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Biomedical subjects

H M Edwards

Publications and source records attributed to H M Edwards.

At least 91 records · Page 5Linked to original sources
PubMed1987

Effect of short fasts on the development of tibial dyschondroplasia in chickens.

The length of time each day that feed is available to young broiler-type chickens significantly influenced the development of tibial dyschondroplasia. Birds that were fasted for 8 or 10 h per day had reduced incidences of tibial dyschondroplasia as compared to birds fed ad libitum (5-11% vs. 59-68%). When birds were fasted for only 2 or 4 h each day there was no significant effect on the development of tibial dyschondroplasia. Birds fasted for 8 h every other day or every 4th d had lower incidences of tibial dyschondroplasia compared to ad libitum fed controls. Fasting for 8 h on the 4th d or the 4th and 8th d of a 20-d experiment had no effect on the incidence of tibial dyschondroplasia as compared to controls. Except for the daily fasting there was little effect of fasting on 20-d body weight or gain per feed intake. Fasting increased the percent bone ash in the tibia in all experiments. Fasting had no effect on total calcium, ultrafilterable calcium, dialyzable phosphorus or growth hormone levels in plasma taken from the birds the 18th and 19th day. The hour of the day that the birds were bled had a significant influence on the plasma total calcium, dialyzable phosphorus and growth hormone levels.

Animals↗
PubMed1987

Effects of thiuram, disulfiram and a trace element mixture on the incidence of tibial dyschondroplasia in chickens.

Two experiments were conducted to determine the effect of dietary addition of 30 ppm of thiuram or disulfiram on the development of tibial dyschondroplasia (a large mass of cartilage in the proximal end of the tibia) in chicks in the presence and absence of trace element supplementation: B, Ni, Al, Sr, Br, V, Si, Sn, Cr, F, Mo, Li, Mn, Zn, Fe, Cu and I. In two experiments, the incidence and severity of tibial dyschondroplasia were lower in chicks fed the diet containing the trace element supplement than in those fed the basal diet. Adding thiuram or disulfiram to the diet caused a significantly higher incidence and severity of tibial dyschondroplasia in chicks regardless of the presence or absence of the trace element supplement. In a third experiment not involving thiuram or disulfiram the addition of trace elements had no significant effect on tibial dyschondroplasia. Adding thiuram or disulfiram to the diet in a fourth experiment lowered the absorption of 47Ca from the gastrointestinal tract but did not influence the biological half-life of 47Ca in the chick.

Absorption↗
PubMed1986

Some problems in teaching clinical decision-making.

Evaluation of a number of courses in clinical decision-making (CDM) indicates that there are well-defined problems in teaching this subject. This paper describes some of the difficulties and proposes appropriate remedies. Problems in teaching undergraduates are different from those in the postgraduate years. Three areas where the principles of CDM are particularly useful to undergraduates relate to the structuring of clinical problems, clarifying the place of value judgements and developing new concepts regarding test ordering, particularly the importance of false positive rates and the overwhelming power of prior probabilities. In postgraduate teaching the most important areas relate to the origin of probability and of utility estimates. The complexity of decision analysis also needs critical comment. Two remedies are suggested which will help course developers when faced with these problems. Firstly, the early introduction of concepts regarding sensitivity analysis, making it clear that with the aid of CDM we are able to deal with a wide range of probability estimates, precision rarely being required in clinical medicine. Secondly, the availability of educational support systems will help expert clinicians teach CDM concepts within their own field.

Algorithms↗
PubMed1985

Effects of different soybean meals on the incidence of tibial dyschondroplasia in the chicken.

Interexperimental variation in the incidence of tibial dyschondroplasia of chickens that occurred in studies on the effect of dietary calcium, phosphorus and cholecalciferol metabolites was apparent from previous reports from this laboratory. Since the source of commercial soybean meal used in the diets was known to change, studies were conducted to evaluate different sources of soybean meal on the incidence of tibial dyschondroplasia. A series of experiments demonstrated that the soybean meals from one source consistently produced a high incidence of tibial dyschondroplasia (34-69%); whereas soybean meals from a different source consistently produced low incidences (14-28%). This same relationship was found with soybean meals from these two plants produced a year apart. When the levels of two soybean meals that produced a high incidence of tibial dyschondroplasia were reduced in the diet from 35 to 24 12% the incidence of tibial dyschondroplasia was reduced from 60 and 69% to 25 and 20% to 15 and 10%, respectively. The most striking difference between the meals observed by chemical analysis was in the high antitrypsin and urease values of the meals that induced tibial dyschondroplasia. Chickens fed the soybean meal that reduced tibial dyschondroplasia also had reduced pancreas size in one experiment but not another. The soybean meals that induced tibial dyschondroplasia caused an increase in testes size but had no effect on liver, adrenal and thyroid size or plasma levels of calcium, phosphorus and triiodothyronine (T3). No difference in the utilization of the diets as measured by metabolizable energy values and lipid calcium, phosphorus or phytin phosphorus retention was found between the soybean meals that induced high or low incidence of tibial dyschondroplasia with chickens at 19-21 d of age.

Animal Feed↗
PubMed1985

When students learn numbers: evaluation of a course in clinical decision-making.

This paper describes the evaluation of an innovative course in clinical decision-making (CDM). A traditional course in neurology taught concurrently to the same group of students by the same teacher was used for comparison. The aim of the course was to introduce students to the basic concepts of CDM as an aid to rational decision-making. The end-point of the evaluation was their perception of the immediate clinical relevance of CDM. It was postulated that by seeing this relevance they would be more likely to change their decision-making behaviour than by simply learning factual content or principles. The evaluation used an ongoing formative approach, including ethnographic analysis, questionnaires, small group discussion and supportive feedback for the teacher. The ongoing evaluation of the course resulted in revisions with increasing relevance within the students' level of experience, changes in sequence of presentations and encouragement of active student participation. A pre-test showed that students had difficulty in the correct assessment of the validity of data and in the correct revision of opinion. Results of the evaluation indicated that the CDM course did not achieve its objective of making students aware of the immediate clinical relevance of CDM. Possible reasons for this include the lack of reinforcement from clinicians suitable for modelling and the context specific nature of the learning of thinking processes. For a CDM course to be successful, it may need to be taught within the context of specific clinical topics. It is suggested that the evaluation approach used here is a cost-effective method when considering innovations in the curriculum and useful for generating further questions for study.

Australia↗
PubMed1985

Observations on several factors influencing the incidence of tibial dyschondroplasia in broiler chickens.

The effects of age vs. diet, potassium level, tetramethylthiuram disulfide (thiuram), and ionophores in the diet on the development of tibial dyschondroplasia in broilers was investigated. Changing broiler chicks from a diet that induced tibial dyschondroplasia to one that reduced the disease or vice versa caused a change in the incidence in the direction of the last-fed diet; however, in most cases the chicks did not develop as low or high an incidence of tibial dyschondroplasia as the birds fed the reducing or inducing diet, respectively, for the entire experimental period. Potassium supplementation of a corn-soybean meal diet that contained .88% potassium had no effect on the incidence of tibial dyschondroplasia. However, supplementation of a low potassium (.3%) corn-corn gluten meal-animal protein diet with potassium increased the incidence of tibial dyschondroplasia. The addition of thiuram to the diet caused an increase in tibial dyschondroplasia. When thiuram was added to the tibial dyschondroplasia-inducing diet, it also caused a decrease in bone ash and in the total and ultrafilterable plasma calcium. A significant negative correlation was obtained between incidence and score of tibial dyschondroplasia and bone ash of the ends and middles of the tibia when thiuram was fed. No consistent effects of the ionophores monensin and lasalocid on the development of tibial dyschondroplasia in broilers was noted in three experiments, although significant effects of the ionophores on the incidence or score of the disease was observed in two experiments.

Animals↗
PubMed1984

Studies on the etiology of tibial dyschondroplasia in chickens.

Experiments have been conducted to obtain information on the cause of tibial dyschondroplasia in chickens. All studies were conducted with corn-soybean meal practical-type diets and chicks from 1 day to 3 or 4 weeks of age. A high calcium and low phosphorus content of the diet and a wide calcium:phosphorus ratio in the diet decrease the incidence of tibial dyschondroplasia in broiler chickens. Increasing the chloride level of the diet increased the incidence of tibial dyschondroplasia. Increasing the magnesium content of the diet decreased tibial dyschondroplasia; however, the effect of magnesium was not as strong as that of calcium. The addition of sodium sulfate to the diet had no effect on the incidence of tibial dyschondroplasia. Five broiler strain crosses were all susceptible, although to a variable extent, to the development of tibial dyschondroplasia, whereas Single Comb White Leghorn chickens did not develop the disease. Male chicks developed tibial dyschondroplasia with a higher incidence than did female chicks. Supplementation of the chickens with 20 ng/day of either 1,25-dihydroxycholecalciferol [1,25(OH)2D3] or 24,25-dihydroxycholecalciferol [24,25(OH)2D3] had no effect on the incidence of tibial dyschondroplasia. J. Nutr . 114: 1001-1013, 1984.

24,25-Dihydroxyvitamin D 3↗
PubMed1983

The role of calcium and phosphorus in the etiology of tibial dyschondroplasia in young chicks.

By means of a central composite rotatable design with dietary calcium levels of 0.63, 0.70, 1.10, 1.50 and 1.67% and total phosphorus levels of 0.53, 0.61, 0.81, 1.01 and 1.09%, practical-type rations were fed for 2 weeks to commercial broiler-type chickens. The design involved three replicates for each rotatable point and 15 replicates for the central point with 10 cockerels per replicate or a total of 390 birds. When the experiment was terminated, the chickens were weighted and killed; one tibia was used to determine bone ash and the other tibia for scoring the incidence and severity of tibial dyschondroplasia. The incidence of tibial dyschondroplasia in chickens fed the various diets ranged from 0 to 37%. A high incidence of tibial dyschondroplasia was associated with diets containing high phosphorus and low calcium levels. Tibial dyschondroplasia score and percentage of bone ash were not correlated. No obvious relationships existed between tibial dyschondroplasia incidence and percentage retention of calcium and phosphorus. A second experiment confirmed the finding that increased dietary calcium levels would reduce the incidence of tibial dyschondroplasia when chickens were fed diets high in phosphorus.

Animals↗
PubMed1983

Phosphorus. 1. Effect of breed and strain on utilization of suboptimal levels of phosphorus in the ration.

Single Comb White Leghorn cockerel chickens were able to utilize suboptimal levels of phosphorus in the ration more efficiently than broiler cockerel chickens as measured by growth, livability, and bone calcification. The superiority of the Leghorn-type over the broiler-type in utilizing suboptimal levels of phosphorus was accentuated by high levels of calcium in the ration. Among broiler strains the Athens Canadian Randombred cockerel chicken utilized suboptimal levels of phosphorus more efficiently than the two commercial strains tested. The Single Comb White Leghorn chickens showed higher retention values for calcium, phosphorus, and phytin phosphorus than the broiler strain. High calcium levels in the ration caused a much lower retention of phytin phosphorus by both Single Comb White Leghorn and broiler chickens.

Animals↗
PubMed1982

Impaired nutrient utilization associated with pale bird syndrome in broiler chicks.

Energy utilization and lipid absorption were studied in chickens having the symptoms of the pale bird syndrome (PBS). Chicks with PBS and also ones that appeared "normal" were taken from a commercial farm and compared to control chicks raised at the University of Georgia (UGA). The PBS chicks utilized dietary energy and absorbed lipids substantially less than the normal birds from the commercial farm. Differences in lipid absorption alone did not account for the discrepancy in metabolizable energy between the two groups, suggesting that absorption of non-lipid dietary components was also affected. Both of the commercial groups of chicks showed a lesser ability to utilize dietary energy and absorb lipid than the UGA control chicks, indicating that the normal chicks may also have been affected by the disease.

Animals↗
PubMed1981

Strain variation in 59Fe absorption during aflatoxicosis.

Strain variation of iron absorption in response to dietary aflatoxin was studied using two commercial broiler strains and a nonselected randombred strain. Aflatoxin depressed chick body weights and increased mortalities in each strain. Hematocrits were significantly reduced in the commercial broilers receiving the toxin, but not in the randombreds. Aflatoxin reduced iron absorption in each strain regardless of the presence of anemia.

Absorption↗
PubMed1980

Physiological effects of gentian violet on broiler chickens.

The effects of dietary gentian violet upon certain physiological parameters of broiler chickens were studied. Gentian violet exhibited no effect upon growth rates or feed conversion ratios at dietary levels of 16, 32, or 64 micrograms/g. In vitro intestinal absorption of methionine and glucose was also unaltered. Dietary gentian violet significantly increased hemoglobin concentration without an effect on packed cell volume. Furthermore, commercial gentian violet containing preparations, when incorporated into the diet, resulted in increased intestinal absorption of Fe59 but this increase was dependent upon type of inert carrier used. Dietary gentian violet alleviated some of the growth suppression caused by dietary aflatoxin; however, no effect was observed on plasma pigmentation. These data suggest that dietary gentian violet possesses effects other than those for which it has been traditionally employed.

Animals↗
PubMed1980

Availability of phosphorus from ammonium polyphosphate for growing chickens.

Phosphorus from ammonium polyphosphate was equivalent in availability to that of other phosphate sources commonly used in broiler rations, and it was more available than that from reagent-grade tricalcium phosphate. Two three-week experiments conducted with broiler chickens showed that growth rate, feed efficiency, viability, and bone calcification were improved to a similar extent by adding an equivalent increment of phosphorus from dicalcium phosphate, defluorinated phosphate, or ammonium polyphosphate. The results of these experiments suggest that ammonium polyphosphate may be a useful phosphorus supplement for practical poultry rations.

Animals↗
PubMed1979

Depressed 59 Fe absorption due to dietary aflatoxin.

This study investigated the relationship between 59 Fe absorption and the anemia associated with aflatoxicosis in commercial broilers. A level of 0 or 5 micrograms of aflatoxin per gram of diet was fed for a 21 day period beginning at 1, 7, 14, or 21 days of age in each of two trials. Packed cell volume (PCV) and percent retention of an oral dose of 59 Fe were determined. The feeding of aflatoxin resulted in an anemia when fed from 0 to 3 or 1 to 4 weeks of age. At the conclusion of these treatment periods, percent 59 Fe retention was significantly reduced from the controls. Aflatoxin when fed from 2 to 5 weeks of age resulted in a slight but significant depression in PCV (P less than .05) with a slight but nonsignificant depression in percent 59 Fe retention. At the conclusion of the 3 to 6 week treatment period both percent iron retention and PCV were greater than controls but not significantly so. The iron retentions of birds separated into high and low PCV groups within each treatment combination were compared. Although the iron retentions of the low PCV groups were lower than those of the high PCV groups, none of the differences were statistically significant. However, Pearson correlations of PCV with percent 59 Fe retention were - .28 (P less than or equal to .02, n = 69) for control birds and - .19 (P less than or equal to .14, n = 58) for birds fed aflatoxin, suggesting a relationship between PCV and iron absorption.

Aflatoxins↗
PubMed1975

Influence of genetic differences in feed efficiency on carcass composition of young chickens.

The carcass composition of young chickens differing in efficiency of feed utilization was obtained to study changes in the carcass composition associated with differences in efficiency of feed utilization. As the efficiency of conversion of food to tissue was changed, there were associated changes in carcass moisture and lipid, regardless of differences between different populations in variability for growth rate. Carcass moisture was increased and carcass lipid was decreased in chickens with relatively better conversion of food into carcass. Carcass protein was significantly increased in chickens with better efficiency of feed utilization in one population, but not in another. Changes in carcass composition associated with efficiency of feed utilization were similar regardless of whether differences in efficiency were due to gain or to a combination of gain and consumption. Significant sex differences in carcass moisture, lipid, and protein were observed in the faster-growing broiler population but not in the lines selected from a slower-growing randombred population. There was a significant decrease in 16:1 and an increase in 18:0 fatty acids of chickens with a lower feed conversion ratio.

Adipose Tissue↗
PubMed1975

Influence of genetic differences in feed efficiency of young chickens on derivation of metabolizable energy from the diet and nitrogen retention.

The relationship of efficiency of efficiency of feed utilization with metabolizable energy derived from the diet and nitrogen retention was studied in broiler strains and in lines selected for divergence in feed conversion ratio. Individual feed conversion (g feed/g gain) and metabolizable energy derived from the diet and nitrogen retention (determined by chromic oxide method) of these strains and lines were measured, and correlations were determined at various intervals from 4 to 9 weeks of age to determine the effects of age, sex, strain, feed conversion, growth, and feed consumption on the metabolizable energy derived from the diet and nitrogen retained. Although there were significant differences in feed conversion between sexes, strains, and lines selected for divergence in feed conversion, there were no associated differences in metabolizable energy derived from the diet or in nitrogen retention. There were no significant correlations of consumption, growth, or feed conversion with metabolizable energy derived from the diet or nitrogen retention. Nitrogen retention of the White Plymouth Rock strain was significantly higher for all ages. These results show that differences observed in growth, consumption, or feed conversion do not influence derivation of metabolizable energy from the diet or nitrogen retention.

Age Factors↗
PubMed1975

Carcass composition studies. 2. Influences of breed, sex and diet on gross composition of the carcass and fatty acid composition of the adipose tissue.

A study was conducted to determine the effect of breed, sex and diet on the carcass composition of chickens. Male and female chicks of the Light Brahma, White Plymouth Rock, Single Comb White Leghorn, Black Jersey Giant and Dark Cornish breeds were fed three diets of widely varying calorie:protein ratios to four weeks of age. The Black Jersey Giant chickens attained the greatest weight at 4 weeks followed by the White Plymouth Rock, Dark Cornish and Single Comb White Leghorn with the Light Brahma growing the slowest of the strains tested. Significant differences in the quantity of moisture, protein, total lipid and ash present in the total carcass was found among certain breeds. The Light Brahma contained the largest amounts of total lipid, 10.4%, followed by the White Plymouth Rock, 10.2%, Black Jersey Giant, 9.5%, Single Comb White Leghorn, 8.8%, and the Dark Cornish, 8.6%. Both sex and diet also caused differences in the total body composition. Significant differences in the amounts of certain fatty acids in the carcasses of the various breeds were found; however, these differences were not great.

Adipose Tissue↗