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L R McDougald

Publications and source records attributed to L R McDougald.

At least 37 records · Page 2Linked to original sources
PubMed1992

Characterization in vitro and in vivo of resistance to ionophores in a strain of Eimeria tenella.

A field isolate of Eimeria tenella (FS139) was propagated several times in chickens medicated with 200 ppm of dietary monensin. In a laboratory test with 2-wk-old-chickens, the strain was resistant to monensin, salinomycin, and lasalocid given at double use level and was resistant to narasin and maduramicin at the normal use level. In comparison, a laboratory strain (WIS) was controlled by the normal use level of each product. When free WIS sporozoites were treated in vitro with 1.0 microgram/ml of monensin for 0.5 or 4.0 hr at 41 C and inoculated into primary cultures of chicken kidney cells the invasion was reduced by 35.6% or 96.3%, but invasion of FS139 sporozoites was increased by 18.5% by 0.5 hr treatment and was about the same as controls after 2 hr of treatment. Few sporozoites from the WIS strain developed into schizonts, but numerous sporozoites from the FS139 strain developed into normal first and second generation schizonts. The structure of free WIS sporozoites was distorted after 3 hr of treatment with 2.5 micrograms/ml of monensin at 41 C, as observed by light and scanning electron microscopy, whereas there was no change in structure of most treated FS139 sporozoites.

Animals↗
PubMed1992

Penetration of Eimeria tenella sporozoites under different oxygen concentrations in vitro.

Sporozoites of Eimeria tenella (Wisconsin strain) were inoculated onto monolayers of normal chicken kidney fibroblasts and cultured in RPMI-1640 supplemented with 5% fetal bovine serum, sodium bicarbonate, and gentamicin under either aerobic, 5% CO2/95% air, or anaerobic conditions. Penetration of fibroblasts by sporozoites under CO2 or anaerobic conditions at 2 and 24 hr postinoculation was 3-4 times greater than that in the aerobic atmosphere. Effect of reduced oxygen concentrations, i.e., 20.0, 12.5, and 5.0% oxygen, was also investigated in an N2-O2-CO2 incubator. Under 5.0 and 12.5% oxygen at 2 and 24 hr postinoculation, the number of sporozoites that penetrated was about 4 and 2 times greater, respectively, than under 20.0% O2. These results indicate that lower oxygen concentrations provide for greater penetration by E. tenella sporozoites in cultured cells.

Animals↗
PubMed1992

Electrophoretic and immunologic characterization of proteins of merozoites of Eimeria acervulina, E. maxima, E. necatrix, and E. tenella.

Merozoites of Eimeria acervulina, Eimeria maxima, Eimeria necatrix, and Eimeria tenella were compared by gel electrophoresis, western-blotting with chicken antiserum, indirect fluorescent antibody reactions, and antiserum neutralization. Merozoites from the 4 species had dissimilar patterns of proteins and antigens in soluble and membrane fractions. Coomassie blue staining of SDS-PAGE gels revealed 16-22 protein bands depending on the species of merozoite but only 3 bands per species in the membrane fractions. Homologous and heterologous antisera recognized 5-12 soluble fraction bands and 3-7 membrane fraction bands on immunoperoxidase-stained western blots, depending on the species. When antisera from infected chickens were used in an indirect fluorescent antibody reaction, the merozoites of E. tenella and E. necatrix had a strong reaction with homologous and heterologous antisera. Merozoites of E. acervulina and E. maxima reacted with homologous antisera but had a weak or no reaction with heterologous antisera. Chicken antiserum against E. tenella had no effect on the viability of E. tenella merozoites when they were inoculated into chicken embryos.

Animals↗
PubMed1991

Evaluation of anticoccidial drugs in chicken embryos.

Infections of Eimeria tenella in chicken embryos were used to compare the anticoccidial activity of ten drugs. The minimal inhibitory concentration (MIC) and minimal toxic concentration (MTC) were affected by the time of inoculation into the embryos and by the chemical nature of the compounds. Some compounds (nicarbazin, amprolium) had no effect on the development of coccidia when they were injected into embryos after the day of infection. Drugs that act early in the life cycle of coccidia (robenidine, clopidol, decoquinate, diclazuril, halofuginone, monensin, salinomycin, and lasalocid) were active at 5-125 micrograms/embryo when they were injected on the day of infection. The ionophores and halofuginone were highly toxic to embryos; most synthetic compounds were nontoxic. The incubation of merozoites in drug suspensions prior to the infection of embryos did not result in embryo toxicity, but the resultant MICs were much higher than those obtained when drugs were injected directly into the embryos. Several products were essentially inactive. Neither nicarbazin nor amprolium prevented oocyst formation. The widely divergent endpoints for the MIC and MTC of anticoccidials in embryos seriously limits the application of this technique as a screen for anticoccidial drugs.

Animals↗
PubMed1990

A new method for purification of Eimeria tenella merozoites.

A rapid and simple method for purifying second generation merozoites of Eimeria tenella was developed using a host tissue digestion fluid, containing 0.25% trypsin and 0.5% taurodeoxycholic acid, to liberate merozoites grown in chick embryos or from parasitized ceca. After filtration, the digestion procedure yielded 1.4 x 10(7) or 8.33 x 10(7) merozoites per embryo or cecum, respectively. These yields were nine-fold for embryos and three-fold for ceca in comparison to previous reports. Viability of the merozoites was normal as assessed by their ability to reinfect embryos and cell cultures. The new method has advantages in that large numbers of pure, viable merozoites can be obtained quickly and easily, and the procedures require minimal effort and supplies.

Animals↗
PubMed1990

Reduction in cell entry of Eimeria tenella (Coccidia) sporozoites by protease inhibitors, and partial characterization of proteolytic activity associated with intact sporozoites and merozoites.

The role of proteases in the invasion of host cells by Eimeria tenella (Wisconsin strain) was studied in vitro. Protease inhibitors were used to treat sporozoites before inoculation or were applied to cultured chicken kidney cells before infection. The inhibitors antipain, leupeptin, aprotinin, L-1-tosylamide-2-phenyl-ethyl chloromethyl ketone (TPCK), or N-alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK) reduced parasite invasion to 16-66% of control after treatment of cultured cells or sporozoites with 5- or 50-micrograms/ml concentrations of inhibitors in the culture medium. Phenylmethylsulfonyl fluoride (PMSF) reduced invasion to 32-57.7% at concentrations of 1-4 mM. The optimum pH for hydrolysis of azocasein by intact sporozoites or merozoites was determined over a range of pH 5.0 to pH 9.0. Sporozoites were highly active over a broad range from pH 5.5 to pH 9.0, with an apparent optimum at pH 8.0. Merozoites had a much lower specific activity with pH optima at 7.0 and 8.5. The protease activity of sporozoites or merozoites could be inhibited completely by the addition of 50 micrograms/ml of leupeptin, TPCK, or TLCK or of 4 mM PMSF. Antipain inhibited proteases of sporozoites but not of merozoites. Pepstatin had little effect on either sporozoites or merozoites. The results suggest that parasite proteases of Eimeria may be necessary for invasion of host cells.

Animals↗
PubMed1987

Effects of monensin feeding and withdrawal time on growth and carcass composition in broiler chickens.

Four experiments were conducted to evaluate the effect of monensin feeding and withdrawal on broiler performance and carcass characteristics. It was shown that monensin (100 ppm) feeding depressed growth. Withdrawal of monensin from the feed for 5 or 7 days produced higher feed consumption and weight gain values compared with those of unmedicated broilers. Increasing the withdrawal period to 10 days did not produce greater growth improvement. Whole body composition of protein, water, lipid, and ash were not significantly affected by monensin feeding or withdrawal. Abdominal fat pads of unmedicated female broilers were significantly larger than those of broilers medicated with monensin even when expressed as a percentage of body weight (3.53 vs. 2.99%). Amount of lipid per fat pad was also higher in unmedicated broilers than in medicated broilers (43.5 vs. 30.6 g). Values for fat pad weight (as a percentage of body weight) and grams of lipid per fat pad of unmedicated birds were not different from those measures in medicated birds after 5 or 7 days of withdrawal. Fat pad weights and lipids per fat pad of birds after 10 days of monensin withdrawal were intermediate between those of unmedicated and monensin-medicated broilers. Monensin feeding or its withdrawal for 5 or 10 days did not influence the female broiler abdominal fat pad lipid fatty acid composition when compared with that of unmedicated fat pad lipid.

Animal Nutritional Physiological Phenomena↗
PubMed1986

Halofuginone: laboratory titration of anticoccidial activity in young turkeys.

Halofuginone was tested at 0, 1.5, 3.0, or 6.0 ppm in the feed against single and mixed infections of recent field isolates of Eimeria adenoeides, E. meleagrimitis, and E. gallopavonis. Severe infections were produced in unmedicated, infected controls. Weight gains were significantly improved by 1.5 or 3 ppm of halofuginone, and intestinal lesion scores and fecal droppings scores were greatly reduced. Oocyst shedding was reduced 91 to 100% by halofuginone treatments. Treatment with 6 ppm of halofuginone gave good protection but appeared to depress weight gains slightly. Treatment with 3 ppm was optimal for the control of all species of coccidia and for optimum performance.

Animals↗
PubMed1986

Anticoccidial efficacy of halofuginone in turkeys reared to market weight.

Floor-pen studies were conducted in three geographic locations to study the efficacy of halofuginone (3.0 ppm in feed) against important species of coccidia in turkeys. Severe coccidiosis exposure was obtained in studies in Georgia and Colorado and mild coccidiosis in Wisconsin. Coccidiosis caused by contamination of the feed with oocysts of Eimeria adenoeides, E. meleagrimitis, and E. gallopavonis was almost completely controlled by halofuginone at 3 ppm, even though intestinal lesion scores and weight loss were high in two studies. Halofuginone was also highly effective in preventing buildup of infection in pens contaminated by indirect means (movement by caretakers through the pens, etc.). Weight gains and feed conversion were best in poults receiving halofuginone, whether directly or indirectly exposed. There was no evidence that halofuginone caused any untoward reactions in the poults, even though the drug was fed until turkeys reached market weight.

Animals↗
PubMed1984

Effectiveness of therapeutic anticoccidial drugs against recently isolated coccidia.

Litter samples were collected weekly from 17 broiler houses and coccidial oocysts were counted. Oocysts per gram were low on the Weeks 1 and 2 of the growout, increased to a peak on the Week 4, then declined to near zero on Weeks 6 and 7. Coccidia from each house were propagated and tested for sensitivity to therapeutic formulations of amprolium, sulfaquinoxaline, and sulfaquinoxaline plus pyrimethamine. The degree of control was based on the weight gains and lesion scores of the medicated groups in comparison with those of the unmedicated, infected, and uninfected groups. The predominant species found in the 17 isolates were Eimeria tenella and E. acervulina. Amprolium was effective against E. tenella in all isolates but only partly effective against E. acervulina. Sulfaquinoxaline and the potentiated mixture were effective against the E. acervulina but only partly effective against the E. tenella. The potentiated mixture was better against E. tenella than sulfaquinoxaline alone.

Amprolium↗
PubMed1984

The effect of polyether, ionophorous anticoccidial drugs on feather growth in genetically slow-feathering broilers.

The rate of feather growth was measured in Hubbard X Hubbard broilers given monensin, salinomycin, or lasalocid for 8 weeks in floor pens. Chicks were given a nutritionally adequate diet. Feathers on male chicks were shorter at 10 days of age but grew faster than those on female chicks. Male chicks had longer feathers than female chicks after 31 days of age. Back feather scores were similar in male and female chicks at 52 days of age. Dietary ionophores had no effect on the rate of feather growth or the back feather coverage under the condition of this study.

Animals↗
PubMed1983

Luteinizing hormone release and androgen production of avian hybrids in response to luteinizing hormone releasing hormone injection.

The levels of luteinizing hormone (LH) and androgens were measured in sterile avian hybrids. Guinea fowl-chicken and peafowl-guinea fowl hybrids were bled before and after injection with LH- releasing hormone (LHRH). The preinjection LH levels for the guinea fowl-chicken hybrids were below or at the very lower limit of the assay sensitivity and the peafowl-guinea fowl hybrids averaged 1.3 ng/ml. Within 10 min after LHRH injection, LH had increased dramatically in both hybrids and then began to slowly decline. Androgen levels in the guinea fowl-chicken hybrids increased from 16.2 pg/ml to 95.2 pg/ml and continued to increase, reaching 287 pg/ml at the last bleeding 60 min after injection.

Androgens↗
PubMed1982

Drug responsiveness of field isolates of chicken Coccidia.

Coccidia were isolated from litter samples collected in poultry houses in Georgia and other southeastern states and from intestinal scrapings from chickens submitted to diagnostic laboratories. The most common species of coccidia encountered were E. tenella, E. acervulina, and E. maxima. Each of the 41 isolates was tested for sensitivity to eight commercial anticoccidial drugs. Most of the isolates were resistant to some of the drugs judged by the parameters of percent weight gain, percent lesion score reduction, and a sensitivity index score. There was a high frequency of resistance to clopidol, amprolium/ethopabate, nequinate, zoalene, and sulfaquinoxaline. A very small percentage of the isolates tested were resistant to nicarbazin, robenidine, or halofuginone.

Amprolium↗
PubMed1982

Anticoccidial drugs: growth and performance depressing effects in young chickens.

Monensin, lasalocid, salinomycin, nicarbazin, halofuginone, or arprinocid were fed to 1-week-old male broiler chicks at recommended levels and 1.5, 2, 2.5, and 3 times the recommended level, for 3 weeks. Pair-feeding experiments also were conducted to investigate the extent that growth depression with medicated diets could be attributed to the drop in feed consumption. At the recommended level of drugs, growth and feed conversion were not significantly affected. At elevated drug levels, performance was impaired; the adverse effects of drugs became more pronounced with increasing the concentrations in the diets. Weight gain was significantly depressed at 1.5X with arprinocid, halofuginone, and salinomycin, at 1 to 2X with monensin, at 2X with lasalocid, and at 2.5X with nicarbazin. Feed conversion, however, was adversely affected by 2X with halofuginone or 2.5X with salinomycin, nicarbazin, arprinocid, monensin, or lasalocid. The results of the pair-feeding experiments with 2 to 3 times drug levels indicated that most of the growth depression with medicated diets could be attributed to reduced feed consumption, but all drugs except arprinocid caused some additional growth depression.

Adenine↗
PubMed1981

Anticoccidial activity of arprinocid and halofuginone.

Halofuginone and arprinocid, new anticoccidial drugs, were tested to determine the time of peak activity in the life cycle of Eimeria and whether they were coccidiocidal or coccidiostatic. Halofuginone was completely effective if medication was initiated by Day 3 postinoculation, but only partly effective if given on Days 4-7. Arprinocid was effective if given on Days 2-7 postinoculation, but only partly effective if given on Days 3-7. When medication was started on Day 0 and withdrawn on various subsequent days, good activity was recorded with halofuginone if the drug was given up to Day 1 postinoculation, but arprinocid required feeding up to Day 4 postinoculation. In other studies, medication was given until Days 6 or 7 postinoculation, then discontinued, to allow further development of coccidia that were arrested by the drug. With halofuginone, the oocyst passage was low with E. tenella and E. maxima but moderate with E. mivati. With arprinocid, oocyst passage was low with E. maxima and E. mivati but moderate with E tenella. These results suggest that halofuginone is active over a broader part of the life cycle than arprinocid, but both drugs had a predominantly coccidiocidal action.

Adenine↗
PubMed1981

Effect of amprolium and dinitolmide on sporulation of oocysts of field isolates of Eimeria acervulina.

A laboratory strain of Eimeria acervulina and 9 field isolates consisting principally of E. acervulina were tested for sensitivity to amprolium (125 p.p.m.) or dinitolmide (125 p.p.m.) in the food and for effects of the drugs on sporulation of oocysts. Judged by weight gains and lesion scores, medicaments were only partially effective against the 9 field isolates, but were highly effective against the laboratory strain. Oocysts were produced in all the infections but the percentage sporulation of oocysts from field isolates was much higher than sporulation of oocysts of the "drug sensitive' laboratory strain. These results show that coccidia that are resistant to either amprolium or dinitolmide are able to cause lesions in the presence of the drugs and the oocysts that are produced will sporulate normally.

Amprolium↗