Evaluation of an in-house cat scratch disease IgM ELISA to detect Bartonella henselae in a routine laboratory setting.

Cat scratch disease (CSD) is caused by Bartonella henselae infection and is a common cause of regional lymphadenopathy. The diagnosis of CSD largely depends on serology, but detection of B. henselae in an affected lymph node by PCR is also an important diagnostic tool. We evaluated an IgM in-house ELISA protocol and analyzed its performance in routine CSD serology. Serum samples from PCR-positive patients (n = 126), PCR-negative patients (n = 123), and age-matched controls (n = 126) were used for evaluation. The sensitivity of the IgM ELISA was only 56%, showing that the performance of B. henselae serology under routine laboratory settings is low, probably caused by the wide variability in disease duration in patients suspected of CSD whose samples were submitted to our laboratory. Most patients (46%) with a positive IgM response were between 0 and 20 years of age. We conclude that the serodiagnosis of B. henselae is hampered by the low sensitivity and specificity of the assays when used in a routine laboratory setting. For this reason, a negative IgM or PCR result can never exclude CSD, especially with late sample collection.

[A man who contracted hepatitis E in the Netherlands]. / Een man met in Nederland opgelopen hepatitis E.

A 55-year-old man was admitted to our hospital because of malaise, jaundice en cholestatic liver function impairment, 4 days after his return from vacation in Surinam. Serological tests were positive for IgG and IgM antibodies to hepatitis E virus (HEV) and serum PCR was positive, consistent with HEV infection. The infection was acquired in the Netherlands and not abroad, considering the incubation period. The patient recovered spontaneously. HEV infection is rare in the Netherlands and is associated with travel to tropical or subtropical areas. The virus is transmitted by the faecal-oral route through contaminated water or food. Since 2000 there have been cases reported in the Netherlands, without any association with travelling abroad and in which the infection might be related to zoonotic transmission. The diagnosis is primarily based upon serologic tests for the detection of IgM and IgG antibodies to HEV in serum confirmed by immunoblot. It is important that HEV infection is considered in patients with acute hepatitis in whom no other cause can be found for hepatitis, even without any travel history to endemic areas.

Bayesian estimation of hepatitis E virus seroprevalence for populations with different exposure levels to swine in The Netherlands.

Hepatitis E virus (HEV) is ubiquitous in pigs worldwide and may be zoonotic. Previous HEV seroprevalence estimates for groups of people working with swine were higher than for control groups. However, discordance among results of anti-HEV assays means that true seroprevalence estimates, i.e. seroprevalence due to previous exposure to HEV, depends on choice of seroassay. We tested blood samples from three subpopulations (49 swine veterinarians, 153 non-swine veterinarians and 644 randomly selected individuals from the general population) with one IgM and two IgG ELISAs, and subsets with IgG and/or IgM Western blots. A Bayesian stochastical model was used to combine results of all assays. The model accounted for imperfection of each assay by estimating sensitivity and specificity, and accounted for dependence between serological assays. As expected, discordance among assay results occurred. Applying the model yielded seroprevalence estimates of approximately 11% for swine veterinarians,approximately 6% for non-swine veterinarians and approximately 2% for the general population. By combining the results of five serological assays in a Bayesian stochastical model we confirmed that exposure to swine or their environment was associated with elevated HEV seroprevalence.

The use of Bartonella henselae-specific age dependent IgG and IgM in diagnostic models to discriminate diseased from non-diseased in Cat Scratch Disease serology.

Cat Scratch Disease (CSD) is caused by Bartonella henselae infection and is a common cause of regional lymphadenopathy. The diagnosis of CSD largely depends on serology, but is hampered by both low sensitivity and specificity of the applied IgG and IgM assays. Using an in-house ELISA, we detected a significant age-dependent increase in the IgG levels in the general population compared to CSD patients. With this knowledge, we developed diagnostic models to differentiate diseased from non-diseased persons. Evaluation of these models using samples from PCR-positive patients (n=155) and age-matched controls (n=244) showed an important increase in the assay performance if the combination of the IgG and IgM results were taken into account. If the specificity was set at 98% the sensitivity was only 45% and 32% for the IgM and IgG ELISA, respectively but increased to 59% when these results were combined. Also the use of age-dependent factors further improved the clinical relevance of the outcome raising the sensitivity to 64%. Although the sensitivity of the ELISA remains low we conclude that the use of models using the combination of both IgM and IgG test results and age-depending factors can be a useful diagnostic tool in the serodiagnosis of CSD.

Use of serological assays for diagnosis of hepatitis E virus genotype 1 and 3 infections in a setting of low endemicity.

Because of the occurrence of genotype 3 hepatitis E virus (HEV) in regions of low endemicity, it is important to validate the currently used serological assays for diagnosing infections with viruses belonging to this lineage, since these assays only use antigens derived from genotype 1 and 2 viruses. We evaluated the Genelabs enzyme-linked immunosorbent assay (ELISA) and the RecomBlot from Mikrogen for the detection of HEV-specific immunoglobulin M (IgM) and IgG under conditions of low endemicity. We compared test results of 16 patients with locally acquired genotype 3 HEV, 8 genotype 1 patients, 167 healthy controls from the general population, and 101 cases with hepatitis due to other viral causes. The measured specificities of the ELISA (98%) and the RecomBlot (97%) were comparable to those given by the manufacturer for IgM but were significantly lower for IgG (93% by ELISA and 66% by immunoblotting, versus reported values of 98% for ELISA and 95% for blotting). Antibody levels detected following infections with genotype 3 were lower than those following genotype 1 infections except for those measured in the IgM ELISA. Reactivity to the four antigens used in the immunoblot assay were analyzed and showed differences in the IgM immunoblot reactions between genotype 1 patients and genotype 3 patients. The ORF3 antigen was the most specific antigen. The specificity could be improved by a combined testing regimen with confirmation by immunoblotting of all positive ELISA results and by raising the cutoff of the IgG immunoblot assay without loss of sensitivity. We conclude that a combination of ELISA and immunoblotting is needed for acceptable specificity and sensitivity of HEV assays under conditions of low endemicity.

Serological testing for Bartonella henselae infections in The Netherlands: clinical evaluation of immunofluorescence assay and ELISA.

Cat-scratch disease (CSD), caused by Bartonella henselae infection, can mimic malignancy and can manifest atypically. Reliable serological testing is therefore of great clinical importance. The diagnostic performance of immunofluorescence assay (IFA) and ELISA was evaluated in a group of Dutch patients with proven CSD (clinical diagnosis confirmed by PCR). Sera of 51 CSD patients and 56 controls (patients with similar symptoms, but who were B. henselae PCR-negative and had an alternative confirmed diagnosis) were tested for anti-B. henselae IgM and IgG by IFA and ELISA. A commercially available IFA test for IgM had a sensitivity of 6%. In-house assays for IgM showed specificities of 93% (IFA) and 91% (ELISA), but with low sensitivities (53% and 65%, respectively). With a specificity of 82% (IFA) and 91% (ELISA), in-house IgG testing showed a significantly higher sensitivity in IFA (67%) than in ELISA (28%, p <0.01). Sensitivity was higher for genotype I (38-75%) than for genotype II (7-67%) infections, but this was only statistically significant for IgG ELISA (p <0.05). In conclusion, detection of IgM against B. henselae by in-house ELISA and IFA was highly specific for the diagnosis of CSD. The high seroprevalence in healthy individuals limits the clinical value of IgG detection for diagnosing CSD. Given the low sensitivity of the serological assays, negative serology does not rule out CSD and warrants further investigation, including PCR. Adding locally isolated (e.g., genotype II) B. henselae strains to future tests might improve the sensitivity.

Detection of hepatitis E virus-specific immunoglobulin a in patients infected with hepatitis E virus genotype 1 or 3.

Currently, diagnosis of acute hepatitis E virus (HEV) in patients is primarily based on anti-HEV immunoglobulin M (IgM) detection. However, several investigations suggest the use of HEV-specific IgA for diagnosing acute HEV infections. We evaluated two commercially available assays, an IgA enzyme-linked immunosorbent assay (ELISA) (Diacheck) and an adapted immunoblot protocol (Mikrogen) for IgA detection and compared the performance in genotype 1- and 3-infected patients. The specificity of the IgA assays was high, with no positive reactions in a control group of 18 acute hepatitis patients who were negative for HEV. The sensitivity calculated in nine PCR-positive type 1-infected patients was 100% in both assays but was clearly lower in genotype 3-infected patients (n = 14), with sensitivities of only 67% and 57% for the ELISA and immunoblot assay, respectively. The lower IgA responses detected in genotype 3-infected patients could be caused by the use of only the genotype 1 and 2 antigens in the serological assays. Interestingly in two patients with possible infection through blood transfusion no response or intermediate IgA responses were detected, and this might confirm the parenteral route of transmission. In both the type 1- and type 3-infected patients both the IgA and IgM responses disappeared simultaneously. We conclude that IgA detection is of limited value for the serodiagnosis of acute HEV cases, particularly with genotype 3.

Swine-like hepatitis E viruses are a cause of unexplained hepatitis in the Netherlands.

Hepatitis E virus (HEV) infections in developed countries are recognized as an imported disease related to travel to endemic regions. However, increasing evidence suggests that HEV infection may also occur in the developed countries and that swine may act as a possible reservoir. To investigate the indigenous transmission of HEV in the Netherlands, sera from 50 blood donors and 1027 sera from patients with acute hepatitis were screened with an ELISA for HEV-specific IgG and IgM. Because the Netherlands is considered a nonendemic region, all positive ELISA results were confirmed by immunoblot to exclude false-positive results. Evidence of recent HEV infection was detected in 0% of the blood donors and 4.4% of the cases, based on combined positive IgM and IgG responses. The serodiagnosis was confirmed by a positive polymerase chain reaction (PCR) in 24 patients with hepatitis (2.3% overall, 51% of confirmed IgM+/IgG+ cases). IgG antibodies alone were detected in 4.2% of patients. We found related sequences to virus strains detected in Dutch pigs (genotype 3, 91-97% homology) in 89% of PCR-confirmed HEV patients. The detection of unique swine-like HEV sequences in 16 indigenous hepatitis patients without a recent travel history suggests that HEV is endemic in the Netherlands. We recommend including HEV tests in unexplained acute hepatitis patients, despite their travel history.

Hepatitis E is a cause of unexplained hepatitis in The Netherlands.

BACKGROUND: Hepatitis E virus (HEV) is the major etiologic agent of enterically transmitted viral hepatitis in much of the developing world. Evidence provided in recent years shows that HEV is also prevalent in very low numbers in non-endemic countries. Recently, a cluster of three patients with acute hepatitis E but no history of travel to endemic countries was discovered in the geographical area provided with service by the Public Health Laboratory Groningen and Drenthe, The Netherlands. OBJECTIVE: This lead to the question whether hepatitis E is a cause of unexplained hepatitis in this district. STUDY DESIGN: The prevalence of anti-HEV IgG and IgM among 209 patients with clinical signs of hepatitis, negative test for hepatitis A-C, no history of foreign travel and no other cause of hepatocellular damage was compared with a matched control group of 209 individuals. RESULTS: We found a significant difference in seroprevalence between the two groups for IgG anti-HEV as determined with the Abbot HEV EIA (6.2% versus 0.5%); however this difference could not be confirmed with the Genelabs Diagnostics HEV IgG ELISA (6.7% versus 3.8%). For confirmed cases of IgM anti-HEV we also detected a significant difference between the two groups (3.3% versus 0.5%). Remarkably, the combination of IgG and IgM anti-HEV was only found among hepatitis patients. CONCLUSION: This study provides evidence of locally acquired hepatitis E in The Netherlands. Therefore, in cases of unexplained acute hepatitis, the diagnosis of hepatitis E should be considered even in the absence of foreign travel.

Efficacy of donor vaccination before hematopoietic cell transplantation and recipient vaccination both before and early after transplantation.

Allogeneic hematopoietic cell transplantation is followed by humoral immunodeficiency. We evaluated whether antibody levels can be improved by recipient vaccination on day -1 and 50 and whether the levels can be further improved by donor vaccination on day -20. A total of 85 patients were randomized or assigned to one of the following strategies of immunization with Streptococcus pneumoniae polysaccharides, Haemophilus influenzae polysaccharide-protein conjugate, tetanus toxoid (protein recall antigen) and hepatitis B surface antigen (protein neo-antigen): (1) donor on day -20, recipient on days -1, +50 and +365 (D(-20)R(-1,50,365)); (2) donor nil, recipient on days -1, +50 and +365 (D(N)R(-1,50,365)); or (3) donor nil, recipient on day +365 (D(N)R(365)). For H. influenzae and tetanus, IgG levels after grafting were the highest in the D(-20)R(-1,50,365) patients, intermediate in the D(N)R(-1,50,365) patients and the lowest in the D(N)R(365) patients. For S. pneumoniae and hepatitis B, antibody levels appeared to be similar in all three patient groups. The results suggest that for polysaccharide-protein conjugate antigens or protein recall antigens, recipient immunization on days -1 and 50 improves antibody levels and that donor vaccination on day -20 further improves the levels. In contrast, neither recipient immunization on days -1 and 50 nor donor immunization on day -20 appears to be efficacious for polysaccharide antigens and poorly immunogenic protein neo-antigens.

Factors affecting antibody levels after allogeneic hematopoietic cell transplantation.

To obtain insight into the mechanism(s) of posttransplantation humoral immunodeficiency, we evaluated factors affecting serum antibody levels against polio, tetanus, Haemophilus influenzae, and Streptococcus pneumoniae in 87 patients. Patients with hematologic malignancies were randomized to receive marrow versus blood stem cells, which contain approximately 10 times more lymphocytes than marrow. Blood stem cell recipients did not have higher antibody levels than marrow recipients. Recipient pretransplantation antibody levels were correlated with the posttransplantation levels, especially in the first 6 months after transplantation when the correlation coefficients typically exceeded 0.6. Donor pretransplantation antibody levels had less of a correlation with posttransplantation levels in the recipient. Patient or donor age, total body irradiation, and graft-versus-host disease or its treatment appeared to have no effect. In conclusion, antibody levels in the first year after transplantation are affected primarily by pretransplantation antibody levels in the recipient and, to a lesser degree, in the donor. These findings suggest that immunization of the recipient and the donor before transplantation may be more effective in improving antibody immunity after transplantation than manipulating graft-versus-host disease, changing conditioning, or increasing the number of lymphocytes in the graft.

Poliovirus-specific immunoglobulin A in persons vaccinated with inactivated poliovirus vaccine in The Netherlands.

In The Netherlands the inactivated poliovirus vaccine (IPV) is used for protection against poliomyelitis. It is not clear if parenteral vaccination with IPV can lead to priming of the mucosal immune system. We developed and evaluated enzyme-linked immunosorbent assays for the detection of poliovirus serotype-specific immunoglobulin A (IgA) and secretory IgA antibodies. Using these assays we examined the kinetics of the IgA response in sequential serum samples from 15 poliomyelitis patients after natural infection with serotype 3 poliovirus. In 36% of the patients IgA remained present for up to 5 months postinfection. Furthermore, we examined, in an IPV-vaccinated population, the presence of IgA antibodies in sera from young children (4 to 12 years of age; n = 177), sera from older children (between 13 and 15 years of age; n = 123), sera from healthy blood donors (n = 66), and sera from naturally immune elderly persons (n = 54). The seroprevalence of IgA to all three serotypes was low in young vaccinated children (5 to 7%), and the seroprevalence of IgA types 2 and 3 was low in older vaccinated children (2 to 3%). The seroprevalence of antibodies to type 1 was significantly higher (18%) in older children than in younger children. This higher seroprevalence is most likely explained by the persistence of IgA following infection with the serotype 1 wild-type poliovirus strain during the 1978 epidemic. In healthy adults, the seroprevalence of type 1- and type 2-specific IgA was significantly higher than that in young children. These results suggest that at least part of the IgA found in the older population is induced by infections unrelated to the IPV vaccination schedule. Finally, we found that parenteral vaccination with IPV was able to boost secretory IgA responses in 74 to 87% of a naturally exposed elderly population (n = 54). While the presence of secretory IgA in IPV-vaccinated persons has been documented previously, our findings suggest that mucosal priming with live virus is necessary to obtain an IgA response after IPV booster vaccination.

Evaluation of a poliovirus-binding inhibition assay as an alternative to the virus neutralization test.

An enzyme-linked immunosorbent assay (ELISA)-based poliovirus-binding inhibition (PoBI) test to detect and quantify antibodies to polioviruses was optimized and evaluated for use in population studies as an alternative to the virus neutralization test (NT) in tissue culture. The sensitivities of the inhibition ELISA compared with the NT in an inactivated poliovirus vaccine (IPV)-vaccinated population were 98.6, 97.4, and 92.1% for serotypes 1, 2, and 3, respectively. The specificities of the PoBI test, as determined with sera from nonvaccinated persons, were also high for all three serotypes (99.0, 95.8, and 100%, respectively). Antibodies to other enteroviruses did not cross-react in the serotype 1 and 3 PoBI, and only levels of cross-reactivity were found for serotype 2. We found high correlations between the PoBI and NT titers for serotypes 1 and 2 in IPV-vaccinated blood donors (0.97 and 0.95), in oral poliovirus vaccine (OPV)-vaccinated blood donors (0.91 and 0.95), and in naturally immune persons (0.90 and 0.87). The correlation coefficient for serotype 3, however, was significantly lower in OPV-vaccinated blood donors (0.73) and in naturally immune persons (0.76) than in IPV-vaccinated persons (0.94; P < 0.01). These results indicate that the antibody response to serotype 3 poliovirus in IPV recipients is different from that in OPV recipients and naturally infected persons. We conclude that the PoBI test is a suitable alternative to the NT for estimating the seroprevalence of neutralizing antibodies to poliovirus, especially in large-scale population studies.

The concept of metabolic clearance rate in endocrinology. A case study of growth hormone in different lines of meat-type chickens.

Disappearance of growth hormone from blood (plasma) was studied in young broiler chickens in two experiments: a) following single injection of GH (50 micrograms or 250 micrograms/kg) to anesthetized chicks; b) injection of GH (50 micrograms/kg) (under anesthesia) to two lines of broilers selected for either rapid growth or feed efficiency. Clearance of GH never followed a single negative exponential curve. Characterization of the disappearance by a single metabolic clearance rate and half-life time were found to be inaccurate and inappropriate on methodological grounds. High doses of hormone might disturb receptor or catabolism equilibria and result in aberrant values of MCR which could probably be because of the very dynamic nature of the GH clearance system, which appeared to be influenced by dose, line (or genetics of the animal) and by some indices of clearance. Therefore, physiological significance of such data must be interpreted carefully.

Immunocytochemical demonstration of progesterone and estrogen receptors in feathers and skin of adult hens.

Clinical evidence indicates that ovarian steroids are involved in the control of moulting in the chicken. This immunocytochemical study investigates if feather papillae and growing feathers are target tissues for ovarian steroids. Progesterone (PR) and estrogen (ER) receptors were demonstrated using monoclonal antibodies in feathers and surrounding skin of laying hens. Both receptor types were present in the nuclei of dermal papillae and in the nuclei of the epidermal germinative layer cells of growing and full-grown feathers. In growing feathers most nuclei of the intermediate layer (ramogenic column, rachis, axial plate) were immunostained, but during the final stages of differentiation into barbules, only estrogen receptors remained prominent. Skin adjacent to feathers showed ER and PR receptors in nuclei of cells from epidermis, muscles and arteries. During egg-laying pause, plasma progesterone levels decrease ten-fold and it is supposed that this results in a much greater endocrine efficiency of the remaining estrogen levels which are only reduced by 50% when egg-laying stops. The moult-inhibiting effect of progesterone in laying hens could be due to its well-established downregulation on estrogen receptors and therefore, on the endocrine effect of ER at cellular level in feather papillae. Such may account for the presence of both receptor types on the same feather cells, as observed in the present study.

Growth hormone response to TRH in male broiler chickens selected for body weight gain or food conversion and reared at either a moderate or a high ambient temperature.

The aim of the present experiment was to study the growth hormone (GH) response upon thyrotropin releasing hormone (TRH) challenge (2 micrograms/kg body weight) in broiler chickens selected for body weight gain (GL line: fat line) or for feed efficiency (FC line: lean line) reared at either a moderate (33-23 degrees C) or high (33 degrees C) ambient temperature. A higher plasma GH level at 5 min after TRH administration was observed in the high temperature conditioned chickens of both lines. Also at high ambient temperature, an enhanced GH decrease between 15 min and 30 min post-injection and a higher acute elimination rate was calculated compared to moderate ambient temperature. A significantly higher GH secretory response was observed in the leaner FC line chickens, which was probably related to the more pronounced pulsatory GH secretion rate in these chickens. There was no difference in GH acute elimination rate between both lines in both environments. No interactions between line and rearing temperature for these parameters of GH dynamics were observed.

Concentrations of hormones, glucose, triglycerides and free fatty acids in the plasma of broiler chickens selected for weight gain or food conversion.

1. The concentrations of growth hormone (GH), insulin-like growth factor I (IGF-I), thyroxine (T4), triiodothyronine (T3), reverse-triiodothyronine (rT3), triglycerides (Tri), free fatty acids (FFA) and glucose (Glu) were determined at 2, 4 and 6 weeks of age in blood plasma of male and female chickens of broiler lines selected for body weight (GL) or food conversion (FC). 2. Plasma concentrations measured in the same animal over a 24 h or a 2 week interval were not significantly correlated with each other. For different traits measured in the same plasma sample only the correlation between T4 and rT3 differed significantly from zero. 3. All traits were dependent on age. Line and sex effects were significant (P less than 0.05) for GH, T4, Tri, FFA and Glu. Additionally, line significantly influenced the plasma T3/T4 ratio and sex influenced plasma rT3. Interactions between line, sex and/or age were seldom significant. 4. Within line and sex, GH (at 6 weeks of age) and T3 (at 4 weeks of age) were negatively, and IGF-I and Tri (both at 6 weeks of age) positively correlated with the amount of abdominal fat at 6 weeks of age. No significant correlation between body weight at 2, 4 or 6 weeks of age and any of the plasma traits was found.

The effect of clenbuterol supplementation on growth performance and on plasma hormone and metabolite levels of broilers.

In the present experiment, clenbuterol was supplemented (.42 ppm) from Day 1 or from 2 or 4 wk of age until slaughter age (6 wk). The effects on growth performance and on plasma hormone and metabolite profiles were investigated at 2, 4, and 6 wk of age in male and female broilers. There were no consistent or cumulative effects of clenbuterol feeding on growth and feed efficiency. Clenbuterol feeding from Day 1, but not later, depressed subsequent feed intake. Relative abdominal fat pad weight was reduced profoundly and was even more pronounced after prolonged supplementation and for females. Fat content of thigh meat (including skin), but not of breast meat (without skin), was reduced by clenbuterol feeding. No consistent effects of clenbuterol supplementation on plasma thyroid hormones, growth hormone, insulin-like growth factor-I, and corticosterone levels were detected. Very low density lipoprotein (VLDL) concentrations were depressed in male broilers fed clenbuterol for 6 wk, but the plasma triglyceride level did not follow this pattern. There was no evidence for a consistent effect of clenbuterol on lipolysis in vivo, measured by plasma glycerol level. Between 4 and 6 wk of age, plasma VLDL and glycerol levels decreased in females but increased in males. This corresponds to the higher fat deposition in females. However, the most consistent effects were age-related changes in the plasma levels of most hormones and metabolites. From the present study, it seems that clenbuterol acts primarily on fat deposition, the extent being dependent on sex, location of fat, and duration of beta-adrenergic agonist supplementation.

Thyrotropin-releasing hormone (TRH) is not thyrotropic but somatotropic in fed and starved adult chickens.

Adult fed and starved Warren chickens, 2 yr of age, and approaching the end of the second laying year, were injected iv with 1 of the following products: 10 micrograms of thyrotropin releasing hormone (TRH); 100 micrograms of bovine thyrotropin (bTSH); 100 micrograms of ovine growth hormone (oGH); saline. The influence on plasma concentrations of thyroxine (T4), triiodothyronine (T3) or chicken GH (cGH) were followed. Prior to injection, it was clear from the control values that starvation for 3 d decreased plasma levels of T3 and increased cGH, whereas 7 d of fasting increased T4 and cGH. The plasma levels of cGH were elevated greater than 10-fold at 15 min following the TRH challenge in food-deprived chickens compared to a less than 4-fold increase in normal fed hens. This increase was followed by a rise in T3 after 1 h, which was also more pronounced in the starved animals, whereas T4 decreased or remained unaffected. Increases in T4 can, however, be obtained with 100 micrograms TSH in normal fed (2-fold) or starved animals (greater than 3-fold). Following injection of 100 micrograms oGH, a significant increase in T3 levels was observed which in fed animals was already present at 30 min, but the higher levels persisted for 1 and 2 h in fed and starved hens. At the same time, a decrease in T4 was observed in both groups of GH-treated chickens. It is concluded that TRH at the dose used is not thyrotropic but has a somatotropic effect and is responsible for the peripheral conversion of T4 into T3.

Effect of plumage renewal after induced moulting on subsequent laying efficiency and persistence.

1. Brown egg layers and dwarf broiler breeder females were force-moulted by different diets. The relationship between the extent of feather replacement and subsequent laying performance was studied. Some brown hens were subjected to metabolic experiments in order to compare post-moult heat production in relation to moulting success. 2. The extent of moulting had a clear effect on the post-moult heat production, and the differences were still present after 6 months in the second year of laying. 3. The extent of feather renewal during moulting showed high and very significant rank correlations with efficiency of food utilisation during the subsequent laying cycle. These correlations were generally higher than those of other features of the moulting procedure (body-weight-loss, minimum weight, duration of pause in laying). 4. The long-term energetic implications of the extent of moulting play an important role in subsequent performances and the persistence of lay during the following year is related to the extent of feather replacement.