PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “layer chicken”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1982

The influence of diflubenzuron on several reproductive characteristics in male and female-layer-breed chickens.

The possibility exists for the accidental contamination of feedstuffs used in poultry and livestock feeds with diflubenzuron (Dimilin, TH 6040; N-[[(4-chlorophenyl)amino]-carbonyl]-2, 6-difluorobenzamide), an insect growth regulator. The effect of this insecticide on reproduction in chickens was tested by feeding diflubenzuron at levels of 1, 2.5, 25, and 250 ppm to male and female layer-breed chickens from 1 day of age through a laying cycle. Characteristics measured were egg production, egg weight, eggshell weight, fertility, hatchability, and effects on the progeny. Feeding diflubenzuron at levels up to 250 ppm did not affect the characteristics measured. These results will be useful in evaluating the use of diflubenzuron in the field.

Animals↗
PubMed1999

Comparison of direct and enrichment methods for the selective isolation of vancomycin-resistant enterococci from feces of pigs and poultry.

Isolation results of vancomycin-resistant enterococci (VRE) of fecal samples from pigs and broiler and layer chickens obtained with two vancomycin-supplemented enrichment media, kanamycin aesculin azide (KAA) broth and Enterococcosel (ECC) broth, and three isolation media, KAA agar, ECC agar, and Slanetz and Bartley (SL) agar, were compared. Direct isolation on vancomycin-containing agar plates was not efficient in swine and layer chickens, which had only low numbers of VRE. In broilers chickens, the VRE content of the samples was high, and SL as well as ECC were found to perform better than KAA agar. The same three agar media were used as selective plating media after 1 and 2 days incubation of the samples in KAA and ECC enrichment broths. Sensitivities of the 12 different enrichment-plate combinations tested ranged from 0 to 81% in layer chickens and from 5 to 44% in samples from pigs. In the high prevalence type of samples from broilers, sensitivities still varied substantially from 52 to 78%. Incubating vancomycin-containing enrichment broths for 2 days compared with 1 day was favorable for the isolation of vancomycin-resistant Enterococcus faecalis, E. gallinarum, and E. casseliflavus but not for E. faecium and E. hirae/E. durans. ECC broth and ECC plates yielded the highest number of E. gallinarum and E. casseliflavus. In layer as well as in broiler chickens, ECC broth incubated for 2 days and plated on ECC agar was the most sensitive method. In pigs, however, KAA broth incubated for 2 days and plated on ECC medium yielded the highest number of VRE.

Animals↗
PubMed2006

The melanocortin circuit in obese and lean strains of chicks.

Agonists of membranal melanocortin 3 and 4 receptors (MC3/4Rs) are known to take part in the complex control mechanism of energy balance. In this study, we compared the physiological response to an exogenous MC3/4R agonist and the hypothalamic expression of proopic melanocortin (POMC) gene, encoding few MC3/4R ligands, between broiler and layer chicken strains. These strains, representing the two most prominent commercial strains of chickens grown for meat (broilers) and egg production (layers), differ in their food intake, fat accumulation, and reproductive performance and, therefore, form a good model of obese and lean phenotypes, respectively. A single i.v. injection of the synthetic peptide melanotan-II (MT-II; 1 mg/kg body weight) into the wing vein of feed-restricted birds led to attenuation of food intake upon exposure to feeding ad libitum in both broiler and layer chickens. A study of the POMC mRNA encoding the two prominent natural MC3/4R agonists, alpha-MSH and ACTH, also revealed a general similarity between the strains. Under feeding conditions ad libitum, POMC mRNA levels were highly similar in chicks of both strains and this level was significantly reduced upon feed restriction. However, POMC mRNA down-regulation upon feed restriction was more pronounced in layers than in broilers. These results suggest: (i) a role for MC3/4R agonists in the control of appetite; (ii) that the physiological differences between broilers and layers are not related to unresponsiveness of broiler chickens to the satiety signal of MC3/4R ligands. Therefore, these findings suggest that artificial activation of this circuit in broiler chicks could help to accommodate with their agricultural shortcomings of overeating, fattening, and impaired reproduction.

Animals↗
PubMed2001

VanA-type vancomycin-resistant enterococci (VRE) remain prevalent in poultry carcasses 3 years after avoparcin was banned.

Avoparcin was used as a growth promoting feed additive in Norwegian broiler and turkey production from 1986 until it was banned in 1995, when an association between vancomycin-resistant enterococci (VRE) and avoparcin use became apparent. A recent study regarding faecal samples documented a continuing high prevalence of VRE among Norwegian poultry 3 years after avoparcin was banned. In the present study, carcasses of broilers and turkeys from farms where avoparcin had previously been in use and carcasses of layer chickens from farms where avoparcin had never been used were examined for the presence of VRE. One carcass from each of 150 different farms was included. By a direct plating method, VRE were isolated from 30 of 100 samples of broilers and turkeys, but not from any samples of layer chickens. When an enrichment step was included, VRE were isolated from a total of 81 of the 100 samples of broilers and turkeys and from nine of the 50 samples of layer chickens. All VRE isolated were highly resistant to vancomycin (MIC > or = 256 microg/ml) and possessed the vanA gene. These results correspond to the prevalence of VRE recently documented in faecal samples from Norwegian poultry. The present study reveals a high prevalence of VRE in broiler and turkey carcasses. Consequently, consumers are exposed to VRE when handling raw poultry meat, although the public health significance of such exposure is unclear.

Animals↗
PubMedDate not supplied

Interaction of infectious bursal disease and coccidiosis in layer replacement chickens.

During a floor-pen study on anticoccidial programs for layer-replacement pullets, there was a natural outbreak of infectious bursal disease (IBD). The interaction of coccidiosis and IBD was characterized by: excessive deaths from coccidiosis; and apparent failure of some anticoccidial drug treatments. Immunity to coccidiosis was not blocked by the IBD infection, although immunity was less in some treatments than would be expected with the degree of coccidiosis exposure.

Animals↗
PubMed1997

Expression of messenger ribonucleic acids of luteinizing hormone and follicle-stimulating hormone receptors in granulosa and theca layers of chicken preovulatory follicles.

Expression of luteinizing hormone receptor (LHR) and follicle-stimulating hormone receptor (FSHR) mRNAs was demonstrated in the granulosa and theca layers of the large preovulatory follicles of the chicken ovary by Northern hybridization and reverse transcription-polymerase chain reaction (RT-PCR). Northern hybridization results showed multiple LHR and FSHR mRNA transcripts and the predominant species were 2.3 and 2.5 kb, respectively. The highest abundance of LHR mRNA was found in the granulosa layer of the largest follicle (F1 follicle), while the abundance remained low in the granulosa layers of the third (F3) and fifth largest (F5) follicles. FSH mRNA abundance was the highest in the granulosa layer of F5 follicle, but decreased in the granulosa layers of F3 and F1 follicles. In the theca layers of all the three follicles examined LHR and FSHR mRNAs were extremely low. These results were confirmed by RT-PCR experiment which involved coamplification of LHR or FSHR mRNA and beta-actin mRNA as the internal control. The LHR PCR product was sequenced and indicated 92.2% homology with the corresponding region of the quail LHR cDNA. This study indicated that the marked increase in expression of LHR mRNA in granulosa layer of the F1 follicle might be important for LHR protein synthesis and succeeding bonus progesterone production in F1 follicle destined to ovulation. However, higher expression of FSHR mRNA in the granulosa layer of the less mature follicles may be involved in the differentiation and maturation of granulosa cells in these follicles.

Animals↗
PubMed1985

Genetic parameters and cellularity of adiposity in layer-type chickens.

Genetic parameters concerning weight of abdominal fat pads were determined for a randombred layer-type population. Progeny by the upper (U) and lower (L) 10% of the sires with respect to weights of fat pads were compared. Cellularity measures were made of the fat pads from random samples of the two groups of progeny. Progeny of U sires had fat pads numerically heavier than those of progeny by all sires. However, progeny of L sires had fat pad weights similar to those of all sires. Heritability estimates of abdominal fat pad weight, as calculated from half-sib correlation and regression of offspring on sires, were .29 +/- .36 and .27 +/- .06, respectively. Genetic estimates indicated fat pad weight to be highly correlated with growth but essentially uncorrelated with egg production. Progeny of the L and U sires had the same number of adipocytes, but progeny by U sires had larger adipocytes than progeny by L sires.

Abdomen↗
PubMed1995

Expression of P450 17 alpha-hydroxylase and P450aromatase genes in isolated granulosa, theca interna, and theca externa layers of chicken ovarian follicles during follicular growth.

Concentrations of estradiol (E), testosterone (T), and progesterone (P) and levels of the 1.9-kb and 4.0-kb mRNA encoding P450 17 alpha-hydroxylase (P450 17 alpha) and P450aromatase (P450arom), respectively, were measured in the isolated granulosa, theca interna, and theca externa of the largest preovulatory (F1-F4) follicles of the chicken 20 h and 3 h before expected ovulation of F1. In the granulosa layer, E and T concentrations remained low throughout this period of follicular growth, whereas P concentrations were high 3 h before ovulation in F2 and F1 follicles. E levels were highest in the theca interna and externa of the smallest (F4) follicle, decreasing progressively with follicular growth. T content of theca interna and granulosa was greater in less mature F4-F2 follicles than in the most mature (F1) follicle, whereas theca externa contained little T. P was quantifiable in significant amounts only in granulosa tissue, peaking in F2 and F1 follicles at 3 h before ovulation, at which time plasma levels of steroids also rose significantly. P450 17 alpha was expressed mainly in theca interna, whereas the P450arom mRNA levels found in theca externa reflected the pattern of E in this compartment. Expression of these two genes was very low in granulosa tissue, remaining unchanged during follicular growth. These results indicate that E and T synthesis in the chicken ovary is regulated, at least in part, at mRNA levels of P450 17 alpha and P450arom in the theca interna and theca externa layers during follicular growth.

Animals↗
PubMed2005

Supplementation of coated butyric acid in the feed reduces colonization and shedding of Salmonella in poultry.

Short-chain fatty acids have been widely used as feed additives to control Salmonella in poultry. Data on the use of butyric acid in poultry are lacking. In this study, powder form and coated butyric acid were compared in their ability to reduce Salmonella colonization of ceca and internal organs shortly after infection of young chickens with Salmonella enteritidis. In the first trial, 4 groups of 25 specific pathogen free layer chickens were given feed either supplemented with powder form butyric acid, coated butyric acid, a combination of powder form and coated butyric acid (all groups received a total of 0.63 g of butyric acid/kg) or nonsupplemented feed. The specific pathogen free layer chickens were orally infected with 10(6) cfu of S. enteritidis. Coated butyric acid significantly decreased cecal colonization 3 d post-infection compared with control chickens, and powder form butyric acid had no effect. To study long-term shedding and colonization of Salmonella in broilers given coated butyric acid as feed additive (0.63 g of active product butyric acid/kg), 10 Ross broiler chickens were infected at d 5 with 10(5) cfu of S. enteritidis and housed together with 40 noninfected broilers. A control group received nonsupplemented feed. The group of broilers receiving coated butyric acid had a significantly lower number of broilers shedding Salmonella bacteria, but cecal colonization at slaughter age was equal for both groups. In conclusion, butyric acid decreases cecal colonization shortly after infection, decreases fecal shedding, and as a consequence, decreases environmental contamination by S. enteritidis-infected broilers. However, complete elimination can probably only be achieved with a combined approach using both hygienic measures and different protection measures, as the broilers still carried S. enteritidis bacteria in the ceca at slaughter age, although at enrichment level.

Aging↗
PubMed1996

[Dust emission from chicken and layer houses].

Dust concentration was measured by Laser-monitor in two at a time houses for layers with litter or with cages and in two at a time houses for growing chicken with litter or with cages in the middle of the keeping area, in the outlet opening and in 3, 10, 50 and 100 m distance over a period of 8 weeks in winter, summer and spring/autumn. Dust values have shown only less dynamics between 8 am and 5 pm. Significant positive correlation was found between dust concentration and age of poultry, keeping time resp. in litter housing system but not in cage housing system. Also, it was demonstrated a significant relation between dust concentration inside of poultry house, at the outlet openings and in 3 m distance in the outdoor air. There was no influence evident of indoor dust concentration on the dust value in the environment in more than 3 m distance to the poultry house. It was shown a low dust concentration of 0.1% up to 2.1%--compared to the indoor dust values--in 50 and 100 m distance to outlet ventilation system independent on housing, climatic and topographic factors.

Aging↗
PubMedDate not supplied

High virus titer in feather pulp of chickens infected with subgroup J avian leukosis virus.

Subgroup J avian leukosis viruses (ALVs), which are a recombinant virus between exogenous and endogenous ALVs, can spread by either vertical or horizontal transmission. Exogenous and endogenous ALVs can be detected in feather pulp. In this study, virus titers in feather pulp of chickens infected with subgroup J ALV were compared with those of plasma and cloacal swab. All of the broiler chickens inoculated with subgroup J ALV at 1 day old were positive for virus from feather pulp during the experimental period of between 2 wk and 8 wk of age. Virus titers in feather pulp of some broiler chickens infected with subgroup J ALV were very high, ranging from 10(7) to 10(8) infective units per 0.2 ml. Virus titers in feather pulp were usually the highest among the samples of plasma, cloacal swab, and feather pulp tested. In another experiment in which layer chickens were inoculated with subgroup J ALV at 1 day old, virus was detected in feather pulp from 2 wk until 18 wk of age, and virus persisted longer in feather pulp than in plasma. Almost all of the layer chickens tested were positive for virus by polymerase chain reaction (PCR) with DNA extracted from feather pulp samples at 2, 4, and 10 wk of age, and the PCR from feather pulp was more sensitive than virus isolation from plasma, cloacal swab, and feather pulp. All above results indicate that samples of feather pulp can be useful for virus isolation and PCR to confirm subgroup J ALV infection.

Animals↗
PubMed2002

Increased fat deposition after repeated immunization in growing chickens.

We investigated the effects of sequential immunizations with seven different protein antigens (bovine gamma-globulin, keyhole limpet hemocyanin, rabbit gamma-globulin, tetanus toxoid, SRBC, human serum albumin, and BSA) on metabolic parameters (growth, food uptake, total heat production, metabolizability, energy retention as fat, and energy retention as protein) and antibody responses to these antigens in growing layer chickens. Energy and immune parameters of repeatedly immunized birds were compared with control birds in climate-respiration chambers in three trials. The last antigen (BSA) was given to both groups. Energy retention as fat was significantly higher in the repeatedly immunized group (P < 0.05). Antibody titers directed to BSA were similar for the repeatedly immunized groups and the control group. In addition, the separate antibody responses of the repeatedly immunized group to the administered antigens were compared with the antibody response of a control group receiving only a single antigen at the same age. With respect to several antigens, differences between groups were found. In the repeatedly immunized group, higher Day 0 (base line) titers were found to new antigens, introduced especially during the second half of the experiment. In these birds, significantly lower increases of antibody titers to some, but not all, antigens were found as compared to birds that were immunized only with the same antigen. It was concluded that repeated activation of the humoral immune response in growing layer chickens stimulated fat deposition but had little effect on other metabolic parameters. Repeated immunization had little effect on the immune response to separate antigens in the present experiments.

Adipose Tissue↗
PubMed1981

Kainic acid affects both plexiform layers of chicken retina.

Intraocular injections of kainic acid produce marked lesions of the chicken retina. Low doses (6-20 nmol/retina) appear to cause lesions of the inner part of the retina, primarily involving amacrine cells. At around 60 nmol/retina there is a qualitative change in the nature of the lesion, as the horizontal and bipolar cells begin to degenerate. Higher doses of kainic acid lead to disappearance of both the outer and inner plexiform layers. At all doses used, the photoreceptors and ganglion cells survive exposure to kainic acid. Low doses of kainic acid reduce the content of the amacrine and horizontal cell markers acetylcholine and gamma-amino-butyric acid, but have little effect upon taurine. These results are consistent with a role for glutamic and/or aspartic acid as bipolar cell and photoreceptor transmitters.

Animals↗
PubMed1987

[Toxicological and pharmacokinetic research on lincomycin hydrochloride in broiler chickens and layer hens].

Tested was the activity of linkomycin hydrochloride at the rate of 820 IU/mg. The LD50 of the preparation was found to exceed 12.0 g/kg body mass at intracrop application to broiler birds. When offered with the drinking water or the feed in amounts that were 3 to 5 times higher than the therapeutic ones for broilers in the course of 45 days it did not cause mortality nor induced changes in the white and red blood cell counts, in the total protein, and in the levels of urea, blood sugar, AlT, and AcT. Neither were there any structural changes in the internal organs. Upon the single intracrop treatment of broilers with linkomycin at 50 and 100 mg/kg most of the amount introduced was established in the blood serum at the second hour and up to the 6th and 8th hour, respectively. Studies on the effect of age on the serum concentrations at this route of introduction revealed that the preparation was absorbed at higher rates in the broilers than in the layers, while with the persistence of the levels there were no essential differences. At the single oral administration with broilers in amounts of 100 mg/kg linkomycin was chiefly retained in the kidneys, liver, and lungs as well in the content of the small and large intestines. At intracrop application to layers in doses of 100 mg/kg in the course of 7 days the antibiotic was excreted with the eggs at the time of treatment and in the course of 4 days later in bacteriostatic concentrations of 0.6-5.9 micrograms/cm3.

Animals↗
PubMedDate not supplied

Concentrations of biogenic amines in fundal layers in chickens with normal visual experience, deprivation, and after reserpine application.

Previous experiments in chickens have shown that dopamine released from the retina may be one of the messengers controlling the growth of the underlying sclera. It is also possible, however, that the apparent relationship between dopamine and myopia is secondary and artifactual. We have done experiments to assess this hypothesis. Using High Pressure Liquid Chromatography with electrochemical detection (HPLC-ED), we have asked whether changes in dopamine metabolism are restricted to the local retinal regions in which myopia was locally induced. Furthermore, we have measured the concentrations of biogenic amines separately in different fundal layers (vitreous, retina, choroid, and sclera) to find out how changes induced by "deprivation" (= removal of high spatial frequencies from the retinal image by translucent eye occluders which produce "deprivation myopia") are transmitted through these layers. Finally, we have repeated the deprivation experiments after intravitreal application of the irreversible dopamine re-uptake blocker reserpine to see how suppression of dopaminergic transmission affects these changes. We found that (1) Alterations in retinal dopamine metabolism were indeed restricted to the retinal areas in which myopia was induced. (2) The retina was the major source of dopamine release with a steep gradient both to the vitreal and choroidal side. Vitreal content was about one-tenth, choroidal content about one-third, and scleral content about one-twentieth of that of the retina. (3) There was a drop by about 40% in vitreal dopamine, DOPAC (3,4-dihydroxyphenylacetic acid) and HVA (homovanilic acid) concentrations following deprivation which occurred already at a time where little changes could yet be seen in their total retinal contents. (4) Choroidal and scleral dopamine levels were not affected by deprivation, indicating that other messengers must relay the information to the sclera. (5) A single intravitreal injection of reserpine lowered dopamine and HVA levels in retina and vitreous for at least 10 days in a dose-dependent fashion and diminished or suppressed further effects of deprivation on these compounds. DOPAC levels continued to change upon deprivation even after reserpine injection (Fig. 3). Our results suggest that the release rates of dopamine from retinal amacrine cells can be estimated from vitreal dopamine concentrations; furthermore, they are in line with the hypothesis that there is an inverse relationship between dopamine release and axial eye growth rates. Although our experiments do not ultimately prove that dopamine has a functional role in the visual control of eye growth, they are in line with this notion.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1999

Infectious coryza: overview of the disease and new diagnostic options.

Infectious coryza is a well-recognized and commonly encountered upper respiratory tract disease of chickens that is caused by the bacterium Haemophilus paragallinarum. The occurrence of recent outbreaks in North America has emphasized that the disease can be significant in meat chickens as well as layer chickens. In developing countries, coryza is commonly complicated by the presence of a range of other infections, resulting in severe disease and significant economic losses. Unusual forms of the disease, involving arthritis and septicemia, again associated with the presence of other pathogens, have been found in South America. Newly recognized bacteria such as Ornithobacterium rhinotracheale and phenotypic variant forms of both H. paragallinarum and close relatives (variant in that they no longer require V-factor for growth in vitro) have increased the difficulty associated with diagnosing the disease. There have been suggestions in both South America and South Africa that new serovars or serovar variants, associated with unusual clinical manifestations and causing vaccine failures, are emerging. Definitive evidence to confirm or deny the role of these "variants" in vaccine failures is currently not available. A new DNA-based diagnostic technique, involving PCR, has been recently described and will greatly assist in the diagnosis of infectious coryza.

Animals↗
PubMed1985

Performance of layer-type chickens as related to body conformation and composition. 1. A static analysis of shank length and body weight at 20 weeks of age.

The growth of an animal part (y) relative to the whole (x), is expressed in terms of an exponential equation, y = alpha x beta, where alpha and beta are growth constants. For the present study x is body weight and y is shank length determined for 10 lines of chickens at 20 weeks of age. The derived values of alpha and beta, assumed to be limiting relative growth constants for bone, were estimated by least squares of the log-transformed (linear) exponential equation. From the means of alpha and beta, calculated for each of seven Leghorn and three Fayoumi lines, individual values of alpha i and beta i were calculated for more than 24,000 pedigreed birds included in 9 years of records. The individual values (i) were calculated as: (formula; see text) If the initial growth constant, alpha, is the primary hereditary growth parameter governing conformation, then the parameter, beta, should not be as highly heritable as alpha. To test this hypothesis, the heritability (h2) of both alpha and beta were calculated for each of the 10 lines. For alpha sire component h2 values ranged from .12 +/- .05 to .45 +/- .10 and for beta from .05 to .41. The pooled h2 estimate of alpha over lines (.31 +/- .02) was not significantly different from that for beta (.31 +/- .02). Compared with the original data on body weight and shank length, the transformation significantly reduced the heritability estimated. We conclude that the parameters, alpha and beta, are useful only in describing phenotypic and not genetic differences in relative growth.

Animals↗