Sperm drastically change their flagellar movement in response to the surrounding physical and chemical environment. Testicular sperm are immotile; however, they gain the competence to initiate motility during passage through the male reproductive tract. Once ejaculated, the sperm are activated and promptly initiate motility. Unlike mammals, ejaculated sperm in birds are stored in specialized tubular invaginations referred to as sperm storage tubules (SSTs), located between the vagina and uterus, before fertilization. The resident sperm in the SSTs are in a quiescent state and then re-activated after release from the SSTs. It is thought that avian sperm can undergo motility change from quiescent to active state twice; however, the molecular mechanism underlying sperm motility regulation is poorly understood. In this short review, we summarize the current understanding of sperm motility regulation in male and female bird reproductive tracts. We also describe signal transduction, which regulates sperm motility, mainly derived from in vitro studies.

Many behavioral studies and histological analyses of the sense of taste have been conducted in chickens, as it plays an important role in the ingestion of feed. In recent years, various taste receptors have been analyzed, and the functions of fatty acids, umami, and bitter taste receptors in chickens have become clear. In this review, the bitter taste sense in chickens, which is the taste quality by which animals reject poisons, is discussed among a variety of taste qualities. Chickens have taste buds in the palate, the base of the oral cavity, and the root of the tongue. Bitter taste receptors, taste receptor type 2 members 1, 2, and 7 (T2R1, T2R2, and T2R7) are expressed in these tissues. According to functional analyses of bitter taste receptors and behavioral studies, T2R1 and T2R7 are thought to be especially involved in the rejection of bitter compounds in chickens. Furthermore, the antagonists of these two functional bitter taste receptors were also identified, and it is expected that such antagonists will be useful in improving the taste quality of feed materials and poultry drugs that have a bitter taste. Bitter taste receptors are also expressed in extra-oral tissues, and it has been suggested that gastrointestinal bitter taste receptors may be involved in the secretion of gastrointestinal hormones and pathogen defense mechanisms. Thus, bitter taste receptors in chickens are suspected to play major roles in taste sensing and other physiological systems.

There has been an upsurge of interest in the phytobiotics coincident with the onset of the potential ban on the use of antibiotic growth promoters (AGPs) in the broiler industry and because many kinds of nutraceuticals play an important role in improving growth performance, feed efficiency, and gut health of broilers. In the previous years, significant biological activities of essential oils (EOs) belonging to phytobiotics were observed, including antibacterial, antifungal, antiviral, and antioxidant properties. We found new perspectives on the roles of EOs, particularly extracts from the Apiaceae family, which is one of the largest plant families, in potential replacement of AGPs, and on the chemical composition involved in regulating microorganism activity and oxidative damage. Furthermore, the positive effects of EOs on broiler production and the possible mechanisms inducing the involvement of gut health and growth performance have been studied.

Japanese indigenous chickens include approximately 50 breeds exhibiting various morphological traits, such as a long tail. These genetic resources will be important for revealing the genetic basis of morphological traits in the future. However, little is known about the phenotypic characteristics of each breed during the growth stages. To understand age-dependent changes in growth and morphological traits, we investigated tail length, tail number, body weight, and shank length at several time points using three genetically distinct Japanese indigenous chicken breeds. A total of 155 birds from the Tosa-jidori, Chabo, and Minohikichabo breeds were used for trait measurements from 1 to 36 weeks of age to reveal breed and sex effects. Significant sex differences through the growth stages were observed for all traits except for tail number. Although there were no clear breed differences in tail length traits at the 6- and 20-week stages, Minohikichabo ultimately had a significantly longer tail due to extended tail feather growth at later stages (28 and 36 weeks). By measuring two tail length variables (central and maximum), it was revealed that the shape of the tail feathers varies with the growth stage. Minohikichabo’s tail number was higher than that of Tosa-jidori and Chabo at earlier ages (8 and 16 weeks), which leads to an elegant visual in Minohikichabo. Tosa-jidori’s body weight was higher than that of Chabo and Minohikichabo, whereas the shank lengths of Chabo and Minohikichabo were shorter than those of Tosa-jidori. These differences in body weight and shank length were consistent from the early to late growth stages. These results revealed the age-dependency of growth and morphological trait breed characteristics.

A 35-day experiment was conducted to evaluate the effects of the supplementation of mineral detoxified sulfur dispersion ((DSD); Patent No.: 10-1997773) on the growth performance, meat quality, excreta microbiota, gas emissions, nutrient digestibility, and blood profiles of broilers. In total, 720 one-day-old ROSS 308 broilers, with an initial body weight of 41.9±0.8 g, were divided into two (2) treatment groups with 20 replicate pens/groups composed of 18 birds per pen. Treatments consisted of 1) CON (the control), normal drinking water and 2) TRT (the treatment group), CON+0.001% DSD (1000:1 dilution ratio). Average daily feed intake (ADFI) and feed conversion ratio (FCR) increased in the TRT group (P<0.05) between days 1 to 7 and days 7 to 21 of the experimental period. Similarly, body weight gain (BWG) showed a significant increase (P<0.05) in the DSD-supplemented group throughout in the length of the experiment. With regard to meat quality, redness (a*) was higher, while drip loss was lower, on the 7^th day in the DSD group. Furthermore, DSD supplementation increased (P<0.05) Lactobacillus excreta but decreased E. coli concentrations in the TRT group compared to the CON group. Notably, nutrient digestibility, excreta gas emission, and blood profiles did not show any significant differences (P>0.05). DSD supplementation, administered through drinking water, has a positive impact on the growth performance, meat quality, and excreta microbiota of broiler chickens.

Inorganic trace minerals may exacerbate lipid peroxidation, thereby impacting lipid metabolism. This study aimed to compare the effects of inorganic and coated trace minerals in diets with different fat sources, on the performance, slaughter characteristics, and antioxidant status of broiler chickens. A total of 576 21-day-old Abor Acres broiler birds were randomly divided into four dietary treatment groups in a 2 (non-coated and coated trace minerals)×2 (soybean oil and lard) factorial design. Each treatment was replicated 12 times (12 birds per replicate). The results showed that coated minerals significantly improved the average daily gain (ADG) in weight and the feed conversion ratio (P<0.01), increased serum iron, zinc, selenium, and thyroxine contents, increased the activities of glutathione peroxidase, superoxide dismutase, total antioxidant capacity, and lipoprotein lipase (P<0.05), and decreased the serum and muscle malondialdehyde (MDA) contents (P<0.01). The use of soybean oil as the fat source resulted in a high ADG in weight, a low F/G ratio, reduced serum MDA content, and drip loss of breast and leg muscles (P<0.05). In conclusion, the supplementation of coated trace minerals improved growth performance, antioxidant status, trace mineral retention within serum, and lipid metabolism. Additionally, soybean oil also improved the growth performance, antioxidant performance, and meat quality of broilers. The combination of coated trace minerals and soybean oil generated the best growth performance, antioxidant status, and meat quality characteristics.

The aim of this study was to evaluate the effects of dietary supplementation of calcium propionate and calcium butyrate on the laying performance, eggshell quality, and expression of genes related to calcium and phosphorus metabolism in the tibia. One hundred and twenty 70-week-old Isa Brown hens were randomly assigned to three treatments, and each treatment had four replicates of 10 birds fed a basal diet (control) or a basal diet supplemented with 0.5% calcium propionate (CP) or 0.5% calcium butyrate (CB) for 8 weeks. The CB and CP treatments had no significant effect (P>0.05) on the laying rate, egg production, egg weight, and feed efficiency. The eggshell percentage was increased from week 2 (P<0.05) and eggshell thickness was elevated at week 8 (P<0.01) by both CP and CB treatments. Compared to the control treatment, the CB treatment increased serum calcium and phosphorus levels at week 4 (P<0.05), whereas the CP and CB treatments decreased serum phosphorus at weeks 6 and 8, respectively (P<0.05). Dietary supplementation had no effect on the bone index and bending strength of the tibia (P>0.05). The calcium and phosphorus content of the tibia was decreased by the CB treatment (P<0.05). In the spleen, NF-κB and IL-6 transcript levels were not influenced (P>0.05) but TNF-α transcript levels were decreased by the CP treatment (P<0.05). In the tibia, the expression levels of NF-κB, TNF-α, and IL-17 were not affected by the CP or CB treatment (P>0.05). The CP and CB treatments had no significant effect on the transcript levels of RANKL, OPG, RNUX2, OPN, α-Clotho, and VDR (P>0.05). In contrast, PHEX transcript levels were increased by the CP treatment (P<0.05). The expression levels of osteocalcin (P＝0.094) and FGF23 (P＝0.087) tended to decrease under the CB treatment. In conclusion, dietary supplementation of 0.5% calcium butyrate or 0.5% calcium propionate improved the eggshell quality of aged laying hens, possibly as a result of decreased deposition or enhanced mobilization of bone calcium and phosphorus.

This study was conducted to evaluate the effects of dietary supplementation of dried neem (Azadirachta indica) leaf extract (DNE) on lipid peroxidation and the expression of genes encoding mRNAs in antioxidant enzymes in the pectoralis major muscle of chickens. A total of 24 male broiler chickens (ROSS308) were divided into three groups (n＝8) at 21 days of age. The control group of chickens was fed a basal diet, and the remaining two groups of chickens were fed a basal diet supplemented with DNE at a concentration of 0.5% or 2.0% until 35 days of age. Growth performance (body weight, weight gain, feed intake, and feed conversion ratio) and tissue weights did not differ among the three groups. The 2.0% DNE-supplemented diet decreased the muscle malondialdehyde content, a marker of lipid peroxidation, and drip loss compared to the control chickens. In addition, the expression of genes encoding mRNAs of antioxidant enzymes (i.e., Cu/Zn-superoxide dismutase, Mn-superoxide dismutase, glutathione peroxidase 7, and catalase) were higher in the pectoralis major muscle of chickens fed the 2.0% DNE-supplemented diet than in the control chickens. Therefore, DNE supplementation increased the expression of genes encoding mRNAs in antioxidant enzymes and reduced lipid peroxidation and drip loss in the pectoralis major muscle of broiler chickens.

Protein synthesis in skeletal muscle is considered one of the most energy-consuming cellular processes. AMP-activated protein kinase (AMPK) is a metabolic master switch that regulates glucose and lipid metabolism, and it is implicated in protein synthesis control in skeletal muscles. The mechanistic target of rapamycin complex 1 (mTORC1) is a central regulator of protein metabolism in cells. However, the effect of AMPK activation on protein synthesis and mTORC1 signaling in chicken skeletal muscle remains unclear. Therefore, in this study, we aimed to investigate the effect of 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), an AMPK activator, on protein synthesis and mTORC1 signaling in chick myotube cultures. The incubation of chick myotubes with AICAR (1 mM) for 3 h led to a significant increase in AMPK (Thr172) phosphorylation. Nonetheless, protein synthesis, measured using the surface sensing of translation method, was significantly decreased by AICAR. In addition, the phosphorylation of p70 ribosomal S6 kinase 1 (S6K1, Thr389), S6 ribosomal protein (Ser240/244), and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1, Thr37/46) was significantly reduced by AICAR. These results suggest that AMPK activation suppresses protein synthesis and mTORC1 signaling (through the phosphorylation of S6K1, S6 ribosomal protein, and 4E-BP1) in chick myotubes.

We evaluated the effects of 6-phytases on the growth performance of broilers (UK Chunky) under the recommended supplier-application dosage of each phytase. A nutritionally sufficient standard diet was administered as the base diets in the positive control feed. The diet in the negative control feed was designed by reducing total phosphorous, non-phytate phosphorus, and calcium by 0.1% to evaluate the effect of the nutrient restriction on broilers. Four 6-phytases were added to negative control feeds at the level of the recommended dosage of each product to compare the effect of phytases on broiler technical performance, tibia ash, and feed digestibility. Nine hundred one-day-old broiler chicks (males and females) were distributed in a completely randomized design composed of six treatments and three replicates of 50 chicks each. Chicks were fed ad libitum for 49 days. Body weight gain and feed intake were recorded on days 21 and 49, tibia ash was measured on day 21, and apparent ileal digestibility of dry matter, crude protein, and total phosphorus were analyzed on day 49. Birds reared with test feeds supplemented with phytase showed higher body weight gain and feed intake compared to those of the negative control birds. No significant differences in traits were observed among different phytase treatments. Similarly, the percentage of tibia ash increased when phytase was supplemented, resulting in higher bone levels compared to that of the positive control. The apparent ileal digestibility of crude protein and total phosphorus was enhanced by supplementing negative control diets with phytases.

DNA methylation regulates gene expression by modifying the nucleosome structure of DNA, without altering the gene sequence. It has been reported that DNA methylation reactions are catalyzed by several enzymes. In chickens, thermal conditioning treatment affects the central DNA methylation levels. The purpose of this study was to clarify the changes in DNA methylation and demethylation factors during thermal conditioning in the hypothalamus of 3-day-old chicks. Male chicks (3-days old) were exposed to 40±0.5°C as a thermal conditioning treatment for 1, 2, 6, 9, or 12 h. The control chicks were kept in a thermoneutral zone (30±0.2°C). After thermal conditioning, the mRNA levels of DNA methyltransferase (DNMT)-1, -3a, -3b, and ten-eleven translocation (TET)-1, -2, and -3 in the hypothalamus were measured by q-PCR. The mRNA levels of DNMT-3a and TET-1 were increased by thermal conditioning. Moreover, the expression level of TET-1 increased with the loading time of the thermal conditioning. The gene expressions of DNMT-1, DNMT-3b, TET-2, and TET-3 were not affected by thermal conditioning. Since DNMT-3a is a catalyst for de-novo DNA methylation and TET-1 catalyzes the oxidation of methylated cytosine, it is suggested that the thermal conditioning increased the activation of DNA methylation and demethylation factors, which occur in the hypothalamus of neonatal chicks.

The reproductive performance of broiler breeder chickens noticeably decreases toward the end of their commercial lives. Herein, we determined the effects of vitamin E and selenium dietary supplementation on semen traits, egg fertility (defined as fertilization and hatching rates) of adult (49-week-old) and older (63-week-old) Red Cornish breeders. We found that both vitamin E and selenium were concentrated in the liver and adipose tissue of adult and older Red Cornish breeders, and were transferred to the semen and egg yolk, respectively, in proportion to the level of supplementation. Vitamin E supplementation, in particular, improved ejaculate volume, total sperm count, sperm motility, and viability in both adult and older roosters, whereas selenium improved sperm motility and viability in the adult roosters. Egg fertility increased following supplementation with either vitamin E or selenium. The hatching rate also improved by both supplements in proportion to the level of supplementation. No significant synergistic effects of vitamin E and selenium were found. The levels of egg fertility and sperm trait improvements diminished with the age of the birds and depended on vitamin E and/or selenium doses. Thus, as dietary vitamin E and selenium supplements improved semen quality and egg fertility in these older Red Cornish broiler breeders, such birds could be maintained in flocks to prolong their reproductive output.