Biomedical subjects

P C Allen

Publications and source records attributed to P C Allen.

At least 19 recordsLinked to original sources

PubMed2003

The effect of dietary betaine on intestinal and plasma levels of betaine in uninfected and coccidia-infected broiler chicks.

Chicks fed betaine supplemented diets and infected with Eimeria acervulina and Eimeria maxima had markedly higher levels of betaine in the duodenum and mid-gut than unsupplemented, infected chicks. Uninfected chicks fed betaine exhibited almost twice the levels of betaine in the gut as infected chicks. Plasma betaine levels were lower in E. maxima-infected chicks than in E. acervulina-or Eimeria tenella-infected chicks. Betaine supplementation reversed the decrease in weight gain in E. maxima- infected chicks but had no effect on the decrease in weight gains in E acervulina- and E. tenella-infected chicks. Coccidia-infected birds on normal diets regularly exhibit increases in plasma NO(2)(+)NO(3). This increase was abolished in E.tenella-infected birds on betaine supplement. Betaine feeding did not alter this effect in E. acervulina- and E. maxima-infected birds. Results indicate that betaine supplementation has a positive effect on gut betaine levels in birds infected with E. acervulina and E. maxima. In all treatment groups, infection lowered the levels of betaine.

Animals↗

PubMed2003

Mapping quantitative trait loci associated with resistance to coccidiosis and growth.

To map QTL associated with disease resistance to avian coccidiosis and growth, two commercial broiler lines with different degrees of resistance to the disease were crossed to generate an F1 generation that was intercrossed to produce 314 F2 generation offspring. The F2 offspring were inoculated with sporulated oocysts of Eimeria maxima. Five disease-associated phenotypes were measured after the infection. Intertrait comparisons revealed that oocyst shedding was a good parameter for evaluating disease resistance or susceptibility. One hundred nineteen microsatellite markers, covering 80% of the chicken genome with an average marker interval of 25 cM, were used for genotyping of F1 parents and F2 offspring. Statistical analysis based on the data of four families revealed a locus on chromosome 1 associated with oocyst shedding (logarithm of odds = 3.46). The genetic mechanism of this locus appeared additive. The genomic scan also identified three potential growth QTL on chromosomes 1, 6, and 8. These results provide the foundation for further investigation to validate the QTL.

Animals↗

PubMed2002

Interaction of dietary vitamin E with Eimeria maxima infections in chickens.

In two trials, broiler chickens, processed similarly to those placed in commercial operation, were fed, from 1 d of age, a range (13 to 200 ppm) of DL-alpha-tocopheryl acetate (VE-AC) levels, and the effects on the pathology of Eimeria maxima infections were assessed at 6 d postinoculation (PI). In Trial 1, dietary levels of VE-AC had little significant effect on variables characterizing pathology except for the number of oocysts shed, which was significantly increased in chicks treated with higher VE-AC levels. The infection was judged to be mild based on moderate lesion scores (2.2+/-0.2), lack of significant effects on weight gain (7+/-1.6% decrease), moderate reduction in plasma carotenoids (21+/-2%) and small increases in plasma NO2-+NO3- (141+/-12%). In uninfected and infected chickens, plasma alpha-tocopherol (AT) increased with dietary levels of VE-AC; however, E. maxima infection caused a fairly constant decrease in AT of 35.3+/-3.2% across these levels. Plasma gamma-tocopherol (GT) levels were unaffected by dietary VE-AC or E. maxima infection. In Trial 2, pathology, again, was relatively unaffected by dietary VE-AC level. The infection was judged to be severe based on lesion scores (3.5+/-0.1), reduction in weight gain (30.7+/-3%), plasma carotenoids (72.4+/-1.5%), uric acid (16.3+/-3.4), albumin (37.8+/-2.8%), large increases (261+/-8%) in plasma NO2-+NO3-, and high numbers of oocysts shed per chick (4.12+/-0.4 x 10(7)). Plasma AT again increased with increasing dietary VE-AC levels in uninfected and infected chicks, but the mean decrease across VE-AC levels caused by E. maxima infection was 73.14+/-3.3%. GT levels were erratic and unrelated to dietary VEAC or infection. Thus, in processed broiler chickens, high dietary VE-AC did not prevent or lessen the pathology caused by mild or severe infections with E. maxima. The main effect of E. maxima infection appeared to be reduction in plasma AT levels. We postulate that this reduction may be due to malabsorption of AT, which results from physical damage to the absorptive mucosa, reduction in esterases required to hydrolyze the VE-AC, and a generalized lipid malabsorption, preventing movement of the free AT to circulating blood and infected tissues.

Animal Feed↗

PubMed2002

Recent advances in biology and immunobiology of Eimeria species and in diagnosis and control of infection with these coccidian parasites of poultry.

Avian coccidiosis, an intestinal disease caused by protozoan parasites of the genus Eimeria, occurs worldwide. It is considered to be one of the most economically important diseases of domestic poultry. For many years, prophylactic use of anticoccidial feed additives has been the primary means of controlling coccidiosis in the broiler industry and has played a major role in the growth of this industry, which now can produce about 7.6 billion chickens annually. However, development of anticoccidial resistance has threatened the economic stability of the broiler industry. Although there has been little effort by the pharmaceutical industry to develop new anticoccidials, the mounting problem of drug resistance of Eimeria species has prompted major research efforts to seek alternative means of control through increased knowledge of parasite biology, host response, and nutritional modulation. As a consequence, important advancements have been made, particularly in defining parasite antigens that have potential use in vaccines, defining the Eimeria genome, understanding the immunology of coccidial infections, and the practical applications of live vaccines. This review describes the progress in these areas, most of which has occurred within the past 10 to 15 years.

Animals↗

PubMed2001

Eimeria tenella infection in chickens: effect on plasma and muscle 3-methylhistidine.

To assess muscle breakdown during avian coccidiosis, the level of the nonmetabolizable amino acid 3-methylhistidine (3MH) was determined in muscle and plasma from chickens infected with the cecal parasite Eimeria tenella. The change in 3MH level during infection was determined in birds, each inoculated with 0 to 200,000 sporulated oocysts. The effect of levels of parasitism was evaluated at 6 d postinoculation. The 3MH levels of plasma and muscle were determined by HPLC after derivatization with fluorescamine. Weight gains, packed cell volumes, and gross lesion scores were also determined. E. tenella infected birds with lesion scores of 3 or 4 had significantly elevated plasma and muscle 3MH, whereas infected birds with lesion scores of 0, 1, or 2 did not have elevated plasma and muscle 3MH; however, there was a linear inverse relationship between weight gain and both plasma and muscle 3MH. The results suggested that muscle breakdown, as assessed by plasma and muscle levels of 3MH, was elevated during the acute stage of E. tenella infection and was most likely associated with anorexia caused by infection. However, the correlation of 3MH levels with severity of infection was not as strong as that previously observed for E. acervulina infection, most likely due to the differences in pathology caused by the two species.

Animals↗

PubMed2000

Effect of Eimeria acervulina infections on plasma L-arginine.

As part of a program to study the pathological effects of coccidia infections on growth, we have examined the relationship of plasma L-arginine (ARG) levels to infective doses of Eimeria acervulina and infection-associated changes in weight gain, plasma carotenoids, and plasma NO2- + NO3-. Chickens consuming a starter ration containing 1.68% ARG were infected with a range of doses of E. acervulina. At 6 d postinoculation (PI), weight gains were significantly reduced by infections with 5 x 10(5) and 1 x 10(6) oocysts per chick (OPC). Gross lesion scores of chickens infected with 5 x 10(4) through 1 x 10(6) OPC were significantly greater than scores of chicks infected with 1 x 10(3) OPC. Compared with levels from uninfected controls, plasma NO2- + NO3- concentrations were significantly increased by infection with 5 x 10(5) and 1 x 10(6) OPC, plasma concentrations of ARG were significantly decreased by infection with 5 x 10(4) through 1 x 10(6) OPC, and plasma carotenoids were significantly decreased by all infection doses. Plasma arginine was significantly correlated with plasma carotenoids (P > 0.0187), but not with infection dose or weight gain; plasma NO2- + NO3- was positively correlated (P > 0.0043) with infection dose and negatively correlated (P > 0.0158) with weight gain. Regression analysis of the measured variables indicated that the strongest relationship existed between plasma ARG and carotenoids. This finding suggests that in this infection model, reduction in plasma ARG is most likely associated with nutrient malabsorption that accompanies infection and is likely not significantly impacted by synthesis of nitric oxide that is associated with the immune response.

Animals↗

PubMed2000

Effects of nutritionally balanced and stabilized flaxmeal-based diets on Eimeria tenella infections in chickens.

Twenty Sex Sal cockerels were randomly assigned to each of eight groups; each of four nutritionally balanced diets were fed to two groups from 1 d through 4 wk of age. These diets contained 0, 2, 5, or 10% stabilized flaxseed meal that provided a calculated 0, 0.45, 1.11, or 2.22% n-3 fatty acids, primarily linolenic acid. At 3 wk of age, one group of chickens from each diet treatment was infected with Eimeria tenella and was housed in separate but similar conditions to uninfected control chickens. At 6 d postinfection, chickens were weighed, bled, killed, and scored for lesions. No level of dietary flaxmeal tested provided protection against weight gain depression, increased feed conversion ratios, or lesions. We concluded that these diets did not protect against E. tenella infection because levels of linolenic acid were not high enough, and the oxidative potentials were well suppressed by vitamin E and other stabilizers present.

Animal Nutritional Physiological Phenomena↗

PubMed2000

Analysis of disease resistance-associated parameters in broiler chickens challenged with Eimeria maxima.

To determine an optimal dose for coccidial inoculation and to evaluate genetic resistance or susceptibility in individual chickens, broilers were inoculated with four different doses of Eimeria maxima oocysts. Body weight gain, fecal oocyst shedding, concentrations of plasma NO2- + NO3-, carotenoid, and interferon-gamma were measured at two different time periods postinfection. The results showed significant dose and sex effects on most parameters and interaction between dose and sex in some parameters. The dose effects were generally linear; however, some significant quadratic effects were also observed. The measurements from chickens inoculated with 10(4) oocysts displayed the highest correlation coefficients among oocyst shedding, body weight gain, and concentrations of carotenoid and NO2- + NO3-. An infection index, calculated from the correlated parameters, displayed high correlation coefficients with the parameters. The infection index may be a better parameter for evaluating individual genetic resistance against coccidial infection.

Animals↗

PubMed2000

Effects of treatments with cyclooxygenase inhibitors on chickens infected with Eimeria acervulina.

Reduced weight gains and feed conversions are major sources of economic losses from avian coccidiosis. Experiments were conducted to determine possible involvement of up-regulation of cyclooxygenase (COX) activity during coccidia infections that might contribute to reduced weight gain. In a series of trials, young (3 to 5 wk of age) cockerels infected with Eimeria acervulina, a duodenal parasite, received oral treatments with indomethacin (IM), an inhibitor of both COX-1 and COX-2, or nimesulide (NIM), a specific inhibitor of COX-2. Infection doses varied with experiment (from 10(5) to 10(6) oocysts per chick). Effects of infection on weight gain, duodenal lesions, plasma carotenoids, and levels of NO2+ NO3- were determined at 6 d postinoculation. Total oocysts were enumerated in feces collected from 5 through 8 d postinoculation from separate replicate groups. In no trials did treatment with IM reverse effects of infection on weight gain or significantly reduce lesion scores. However, in all trials, IM treatment reduced oocyst output per chick (Trial 1, 15%; Trial 2, 19%; Trial 3, 53%; Trial 4, 29%; Trial 5, 28.5%). Supplementation of feed with 400 and 100 ppm NIM significantly reduced weight gain of, and increased oocyst output from, infected chicks, whereas supplementation with 50 ppm NIM had no beneficial effects on weight gain or lesion scores, but reduced oocyst shedding. The inability of the IM and NIM treatments to reverse infection-associated weight gain suppression suggests that this pathological effect is not linked to increased prostanoid synthesis as a result of COX-2 up-regulation during infection. The inhibitory effects of IM treatment on oocyst shedding suggest that COX-2 products may have immunosuppressive effects in coccidia infection at local sites of infection. The stimulating effects of high-dose NIM treatments on oocyst shedding suggest that this compound may inhibit synthesis of other prostanoids as well.

Animals↗

PubMed2000

Eimeria acervulina infection elevates plasma and muscle 3-methylhistidine levels in chickens.

To assess muscle breakdown during avian coccidiosis, the level of the nonmetabolizable amino acid 3-methylhistidine (3MH) was determined in muscle, plasma and excreta from chickens infected with Eimeria acervulina. The changes in 3MH levels during infection were assessed at 1-29 days postinoculation (DPI) in animals given 5 x 10(5) oocysts per bird. The effect of levels of parasitism were evaluated at 8 DPI in birds receiving 5 x 10(3), 5 x 10(4), 5 x 10(5) or 1 x 10(6) oocysts each. The 3MH levels of plasma, muscle, and excreta samples were determined by high-pressure liquid chromatography after derivatization with fluorescamine. Weight gains, breast muscle weight, eviscerated weight, plasma carotenoid levels, dry weight of muscle, and gross lesion scores were also determined. Infected birds had significantly elevated plasma and muscle 3MH at 4 and 8 DPI following a single dose of E. acervulina. The increase in 3MH levels had an inverse relationship with the time course of weight gain and plasma carotenoid levels. Plasma and muscle 3MH levels returned to control values by 15 DPI and remained unchanged from control values through the remainder of the experiment (29 DPI). Breast weight was decreased in infected birds, but the ratio of breast weight to eviscerated body weight was unchanged. Excretion of 3MH decreased relative to controls at 4 and 8 DPI and returned to control levels on 15 DPI. The plasma and muscle levels of 3MH were related to severity of infection; however, levels of excreted 3MH were not. The results suggested that muscle breakdown, as assessed by plasma and muscle levels of 3MH, increased during the acute stage of E. acervulina infection. The underlying causes for this muscle breakdown was unclear but could involve a physiological response to anorexia and decreased food intake during the acute phase of infection. Levels of excreted 3MH did not increase during infection and this may be the result of decreased excreta output during infection. Plasma and muscle levels of 3MH were correlated with severity of E. acervulina infections but may not be as sensitive an indicator of infection as plasma carotenoid levels or other physiological parameters.

Animals↗

PubMed1999

Effects of daily oral doses of L-arginine on coccidiosis infections in chickens.

L-arginine is an essential amino acid for chickens, as well as the substrate for biosynthesis of nitric oxide (NO), a bioregulatory free radical molecule known to have antimicrobial activity. Biosynthesis of NO by induced nitric oxide synthase (iNOS) can be stimulated during immunological response to infection. Therefore, in chickens, production of NO as a response to an infection should be influenced by dietary levels of L-arginine. Two experiments were carried out to determine whether oral dosing with L-arginine during coccidia infections could influence the associated pathology or the development of the parasites. Neither single nor dual daily doses (500 mg/kg) of L-arginine reversed weight gain reduction, augmented plasma NO2- + NO3- levels, or lessened lesion scores in chicks infected with Eimeria acervulina, Eimeria maxima, or Eimeria tenella. Although the oocyst shedding from E. maxima (1x dose) or E. acervulina (2x dose) infections were not affected, the oocyst shedding from E. tenella infections was significantly reduced by both dose regimens.

Animals↗

PubMed1998

Dietary modulation of avian coccidiosis.

During the past several years, our laboratory has been investigating the anticoccidial activities of various natural products that have potential use as dietary supplements for coccidiosis control. Sources of fats containing high concentrations of n-3 fatty acids such as menhaden oil and flaxseed oil and flaxseed, when added to starter rations and fed to chicks from one day of age, effectively reduce lesions caused by the caecal parasite Eimeria tenella, but not lesions caused by Eimeria maxima. Our results are consistent with reports of effects of diets high in n-3 fatty acids on other protozoan parasites which suggest that the state of oxidative stress induced by these diets in the cells of both host and parasites is responsible for their parasitic actions. Artemisinin, a naturally occurring (Artemisia annua) endoperoxide and effective antimalarial significantly lowers lesions from E. tenella when given at low levels as a feed additive. The mechanism of its action is also considered to involve induction of oxidative stress. Diets supplemented with 8 p.p.m. gamma-tocopherol (abundant in flaxseeds) or with 1% of the spice tumeric, reduce mid-small intestinal lesion scores and improve weight gains during E. maxima infections. These compounds may exert their anticoccidial activity because they are effective antioxidants. Betaine, a choline analogue found in high concentrations in sugar beets, improves nutrient utilisation by animals under stress. When provided as a dietary supplement at a level of 0.15% it has enhanced the anticoccidial activity of the ionophore, salinomycin. Betaine may act as an osmoprotectant whereby it improves the integrity and function of the infected intestinal mucosa. In in vivo studies, betaine plus salinomycin significantly inhibit invasion of both E. tenella and E. acervulina. However, subsequent development of E. acervulina is inhibited more effectively with this combination treatment than development of E. tenella.

Animals↗

PubMed1998

Effects of dietary supplementation with n-3 fatty acid ethyl esters on coccidiosis in chickens.

The ethyl esters of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids were added to a broiler starter diet singly or in combination [as bulk purified ethyl ester concentrate from menhaden oil (n3FAC)] in quantities similar to those found in a diet supplemented with 5% menhaden oil (MO). Diets were fed to chickens from 1 d of age through 3 wk of age. At 2 wk of age, the chickens were infected with Eimeria tenella, Eimeria acervulina, or Eimeria maxima. At 6 d postinfection (PI), the effects of the diets were assessed on weight gains, plasma carotenoids, gross lesion scores, and histological parasite scores in gut cross sections, or oocyst output. Significant ameliorating effects of diet on lesion scores and parasite scores were only seen in E. tenella infections and were only produced by the n3FAC and MO supplements. These two supplements, which contained higher molar concentrations of double bonds than the other supplements, also significantly reduced plasma carotenoids in uninfected chickens, indicating that they promoted a state of oxidative stress. These results are consistent with previous reports on the interaction of coccidiosis with dietary n-3 fatty acids and strengthen the hypotheses that dietary-induced oxidative stress is an effective deterrent against cecal coccidiosis in chickens.

Animals↗

PubMed1997

The effect of high n-3 fatty acids diets on the ultrastructural development of Eimeria tenella.

A study of development of Eimeria tenella in chickens fed high n-3 fatty acids (n-3FA) diets showed ultrastructural degeneration of both asexual and sexual parasite stages. Abnormal shedding of asexual and sexual parasite developmental stages into the cecal lumen was also observed. Ultrastructural degeneration was characterized by cytoplasmic vacuolization, chromatin condensation within the nucleus, a lack of parasitophorous vacuole delineation, and, in some cases, a complete loss of parasite ultrastructural organization. The results of this study indicate that diets high in n-3FA may be useful in the control of avian coccidia.

Animal Feed↗

PubMed1997

Effects of combined treatment with recombinant bovine somatotropin and immunization with live oocysts on performance of broiler chicks raised in coccidia-seeded floor pens.

In our laboratory, preliminary studies have indicated that recombinant bovine somatotropin (rbST) can stimulate protective immunity against coccidia infection. A floor pen trial on coccidia-seeded litter was run to further test its activity as an adjuvant during immunization of chicks with a live oocyst vaccine. Five hundred day-old male broiler strain chicks were randomly assigned to five experimental Treatments: 1, medicated controls; 2, unimmunized, not treated with rbST; 3, unimmunized, rbST-treated; 4, immunized, not treated with rbST; 5, immunized, rbST-treated. Each treatment consisted of four pens of 25 chicks each. At the end of the growout period (7 wk), the chicks in Treatment 1 (medicated controls) had the highest mean BW, but mean BW of chickens in Treatment 3 (rbST treatment only) were not significantly less. On the other hand, the mean weights of chicks in Treatments 4 (immunized only) and 5 (immunized plus rbST) were significantly reduced, and not different from those of the untreated chickens (Treatment 2). However, when challenged at 3 wk, the chicks in Treatment 5 had a mean combined total lesion score that was significantly lower than that from Treatment 3, indicating that they had developed a higher degree of specific immunity, but of the expense of weight gain. The results suggest that rbST has a potential for use as an adjuvant with live oocyst vaccination, but that the ratio between rbST dose and numbers of oocysts in the live vaccine needs to be carefully controlled.

Animals↗

PubMed1997

Nitric oxide production during Eimeria tenella infections in chickens.

The objective of this study was to gather evidence for production of nitric oxide (NO) during a primary infection with the protozoan parasite Eimeria tenella, which carries out its life cycle in the ceca of chickens. Relationships of plasma levels of NO2(-)+NO3-, stable metabolites of NO, with parasite dose and with time after infection were examined, as well as effects of administration of aminoguanidine, an inhibitor of induced nitric oxide synthase (iNOS). Inoculation with 5 x 10(4) and 1 x 10(6) but not 1 x 10(3) oocysts per chick caused significant (P < or = 0.05) increases in micromolar concentrations of plasma NO3(-)+NO3- when measured at 7 d postinoculation (PI). In chickens inoculated with 5 x 10(4) oocysts, significant (P < or = 0.05) increases in plasma NO2(-)+NO3- were seen at 5 and 7 but not 3 d PI. Daily intraperitoneal administration of 1.25 mg per chick aminoguanidine during the period of infection did not lower the increases in plasma NO2(-)+NO3- seen at 5 and 7 d PI, and did not affect the degree of colonization of the cecal tissue by the parasite. However, administration of aminoguanidine did alter the gross appearance of the ceca, which were less swollen and filled with blood at 5 and 7 d PI as compared with ceca from untreated chickens. Hemorrhage is a major pathological manifestation of E. tenella infections, associated with the disruption of the cecal mucosa by the developing parasite. The results of this experiment are consistent with the hypothesis that an aminoguanidine-inhibitable NO synthase, perhaps in the vascular endothelium of the cecal blood vessels, may contribute to hemorrhage by causing vasodilation.

Animals↗

PubMed1997

Production of free radical species during Eimeria maxima infections in chickens.

Five experiments were conducted to investigate the production of nitric oxide (NO) and superoxide anion (O2-) during infections of chickens with the coccidial parasite, Eimeria maxima, in order to assess the importance of these free radical species in the pathogenesis of the infections. Nitric oxide production was estimated by analyzing NO2(-)+NO3-, stable metabolites of NO, in the plasma and intestinal mucosa. The potential for O2- production was estimated from activities of beta-nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in mucosal homogenates. Levels of NO2(-)+NO3- reached maximum values at about 6 d postinoculation, a time when mucosal damage was high and oocysts were being shed. The activity of NADPH oxidase in infected mucosa was also increased. Thus, at that time, there was a potential for oxidative destruction of mucosal tissue from these free radicals and their reaction products. Levels of NO2(-)+NO3- did not increase in a stepwise manner with increasing infective dose, suggesting that production of NO may be regulated post-transcriptionally by other factors elaborated by the immune response to infection, or may be controlled by substrate limitations. A comparison of two E. maxima strains indicated that the virulence of a strain was not directly related to NO production. Increased production of O2- due to increased NADPH oxidase activity during infection may cause a reduction in levels of carotenoid pigments that is unrelated to malabsorption.

Animals↗

PubMed1997

Interaction of dietary flaxseed with coccidia infections in chickens.

Two experiments were conducted to determine effects of diets containing n-3 fatty acids (n-3FA) from whole as well as ground flaxseed on the performance of broilers during coccidia infections. Diets were fed from 1 d of age through 3 wk of age. Chickens were infected with coccidia at 2 wk of age and the effects of infection assessed at 6 d postinfection. The first experiment contrasted effects of several high n-3FA-containing diets, including one supplemented with whole flaxseed, on infections with Eimeria tenella or Eimeria maxima. Infected chickens that consumed the flaxseed-supplemented diet had the lowest weight gains, but they were not significantly different from gains of infected chickens on the control diet. Diets supplemented with 5% menhaden oil or 15% flaxseed significantly reduced lesions caused by E. tenella, but had no effect on lesions caused by E. maxima. In a second experiment, diets supplemented with 5 or 10% ground flaxseed were assessed for effects on the performance of broilers infected with three dose levels (500, 5,000, or 50,000 oocysts) of E. maxima. Neither flaxseed diet protected weight gain during infection with 50,000 oocysts. However, a 5% flax diet protected weight gains in chickens infected with 500 or 5,000 oocysts. Diets supplemented with 5 or 10% ground flaxseed exacerbated lesions in chickens infected with 5,000 or 50,000 E. maxima oocysts compared to the control diet. Thus, diets containing high amounts of n-3 fatty acids do not affect the development of all Eimeria sp. in the same manner. The oxidative stress produced by these diets may more adversely affect development of E. tenella, which infects the relatively oxygen-poor ceca, whereas it does not affect development of E. maxima which parasitizes the middle portion of the small intestine.

Animals↗