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PubMed1991

Multiple steroidogenic cell populations in the thecal layer of preovulatory follicles of the chicken ovary.

The thecal layer of the preovulatory follicle of the chicken ovary produces primarily androgens and estrogens. However, the precise cellular sites of androgen and estrogen synthesis in the thecal layer have not been identified. Therefore, our aims were 1) to identify steroidogenic cells in the thecal layer of the preovulatory follicles by localizing specific steroidogenic enzymes in these cells by immunocytochemistry, and 2) to confirm that these cells which contained the specific steroidogenic enzymes secreted the expected steroid in a short term cell incubation. Follicles were collected 2 h after oviposition and prepared for immunocytochemistry and short term cell incubation. Immunocytochemistry for cholesterol side-chain cleavage cytochrome P450 (P450SCC), 17 alpha-hydroxylase cytochrome P450 (P450C17), and aromatase cytochrome P450 (P450AROM) was performed to localize pregnenolone-, androgen-, and estrogen-producing cells, respectively, on frozen sections and paraffin sections of the five largest preovulatory follicles. Interstitial cells showed immunoreactivity for both P450SCC and P450C17, whereas a specific cell population of the theca externa, hereafter termed aromatase cells, showed immunoreactivity for P450AROM. Furthermore, fibroblasts in the theca externa indicated immunoreactivity for P450C17. The immunoreactivity of P450C17 and P450AROM enzymes in specific cells in the theca externa appeared to decrease with follicular maturation. The third largest, fourth largest, and fifth largest follicles were selected for short term cell incubations because the immunoreactivity for P450 enzymes in the thecal layer of these follicles was high. Isolated theca interna cells, theca externa cells, and a combination of interna and externa cells were incubated with/without ovine LH (oLH) for 3 h. The medium was assayed for progesterone, testosterone, and 17 beta-estradiol by RIAs. Incubation of theca interna cells with oLH increased progesterone and testosterone production in a dose-dependent manner. However, we did not observe any production of progesterone and testosterone by theca externa cells. Theca externa cells produced 17 beta-estradiol, and its production was increased significantly when theca interna and externa cells were coincubated in the present of oLH. Based on these data, we propose a multiple cell theory for steroidogenesis in the thecal layer of preovulatory follicles of the chicken ovary which states that interstitial cells in the theca interna produce progestins and androgens, fibroblasts in the theca externa may function as an additional site for the conversion of progestins to androgens, and aromatase cells in the theca externa require androgens as substrate to produce estrogens.

Animals↗
PubMed1996

The influence of Lactobacillus acidophilus and bacitracin on layer performance of chickens and cholesterol content of plasma and egg yolk.

1. The influence of Lactobacillus acidophilus alone or in combination with zinc bacitracin on the performance of laying hens was monitored over a period of 4 months. 2. Lactobacillus acidophilus improved egg production, food conversion and reduced the cholesterol concentration in the eggs, but zinc bacitracin had no effect when administered alone. 3. In combination, bacitracin had an adverse effect on the otherwise beneficial activity of the culture.

Animal Feed↗
PubMed2006

Polymorphisms in vitamin D receptor, osteopontin, insulin-like growth factor 1 and insulin, and their associations with bone, egg and growth traits in a layer--broiler cross in chickens.

Bone strength traits in chickens are gaining importance due to economic losses and welfare concerns associated with bone fractures and other abnormalities. A chicken F2 resource population was generated from layer and broiler genetic lines, and traits relating to bone strength, egg production, egg quality and growth rate were measured in approximately 500 F2 hens. Four biological candidate genes (vitamin D receptor, VDR; insulin, INS; insulin-like growth factor 1, IGF1; and osteopontin, SPP1) were selected for investigation. Single nucleotide polymorphisms (SNPs) were identified for each candidate gene by comparing sequences between grandparent lines. Polymerase chain reaction restriction-fragment length polymorphism or SNaPshot assays were developed to genotype the F2 population and to evaluate associations between each SNP genotype and multiple phenotypes. Significant associations (P < 0.0125) were found between VDR and bone mineral content of the humerus at 35 weeks of age; between IGF1 and SPP1 and 5-week body weight; and between INS and 55-week body weight.

Animals↗
PubMed2002

Immunological differences between layer- and broiler-type chickens.

In commercial poultry husbandry, alternatives for the use of antibiotics and vaccines are under investigation, which preferably have to be applicable for both layer- and broiler-type chickens. There are indications that the defense mechanisms vary between layer- and broiler-type chickens. Therefore, the difference in immune response between layer- and broiler-type chickens of the same age was investigated, using TNP-KLH (trinitrophenyl-conjugated keyhole limpet hemocyanin) as antigen without adjuvant. First different routes of immunization (intravenously, intramuscular, subcutaneous and ocular) were examined to find out which immunization route gives the highest antibody titers. The intravenous immunization route resulted in higher TNP-specific antibody responses than the other immunization routes tested and therefore this immunization route was used in both following experiments. In order to investigate the optimal dose of antigen needed for immunization, a dose-response curve in broiler- and layer-type chickens was completed. The humoral immune response was measured in serum by a TNP-specific ELISA and the in vitro cellular immune response by an antigen-specific lymphocyte proliferation assay. The antibody response of layer- and broiler-type chickens appeared to differ, not only in optimal dose and response, but also in kinetics of the response itself. Broiler chickens generated higher IgM anti-TNP titers whereas layer-type chickens generated higher IgG anti-TNP titers. This specific antibody response in broiler-type chickens did not last as long as in layer-type chickens. The TNP-specific cellular immune response was detectable in layer-type chickens, but not in broilers. Both types generate a non-specific cellular immune response, although this response in broilers is lower than in layer-type chickens. From these results, we conclude that broilers primarily respond to TNP-KLH with a high IgM antibody response whereas layer-type chickens respond with a high IgG response. In addition, the cellular response of layer-type chickens is much higher than the response of broilers. The results suggest that broilers are specialized in the production of a strong short-term humoral response and layer-type chickens in a long-term humoral response in combination with a strong cellular response, which is in conformity with their life expectancy.

Animals↗
PubMed1985

Field trials to test the efficacy of polyvalent Marek's disease vaccines in layer and broiler breeder chickens.

As a follow-up to earlier trials to evaluate the efficacy of polyvalent Marek's disease (MD) vaccines in broilers, four trials were conducted with layer or broiler breeder flocks. Chickens caccinated with trivalent (Md11/75C plus SB-1 plus HVT) and bivalent (SB-1 plus HVT) vaccines were compared with those vaccinated with turkey herpesvirus (HVT) alone. Data from three of the four trials indicated polyvalent vaccines were more efficacious than HVT. However, critical interpretations were confounded by low MD lesion frequencies, unequal exposure in different houses on a farm, and difficulty in the differential diagnosis of mortality due to neoplasms. The data confirmed our earlier observation that trivalent and bivalent vaccines were equally effective. Broiler progeny of breeders vaccinated or contact-infected with Serotype 2 MD virus were well protected by either bivalent or HVT vaccines against challenge with very virulent MD virus strains in the laboratory. A high incidence of lymphoid leukosis was observed in two trials and may have been due to post-hatch exposure to an unidentified environmental source of avian leukosis virus.

Animals↗
PubMed2004

Peripheral leptin effect on food intake in young chickens is influenced by age and strain.

The acute effect of leptin on the regulation of food intake was investigated in layer and broiler chickens. In an initial study, we observed that a single intraperitoneal injection of recombinant chicken leptin (1 mg/kg BW) dramatically reduced (38%) food intake in 56-day-old layer chickens, more moderately reduced (15%) food intake in 9-day-old layer chicks, and had no significant effect in 9-day-old broiler chicks. In a subsequent study, body weight and plasma concentrations of leptin were measured weekly in layer and broiler chicks from day 1 to 35 of age and brain leptin receptor and neuropeptide Y (NPY) mRNA expression were analyzed at 1, 9, and 35 days of age. At day 1 of age, peripheral concentrations of leptin were significantly greater in layer than broiler chicks. Subsequently, despite increases in body weight and differences in growth rates between layer and broiler chicks from day 8 to day 35 of age, peripheral concentrations of leptin were constant and similar in both genotypes. Leptin receptor and NPY mRNA were expressed in brain from day 1 in chicks of both genotypes and increased significantly to day 35 of age. These observations provide evidence that the inhibitory effect of leptin on the regulation of food intake in growing chicks is an age dependent process. Furthermore, acquisition of the anorectic effect of leptin is likely to be associated with greater expression of the leptin receptor and NPY mRNAs than to changes in blood levels of leptin. Finally, this study provides evidence that chickens selected for high growth rates may be less sensitive or responsive to peripheral concentrations of leptin than chickens with low growth rates (layers), suggesting that the faster growth of broiler chicks may be related to a lessened responsiveness to anorexigenic factors.

Age Factors↗
PubMed2003

Genetic diversity of avian infectious bronchitis virus California variants isolated between 1988 and 2001 based on the S1 subunit of the spike glycoprotein.

Twenty-nine isolates of avian infectious bronchitis virus (IBV) recovered from commercial chicken flocks in California between 1988 and 2001 and identified as California variants by serotype and direct automated cycle sequencing of the IBV spike glycoprotein S1 subunit, were further characterized phylogenetically and by nucleotide sequence comparison. California variants were grouped according to production type of chicken, by comparison with public access sequence databases (NCBI GenBank and EMBL), or based on phylogenetic analysis. Fisher's Exact test was used to compare mutations per year, purifying and positive selection, predictive antigenicity, and a > or = 6 bp deletion between California variant groups.A high number of mutations at the nucleotide level ( p = 0.013) and a > or = 6 bp deletion in the nucleotide sequence ( p = 0.006) was significantly associated with broiler-type chickens. However, 88% of significant comparisons at the amino acid level such as purifying and positive selection were seen in layer-type chickens. A pronounced predictive antigenicity in the HVR2 region was also associated with layer-type chickens ( p = 0.001). The study indicates that IBV in California is in a phase of slow evolution with different evolutionary patterns being associated with the production type of chicken.

Amino Acid Sequence↗
PubMed2004

Immunomodulation by probiotic lactobacilli in layer- and meat-type chickens.

1. The aim of the experiments was to evaluate whether selected probiotic lactobacillus strains have different immunomodulating effects in layer- and meat-type strain chickens. 2. Humoral and cellular specific and non-specific immune responses were studied by experiments on cellular proliferation, entry and survival of Salmonella bacteria in gut and spleen leukocytes, immunoglobulin isotypes and specific immunoglobulin titres. 3. The effects of two different feeding regimes (short and continuous feeding) and doses for administration of lactobacilli were studied. 4. The lactobacillus strains that were evaluated showed modulating effects on the immune system of layer- and meat-type chickens. 5. In meat-type strain chickens the lactobacilli had a stimulating effect when the chickens were young (up to 3 weeks) and the dose was relatively high, whereas in layer-type chickens a lower effective dose and discontinuous administration was also effective. 6. Immunoprobiotic lactobacilli can have a positive effect on humoral and cellular immune responses in layer- and meat-type strain chickens, but the lactobacillus strain to be used, the age of the animals and effective dose of lactobacilli to be administered need to be optimised.

Animals↗
PubMed2002

Comparative pathogenesis of experimental infections with Salmonella gallinarum in local and commercial chickens.

The pathogenicity of a virulent strain of Salmonella gallinarum was studied in local chickens and commercial layers. Sixty 4-month-old chickens were used. Of these, 50 chickens were orally infected with S. gallinarum, comprising 25 commercial layers and 25 local chickens. Five chickens in each group were used as uninfected negative controls. The clinical signs and pathological features of acute, subacute and chronic fowl typhoid were observed in both groups. Chickens in both groups seroconverted, but the antibody titre was significantly higher (p < 0.001) in the commercial layers. The antibody titre remained high to the end of the experiment in all the surviving chickens. Only one commercial layer chicken died during the course of the experiment. The PCV decreased significantly (p < 0.001) in the infected chickens of both groups as compared to the controls. The viable cell count of S. gallinarum in the liver and spleen reached a maximum on day 9 after infection in both groups. However, there was a significantly higher cell count (p < 0.05) in the commercial layers. The severity of the disease appeared to be slightly greater in the commercial layers, although the susceptibility was similar in both groups. It was concluded that, under experimental conditions, local chickens are just as susceptible to S. gallinarum infection as are commercial layers.

Animals↗
PubMed1997

Quantitative aspects of sperm:egg interaction in chickens and turkeys.

Spermatozoa embedded in the outer perivitelline layer and points of hydrolysis (holes) produced by spermatozoa in the inner perivitelline layer of chicken and turkey eggs were found to be evenly distributed and linearly correlated (r = 0.80 for both species) throughout the layers from most regions of the egg, except from those directly over the germinal disc, in which there were more holes. In turkey eggs there appeared to be relatively fewer perivitelline spermatozoa, since many had degenerated beyond recognition. In eggs from both species, there were approximately 25 times more holes mm-2 in the inner perivitelline layer from over the germinal disc region than that from other regions of the egg. The relationship between these two frequencies could also be described as linear (r = 0.81 for chicken and 0.78 for turkey eggs), although there was some evidence for a saturation effect for holes over the germinal disc. The fertile status of eggs was shown to be a function of all of the above parameters. Eggs from both species had a 50% probability of being fertile when around 3 spermatozoa penetrated the inner perivitelline layer over the germinal disc and showed maximum fertility when more than 6 spermatozoa penetrated this region. Spermatozoa in the outer perivitelline layer and holes in the inner perivitelline layer from regions other than over the germinal disc could also be used to predict fertility, although with less certainty. Since the number of spermatozoa interacting with the egg reflects the numbers of those stored in the uterovaginal sperm storage tubules, the relationships derived in this work should be useful for understanding how fertility in chickens and turkeys is a function of oviducal sperm storage and transport.

Animals↗
PubMed2001

Autoradiographic evidence for the sliding of the upper layer over the basement membrane in chicken blastoderms during gastrulation.

An upper layer (epiblast) fragment taken laterally from the Anlage fields of neural plate or chordamesoderm of a quail blastoderm, labelled with 3H-glucosamine, was grafted isotopically (in a similar region), isochronically (at the similar stage of development) and isotropically (with the same caudocranial and dorsoventral polarity) in the epiblast of a mesoblast free area of a chicken blastoderm (St 4-5 Vakaet, 1970: full grown primitive streak). On the autoradiographs of the sections through such cultured blastoderms with fully integrated quail grafts, we observed a labelling of the basement membrane laterally and slightly cranially from the labelled graft in its final position. Since only the epiblast and its basement membrane are involved, the pattern of the observed labelling indicates that the grafted and integrated quail epiblast fragment glides in toto over the mediocaudally localized basement membrane, leaving behind a track of radioactivity. Sliding of whole groups of epiblast cells over the basement membrane seems thus to be a normal phenomenon during avian gastrulation.

Animals↗
PubMed2003

Anatomy and physiology of horizontal cells in layer 5b of the chicken optic tectum.

In the visual midbrain of birds, a variety of cell types has recently been characterized with both anatomical and physiological techniques to gain insight into the mechanisms of visual information processing. Here we present data from a horizontal cell type located in the retinorecipient layer 5b of the chick optic tectum. Intracellular labeling revealed that these neurons are multipolar, have no axonal structures and arborize completely within the layer 5b where they extend over considerable distances. Immunohistochemistry with an antibody against calbindin labeled a population of horizontal cells in layer 5b; however, double labeling showed that these neurons represent a subpopulation of approximately one third of the neurons in that layer. Whole-cell patch recordings with additional cell filling from horizontal cells revealed that the physiological responses to depolarization changes with maturation, from a comparatively slow oscillatory pattern reminiscent of hair cell physiology at embryonal stages to a damped series of small action potentials at posthatching. In response to electrical stimulation in the vicinity of the neurons, cells responded with either excitatory postsynaptic potentials or small action potentials. Horizontal cell types are found in the visual midbrain of both avian and mammalian species. On the basis of the data presented here and data from the literature, the functional role of these cells is discussed. As in layer 5b of the chick optic tectum specific synaptic glomeruli have been found, the horizontal cells might constitute local inhibitory circuits within the retino-tectal synapses and, in addition, contribute to mechanisms of directional selectivity in these projections.

Animals↗
PubMed1991

Why are young broiler chickens fatter than layer-strain chicks?

1. The abdominal fat pads of 5 week-old broiler and layer chicks incorporated 6.0 and 3.9% of intravenously-injected 14C-labelled very low density lipoproteins respectively. 2. These proportions of total plasma lipoprotein flux were sufficient to account for about 65-70% of the rate of fat deposition in broilers, but were more than 4-fold greater than that the rate of fat deposition in layers. 3. [14C]Palmitate taken up into adipose tissue of layer chicks had a t1/2 of 2-3 days. 4. There was no significant turnover of adipose tissue triglycerides in broilers and this appears to be a major reason for their relative fatness.

Adipose Tissue↗
PubMed1985

Transfer of extracellular matrix components between germ layers in chimaeric chicken-quail blastoderms.

A chemical basis for the transmission of signals during gastrulation has been investigated by using chimaeric embryos resulting from the combination of 3H-glucosamine-labelled and unlabelled hypoblast with epiblast taken from chicken and quail embryos at stage 3 of Vakaet (1970). The ability to distinguish chicken from quail cells on the basis of their different nuclear distribution of heterochromatin after Feulgen staining made it possible to determine the origin of the cells in the chimaerae. Tritiated quail hypoblast (after incubation of the embryo in the presence of 3H-glucosamine) was transplanted onto unlabelled chicken blastoderm deprived of its hypoblast. After culture of the chimaera for 5 h, the autoradiographic pattern shows silver grains not only over the graft, but also at the ventral surface of the epiblast of the host. Transfer of label may occur to mesoblast cells, but not between chicken and quail hypoblast cells. Chase experiments exclude the possibility that unprocessed, tritiated glucosamine is transferred. Chemical fixation of the host before transplantation of a labelled quail hypoblast also allows visualization of a transfer of macromolecules from hypoblast to the basement membrane of the epiblast, suggesting that an intervention of the epiblast cells in this process is not necessary. The morphology of the chimaeric embryos, as studied by scanning electron microscopy, suggests a direct deposition of these macromolecules by filopodia of the dorsal surface of the hypoblast. The possibility of diffusion of free macromolecules has been considered and can reasonably be discarded on the basis of several observations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Carbohydrate involvement in sperm-egg interaction in the chicken.

The solubilized perivitelline layer (PL) of the chicken ovum contains one or more components which behave in a manner analogous to sperm-receptors. Electrophoretic analyses of solubilized PL confirmed the existence of three major glycoproteins having apparent molecular weights of 33,000, 53,500 and greater than 200,000. The role of carbohydrate in sperm receptor activity was evaluated by extensive deglycosylation of the solubilized PL with trifluoromethanesulfonic acid (TFMS). Sperm receptor activity as measured by an in vitro competition assay was extremely sensitive to TFMS. Pretreatment of spermatozoa with solubilized PL exposed only to TFMS buffers inhibited sperm attachment and digestion of intact PL by 81% (9.67 +/- 1.76 sperm/mm2) as compared with the controls (i.e., no pretreatment of spermatozoa with solubilized PL; 51.33 +/- 6.24 sperm/mm2), a value similar to that observed with spermatozoa exposed to untreated solubilized PL (0.17 +/- 0.17 sperm/mm2). In comparison, PL treated with TFMS inhibited sperm attachment and digestion of intact PL by less than 26% (38.33 +/- 5.88 sperm/mm2) as compared with the control. These data indicate that removal of both N- and O-linked oligosaccharides from components of the chicken PL results in elimination of its sperm receptor activity.

Animals↗
PubMed2006

Identification of single-nucleotide polymorphisms in 5' end and exons of the PRKAG3 gene in Hubbard White broiler, Leghorn layer, and three Chinese indigenous chicken breeds.

5'-AMP-activated protein kinase plays an important role in regulating the level of ATP in the presence of metabolic stress. Previous studies revealed that polymorphisms in 5'-AMP-activated protein kinase gamma 3 subunit (PRKAG3) gene are associated with meat quality in pigs. In the present study, single-nucleotide polymorphisms (SNPs) in the 5'-end and exons of chicken PRKAG3 gene were identified with the method of single-strand conformation polymorphism in Hubbard ISA White broiler, Leghorn layer, and three Chinese indigenous chicken breeds, Tibet Chicken, Shouguang Chicken and Beijing Yellow Chicken. Two SNPs in the 5'-end of the gene and 10 SNPs in exons 3, 4, 9 and 11, of which three caused amino acid substitutions, were identified in the PRKAG3 gene of the five chicken breeds. The results will facilitate further study on the association between the mutations of PRKAG3 and chicken meat quality.

5' Flanking Region↗
PubMed2000

Abdominal fat pad mass reduction by in ovo administration of anti-adipocyte monoclonal antibodies in chickens.

The effect of in ovo administration of antiadipocyte monoclonal antibodies (MAb) on growth and adipose tissue development in chickens was investigated. In Trial 1, 60 fertilized eggs from layer-type chickens were injected into allantoic circulation with different amounts of MAb against chicken adipocyte plasma membranes (0, 0.05, 0.1, 0.2, and 0.4 mg) on Day 15 of embryogenesis. In Trial 2, 180 fertilized broiler eggs were injected into allantoic circulation with 0.2 mg MAb on Day 15 of embryogenesis. In Trial 1, high doses (0.2 and 0.4 mg) of MAb in in ovo injection reduced (P < or = 0.05) abdominal fat pad weight without affecting total body weight at 42 d of age. Only the highest dose (0.4 mg) significantly reduced hatch rate. In Trial 2, adipose tissue (pectoral, femoral, and abdominal), major organ (heart, liver, and spleen), and total body weights at 14 d of age were not affected by in ovo injection. Hatch success rate of eggs was not significantly different among treatments. However, by 6 wk of age, in ovo injection of MAb significantly reduced (P < or = 0.05) abdominal fat pad weight by more than 28%. This relative fat pad mass reduction occurred without affecting femoral or pectoral fat tissues. Total body weight and feed intake were not affected among treatments. Our experiments demonstrated for the first time that in ovo administration of anti-adipocyte MAb on Day 15 of embryogenesis reduced the chicken abdominal fat pad mass by 42 d of age without affecting growth or body weight.

Abdomen↗