Fertilization in animals that employ sexual reproduction is an indispensable event for the production of the next generation. A significant advancement in our understanding of the molecular mechanisms of sperm-egg interaction in mammalian species was achieved in the last few decades. However, the same level of knowledge has not been accumulated for birds because of egg size and the difficulty in mimicking the physiological polyspermy that takes place during normal fertilization. In this review, we summarize the current understanding of sperm-egg interaction mechanism during fertilization in birds, especially focusing on sperm-egg binding, sperm acrosome reaction and the authentic sperm protease required for the hole formation on the perivitelline membrane. We explain that the zona pellucida proteins (ZP1 and ZP3) in the perivitelline membrane play important roles in sperm-egg binding, induction of the acrosome reaction as well as sperm penetration by digestion of sperm protease. We anticipate that a deeper understanding of avian fertilization will open up new avenues to create powerful tools for a myriad of applications in the poultry industries including the production of transgenic and cloned birds.

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We previously reported that a diet containing 65% paddy rice suppressed the colonization of Campylobacter jejuni in the cecum of broiler chicks, suggesting that this type of diet has positive effects on upper gastrointestinal tract function in broilers. To reveal the possible mechanisms involved in this antibacterial effect of the whole-grain paddy rice diet, we performed experiments comparing the digesta passage rate in the crop and gizzard, the development of gizzard, and the pH distribution in the gizzard between groups of chicks fed two different diets, such as ground corn and whole-grain paddy rice. During these experiments, we made the following observations: the chicks in the group fed the whole-grain paddy rice diet had more developed gizzards and significantly larger crop content than the chicks in the group fed the ground corn diet. The chicks fed the whole-grain paddy rice diet retained the digesta in the crop for much longer and had less variation in the pH values in the gizzard than those fed ground corn. On the basis of these observations, we concluded that the hardness of the rice hull in whole-grain paddy rice leads to a larger amount and longer retention of content in the crop, as well as the uniformity of the internal pH of the gizzard, by promoting gizzard activity. We speculate that the hardness of the rice hulls promoted the grinding activity of the gizzard, resulting in the long retention time of the digesta in the crop and uniformity of the internal pH of the gizzard, which may sterilize or suppress Campylobacter growth in the gastrointestinal tract of broiler chicks.

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Two factorial completely randomized design trials 2×2 and 2×2×2 were conducted to evaluate the effect of a blend of essential oils and organic acids (Biacid^TM) in broiler breeder diets at two levels, two dietary non-starch polysaccharides (NSPs) levels and in ovo injection of Biacid^TM on their progenies performance, respectively. 240 broiler breeders of Ross 308 strain were fed from the age of week 44^th for 12 weeks in four groups. 120 produced eggs from each group were divided in two groups of 60 eggs for injecting by 0.5 ml of Biacid^TM or distilled water. Injection was done during transferring from setter to hatcher in day 18^th of incubation. Twenty-five cockerels from each of 8 treatments were housed into separate pens. Using Biacid^TM and high NSPs in broiler breeders’ ration affected hatchability, embryo mortality, weight of day old chicks and progenies’ carcass yield significantly (p<0.05) whereas in ovo injection of Biacid^TM did not show significant effects in this regards (p≥0.05). Offspring’s abdominal fat was neither affected by broiler breeders’ rations nor in ovo injection of Biacid^TM (p≥0.05). Biacid^TM and high NSPs content in broiler breeders’ ration affected all primary and secondary humoral immune responses of progenies against sheep red blood cells (p<0.05). In ovo injection of Biacid^TM increased the primary IgG, primary IgT and secondary IgG responses (p<0.05). The interaction of the effects of Biacid^TM and high NSPs in broiler breeders’ ration and also in ovo injection of Biacid^TM affected progenies’ weight gain, feed intake, feed conversion ratio and European production index significantly (p<0.05). It seems that using Biacid^TM in broiler breeders’ diet can modify the undesirable effects of high NSPs content of breeders’ ration on performance of their offspring.

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The effects of L-carnitine, atorvastatin and their combination on growth and lipid metabolism of broiler chickens is not yet known. Thus, the objective of the present study was to investigate the effects of dietary L-carnitine and atorvastatin on the performance, carcass characteristics and blood parameters in broilers. Different dietary levels of L-carnitine (0, 150 and 300 mg/kg, respectively) and atorvastatin (0, 1 and 2 g/kg, respectively) were added to the daily birds’ ration. Significant positive effects (P<0.05) on broiler body weight for both L-carnitine and atorvastatin were reported, and this effect became clear starting from the 4th week of rearing period till the slaughter age. Dietary treatments had also significant (P<0.05) positive effects on broilers empty carcass, breast and drumstick weights. Conversely, L-carnitine slightly increased abdominal fat, whereas supplementing atorvastatin slightly reduced it (P<0.05). However, Combining the treatments, resulted in reduction of abdominal fat pad, showing also the best development of breast and drumstick muscles (P<0.05). Moreover, the weight of gizzard, liver and heart were significantly higher in birds treated with the highest doses supplied (P<0.05). Dietary treatments had also influence on blood biochemical parameters of broilers. In overall, our findings suggest that combining dietary L-carnitine and atorvastatin supported birds growth and muscles development reducing the body fat deposition. However, further studies are needed to deeply study the potential effect of statins on meat quality.

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This study was conducted to know the effect of formic acid-treated shrimp meal as a protein source on growth performance, digestibilities, and nitrogen (N) retention for broilers. Shrimp meal (SM) was treated with 3% formic acid (w/v) at room temperature for 20 minutes, sun-dried, ground through a 1.0 mm mesh screen, and then ready to use as the treated SM (TSM). Forty-two male broiler chicks (8 d old, Ross 308) were randomly divided into 7 dietary groups (6 birds each), namely control diet, diets containing 5, 10, and 15% of SM, and diets containing 5, 10, and 15% of TSM and offered diets till 35 d old. Final body weight, body weight gain and feed intake decreased significantly with increasing levels of SM in diets. Feed conversion ratio also decreased with increasing levels of the SM (P<0.05). Similar trend was observed in the TSM group, but the adverse effects of the TSM were milder in comparison to the SM group (P<0.05). Dry matter digestibility tended to decrease (P<0.05) with increasing levels of the SM but unchanged with increasing level of the TSM. Availability of ash decreased with increasing levels of the SM and TSM in diets (P<0.05). Although N retention decreased (P<0.05) with increasing level of the SM and TSM in diets but the decreasing trend was milder in the TSM groups than the SM groups. Moreover, chitin digestibility was significantly greater in the TSM groups than the SM groups. In conclusion, broilers received diets containing the TSM showed better growth performance along with improved nutrient digestibility and N retention which suggests that formic acid-treated SM can be used as a potential protein source in broiler diets.

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The skeletal muscle mass is known to be controlled by the balance between protein synthesis and degradation. The fractional rate of protein synthesis has been reported to decrease age-dependently from 1 to 4 weeks of age in the chicken breast muscle (pectoralis major muscle). On the other hand, age-dependent change of the fractional protein degradation rate was reported to be less in the skeletal muscle of chickens. These findings suggest that protein synthesis is age-dependently downregulated in chicken muscle. We herein investigated the age-dependent changes in protein synthesis or proteolysis-related factors in the breast muscle of 7, 14, 28, and 49-day old broiler chickens. IGF-1 mRNA level, phosphorylation rate of Akt, and phospho-S6 content were coordinately decreased in an age-dependent manner, suggesting that IGF-1-stimulated protein synthesis is downregulated with age in chicken breast muscle. In contrast, atrogin-1, one of the proteolysis-related factors, gradually increased with age at mRNA levels. However, plasma N^τ-methylhistidine concentration, an indicator of skeletal muscle proteolysis, did not coordinately change with atrogin-1 mRNA levels. Taken together, our results suggest that the IGF-1/Akt/S6 signaling pathway is age-dependently downregulated in the chicken breast muscle.

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Avian species including chickens are known to be hyperglycemic animals. Hyperglycemia promotes the glycation which at first forms Amadori products undergoing further complex reaction to form advanced glycation end products (AGEs). Our previous study revealed that AGEs derived from glucose and amino acids were predominantly incorporated into spleen, kidney and liver. However, it has not been elucidated whether Amadori products (glycated amino acids) can also be incorporated into cells or not. Therefore, in the present study, radioactive glycated-tryptophan and -valine were prepared and the incorporation of these glycated amino acids into various chicken embryonic cells was studied. Various embryonic cells prepared from muscle, liver, spleen and kidney of chicken embryos were incubated in Medium 199 supplemented with ¹⁴C-labeled glycated-tryptophan or -valine. After incubation, embryonic cells were well-rinsed and then the radioactivity incorporated into cells was measured. It was revealed that both glycated amino acids were incorporated into embryonic cells derived from muscle, liver, spleen and kidney. In muscular cells, the incorporation of glycated-tryptophan was higher than that of glycated-valine. On the other hand, in embryonic cells derived from liver and kidney, the amount of glycated-tryptophan incorporated into cells was almost the same to that of glycated-valine. In conclusion, it was supposed that both glycated-tryptophan and -valine could be incorporated into various cells derived from muscle, liver, spleen and kidney of chicken embryos and that the incorporation might have the organ specificity.

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The in vitro sperm quality parameters (motility, M; viability, V; normal morphology, NM; plasma membrane integrity, PMI; mitochondrial function, MF) in Muscovy drakes (Cairina moschata) were evaluated by using microscopy and flow cytometry, the correlation among sperm quality parameters and results of artificial insemination was also assessed in present study. M, V and NM were detected by phase contrast microscopy assisted with eosin-nigrosin staining, and PMI and MF were detected by using flow cytometry within appropriate fluorescence staining (SYBR-14/PI and R123/PI, respectively). Fertility (F), early embryonic mortality (EEM) and the survival embryo rate (SER) were assessed after the artificial insemination of Muscovy or Kaiya duck (Anas platyrhynchos) females. Sperm PMI and MF, the parameters detected by flow cytometry were positively correlated with sperm M, V, and NM, those were detected by phase contrast microscopy (P<0.05). Sperm V and PMI were negatively correlated with the percentage of early embryo mortality of Muscovy duck fertile eggs (P<0.05). The results of the present study showed the relationships among the AI results and the sperm quality parameters detected by microscopy as well as flow cytometry. In conclusion, flow cytometry assisted with microscopy can be an effective tool to evaluate in vitro sperm quality and may contribute to predict the reproductive performances of individual Muscovy drakes, which helps to improve duck production efficiency.

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Being transcriptionally and translationally inactive, sperm must utilize preassembled pathways into specific compartments in which they function to fertilize ovum. Membrane rafts are specific membrane regions enriched in sterols and glycosphingolipids such as ganglioside G_M1 (G_M1) and play an important role in a variety of cellular functions. Recent findings have demonstrated that membrane rafts are present in mammalian sperm and are involved in regulating the induction of acrosome exocytosis. However, no information is available on whether avian sperm possess membrane rafts. Thus, we investigated the organization of membrane rafts in chicken sperm. Our localization experiments for G_M1 and sterols showed that the plasma membrane overlaying the sperm head possesses specific membrane domains enriched in both aforementioned lipids. Caveolin-1, which localizes into membrane rafts in other systems, was localized only to the sperm tail. Based on the biochemical definition that membrane rafts are insoluble membranes when subjected to a Triton X-100 treatment, we isolated detergent-insoluble membranes from chicken sperm and quantified the G_M1 content, which showed an enrichment of G_M1 in the membrane fraction relative to the detergent-soluble fraction. Together with the results of localization and biochemical experiments, we demonstrate for the first time that membrane rafts exist in chicken sperm. Thus, our results provide a foundation for investigating a novel cellular pathway inherent in avian sperm membranes that might be involved in functions necessary to achieve fertilization.

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The aim of this study was to examine the expression profiles of the cathelicidins (CATHs) in the oviduct and the effects of Toll-like receptor (TLR) ligands of virus-associated molecular patterns on CATHs expression in the vagina of hens. The mRNA expression of cathelicidins (CATH1, -2, -3 and -B1) in the oviductal mucosa was analyzed by RT-PCR. The effects of viral moleculs on the CATHs expression in the vagina was examined by incubating the mucosal tissue with virus molecular patterns, including poly I:C (dsRNA virus, TLR3 ligand), R848 (ssRNA virus, TLR7 ligand) and CpG-ODN (DNA virus, TLR21 ligand), followed by real-time PCR analysis. The expression of CATH1, CATH2 and CATH3 was identified in all oviductal segments, except for CATH2 which was lacked in the magnum. The expression of CATHB1 was not identified at any segments of the oviduct. Poly I:C down-regulated the expression of CATH1, -2 and -3, whereas R848 up-regulated the expression of CATH1 and CATH3 but down-regulated the expression of CATH2. CpG-ODN did not affect the CATHs expression. These results suggest that mucosal tissues of the oviduct express CATHs to provide the defense mechanism against microbes, and the expression of CATH1 and CATH3 is up-regulated against ssRNA viruses, whereas, dsRNA virus may suppress the expression of CATH1, -2 and -3.

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