Robert E. Porter

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.

Microbiological and Histopathological Effects of an Induced-Molt Fasting Procedure on a Salmonella enteritidis Infection in Chickens

A study was undertaken to determine if a 2-week feed-removal protocol, as is used by industry to induce a molt in aging hens, would affect the course of a Salmonella enteritidis infection. White leghorn hens aged 69-84 weeks were deprived of feed to induce a molt, and on day 4 of the fast, the birds were orally infected with 5 x 10(6) S. enteritidis. S. enteritidis organisms were enumerated in the spleen on day 6 and from the alimentary tract on days 7, 14, 21, 28, and 35. Little difference was detected in numbers of S. enteritidis from spleens of molted and unmolted hens. Significantly more molted hens shed detectable intestinal S. enteritidis than unmolted hens on day 14 (one of two trials) and day 21 (one of two trials). Intestinal levels of S. enteritidis were increased 100- to 1000-fold in the molted birds on day 7 (one of two trials) and day 14 (two of two trials), and many of the hens exhibited bloody alimentary secretions. Histological examination of the intestinal tract of S. enteritidis-infected molted hens showed increased inflammation in the epithelium and lamina propria of colons and ceca, compared with unmolted infected hens.

Oral vaccination with alginate microsphere systems

Abstract Oral vaccination is a simple, efficient way of inducing immunity at mucosal surfaces. The slow development of oral vaccines has been mainly due to the lack of suitable delivery systems. We have used hydrogel microspheres to deliver various vaccines to several animal species by oral administration. Oral delivery of vaccines using alginate microspheres elicited the production of secretory IgA (sIgA) at the mucosal surfaces in mice, rabbits, and cattle. Oral vaccination of chicken resulted in an increased delayed-type hypersensitivity, a cell-mediated immune response, indicating a positive response to the vaccine. Our studies have clearly shown that alginate microspheres are effective for the oral administration of vaccines.

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)

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.

Diagnosis of Myeloid Leukosis Induced by a Recombinant Avian Leukosis Virus in Commercial White Leghorn Egg Laying Flocks

SUMMARY. 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.

Use of a pilocarpine-based lavage procedure to study secretory immunoglobulin concentration in the alimentary tract of White Leghorn chickens.

A lavage procedure was used to study the kinetics of alimentary fluid IgA concentration in 15 specific-pathogen-free white leghorn chickens for 8 weeks post-hatch. Lavage solution was administered orally and collected from the distal alimentary tract following an intraperitoneal injection of pilocarpine. Concentrations of IgA, quantitated by enzyme-linked immunosorbent assay, were more than 0.04 mg/ml by 3 weeks and were negligible before this age. This level gradually increased over the next 5 weeks, peaking at nearly 0.4 mg/ml at 8 weeks of age. Alimentary lavage was easy to perform, required no necropsy or surgical manipulation, and facilitated repeated collection of alimentary fluid from live birds. Repeated lavage did not alter concentrations of IgA and IgG in alimentary fluid, and concentrations of IgA and IgG in alimentary fluid were stable during incubation at 37 C for 24-48 hr.

Isolation and Characterization of a Turkey Arthritis Reovirus

SUMMARY. During the spring and summer of 2011, the Minnesota Veterinary Diagnostic Laboratory at the University of Minnesota received 14 submissions of 15-to-18-week-old tom turkeys that were recumbent with wing tip bruises (“wing walkers”) and uni- or bilateral swelling of the hock (tibiotarsal) joints. Gastrocnemius or digital flexor tendons were occasionally ruptured. A total of five turkey arthritis reoviruses (TARV-MN1 through TARV-MN5) were isolated in specific-pathogen-free embryonated chicken eggs and QT-35 cells. The identity of the isolates was confirmed by electron microscopy, reverse transcription-polymerase chain reaction, and gene sequence analysis. BLAST analysis on the basis of a 880 bp nucleotide sequence of the S4 gene confirmed all isolates as a reovirus. Phylogenetic analysis divided the five isolates into two subgroups: subgroup I containing TARV-MN1, -2, -3, and -5, and the other subgroup containing TARV-MN4. Isolates in subgroup I had a similarity of 97%–100% with each other, while subgroup II (TARV-MN4) had a similarity of only 89.2% with subgroup I viruses. This isolate showed 90%–93% similarity with turkey enteric reoviruses in the United States, while the other four isolates in subgroup I had 89%–97.6% similarity. These results indicate divergence within TARVs as well as from enteric viruses, which needs to be confirmed by complete genome sequence analysis. Further experimental studies are planned to determine the role of these isolates in turkey arthritis and to compare them with classical chicken reovirus. RESUMEN. Aislamiento y caracterización de un reovirus asociado con artritis en pavos. Durante la primavera y el verano del año 2011, el Laboratorio de Diagnóstico Veterinario el Estado de Minnesota en la Universidad de Minnesota recibió 14 casos de pavos machos de 15 a 18 semanas de edad, que mostraron recumbencia con moretones en la punta del ala (“aves que caminan con las alas”) e inflamación de la articulación del corvejón (articulación tibiotarsal) uni o bilateral. Ocasionalmente, los tendones del músculo gastrocnemio o flexores digitales se observaron rotos. Un total de cinco reovirus asociados con artritis en pavos (denominados TARV-MN1 al TARV-MN5) se aislaron en huevos embrionados de pollo libres de patógenos específico y en células QT-35. La identidad de los aislados se confirmó mediante microscopía electrónica, por transcripción reversa y reacción en cadena de la polimerasa, y por el análisis de secuencias. Mediante el análisis con la base de datos BLAST de las secuencias de nucleótidos de productos de 880 pares de bases que incluían al gene S4 confirmaron a todos los aislamientos como reovirus. El análisis filogenético dividió a los cinco aislamientos en dos subgrupos: subgrupo I que contenía a los virus TARV-MN1, TARV-MN2, TARV-MN3 y TARV-MN5 y el otro subgrupo que incluía al virus TARV-MN4. Los aislados en el subgrupo I mostraron una similitud de 97% -100% entre ellos, mientras que el subgrupo II (TARV-MN4) mostró una similitud de sólo 89.2% con los virus de subgrupo I. Este aislamiento mostró una similitud de 90%–93% con reovirus de pavo entéricos en los Estados Unidos, mientras que otros cuatro aislados en el subgrupo I mostraon una similitud de 89%–97.6%. Estos resultados indican divergencia dentro de los reovirus asociados con artritis en pavos, así como de los virus entéricos, lo cual debe ser confirmado por el análisis de las secuencias completas del genoma. Se han planeado otros estudios experimentales para determinar el papel de estos aislamientos en la artritis de los pavos y compararlas con reovirus de pollo clásicos.

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.

The occurrence of enteric viruses in Light Turkey Syndrome

Two studies were conducted to determine the role of enteric viruses in Light Turkey Syndrome (LTS), which is characterized by lower weight in market age turkeys than their standard breed character. In the surveillance study, we selected four LTS and two non-LTS turkey flocks in Minnesota and collected faecal samples at 2, 3, 5 and 8-weeks of age. Astrovirus, rotavirus, and reovirus were detected alone or in various combinations in both LTS and non-LTS flocks. No coronavirus was detected in LTS flocks and no corona- or reovirus was detected in non-LTS flocks. In the second study, 2-week-old turkey poults were divided into two groups; Group A (challenged) was inoculated orally with 10% pooled faecal suspension from LTS flocks and group B (control) was inoculated with phosphate buffered saline (PBS). Clinical signs of depression, huddling, and lack of uniform size were observed in the challenged group but not in the control group. diarrhoea was observed in both groups but was more severe in the challenged group than in the control group. Birds in the challenged group shed astrovirus, rotavirus and reovirus, while the control group shed only astrovirus. Virus shedding in both groups was observed for up to nine weeks of age. Significantly lower body weights were seen in the challenged group starting at seven weeks of age and lasting until 20 weeks of age. These findings suggest that viral enteritis at an early age may set up conditions for the development of LTS in adult turkeys.