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Biomedical subjects

W M Reid

Publications and source records attributed to W M Reid.

At least 55 records · Page 3Linked to original sources
PubMed1977

Effects of monensin-feeding regimens on flock immunity to coccidiosis.

Feed medication with monensin caused delays in development of immunity in two floor-pen experiments which simulated commercial broiler production. Development of immunity was retarded with the higher level of monensin (120 p.p.m.) but was progressively less delayed as the monensin level was decreased (100, 60 or 0 p.p.m.). Delay was greatest with Eimeria tenella, but also occured with intestinal species including E. acervulina, E. brunetti, E. maxima, E. mivati, and E. necatrix. Drug withdrawal permitted earlier development of immunity. Plans involving use of monensin on layer replacements which later will be maintained on the floor without medication should consider: 1) prevalence of infective oocyst exposure in the area, 2) the lowest possible level of drug required for protection, and 3) its use for the shortest possible period of time.

Administration, Oral↗
PubMed1977

Effect of infectious bursal disease on the severity of Eimeria tenella infections in broiler chicks.

A study was initiated to determine whether prior exposure to infectious bursal disease virus (IBDV) influenced the susceptibility of young broiler chicks to Eimeria tentella infections. When one-day-old chicks infected with IBDV were subsequently challenged with E. tenella at 7 days of age, they suffered significantly higher mortality and lesion scores than their hatchmates which were not exposed to IBDV. Initial exposure to IBDV also had an effect on the development of E. tenella induced hemorrhaging. Hemorrhaging commenced late on the third day following E. tenella inoculation in chicks infected with both IBDV and E. tenella, while bleeding did not occur in the E. tenella alone group until late on the fourth day post-coccidial challenge. No significant differences in weight gains at 7 or 14 days after E. tenella infection were observed between chicks receiving the double infection and those given only E. tenella.

Animals↗
PubMed1977

Anticoccidial activity of salinomycin in battery raised broiler chickens.

Infections with single species of Eimeria acervulina, E. mivati, E. maxima, E. tenella, E. necatrix, and E. brunetti, and the six species mixed, were utilized in three separate battery experiments to evaluate the anticoccidial efficacy of various levels of salinomycin (AHR-3096), a fermentation product of a strain of Streptomyces albus. At the 60 to 100 p.p.m. treatment levels, this compound showed significant anticoccidial activity for all parameters studied (mortality, weight gain, feed conversion, dropping scores, and lesion scores). The mortality due to coccidiosis was reduced to 0.1% in the medicated infected birds. Some activity, as measured by weight gain, was seen in the lower levels of salinomycin medication (12.5 to 50 p.p.m.), but other parameters, including mortality and lesion scores, indicated less activity than that seen with the higher treatment levels. At 100 p.p.m., there was no apparent effect on the compound on bird performance in uninfected control birds. Salinomycin at the 100 p.p.m. treatment level was statistically as effective as 121 p.p.m. monensin (reference anticoccidial) in controlling coccidiosis.

Animal Feed↗
PubMed1977

Anticoccidial activity of salinomycin in floor-pen experiments with broilers.

The anticoccidial agent salinomycin (AHR-3096) was compared at various treatment levels (60 to 100 p.p.m.) in two experiments against unmedicated and either 100 or 121 p.p.m. monensin-medicated groups to evaluate its performance under floor-pen conditions. Various methods for the initial rearing of birds and coccidial exposure were employed to test the efficacy of salinomycin against severe, moderate, and mild coccidiosis. Salinomycin at all treatment levels showed definite anticoccidial activity resulting in improved weights, feed conversion ratios, lesion scores, and mortality compared with unmedicated controls. In pens with severe coccidiosis, this compound demonstrated a significant improvement in all parameters when compared with the corresponding unmedicated controls. Salinomycin-treated pens exposed to light coccidiosis usually had a numerical increase in the parameters over the unmedicated control groups. Statistical analysis of overall main effects on mortality, weight gain, and feed conversion ratio showed no significant differences between the activity of any level of salinomycin and monensin.

Animal Feed↗
PubMed1976

Effects of high environmental temperatures on cecal coccidiosis.

Maintenance of broiler or White Leghorn cockerels in a high temperature (32 C.), high humidity (90%) environment for six days following artificial infection with Eimeria tenella significantly reduced coccidiosis severity as compared to birds similarly infected and maintained in an ambient environment averaging 24.5 C., and 62% humidity. Disease severity was determined by lesion scores, fecal scores, and hematocrit readings. The heavier broiler stock maintained body temperatures of 0.7-1.6 C. higher than those birds kept at ambient temperatures for the entire six days. Body temperatures of heat-treated Leghorn cockerels were 0.9 C. higher during the first 48 hours post-inoculation (P.I.), but similar to ambient temperature controls for the last four days. Elevated body temperatures during the first two days following inoculation impaired the survival and development of some parasites while shorter periods (24 hours) of heat treatment did not affect parasite survival.

Animals↗
PubMed1976

Coccidiosis: effects of high environmental temperatures on anticoccidial protection.

In a series of nine experiments birds subjected to heat-stress showed decreases of 9 to 61 percent in feed intake. In only one of these experiments, involving E. acervulina and monensin, was there sufficient reduction of anticoccidial intake to partially nullify effects of drug protection. In this case, a 40 percent decrease in monensin intake resulted in significantly higher lesion scores (1.9 vs. 1.0) (P less than or equal to 0.05) in birds maintained at 32 C. for days 1 to 7 postinfection (P.I.) compared to controls maintained at 20C. No other failures due to heat stress occurred with this anticoccidial in three other trials with E. acervulina or or five trials involving E. tenella infection. In one experiment E. tenella coccidiosis (lesion scores 0.7 vs. 1.1) was more severe in the cool environment than in birds under heat-stress from 2 to 7 days P.I. Similarly, less severe lesions of E tenella (0.4 vs. 0.8) occurred during heat-stress (32 C) than in controls maintained at 11 C. in zoalene-fed and unmedicated control birds. No differences in lesion scores occurred in birds in hot versus cool room environments in two experiments involving sulfaquinoxaline or one with robenidene and E. tenella infection. E tenella lesions inunmedicated controls were significantly more severe in the cool than the hot environment in one experiment. Results from these experiments suggest that decreases in feed and anticoccidial intake during heat-stress could seldom be the cause of coccidiosis breaks under field conditions.

Animals↗
PubMed1976

Efficacy of different feeding levels of monensin in the control of coccidiosis in broilers.

The feed level of monensin which gave maximal protection from coccidial infection in broilers reared in floor pens depended on the severity of the coccidial exposure and the criteria of infection studied. With indirect seeding of pens with coccidia (light coccidial exposure), 40 ppm was as efficacious as 100 ppm in improving weight gain, lesion score, and feed conversion. Statistical analysis with direct seeding (seeder birds; severe coccidial exposure) showed that feed levels of 84 and 102 ppm gave maximal improvement of weight gain and 4-week feed conversion, respectively. Further increasing the monensin level from 100 to 121 ppm did not improve weight gain and feed conversion at 8 weeks. Conversely, the relationship of plasma pigmentation and total lesion scores to monensin feed levels indicated that increasing the dosage of monensin from 100 to 121 ppm improved the performance of the broilers on the basis of these 2 infection indicators.

Administration, Oral↗
PubMed1975

Effects of roxarsone on pigmentation and coccidiosis in broilers.

Roxarsone (0.005%) medicated chickens inoculated at seven weeks of age with Eimeria maxima oocysts had significantly higher pigment levels in blood plasma than did unmedicated controls. Unmedicated E. maxima infected birds had significantly lower pigment levels compared to uninoculated controls. Uninoculated roxarsone medicated controls showed no increase in pigment levels over uninoculated unmedicated birds. This experimental design demonstrates that the beneficial effect of roxarsone medication is due to anticoccidial action rather than an increase in pigmentation after feeding the yellow-colored roxarsone. Since uninoculated birds gained more rapidly if roxarsone (0.025%) was added to the diet, the drug also appears to stimulate growth as well as to protect against coccidial infection. In two floor-pen experiments roxarsone demonstrated anticoccidial activity as measured by higher pigment scores than unmedicated infected controls. The coccidial infection was induced after seeding the litter with oocysts from birds infected with E. acervulina, E. brunetti, E. hagani, E. maxima, E. mivati, E. necatrix, E. praecox, and E. tenella. Pigmentation levels were significantly higher in plasma and skin of roxarsone medicated chickens in two experiments and in shanks in one experiment. Similar protection against depigmentation was demonstrated by adding roxarsone to feed medicated with nequinate. These results involving addition of roxarsone may explain some equivocal reports on pigmentation, weight gains or feed conversion. Some previous investigators appear to have used an inadequate experimental design by omitting use of unmedicated uninoculated controls or to have made no attempt to monitor for presence or absence of coccidiosis.

Animals↗
PubMed1975

Progress in the control of coccidiosis with anticoccidials and planned immunization.

New anticoccidials continue to be introduced to the poultry industry on an average of about one every 2 years. Revised requirements have increased costs of discovery, development, and approval by the Food and Drug Administration to several million dollars for each product. Gross sales of anticoccidials are now estimated to be in excess of $30,000,000 annually. Anticoccidials are almost universally used in starter rations for meat-type birds being raised under floor-pen management. Protection is more important with these fast-growing birds than with egg-producing types where immunity and cage layer management modify demands for anticoccidials. Coccidiosis mortality has generally been eliminated by all 25 approved anticoccidials if properly used. Selection of specific anticoccidials is based on the ability of the anticoccidial to: (1) improve weights and (2) feed conversion, and (3) to suppress development of lesions. Costs of the product may influence decisions on which one to use. With some anticoccidials the rapid emergence of drug resistant strains has been the biggest problem. "Switching" among the 13 classes of anticoccidials and the so-called "shuttle program" are common methods used to avoid development of resistance. Preventive medication will probably continue to constitute the major method of coccidiosis control with meat-type poultry if attempts to develop economic cage-type management do not supplant current litter and floor-pen management. Immunity acquired through incidental or planned immunization is more important in control of coccidiosis with layer and breeder flocks raised in floor-pens. Some progress in development of avirulent immunogenic strains of different species of coccidia has been reported and further research efforts in this direction should be encouraged.

Administration, Oral↗