Veterinary medical research: a national resource.
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Animal Welfare↗
Biomedical subjects
O J Fletcher
Publications and source records attributed to O J Fletcher.
Effect of cold acclimation on the broiler chicks' resistance to dietary aflatoxin.
The effect of acclimation to environmental temperatures of 10 to 12 or 28 to 30 C on the resistance of broiler chicks to dietary aflatoxin was examined. Broiler chicks were acclimated from day-of-age for 2 wk to environmental temperatures of 10 to 12 or 28 to 30 C. On Day 14, a single oral dose of aflatoxin (8 mg per kg of body weight) was administered to 50 chicks in each environment. An increase in aflatoxin resistance, as assessed by survival rate, was conveyed by acclimation to cold temperatures. In each environmental chamber, a separate group of chicks was maintained for 2 additional wk, but those groups received 5 mg of aflatoxin per kg feed. By the end of the study, aflatoxicosis was characterized by: 1) a significant (P less than or equal to .05) decrease in body weight; 2) increases in spleen weight, liver weight, liver lipid, and liver dry-matter content; 3) changes in the serum levels of total protein, albumin, glucose, cholesterol, uric acid, potassium, phosphorus, iron and calcium; and 4) increased hepatic hyperplasia. Acclimation to 10 to 12 C was characterized by: 1) an increase in body weight, liver weight, spleen weight and bursa weight; 2) changes in the serum glucose and potassium levels; and 3) a decrease in glutamic-oxaloacetic transaminase activity. Significant aflatoxin by temperature interactions were evident only in serum levels of glucose and phosphorus, and in the serum activity of glutamic-oxaloacetic transaminase. These data suggest that acclimation to cool temperatures does not play a significant role in the resistance by broiler chickens to chronic aflatoxin exposure.
Adaptation, Physiological↗
Effects of dietary aflatoxin in aflatoxin-resistant and control lines of chickens.
The resistance to a single oral dose (12 mg of aflatoxin per kg of BW) and 4 wk of dietary aflatoxin (2.5 mg per kg of feed) were investigated in chicks selected for five generations for resistance to acute aflatoxicosis (AR) and unselected control (C) chicks. The AR chicks were more resistant to a single oral dose of aflatoxin and had significantly decreased sodium pentobarbital sleeping time compared to C chicks. Four-weeks exposure to dietary aflatoxin did not result in any significant change in BW or feed conversion ratios of chicks from either the C or AR line. However, more sensitive indicators of aflatoxicosis including plasma total protein, albumin, cholesterol concentrations, and gamma glutamyl transferase activity were significantly altered in C chicks but not in AR chicks fed aflatoxin. Percentages of liver lipid and liver hyperplasia score were also significantly altered as a result of dietary aflatoxin treatment in C but not AR chicks. These data indicate that selection-associated differences exist between the C and AR lines of chickens that convey resistance to not only a single oral dose of aflatoxin but also to a more chronic dietary exposure to aflatoxin.
Aflatoxins↗
Marek's disease virus-induced transient paralysis in chickens: demonstration of vasogenic brain oedema by an immunohistochemical method.
The presence of vasogenic brain oedema and its distribution in Marek's disease virus (MDV)-induced transient paralysis (TP) were determined in genetically resistant and susceptible inbred White Leghorn chickens. MDV-inoculated TP-susceptible chickens with nervous signs (9 days post-inoculation) had severe vacuolation of cerebellar white matter and associated diffuse leakage of albumin and IgG. The serum protein leakage was associated morphologically with a vasculitis and intramural pseudocyst formation in the walls of blood vessels cuffed by mononuclear cells. This transient vasculitis and resulting vasogenic oedema coincided with the temporary neurological signs seen in TP-susceptible chickens. The vasculitis and vasogenic oedema were not present in brain tissue from recovered MDV-inoculated TP-susceptible chickens, MDV-inoculated TP-resistant chickens, or uninoculated control chickens from either line.
Animals↗
Marek's disease virus-induced transient paralysis in chickens: alterations in brain density.
The presence of brain edema and its distribution in Marek's disease virus (MDV)-induced transient paralysis (TP) was determined in genetically resistant and susceptible inbred White Leghorn chickens. Density measurements on samples from the cerebellum, cerebral cortex, optic chiasm, and optic lobe were determined on continuous density Percoll gradients. At 9 days post inoculation of MDV, the cerebellums from the susceptible line of chickens were significantly less dense than cerebellums from the resistant line or the controls of either line. The cerebellar edema, as measured by tissue density, coincided with the transient neurological symptoms and was not present in brain tissue from clinically recovered TP birds.
Animals↗
Feed refusal in swine fed ochratoxin-contaminated grain sorghum: evaluation of toxicity in chicks.
In an episode of feed refusal in a swine herd, feed specimens were found to be contaminated with mycotoxin. Grain sorghum, the chief ingredient of the swine diet, was found to be the source of contamination and contained 5 mg of ochratoxin/kg of feed. Incorporation of the grain into poultry diets induced renal and hepatic lesions, reduced weight gains, decreased feed utilization, and altered serum uric acid, blood urea nitrogen, and serum creatinine concentrations in chicks.
Animal Feed↗
Togavirus-like agent in SPF chick cell cultures.
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Animals↗
Suppression of humoral immunity in chickens with carrageenans.
Carrageenans (CGN), sulphated polygalactans, have been reported to be cytotoxic for macrophages in vitro. On this basis, the effect of the 3 major CGN types on humoral immune responses in chickens was investigated. Carrageenan had no effect on body and lymphoid organ weights. Histologically, CGN produced a significant proliferation of reticuloendothelial cells in liver and spleen, but no changes were observed in lymphocyte populations of the bursa of Fabricius, thymus, or spleen. Intracoelomic pretreatment with high doses of CGN induced a marked suppression of primary responses to sheep red blood cells (SRBC) given by the same route. However, if SRBC were injected intravenously into chickens already treated intracoelomically with CGN, no evidence of suppression was demonstrated. Antibody responses to Brucella abortus (BA), a T-independent antigen, were not affected by intracoelomic treatment with CGN. Intravenous pretreatment with CGN did not alter antibody responses to SRBC and BA given by the same route.
Animals↗
Influence of ochratoxin A and vanadium on various parameters in growing chicks.
The effects of ochratoxin A (OA) and vanadium (V) singly and in combinations, at levels that could be encountered under field conditions, were determined in male Leghorn chicks. The chicks were fed a control diet containing the following additives: none; 12.5 mg V/kg; 25.0 mg V/kg; 2.5 mg OA/kg; 2.5 mg OA plus 12.5 mg V/kg; and 2.5 mg OA plus 25.0 mg V/kg. These data show that V, singly at levels of 12.5 or 25.0 mg/kg of diet, did not adversely affect body weight gain at 1, 2, 3, or 4 weeks of age. Body weight gains of the chicks receiving the diets containing OA singly were significantly lower than the controls except during the 1- to 7-day period. Body weight gains of chicks receiving the OA in combination with either level of V were significantly lower than any of the other groups during the 1- to 7- and 22- to 28-day periods. The quantity of feed required per unit of gain was increased slightly by the addition of OA at 2.5 mg/kg and the addition of V at 12.5 or 25.0 mg/kg and, to a greater extent, by the OA-V combinations. The relative liver and kidney weights were higher in the groups receiving OA singly or in combination with V. When compared to the controls, relative gizzard weights were significantly higher in the two combination groups; whereas the relative proventriculus weights were significantly higher only in the group receiving the 2.5 mg OA plus 25.0 mg V/kg combination.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Toxicity of ochratoxin A and vanadium to growing chicks.
The effects of ochratoxin A (OA) and vanadium (V), singly and in combination, were determined in male Leghorn chicks from 1 to 28 days of age. The chicks were fed a control diet containing the following additives: A) none; B) 2.5 mg OA/kg; C) 50 mg V/kg; D) 2.5 mg OA plus 50 mg V/kg. These data show that body weight gains were significantly reduced by OA and V singly, and a toxicity-enhancing synergism exists between OA and V, which caused a further reduction in performance. The OA-V combination caused a significant increase in the relative weights of the liver, kidney, gizzard, and proventriculus and a significant decrease in the relative weights of the bursa of Fabricius. This decrease in bursal weight was due to atrophy of lymphoid follicles as indicated by the increase in the histologic lesion score. Uric acid in serum was increased, and albumin, calcium, and phosphorus were decreased in the OA-V combination group. There were also small but significant changes in the hematological parameters measured. Distribution of OA to the liver and kidney was not altered, nor was the distribution of V to the liver, kidney, or muscle tissue. Histologic lesions in kidneys were mild but were more prevalent in chicks in the OA-V combination group.
Animal Feed↗
Performance of broiler progeny of breeder flocks vaccinated with inactivated oil emulsion malabsorption syndrome virus vaccine.
Broiler breeder pullets were vaccinated at 20 to 24 weeks of age with an inactivated, oil emulsion vaccine containing the CO8 strain of avian reovirus. The vaccination induced a high and uniform antibody response that peaked 4 to 5 months postvaccination and persisted up to 11 months postvaccination. Broiler production parameters in progeny of vaccinated breeders were compared weekly with parameters of the total broiler production. There was a consistent improvement in body weight at processing time and a reduction in total production cost in progeny of vaccinated parents. There was also a reduction of percent of parts condemned during the first part of the trial. There were no consistent differences in feed conversion or condemnation of whole carcasses. Progeny of vaccinated parents had reduced livability. This effect was interpreted to be due to the smaller egg size of young breeder flocks.
Animals↗
Evaluation of cytopathologic changes induced in chicken tracheal epithelium by Mycoplasma gallisepticum in vivo and in vitro.
Changes in tracheal epithelial surfaces induced by Mycoplasma infection in vivo and in vitro included release of mucous granules followed by exfoliation of ciliated and nonciliated epithelial cells. Light microscopy, scanning electron microscopy, and transmission electron microscopy confirmed that the loss of cilia from individual cells was infrequent. Epithelial cells typically lost their intercellular connections, rounded up, exfoliated, and then lysed--giving rise to a population of cellular organelles, such as mitochondria and cilia intermixed with mucus to form the exudate found within the tracheal lumen. Repair of the epithelial surface was effected by basilar epithelial cells differentiating and filling in the spaces formed by exfoliated cells. These cells were hypertrophied, nonciliated at 14 days after infection in vivo, and covered with microvilli. In sectioned material obtained during the infection, there was increasing epithelial thickness due to cellular infiltration and edema. Tracheal rings in vitro showed similar changes to those seen in vivo, except that exfoliation was more severe and occurred earlier. In addition, there were no cellular infiltration due to the lack of a vascular supply and only a small amount of mucus due to the smaller number of mucous cells available to release into the tracheal lumen.
Animals↗
Variation in histology and growth characteristics of transplantable Marek's disease lymphomas.
A comparative study was made of the histology and growth characteristics of three different Marek's disease virus-induced transplantable lymphomas. These lymphomas were developed previously in related inbred chicken lines G-B1 and G-B2. The UG1 lymphoma was developed by serial i.m. passage in G-B1 chickens, and the UG2 and UG4 lymphomas were developed similarly in G-B2 chickens. While all three lymphomas grow progressively and cause rapid death in syngeneic hosts, differences in pathogenicity exist. For equivalent passage levels, the mean time to death of syngeneic chickens inoculated with 10(5) lymphoma cells was 10.8, 12.8, and 16.3 days postinoculation for UG1, UG2, and UG4, respectively. Histological features examined at the light microscopic level included tumor necrosis, muscle invasion, mitotic activity, and presence of heterophils (comparable to mammalian neutrophils). The UG2 lymphoma was characterized by a high degree of necrosis during all stages of growth. This feature was least pronounced in UG4 lymphomas, which generally grow to a much larger size than UG1 or UG2 lymphomas. Vascular invasion was a feature of UG2 lymphoma cells in skeletal muscle and may account for the necrosis. The UG2 cells, which are somewhat larger than UG4 cells, occasionally contained cytoplasmic vacuoles. While the number of heterophils was highest in early stages of UG2 tumors, the role of these cells is unclear. The findings provide the basis for utilizing the transplantable lymphomas as a model to study mechanisms underlying variable pathogenicity of malignant tumors.
Animals↗
Quantitation of intestinal D-xylose absorption in normal turkeys.
Both a standard method and a modified micromethod of quantitating intestinal D-xylose absorption were successfully performed in turkeys. Absorption peaks and curves for both tests closely resembled those observed in humans. The micromethod was preferred because it could be performed in poults as young as 3 days of age, required a smaller sample size, and was more economical and less time-consuming. Both tests were suitable for experimental and clinical determination of small intestinal absorptive function in the turkey.
Animals↗
Vaccination against Marek's disease and infectious bursal disease. II. Titration and in vivo efficacy of the coinfection-derived bivalent live vaccine for turkey herpesvirus and infectious bursal disease virus.
The bivalent HVT/IBDV live vaccine, developed by cocultivation of the turkey herpesvirus (HVT) and infectious bursal disease virus (IBDV) vaccine in cell cultures, was quantitated. The titer of each constituent virus could be successfully determined in vitro by pretreatment of the vaccine with anti-IBDV serum or chloroform (CHCl3). Studies in vivo further demonstrated that the anti-IBDV serum-treated HVT/IBDV vaccine lost its immunogenicity by failing to induce IBDV-neutralizing antibody or to protect vaccinates from bursal atrophy after challenge exposure to infectious bursal disease. The CHCl3 treatment significantly reduced the efficacy of the vaccine to protect vaccinates against Marek's disease challenge.
Animals↗
Vaccination against Marek's disease and infectious bursal disease. I. Development of a bivalent live vaccine by co-cultivating turkey herpesvirus and infectious bursal disease vaccine viruses in chicken embryo fibroblast monolayers.
Vaccine viruses of Marek's disease (MD), the FC-126 strain of the herpesvirus of turkeys (HVT), and infectious bursal disease (IBD), the Bursa-Vac-M strain of IBD virus (IBDV), were propagated in the same chicken embryo fibroblast (CEF) monolayers by superinfection. Co-infection of the two viruses in the same CEF culture or in a single cell can be demonstrated by staining with acridine orange and by electron microscopy.l This study was conducted with a superinfected live bivalent vaccine (HVT/IBDV) in one-day-old specific pathogen-free (SPF) and conventional White Leghorn (CWL) chicks. Chickens vaccinated with HVT/IBDV produced persistent HVT viremia for at least 6 weeks postvaccination; significantly higher IBD virus neutralizing antibody levels were observed for the entire 8-week experimental period when compared to unvaccinated controls. Differences between virus neutralizing antibody titers stimulated by HVT/IBDV and IBDV alone were not statistically significant in SPF chickens; however, due to maternal antibody there were some significant differences in CWL chickens. Both the HVT/IBDV bivalent vaccine and the monovalent IBDV vaccine protected the chickens against challenge with virulent IBDV. Based on microscopic lesions and bursa: body weight indexes, challenge of vaccinated chickens with virulent IBDV caused no atrophy in the bursa of Fabricius, but severe tissue destruction was observed in unvaccinated challenged controls. Chickens vaccinated with HVT/IBDV vaccine or with HVT alone were effectively protected against MD when compared to the controls.
Animals↗
Tissue residues of dietary cadmium in wood ducks.
One-week-old wood ducks were fed cadmium in diets containing 18 or 30% protein for a period of three months. Seven drakes from each group were sacrificed, and blood, brain, muscle, kidney, liver, and wing feather tissues were collected and analyzed for cadmium. Highest cadmium concentrations were found in the kidney, liver, and feather tissues; blood, muscle, and brain cadmium residue levels were undetectable. Except in the kidney tissue, protein level of the diet did not affect cadmium residue levels. For birds that were changed to a cadmium-free, high-protein ration at 13 weeks of age, regression analysis indicated a significant decrease in cadmium residue levels for the kidney tissue only. Growth, as measured by bodyweight at 13 weeks of age, was not affected by the various cadmium treatment levels. Histopathological examination revealed lesions in the kidney tissues of the 100 ppm cadmium treatment groups, which were more severe in those birds receiving the 18% protein diet. Vacuolation of the pancreatic acinar cells was observed in all groups, but tended to occur more frequently in the higher cadmium level groups.
Animals↗
Serological responses to Mycoplasma synoviae in chickens infected with virulent or avirulent strains of Marek's disease virus.
The pathogenicity and immunosuppressive capability of five strains of Marek's disease herpesvirus (MDHV) was examined. Three of the strains (ALA, MISS, NCS) were isolated from flocks experiencing vaccine breaks while the other two strains (GA, HN) represented prototype virulent and avirulent viruses. Pathogenicity of MDHV strains was evaluated on their ability to cause mortality, their ability to cause gross or microscopic lesions, and the median latent period to death (MLPD) for each strain. Antibody responses to Mycoplasma synoviae (MS) were tested by the serum plate agglutination and hemagglutination inhibition tests. Chicks infected with the virulent strains of MDHV had greater mortality, greater lesion incidence, and shorter MLPD that did chicks infected with the avirulent HN strain. Infection with virulent strains reduced the antibody response to MS and caused severe bursal lesions. Chicks infected with the avirulent HN strain exhibited a slight immunosuppression, but they had no evidence of bursal destruction.
Animals↗