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Sacranie A.,University of New England of Australia | Sacranie A.,Poultry Cooperative Research Center | Svihus B.,Norwegian University of Life Sciences | Denstadli V.,Norwegian University of Life Sciences | And 4 more authors.
Poultry Science | Year: 2012

Two experiments were conducted to test the following hypothesis: exposing broiler chickens to coarse insoluble fiber in the diet will result in enhanced gizzard function and performance, improved adaptability to an intermittent feeding program, and an increase in the occurrence of reverse peristalsis. In experiment 1, 102 Ross 308 broiler chickens were either intermittently or ad libitum fed a basal diet, the basal diet diluted with 15% coarse hulls (consisting of equal weights of hulls from oats and barley), or the basal diet diluted with 15% of the same hulls finely ground in a 2 × 3 factorial arrangement with 17 individually caged birds per treatment. Birds fed ad libitum had access to feed continuously for 18 h/d, whereas those on intermittent feeding had restricted access to feed from 7 d of age. From 18 d of age, the restrictive-feeding program consisted of four 1-h meals and one 2-h meal per day. In experiment 2, 156 broiler chickens in 12 pen cages with wood shaving-lined floors were exposed to 1 of 4 treatment groups with 3 pens/treatment: intermittent or ad libitum feeding of a basal diet and intermittent or ad libitum feeding of a coarse hull diet, as described above. At 31 and 32 d of age, birds in experiment 1 were inoculated with chromium EDTA via the cloaca. There was no interaction between diet and feeding regimen. The addition of hulls increased gizzard weight and content and lowered (P < 0.001) gizzard pH, but it had no effect on the ability of the birds to handle intermittent feeding. Despite the dilution with coarse hulls, weight gain and the gain:feed ratio were not affected, which could partly be explained by an increased (P < 0.001) starch digestibility. Dietary reflux was confirmed by the presence of chromium in all intestinal tract sections. Broilers exhibited reverse peristaltic contractions of sufficient magnitude to propel the marker from the cloaca to the gizzard. © 2012 Poultry Science Association Inc.


Wu D.,University of New England of Australia | Wu S.B.,University of New England of Australia | Choct M.,Poultry Cooperative Research Center | Swick R.A.,University of New England of Australia
Poultry Science | Year: 2015

The net energy (NE) value may be a better measure than apparent metabolizable energy (ME) of the effect of supplemental phytase on energy utilization in broilers. The present study was conducted to assess the impact of 3 microbial phytases supplemented at an unconventionally high level (1,000 FTU/kg feed) on performance and NE of broilers using the indirect calorimetric method (IC). Four treatments included: 1) Control, formulated to be deficient in ME (12.35 MJ/kg in the starter diet; 12.56 MJ/kg in the grower diet), calcium (0.72% in the starter diet; 0.60% in the grower diet), and available phosphorus (0.25% in the starter diet; 0.20% in the grower diet); 2) control + intrinsically thermostable phytase A; 3) control + intrinsically thermostable phytase B; and 4) control + coated phytase C. A completely randomized design was employed. A total of 384 male broiler chicks were used, and each treatment had 6 replicates with 16 birds per replicate. The birds were reared until d 21 in floor pens with hardwood shavings. Thirty-two birds (8 birds per treatment) were randomly selected to determine heat production and NE (from 25-28 d) following a 3-d acclimatization in the respiratory chambers. Performance results at d 21 showed that supplementation with either of the 3 phytases improved body weight (P < 0.001) and feed intake (P < 0.05), and increased the relative weights of tibia ash (P < 0.05) and toe ash (P < 0.01). Phytases A and B increased the NE value of the diet (P < 0.05). It may be concluded that the negative effects imposed by calcium and available phosphorus down-specification can be compensated by phytase supplementation in general, and intrinsically thermostable phytases improve the ME and NE value. However, phytase did not reduce heat production, heat increment, or increase NE:ME in birds. © 2015 Poultry Science Association Inc.


PubMed | University of New England of Australia and Poultry Cooperative Research Center
Type: Comparative Study | Journal: Poultry science | Year: 2015

The net energy (NE) value may be a better measure than apparent metabolizable energy (ME) of the effect of supplemental phytase on energy utilization in broilers. The present study was conducted to assess the impact of 3 microbial phytases supplemented at an unconventionally high level (1,000 FTU/kg feed) on performance and NE of broilers using the indirect calorimetric method (IC). Four treatments included:1) Control, formulated to be deficient in ME (12.35 MJ/kg in the starter diet; 12.56 MJ/kg in the grower diet), calcium (0.72% in the starter diet; 0.60% in the grower diet), and available phosphorus (0.25% in the starter diet; 0.20% in the grower diet); 2) control + intrinsically thermostable phytase A; 3) control + intrinsically thermostable phytase B; and 4) control + coated phytase C. A completely randomized design was employed. A total of 384 male broiler chicks were used, and each treatment had 6 replicates with 16 birds per replicate. The birds were reared until d 21 in floor pens with hardwood shavings. Thirty-two birds (8 birds per treatment) were randomly selected to determine heat production and NE (from 25-28 d) following a 3-d acclimatization in the respiratory chambers. Performance results at d 21 showed that supplementation with either of the 3 phytases improved body weight (P < 0.001) and feed intake (P < 0.05), and increased the relative weights of tibia ash (P < 0.05) and toe ash (P < 0.01). Phytases A and B increased the NE value of the diet (P < 0.05). It may be concluded that the negative effects imposed by calcium and available phosphorus down-specification can be compensated by phytase supplementation in general, and intrinsically thermostable phytases improve the ME and NE value. However, phytase did not reduce heat production, heat increment, or increase NE:ME in birds.


Keyburn A.L.,CSIRO | Keyburn A.L.,Monash University | Keyburn A.L.,Poultry Cooperative Research Center | Portela R.W.,CSIRO | And 11 more authors.
Veterinary Research | Year: 2013

NetB toxin from Clostridium perfringens is a major virulence factor in necrotic enteritis in poultry. In this study the efficacy of NetB as a vaccine antigen to protect chickens from necrotic enteritis was examined. Broiler chickens were immunized subcutaneously with purified recombinant NetB (rNetB), formalin treated bacterin and cell free toxoid with or without rNetB supplementation. Intestinal lesion scores and NetB antibody levels were measured to determine protection after mild oral gavage, moderate in-feed and heavy in-feed challenges with virulent C. perfringens isolates. Birds immunized with rNetB were significantly protected against necrotic enteritis when challenged with a mild oral dose of virulent bacteria, but were not protected when a more robust challenge was used. Bacterin and cell free toxoid without rNetB supplementation did not protect birds from moderate and severe in-feed challenge. Only birds immunized with bacterin and cell free toxoid supplemented with rNetB showed significant protection against moderate and severe in-feed challenge, with the later giving the greatest protection. Higher NetB antibody titres were observed in birds immunized with rNetB compared to those vaccinated with bacterin or toxoid, suggesting that the in vitro levels of NetB produced by virulent C. perfringens isolates are too low to induce the development of a strong immune response. These results suggest that vaccination with NetB alone may not be sufficient to protect birds from necrotic enteritis in the field, but that in combination with other cellular or cell-free antigens it can significantly protect chickens from disease. © 2013 Keyburn et al.; licensee BioMed Central Ltd.


Lambeth L.S.,Murdoch Childrens Research Institute | Lambeth L.S.,Poultry Cooperative Research Center | Raymond C.S.,University of Minnesota | Raymond C.S.,Merck And Co. | And 7 more authors.
Developmental Biology | Year: 2014

DMRT1 encodes a conserved transcription factor with an essential role in gonadal function. In the chicken, DMRT1 in located on the Z sex chromosome and is currently the best candidate master regulator of avian gonadal sex differentiation. We previously showed that knockdown of DMRT1 expression during the period of sexual differentiation induces feminisation of male embryonic chicken gonads. This gene is therefore necessary for proper testis development in the chicken. However, whether it is sufficient to induce testicular differentiation has remained unresolved. We show here that over-expression of DMRT1 induces male pathway genes and antagonises the female pathway in embryonic chicken gonads. Ectopic DMRT1 expression in female gonads induces localised SOX9 and AMH expression. It also induces expression of the recently identified Z-linked male factor, Hemogen (HEMGN). Masculinised gonads show evidence of cord-like structures and retarded female-type cortical development. Furthermore, expression of the critical feminising enzyme, aromatase, is reduced in the presence of over-expressed DMRT1. These data indicate that DMRT1 is an essential sex-linked regulator of gonadal differentiation in avians, and that it likely acts via a dosage mechanism established through the lack of global Z dosage compensation in birds. © 2014 Elsevier Inc.


Cutting A.D.,CSIRO | Cutting A.D.,Murdoch Childrens Research Institute | Cutting A.D.,Poultry Cooperative Research Center | Cutting A.D.,University of Melbourne | And 10 more authors.
Chromosome Research | Year: 2012

Differential gene expression regulates tissue morphogenesis. The embryonic gonad is a good example, where the developmental decision to become an ovary or testis is governed by female- or male-specific gene expression. A number of genes have now been identified that control gonadal sex differentiation. However, the potential role of microRNAs (miRNAs) in ovarian and testicular pathways is unknown. In this review, we summarise our current understanding of gonadal differentiation and the possible involvement of miRNAs, using the chicken embryo as a model system. Chickens and other birds have a ZZ/ZW sex chromosome system, in which the female, ZW, is the heterogametic sex, and the male, ZZ, is homogametic (opposite to mammals). The Z-linked DMRT1 gene is thought to direct testis differentiation during embryonic life via a dosage-based mechanism. The conserved SOX9 gene is also likely to play a key role in testis formation. No master ovary determinant has yet been defined, but the autosomal FOXL2 and Aromatase genes are considered central. No miRNAs have been definitively shown to play a role in embryonic gonadal development in chickens or any other vertebrate species. Using next generation sequencing, we carried out an expression-based screen for miRNAs expressed in embryonic chicken gonads at the time of sexual differentiation. A number of miRNAs were identified, including several that showed sexually dimorphic expression. We validated a subset of miRNAs by qRT-PCR, and prediction algorithms were used to identify potential targets. We discuss the possible roles for these miRNAs in gonadal development and how these roles might be tested in the avian model. © 2011 Springer Science+Business Media B.V.


Guo P.,CSIRO | Guo P.,Poultry Cooperative Research Center | Guo P.,Guangdong Academy of Agricultural Sciences | Thomas J.D.,CSIRO | And 8 more authors.
Developmental and Comparative Immunology | Year: 2013

The outcomes of viral infections are costly in terms of human and animal health and welfare worldwide. The observed increase in the virulence of some viruses and failure of many vaccines to stop these infections has lead to the apparent need to develop new anti-viral strategies. One approach to dealing with viral infection may be to employ the therapeutic administration of recombinant cytokines to act as 'immune boosters' to assist in augmenting the host response to virus. With this in mind, a greater understanding of the immune response, particularly cell mediated T-helper-1 (TH1) type responses, is imperative to the development of new anti-viral and vaccination strategies. Following the release of the chicken genome, a number of TH1-type cytokines have been identified, including chicken interleukin-12 (ChIL-12), ChIL-18 and interferon-γ ChIFN-γ), highlighting the nature of the TH1-type response in this non-mammalian vertebrate. To date a detailed analysis of the in vivo biological function of these cytokines has been somewhat hampered by access to large scale production techniques. This review describes the role of TH-1 cytokines in immune responses to viruses and explores their potential use in enhancing anti-viral treatment strategies in chickens. Furthermore, this review focuses on the example of ChIFN-γ treatment of Chicken Anemia Virus (CAV) infection. CAV causes amongst other things thymocyte depletion and thymus atrophy, as well as immunosuppression in chickens. However, due to vaccination, clinical disease appears less often, nevertheless, the subclinical form of the disease is often associated with secondary complicating infections due to an immunocompromised state. Since CAV-induced immunosuppression can cause a marked decrease in the immune response against other pathogens, understanding this aspect of the disease is critically important, as well as providing insights into developing new control approaches. With increasing emphasis on developing alternative control programs for poultry diseases, novel therapeutic strategies provide one approach. We show here that the in ovo administration of ChIFN-γ impacts the depletion of T-cell precursors during CAV infection. Therefore, it appears that ChIFN-γ may have the potential to be used as a novel therapeutic reagent to impact virus infection and alter immunosuppression caused by CAV and potentially other pathogens. © 2013.


Ayers K.L.,Murdoch Childrens Research Institute | Ayers K.L.,Poultry Cooperative Research Center | Smith C.A.,Murdoch Childrens Research Institute | Smith C.A.,Poultry Cooperative Research Center | And 3 more authors.
Genesis | Year: 2013

The chicken (Gallus gallus domesticus) has long been a useful model for developmental biologists. The developing avian embryo is easily accessible and fertile eggs are widely available. In addition, the embryo is also amenable to genetic manipulation allowing studies on many important morphological and cellular processes. More recently, the ability to directly manipulate gene expression through the production of transgenic or mutant chicken embryos by viral delivery methods has been useful to analyse gene function in a wide range of tissues, including the developing gonads. Chickens are amniotes and their development closely resembles that of mammals, implying underlying genetic conservation of key pathways, including sex development. Studies of sex determination and gonadal development in this model are providing insight into avian ovarian and testis developmental pathways and their evolution. Indeed, the chicken embryo is a suitable model for the functional analysis of genes implicated in human disorders of sex development, and studies in this model will complement those carried out in mammalian models such as the mouse. In this review we discuss the current knowledge of sex determination and sexual differentiation in avians, using chicken as model. We review how sex chromosomes contribute to this process and provide current information on our understanding of gonadal sexual differentiation at both the cellular and molecular level in the chicken embryo. Finally, we review the methods currently used to investigate the role of genes and signaling pathways during sexual differentiation, and discuss how these methods may contribute to further understanding of vertebrate gonadogenesis. © 2013 Wiley Periodicals, Inc.


Ayers K.L.,Murdoch Childrens Research Institute | Ayers K.L.,University of Melbourne | Sinclair A.H.,Murdoch Childrens Research Institute | Sinclair A.H.,University of Melbourne | And 4 more authors.
Sexual Development | Year: 2013

In birds as in mammals, sex is determined at fertilization by the inheritance of sex chromosomes. However, sexual differentiation - development of a male or female phenotype - occurs during embryonic development. Sex differentiation requires the induction of sex-specific developmental pathways in the gonads, resulting in the formation of ovaries or testes. Birds utilize a different sex chromosome system to that of mammals, where females are the heterogametic sex (carrying Z and W chromosomes), while males are homogametic (carrying 2 Z chromosomes). Therefore, while some genes essential for testis and ovarian development are conserved, important differences also exist. Namely, the key mammalian male-determining factor SRY does not exist in birds, and another transcription factor, DMRT1, plays a central role in testis development. In contrast to our understanding of testis development, ovarian differentiation is less well-characterized. Given the presence of a female-specific chromosome, studies in chicken will provide insight into the induction and function of female-specific gonadal pathways. In this review, we discuss sexual differentiation in chicken embryos, with emphasis on ovarian development. We highlight genes that may play a conserved role in this process, and discuss how interaction between ovarian pathways may be regulated. Copyright © 2012 S. Karger AG, Basel.


Lambeth L.S.,Murdoch Childrens Research Institute | Lambeth L.S.,Poultry Cooperative Research Center | Cummins D.M.,Poultry Cooperative Research Center | Cummins D.M.,CSIRO | And 8 more authors.
PLoS ONE | Year: 2013

Estrogens play a key role in sexual differentiation of both the gonads and external traits in birds. The production of estrogen occurs via a well-characterised steroidogenic pathway, which is a multi-step process involving several enzymes, including cytochrome P450 aromatase. In chicken embryos, the aromatase gene (CYP19A1) is expressed female-specifically from the time of gonadal sex differentiation. To further explore the role of aromatase in sex determination, we ectopically delivered this enzyme using the retroviral vector RCASBP in ovo. Aromatase overexpression in male chicken embryos induced gonadal sex-reversal characterised by an enlargement of the left gonad and development of ovarian structures such as a thickened outer cortex and medulla with lacunae. In addition, the expression of key male gonad developmental genes (DMRT1, SOX9 and Anti-Müllerian hormone (AMH)) was suppressed, and the distribution of germ cells in sex-reversed males followed the female pattern. The detection of SCP3 protein in late stage sex-reversed male embryonic gonads indicated that these genetically male germ cells had entered meiosis, a process that normally only occurs in female embryonic germ cells. This work shows for the first time that the addition of aromatase into a developing male embryo is sufficient to direct ovarian development, suggesting that male gonads have the complete capacity to develop as ovaries if provided with aromatase. © 2013 Lambeth et al.

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