-Weinberg equilibrium. The genetic distance ranged from 0.090 to 0.704. Generally, genetic variations were mainly made up of the variations among populations and within individuals. There were rich gene diversities in the populations for the detected loci. Meanwhile, frequent genes exchange existed among the populations. This can lead to extinction of the peripheral species, such as the Tibetan chicken breed.
A total of 800 day-old broiler chicks were assigned to four test diets to assess the efficacy of phytase, fermented from Aspergillus niger, and boron, as boric acid, on the growth performance and mineral profile in chickens. The dietary treatments included the basal diet and the basal diet supplemented with boron (20 mg/kg), phytase (500 phytase units/kg diet), or a combination of boron and phytase. The following parameters were measured: growth performance indices, serum biochemicals, ash and the mineral profile of the tibia, breast muscle, liver and excreta. Boron decreased the overall feed conversion ratio by 1.9% (P<0.05) but did not affect the body weight and feed consumption of chickens grown for 42 days (P>0.05). The performance indices were not significantly influenced by dietary regimens for the first 21 days of the experiment (P>0.05). The addition of boron alone and boron+phytase resulted in significant increases in the boron concentrations of serum, bone, breast muscle, liver and excreta (P<0.001). The serum alanine aminotransferase activity of chicks fed phytase was higher (P<0.05) than all other treatments. The ash content and mineral composition of the breast meat, liver and tibia did not respond to individual or combined dietary modifications (P>0.05). The chickens administered a diet with boron excreted less Cathrough excreta. However, the ash content and Fe and Cu concentrations in the excreta increased in response to phytase supplementation (P<0.05). In summary, supplementation with boron alone improved the feed conversion efficiency of broiler chickens fed diets containing adequate levels of nutrients. However, the combination of boron and phytase did not cause further improvements in broiler performance or the bioavailability of minerals.
The present study was conducted to investigate the effects of zinc (Zn) bearing palygorskite (ZnPal) inclusion on the carcass traits, chemical composition of muscle, and muscular lead (Pb) and chromium (Cr) contents of broilers. A total of 240 1-day-old Arbor Acres broiler chicks were randomly divided into 5 dietary treatments with 6 replicates of 8 chicks each. Broilers in the 5 treatments were fed a basal diet supplemented with 0 (Control group), 20, 40, 60, and 80 mg/kg Zn in the form of ZnPal for 42 days, respectively. There were no differences in the carcass yield, abdominal fat yield, subcutaneous fat thickness, and intramuscular fat width among treatments (P>0.05). Compared with the control group, the eviscerated yield (P=0.010) and thigh muscle yield (P=0.046) were quadratically increased by the supplementation of ZnPal (P<0.05). Similarly, the breast muscle yield was linearly (P=0.024) and quadratically (P=0.011) increased by ZnPal inclusion. The addition of ZnPal to diets of broilers also linearly (P=0.002) increased fat content in the thigh. Moreover, the supplementation of ZnPal linearly and quadratically reduced the content of muscular Pb and the content of Cr in the thigh muscle (P<0.05). It was concluded that ZnPal inclusion could improve carcass traits, increase fat content in the thigh, and reduce the accumulations of Pb and Cr in the muscles, and this effect was more pronounced when extra Zn dosage in the form of ZnPal was 40 mg/kg.
Availability of feed crops for animal production is decreasing, creating a need to identify alternative food sources. With their high protein content, mulberry leaves are a likely candidate for feed supplementation and have been trialed on pigs and chickens, but little is known about their effect as a feed supplement on geese. Here, we determine the nutritive value of mulberry leaf meal (MLM), measure the digestibility of energy and amino acid of MLM in male Sichuan white geese, and evaluate the performance of these geese fed an MLM-supplemented diet. The composition of MLM was as follows: gross energy 4.94 Mcal/kg, crude protein 18.81%, ether extract 11.65%, crude fiber 12.45%, calcium 2.46%, phosphorous 0.24% and amino acids 0.26-1.92% (all % on a dry matter basis). Using the emptying then force-feeding method on 24 geese aged 194 days, we measured the apparent metabolizable energy of MLM as 1.58 Mcal/kg (on a dry matter basis), and the true total tract digestibility of the amino acids in MLM as 50.54-79.98%. We then randomly allocated a further 210 geese aged 35 days to one of five dietary treatments (control diet alone or supplemented with 4%, 8%, 12% or 16% MLM). Each treatment contained six replicate pens of seven birds per pen, and birds were maintained on their treatment until 70 days of age. Geese fed diets containing MLM exhibited lower weight gains, elevated feed consumption and an increased feed to gain ratio (P<0.05) compared with geese fed the control diet. Moreover, geese fed diets supplemented with MLM all experienced diarrhea, reduced amounts of subcutaneous fat and lower percentages of skin and abdominal fat (P<0.05) compared with control geese. In conclusion, MLM should be used with caution as a feed supplement for geese.
This study aims to understand the relationships among morphological characteristics, their functional roles, and breeder preferences in Japanese native fowls. We analyzed and compared the shapes and sizes of the skeletal forelimb, pectoral girdle, and sternum among six breeds: Chabo, Oh-Shamo, Onagadori, Shokoku, Tosajidori, and Totenko. Because skeletal forelimb, pectoral girdle, and sternum are one of the bases for composing body appearance and for movement of birds such as flapping, we treated those skeletons. All measurements of size were smaller in Chabo than those in other breeds except Tosajidori. The largest measurement values of all parameters were observed in Oh-Shamo. The largest measurement values were observed in all measurements of Oh-Shamo. Short and wide forelimb bones and a short coracoid were observed in Chabo. Oh-Shamo was equipped with a wide sternum and a widely articulated coracoid. Shokoku and Totenko possessed longer bones that constitute the thoracic cavity. We suggest that the small bone size in ornamental fowls contributes toward a cute appearance and that the large bone size of fighting fowls is correlated with their masculinity and aggressiveness. The short forelimb bones, wide articulation, and corpus of forelimb bones in Chabo create a round and soft body silhouette. The observed short coracoid prevents Chabo from dragging its body on the ground while walking. The wide sternum and articulation of the coracoid observed in Oh-Shamo are considered to contribute to the ability to pounce on an opponent by flapping during a fight. The wide sternum of Oh-Shamo is considered to affect its body outline, producing a strong, masculine physical appearance. We also suggest that the characteristics observed in Shokoku and Totenko create a space for the vocal organs, such as clavicle air sacs. We suggest that the observed morphological characteristics underlie the function and breeder preferences of each breed.
A macroscopic examination of the huge leg of the Dong Tao breed from North Vietnam was conducted. Bone and muscular tendon morphometric data demonstrated that the Dong Tao breed was equipped with the extraordinarily thick and large tarsometatarsal bone and distal parts of the related tibiotarsus regions. Morphological differences between dorsal and plantar sides were clearly observed. First, on the dorsal side, fleshy bundles were extended effectively using the enlarged dorsal surface of tarsometatarsal bone shown as Musuculus extensor digitorum brevis, M. extensor digiti I brevis and M. adductor digiti IV. The strong and fleshy extensor bellies of M. tibialis cranialis and M. extensor digitorum longus were enlarged in the crural region, functioning to dorsally pull the heavy tarsometatarsal region through the ankle joint. Second, on the plantar side, the flexor tendon groups around the ankle joint were wider and thicker than those of other ordinary breeds, possibly to stabilize the tarsometatarsal bone and to flex the phalange as observed in M. flexor perforatus digiti II, M. flexor perforans et perforatus digiti II, M. flexor perforatus digiti III, M. flexor perforans et perforatus digiti III, M. flexor perforatus digiti IV, and M. flexor perforans digitorum profundus. The mass of the huge tarsometatarsal region does not contribute to effective locomotion in the Dong Tao fowl in comparison with that associated with normal breeds. However, we suggest that these morphological changes in the musculoskeletal system may functionally compensate for the physical disadvantages of the large weight of the distal part of the hindlimb in the Dong Tao fowl.
Two experiments determined the effects of various monochromatic light emitting diode (LED) light colors on performance, blood properties, bone mineral density, meat quality properties, and fatty acid composition of ducks. In Experiment 1, 720 1-d-old Cherry Valley ducklings were divided into four light treatments (six replicate pens/treatment; 30 ducks/pen) and were assigned to 1) yellow (Y), 2) green (G), 3) blue (B), or 4) control white (fluorescent lamps). In Experiment 2, six LED light treatments with four replicates were assigned as blue (PB), bright blue (BB), sky blue (SB), greenish blue (GB), green (PG), and fluorescent white as a control treatment. In Experiment 1, G light increased body weight and weight gain compared with the control and Y light during the first 21 d. During d 22-42, weight gain increased in the G and B treatments (P<0.034). Body weight and weight gain were increased under the G light treatment (P<0.036) in Experiment 2. Blood values were not influenced by the light treatments but serum cholesterol level decreased under the PB treatment (P<0.015) compared to PG treatment. Whole blood viscosity at a shear rate of 1 per second decreased significantly under the PG treatment than that of control W treatment. Ducks reared under GB and PG light had increased monounsaturated fatty acids and unsaturated fatty acids/saturated fatty acids by altering the fatty acid composition in muscle. These results suggest that monochromatic PG and GB light color increased growth performance, blood properties, and muscular fatty acid composition, while providing similar bone and meat properties in Cherry Valley ducks.
Sperm motility is an essential trait for successful fertilization in animals. In birds, ejaculated sperm migrate into sperm storage tubules before fertilization and are stored in a quiescent state. We previously reported that this type of sperm’s flagellar quiescence was induced by lactic acid through flagellar dynein ATPase inactivation following cytoplasmic acidification (<pH 6.0). However, signal transduction in the sperm cells leading to motility inactivation is not well understood. The aim of the present study was to investigate the role of protein kinases in putative signal transduction in quail spermatozoa motility in vitro. Following incubation with bisindolylmaleimide II (BisII), a potent-competitive protein kinase C (PKC) inhibitor, sperm motility decreased in a dose related-manner. However, no such inhibitory effect was found in sperm exposed to bisindolylmaleimide V, H-89, or LY294002, a weak inhibitor of PKC, a potent inhibitor of protein kinase A (PKA) and a selective inhibitor of phosphatidylinositol 3-kinase, respectively. BisII-treated sperm exhibited no significant differences in pHi, [Ca2+]i, mitochondrial activity, intracellular cAMP or ATP concentration, as well as dynein ATPase activity, compared to the control sperm. However, when the phosphorylated substrate proteins by PKC were detected by Western blot analysis, the intensity of the band in sperm incubated in the presence of BisII decreased. Moreover, immunoreactive PKCι and μ isoforms in the sperm lysates were also detected. These results indicated that the PKC signaling pathway may be involved in sperm motility regulation, and protein phosphorylation by PKC may be required to maintain flagellar movement in the Japanese quail.
Fertilization is indispensable for zygotic formation leading to the birth of animals and the species-specific sperm-egg binding thought to be the initial step in this important process. In birds, the oocyte, which encounters the spermatozoa at the time of fertilization, is enclosed in a perivitelline membrane (pvm) constructed of several zona pellucida glycoproteins (ZP proteins: ZP1, ZP2, ZP3, ZP4 and ZPD). The aim of this study was to determine the ZP protein in the pvm responsible for sperm-pvm binding in Japanese quail. We tested the effects of anti-ZP protein antibodies on in vitro sperm perforation in the pvm. The results showed that the anti-ZP1 and ZP3 antibody significantly blocked hole formation by sperm, whereas anti-ZP2, ZP4 and ZPD as well as normal rabbit serum had no such effect. When the sperm acrosome reaction was inhibited in the presence of pertussis toxin, sperm-pvm binding was observed. This sperm-pvm binding was significantly prevented when the purified ZP1 or ZP3 was included in the reaction mixture. Moreover, both digoxigenin-labeled ZP1 and ZP3 were found to interact with the sperm head by immunocytochemical observation. Our results indicate that sperm binding to the pvm is, at least in part, mediated by the interaction of ZP1 and ZP3 with the sperm head during fertilization in Japanese quail.
The texture of jidori-niku (Japanese indigenous native chicken meat) was characterized and compared with those of Chunky broiler chicken meat. Experiment 1: A qualitative sensory test using jidori-niku and broiler breast (pectoralis major, PM), thigh (biceps femoris, BF) and sasami (deep pectoral) meat cooked to the end-point temperature 75°C by steam-heating was administered to a trained sensory panel (n＝16-17) for the selection of descriptive texture items from ISO5492 texture words. By the correspondence analysis, the characteristics of ‘chewiness,’ ‘hardness’ and ‘springiness’ were found to be different between jidori-niku and broiler: they likely characterize jidori-niku texture. Experiment 2: Texture characteristics in the three above-mentioned muscles in jidori-niku and broiler were compared quantitatively using the three above-mentioned texture items by the trained sensory panel. Sensory chewiness and hardness were the highest in the broiler PM and second highest in the jidori-niku BF, whereas sensory springiness was the highest in the jidori-niku BF. These results suggest that jidori-niku-like texture was characterized as a springy texture as compared to broiler meat.
This study demonstrates a novel concept of salted yolk processing using fresh duck egg yolk. Salted yolks are produced to comply with good agricultural practice and allow better traceability of the raw materials. This methodology also prevents the curing of albumin as in the normal whole-egg brining protocol, and the spare egg whites can be used as raw material for other food products. This new brining process accelerated the curing time from 4 weeks to 4 days. The brining solution was a mixture of sodium chloride and maltodextrin. The sensory results suggested that this novel separated yolk brining process generated salted yolks of similar quality to those using the traditional shell egg brining protocol.