Prevalence of parvovirus in Minnesota turkeys.

Poult enteritis syndrome (PES) is characterized by enteritis and decreased body weight gain in growing turkey poults between one d and 7 wk of age. Another syndrome called light turkey syndrome (LTS) causes a decrease in body weight of adult tom turkeys in Minnesota leading to huge economic losses. Reovirus, rotavirus, and astrovirus have been found in LTS and PES flocks in Minnesota. We tested 80 fecal pools collected from four LTS flocks and 35 fecal pools from non-LTS flocks for the presence of parvovirus. In addition, 116 fecal and meconium samples from turkeys submitted to the Minnesota Veterinary Diagnostic Laboratory (MVDL) also were tested. The samples were tested by PCR using primers for the non-structural 1 (NS1) gene of parvovirus. Of the 80 samples from LTS flocks, 41 were positive for parvovirus while 20 of 35 samples from non-LTS flocks were positive. The prevalence of parvovirus in fecal samples submitted to MVDL was relatively low; only five of the 116 pools were positive. The partial NS1 gene sequences from LTS and non-LTS samples showed 98 to 100% nt identity except for one divergent turkey parvovirus (TuPV) strain that revealed 90% identity and clustered with chicken-like parvoviruses. The presence of this divergent strain suggests circulation of a recombinant strain of TuPV in Minnesota turkeys. Our results indicate that TuPVs are circulating in both LTS and non-LTS flocks of turkeys in Minnesota, and further experimental studies are indicated to study the role of TuPV in LTS.

Hen welfare in different housing systems.

Egg production systems have become subject to heightened levels of scrutiny. Multiple factors such as disease, skeletal and foot health, pest and parasite load, behavior, stress, affective states, nutrition, and genetics influence the level of welfare hens experience. Although the need to evaluate the influence of these factors on welfare is recognized, research is still in the early stages. We compared conventional cages, furnished cages, noncage systems, and outdoor systems. Specific attributes of each system are shown to affect welfare, and systems that have similar attributes are affected similarly. For instance, environments in which hens are exposed to litter and soil, such as noncage and outdoor systems, provide a greater opportunity for disease and parasites. The more complex the environment, the more difficult it is to clean, and the larger the group size, the more easily disease and parasites are able to spread. Environments such as conventional cages, which limit movement, can lead to osteoporosis, but environments that have increased complexity, such as noncage systems, expose hens to an increased incidence of bone fractures. More space allows for hens to perform a greater repertoire of behaviors, although some deleterious behaviors such as cannibalism and piling, which results in smothering, can occur in large groups. Less is understood about the stress that each system imposes on the hen, but it appears that each system has its unique challenges. Selective breeding for desired traits such as improved bone strength and decreased feather pecking and cannibalism may help to improve welfare. It appears that no single housing system is ideal from a hen welfare perspective. Although environmental complexity increases behavioral opportunities, it also introduces difficulties in terms of disease and pest control. In addition, environmental complexity can create opportunities for the hens to express behaviors that may be detrimental to their welfare. As a result, any attempt to evaluate the sustainability of a switch to an alternative housing system requires careful consideration of the merits and shortcomings of each housing system.

Validation of a modified PCR-based method for identifying mutant restricted ovulator chickens: substantiation of genotypic classification by phenotypic traits.

Upon photostimulation, restricted ovulator (RO) female chickens exhibit endogenous hyperlipidemia, develop atherosclerotic lesions, and generally fail to lay eggs. This phenotype results from a point mutation in the gene specifying the very low density lipoprotein receptor (VLDLR), whose protein product normally mediates the massive oocytic uptake of egg yolk precursors from the circulation. Taking advantage of the single base change in the mutant VLDLR allele, a PCR-based method for the rapid identification of RO chickens was developed at the Biocenter and University of Vienna, Austria. However, this procedure was incompletely validated because phenotypic data were not obtained and conventional progeny testing of sons and grandsons was not performed. Here, the assay validation was completed by providing plasma lipid concentrations, plasma very low density lipoprotein particle sizes, or egg production records of PCR-genotyped females and their brothers and sires to demonstrate that each bird's phenotypic traits substantiated their genotypic classification. Moreover, several methodological modifications resulted in improved chemical safety, speed, and cost of preparing and analyzing genomic DNA from chicken erythrocytes. Because the ovaries of mutant RO females generally contain numerous vitellogenic follicles in the absence of a functional oocyte plasma membrane VLDLR, the existence of an alternate system for the oocytic uptake of plasma very low density lipoprotein and vitellogenin is suggested, whereas a physiological explanation as to why some, but not all, mutant RO hens are able to ovulate and lay eggs is lacking.

Diagnosis of myeloid leukosis induced by a recombinant avian leukosis virus in commercial white leghorn egg laying flocks.

Commercial white leghorn egg layer flocks being used to produce fertile eggs for human vaccine production exhibited dramatically low peaks in egg production, two to four times higher than normal weekly mortality, and high numbers of cull, nonlaying birds after the onset of sexual maturity. These lower production characteristics could not be associated with management-related problems. Gross lesions of cull and fresh dead birds necropsied showed approximately 60% lacked ovarian activity and had lesions of a bacterial bursitis or synovitis, whereas the other 40% had tumors of the viscera but not of the bursa of Fabricius. Histologic examination of tumor-containing tissues showed lesions typical of myelocytomatosis. The diagnosis of myeloid leukosis was confirmed by the isolation of a recombinant avian leukosis virus (ALV) containing the LTR of subgroup J and the envelope of subgroup B ALV. A positive polymerase chain reaction with primers specific for the 3' untranslated region LTR confirmed the presence of LTR of ALV-J. The source of infection with this recombinant ALV was not determined; however, it is likely that commingling of the day-old egg-type chicks with ALV-J-infected meat-type chicks in a common hatchery had contributed to this outbreak.

Palatability of bird repellents to Rattus norvegicus.

The palatability to captive, mostly laboratory-bred, Norway rats (Rattus norvegicus) of cereal-based baits containing 0.02 g kg-1 brodifacoum, with and without bird-repellent additives, was compared in a no-choice experimental design. Methyl anthranilate (25 g kg-1), dimethyl anthranilate (25 g kg-1) and cinnamamide (2.5 g kg-1) reduced bait consumption by the rats, but all except one rat ate enough bait to receive a lethal dose. Cinnamamide (1 g kg-1), ortho-aminoacetophenone (0.1 g kg-1) and tannic acid (20 g kg-1) did not reduce bait consumption and all rats died after eating baits. The concentration of cinnamamide palatable to rats has only a low and short-lived repellency to birds, so it does not warrant further investigation. However, ortho-aminoacetophenone and tannic acid should now be field-tested for palatability to all three rat species in New Zealand and for repellency to native New Zealand birds.

Hyporesponsiveness of the systemic and mucosal humoral immune systems in chickens infected with Salmonella enterica serovar enteritidis at one day of age.

Newly hatched chicks lack immunological maturity, which could compromise their ability to respond to infection by pathogens such as Salmonella enterica serovar enteritidis (S. enteritidis; SE). A study was conducted in which chicks were infected with a sublethal dose of SE at 1 d posthatch, and the systemic and intestinal immune responses to the challenge were followed over time. Birds infected at this age experienced difficulty in clearing the infection, and 50% of the individual birds remained persistently infected until 23 wk of age. These birds exhibited only a marginal systemic and mucosal humoral immune response to the infection. No response or little response was observed 1 wk postchallenge; responses increased somewhat over time. On many of the sampling times, 50% or more of the culture-positive birds lacked a detectable plasma or intestinal response. Levels of 10(3) to 10(5) SE/g of feces could be found in the intestines of birds eliciting a good IgA response, indicating that, when these birds did respond mucosally, the IgA produced was incapable of clearing the organism once the infection was established. Birds infected during this time also experienced reduced ability to respond to vaccination. Compared with uninfected controls, depressed responsiveness to an S. enteritidis bacterin was observed in infected birds 1 and 2 wk after administration, whereas those individuals receiving an inactivated Newcastle disease vaccine (NDV) experienced a reduced response 4 and 6 wk postvaccination, indicating that the persistent infection affected the ability of the immune system to respond to homologous and heterologous antigens. These results demonstrate that exposure of chickens to SE early in life interferes with the ability of these individuals to respond humorally to the infection and to other antigenic stimuli; such effects can be observed for at least 23 wk.

Select 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors vary in their ability to reduce egg yolk cholesterol levels in laying hens through alteration of hepatic cholesterol biosynthesis and plasma VLDL composition.

The inability to markedly attenuate cholesterol levels in chicken eggs has led to speculation that cholesterol is essential for yolk formation and that egg production would cease when yolk cholesterol deposition was inadequate for embryonic survival. However, this critical level hypothesis remains unproven. Here, we determine the relative responsiveness of laying hens to three select inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR), the rate-limiting enzyme of cholesterol biosynthesis. A control diet, either alone or supplemented with one of two dietary levels (0.03 or 0.06%) of atorvastatin, lovastatin, or simvastatin, was fed to White Leghorn hens for 5 wk. Liver cholesterol concentrations (mg/g tissue) were decreased (P 0.05), and 22% (P 0.05), and -3% (P > 0.05)], was much less affected. We concluded that cholesterol per se may not be an obligatory component for yolk formation in chickens and, as such, may be amenable to further pharmacological manipulation

The effect of route of inoculation on the virulence of raptorial Pasteurella multocida isolates in Pekin ducks (Anas platyrhynchos).

The purpose of this study was to determine the virulence of raptorial Pasteurella multocida for ducks and the effect of various routes of inoculation on virulence. Four-week-old Pekin ducks (Anas platyrhynchos) were challenged with one of three raptorial isolates (RTHA-2, RTHA-4, or WESO-1) by one of five inoculation routes (intranasal, intraocular, intravenous, oral, and subcutaneous). Ducks were monitored daily for mortality until 2 wk postchallenge. Results indicated that the intravenous route caused the most mortality for all isolates and that significant variation existed in the virulence among the sources of P. multocida, with WESO-1 causing the least mortality of the isolates tested.

Delayed-type hypersensitivity reaction induced in broilers by killed Staphylococcus aureus.

A trial was conducted to determine whether the delayed footpad reaction (DFR) induced by killed Staphylococcus aureus in chickens is a delayed-type hypersensitivity (DTH) reaction. Five criteria were used to assess DTH: 1) DFR with a peak response at 24 to 48 h postchallenge, 2) inhibition of monocyte/macrophage migration, 3) lymphocyte blastogenic response, 4) mononuclear cell infiltration at the challenge site, and 5) passive transfer of DFR by splenic lymphocytes. Broilers were sensitized twice with a s.c. injection in the neck of S. aureus antigen (150 microg/bird) diluted in polyethylene glycol at 3 and 4 wk of age. Controls were s.c. injected with polyethylene glycol. At 6 wk of age, a migration inhibition test was conducted before the birds were challenged intradermally with S. aureus antigen (75 microg/bird) in PBS in the right footpad. The left footpad was injected with PBS. The thickness of the footpad was measured at 0, 4, 24, and 48 h postchallenge to evaluate the DFR. After challenge, blood was collected for the lymphocyte blastogenesis assay. Birds were euthanatized, and both footpads were removed for histology. The spleens were collected aseptically; splenic lymphocytes were injected i.v. into recipient birds. Sensitized birds showed an increase in the DFR (P < 0.02) and blastogenic response (P < 0.01) compared with nonsensitized birds. Delayed footpad reaction reached a maximum response at 24 h postchallenge. The in vitro migration of monocytes/macrophages from sensitized birds was significantly inhibited (P < 0.01). The histological appearance of S. aureus-injected footpads was characterized by dermal edema and perivascular infiltrates of small lymphocytes and macrophages. Birds that received sensitized splenic lymphocytes had a significantly pronounced DFR following challenge with S. aureus when compared with birds that received nonsensitized lymphocytes (P < 0.0001). These results indicated that the DFR can be used as a standard in vivo test for cell-mediated DTH reaction induced by killed S. aureus antigen in chickens.

Delayed-type hypersensitivity reaction induced in broilers via trachea inoculation of killed Staphylococcus aureus.

A study was conducted to determine whether the delayed-type hypersensitivity (DTH) reaction to killed Staphylococcus aureus antigen in chickens could be induced through multiple intratracheal inoculations. Three criteria were used to assess DTH: 1) delayed footpad reaction (DFR) with a peak response at 24 to 48 h postchallenge, 2) inhibition of monocyte/macrophage migration, and 3) mononuclear cell infiltration at the challenge site. Broilers were sensitized three times with a s.c. injection in the neck or intratracheal inoculation of killed S. aureus in polyethylene glycol at 2, 3, and 4 wk of age. Controls were given polyethylene glycol with a s.c. injection in the neck or intratracheal inoculation. Migration inhibition tests were conducted at 6 wk of age. At 7 wk of age, all birds were challenged intradermally with S. aureus antigen in PBS in the right footpad. The left footpad was injected with PBS. The thickness of the footpad was measured at 0, 4, 24, and 48 h postchallenge to evaluate the DFR. Birds were euthanatized, and both footpads were removed for histopathological examination. Subcutaneously or intratracheally sensitized birds showed significant DFR compared with nonsensitized birds (P < 0.0001), which reached maximum response at 24 h postchallenge. The s.c. sensitization resulted in an inhibition of the in vitro migration of monocytes/macrophages (P < 0.0001), whereas intratracheally sensitized birds did not show migration inhibition of monocytes/macrophages. Histological examination showed typical perivascular infiltration of small lymphocytes in S. aureus-injected footpads from s.c. and intratracheally sensitized birds. These results indicate that multiple intratracheal inoculation, as well as s.c. injection of killed S. aureus antigen, can be used to induce a cell-mediated DTH reaction in chickens.

Bacterial enteritides of poultry.

Enteric bacterial infections in poultry pose a threat to intestinal health and can contribute to poor feed efficiency and livability of a flock. A variety of enteric bacterial diseases are recognized in poultry. Three of these bacterial diseases, necrotic enteritis, ulcerative enteritis, and spirochetosis, primarily infect the intestine, whereas other bacterial diseases, such as salmonellosis, colibacillosis, mycobacteriosis, erysipelas, and fowl cholera, affect a variety of organ systems in addition to the intestine. Diagnosis of bacterial enteritis requires monitoring of clinical signs in the flock and proper use of diagnostic methods such as necropsy, histopathology, bacteriology, and serology.

Assessing the sensitivity of egg yolk antibody testing for detecting Salmonella enteritidis infections in laying hens.

The identification of infected commercial poultry flocks has become a pivotal component of efforts to reduce the incidence of egg-associated transmission of Salmonella enteritidis to humans. To assess the sensitivity with which testing for specific antibodies in egg yolks can be applied to detect S. enteritidis infection in laying chickens, groups of hens were orally inoculated with either 10(3), 10(5), or 10(7) cfu of a phage type 13a strain of S. enteritidis. Eggs from these hens were collected for 4 wk after inoculation and yolk samples were tested for antibodies to S. enteritidis flagella by ELISA. All hens that were inoculated with 10(7) cfu of S. enteritidis were detected as infected by the egg yolk ELISA when eggs were tested individually, as were up to 66 and 35% of hens inoculated with 10(5) or 10(3) cfu, respectively. Even when yolks from infected hens were diluted 1:10 in yolk from uninfected hens, specific antibodies could still be found in eggs from 31% of hens given 10(7) cfu of S. enteritidis and 13% of hens given 10(3) cfu. These results demonstrate that egg yolk antibody testing can provide a highly sensitive indication of prior exposure to S. enteritidis, and should accordingly be useful for verifying the effectiveness of programs designed to reduce the incidence of S. enteritidis infection in poultry.

The effects of induced molting on the severity of acute intestinal inflammation caused by Salmonella enteritidis.

This study describes and compares early inflammation caused by Salmonella enteritidis in molted and nonmolted hens. Adult white leghorn chickens were orally infected with Salmonella enteritidis 4 days after feed removal. At 2, 4, 8, 10, 24, 48, 72, and 96 hr after infection, the hens were euthanatized, and the duodenum, jejunum, ileum, cecum, and colon were evaluated by light microscopy. Two trials were conducted, and in both trials inflammation occurred more frequently and was significantly greater in the cecum and colon of molted-infected hens compared with nonmolted-infected hens beginning at 8 hr after infection. In one trial, inflammation was more severe in the ileum of molted-infected hens compared with nonmolted-infected hens. Results indicated that molting by feed deprivation shortened the time of onset and increased the severity of acute intestinal inflammation caused by Salmonella enteritidis.

Applying tests for specific yolk antibodies to predict contamination by Salmonella enteritidis in eggs from experimentally infected laying hens.

Detecting Salmonella enteritidis contamination in eggs has become the cornerstone of many programs for reducing egg-borne disease transmission, but egg culturing is time consuming and laborious. Preliminary screening tests are thus generally applied to minimize the number of flocks from which eggs must be cultured. The usefulness of such tests is directly proportional to both their detection sensitivity and their ability to predict the likelihood of egg contamination. In the present study, samples were collected for 24 days after groups of laying hens were orally inoculated with S. enteritidis. Eggs from each hen were cultured for S. enteritidis in the contents and samples of egg yolk were diluted and tested for specific antibodies to S. enteritidis flagella using both experimental and commercially available enzyme-linked immunosorbent assay (ELISA) methods. Samples of voided feces were also collected regularly from each bird and cultured for S. enteritidis. Although fecal shedding and egg yolk antibody production followed opposite patterns over time (fecal shedding was decreasing as egg yolk antibody titers were increasing), tests for both parameters were effective in predicting whether particular hens would lay contaminated eggs. Among hens that laid at least one egg contaminated by S. enteritidis, 82% were detected as infected by fecal culturing and 96% by the experimental egg yolk ELISA test. Using easily collected samples, egg yolk antibody testing offers a rapid and effective screening method for identifying S. enteritidis-infected laying flocks that might lay contaminated eggs.

Microsphere uptake by the intestine of White Leghorn chickens.

A study was conducted to determine the effective size for latex microsphere uptake in the intestine of white leghorn chickens. Three trials were conducted in which ligated intestinal segments of anesthetized 8-wk-old chickens were injected with 0.2-, 0.5-, 2-, 6-, 10-, or 20-mu diameter fluoresceinated latex microspheres. Microspheres were counted in brush border, epithelium, and lamina propria of each intestinal segment, liver, and spleen. After 1 hr, the 0.2-, 0.5-, and 2-mu microspheres were oriented along the brush border of epithelial cells and microsphere uptake into the epithelium and lamina propria was observed in the duodenum, ileum, cecum, cecal tonsil, and colon. Uptake of microspheres of 6, 10, and 20 mu diameter into epithelium and lamina propria was not observed in any intestinal segment. Also, no microspheres of any diameter were observed in sections of liver and spleen to suggest that there was no appreciable entry of microspheres into the bloodstream within 1 hr after administration. The results indicated that uptake of microspheres by the chicken intestine is a size-dependent process with microspheres < or = 2 mu being taken up to an equal extent by most segments of intestine.

World Health Organisation--supervised interlaboratory comparison of ELISAs for the serological detection of Salmonella enterica serotype Enteritidis in chickens.

A collaborative exercise, supervised by the World Health Organisation, was set up to compare ELISAs used for the serological detection of Salmonella enteritica serotype Enteritidis in chickens. The aim was to ascertain how far agreement could be reached on the interpretation of optical density readings for high titre, intermediate titre and low titre sera. Two sets of sera were sent to 14 participants. The first set compared high, medium and low titre sera raised in specified-pathogen-free and commercial broiler breeder chickens. The second set comprised 20 sera of different antibody titres raised in commercial birds reared under laboratory conditions and sent blind. Both indirect and double-antibody sandwich blocking ELISAs were used with a number of different detecting antigens. With a few exceptions good agreement was reached on the interpretation of results obtained from high and low titre sera from the optical density obtained with a single serum dilution. Differences were observed in the interpretation of medium titre sera. The results suggested that most ELISAs produce reasonably comparable results and that practical problems may arise from interpretation of the results mainly as a result of the choice of the criteria used for differentiating sera obtained from infected and uninfected chickens. These problems are discussed.

Microbiological analysis of the early Salmonella enteritidis infection in molted and unmolted hens.

A study was conducted in which the early kinetics (4 hr to 96 hr) of an infection by Salmonella enteritidis in older white leghorn hens was examined, and a molt was induced through withholding feed to determine its effect on the progression of this infection. Molted and unmolted hens were orally infected with 5-10 x 10(6) S. enteritidis on day 4 of the feed removal. At 4, 24, 48, 72, and 96 hr postinfection, liver, spleen, ileum, colon, cecum, and feces were removed from six hens per group and sampled for the presence of the challenge organism. By 24 hr postinfection, S. enteritidis was most prevalent in the cecum and feces of unmolted hens, and this prevalence continued throughout the experimental period. In molted hens, however, S. enteritidis could be detected in a high percentage (90-100%) of colon, cecum, and feces samples at 24 to 96 hr postinfection and in 67% or more of ileum samples at 48 to 96 hr postinfection, indicating a much wider distribution of the S. enteritidis along the intestinal tract than in unmolted hens. The numbers of S. enteritidis recovered from these alimentary samples were also significantly higher in molted than unmolted hens. S. enteritidis could not be detected in livers or spleens of either treatment group at 4 or 24 hr postinfection. At 48, 72, and 96 hr postinfection, 50% or more of the livers and spleens in both the molted and unmolted hens were positive for the challenge organism, but significantly more S. enteritidis was recovered from the organs of the molted hens at these three sampling times.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential diagnosis of infectious laryngotracheitis from other avian respiratory diseases by a simplified PCR procedure.

A simple polymerase chain reaction (PCR)-based procedure was developed for the detection of avian infectious laryngotracheitis virus (ILTV) in chicken trachea, chorio-allantoic membrane (CAM), infected hepatoma cells and infectious cell culture supernatant. Samples were prepared by dilution in distilled water. After boiling and low speed centrifugation, samples were used for PCR analysis with two primers without special labeling. The PCR analysis for ILT virus could be completed in less than 8 h. Standard agarose gel electrophoretic analysis of the PCR products revealed a prominent band of 300 base-pairs in samples from ILTV-infected specimens, but not from specimens containing Newcastle disease virus, infectious bronchitis virus, avian adenovirus, fowlpox virus, Pachecoz or Marek's disease virus. One single ILTV infected cell or 10 plaque forming units of ILTV could be detected with this procedure. The procedure can be used for the identification of ILTV and the differentiation of ILTV from other avian respiratory tract infectants.

Effect of two different molting procedures on a Salmonella enteritidis infection.

Previous studies have shown that inducing a molt using feed removal exacerbated an intestinal infection by Salmonella enteritidis (SE). The current study was conducted to determine whether inducing a molt using a molt diet would still cause a pause in egg laying but not exacerbate an intestinal SE infection. In Experiments 1 and 2, hens were either provided ad libitum access to layer feed (control), fed 45 g molt diet (molt-feed) daily, or deprived of feed for 14 d (molted), and were orally infected with 1 x 10(7) SE on Day 4 of molt. Egg lay ceased in hens subjected to both molt treatments. The percentage of hens shedding SE did not differ among treatment groups in Experiment 1, whereas in Experiment 2 the molted hens had significantly higher shed rates than the controls on Days 10, 17, and 24 postinfection and the molt-feed hens on Days 17 and 24 postinfection. Compared with both fed groups of hens, the molted hens shed significantly more SE in Experiment 1 on Day 10 postinfection, and in Experiment 2 the molted hens shed significantly more SE on all 4 sampling days. In Experiment 3, subgroups of hens within each treatment group received serial 10-fold dilutions of SE and intestinal shedding of the organism in each subgroup was determined 7 d later. The 50% infectious dose (ID50) was calculated for each treatment group from these shedding results.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of induced molting on the recurrence of a previous Salmonella enteritidis infection.

Previous work in the authors' laboratory had shown that hens infected with Salmonella enteritidis (SE) during the feed removal phase of an induced molt shed significantly more SE and more readily transmitted SE to uninfected hens in adjacent cages when compared with unmolted hens. A study was conducted to examine the effect of induced molting on the recurrence and horizontal transmission of a previous SE infection. Hens aged 59 and 69 wk in Trials 1 and 2, respectively, were infected with SE and then molted 21 days later. In Trial 1, more molted hens were SE-culture-positive on Days 38 (P < or = .005) and 45 (P < or = .005) postinfection, and these hens shed more SE on these days (P < or = .05 and P < or = .005, respectively) than unmolted hens. Horizontal transmission of SE to previously uninfected but contact-exposed hens in adjacent cages was also higher in the molted group than the unmolted group on Days 38 (P < or = .05) and 45 (P < or = .001). Molted, contact-exposed hens also shed significantly more SE than unmolted hens. In Trial 2, the molted infected hens shed progressively more SE than the unmolted hens but the differences were not significant. However, more molted contact-exposed hens became SE-positive at Day 31 (P < or = .05) and 38 (P < or = .005) and also shed more SE on these days (P < or = .05 and P < or = .01), respectively) than the unmolted hens. Serum and intestinal antibody titers to SE were also examined in Trial 2. Molting appeared to exert no effect on the serum SE titers, but antibody titers in the alimentary tract were lower in the molted hens than the unmolted hens on Days 45 (P < or = .005) and 52 (P < or = .05). In Trial 1, three of eight molted directly infected hens and two of eight molted contact-exposed hens produced any SE-contaminated eggs. In Trial 2, no SE-contaminated eggs were produced.