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Biomedical subjects

R A Leng

Publications and source records attributed to R A Leng.

At least 37 records · Page 2Linked to original sources
PubMed1979

Secondary fermentation in the runen of a sheep given a diet based on molasses.

1. The extent of conversion of acetate-carbon to carbon dioxide in the rumen of a 40 kg wether consuming 1 kg molasses/d was estimated using isotope-tracer-dilution techniques. 2. There was a high rate of conversion of acetate to CO2 (6.0 g C/d) in the rumen. There were high concentrations in the rumen of Methanosarcina approximately 6 x 10(9)/ml which represents a significant proportion of the rumen bacterial biomass. These organisms are usually found in mud and sludge and are capable of oxidizing acetate. 3. The most likely explanation of these results was that there was an extensive secondary or sludge-type fermentation occurring in the rumen which results in volatile fatty acids being converted to CO2 and methane. In similar studies with sheep given lucerne (Medicago sativa) diets, conversion of acetate-C to CO2 within the rumen was not evident. 4. It is suggested that a major effect of the presence of secondary fermentation processes in the rumen may be to reduce availability of energy nutrients to the animal, and to alter the ratio protein:energy in the absorbed nutrients.

Acetates↗
PubMed1979

The effects of defaunation of the rumen on the growth of lambs on low-protein-high-energy diets.

1. The effects of defaunation of the rumen of lambs given low-protein-high-energy diets were studied using animals fed ad lib. a basal diet of sugar and oaten chaff which was supplemented with fish meal at various levels. These diets supported relatively large populations of protozoa in the rumen. 2. A nonyl phenol ethoxylate (15 g. Teric GN9:ICI Australian Ltd) given intraruminally, was shown to be an effective means of defaunating the rumen and the lambs were maintained protozoa-free by isolation. 3. In lambs given low levels of fish meal in the diet, the absence of rumen protozoa increased growth rate and improved the food conversion efficiency (g dry matter intake/g growth). These effects were not apparent at high levels of protein supplementation. 4. These results suggested that the absence of rumen protozoa resulted in an increased availability of nutrients supplying both energy and amino acids since the efficiency of food utilization and the rate of wool growth (which is sensitive to amino acid supply) were increased in lambs on the low level of protein supplementation without apparently increasing food intake.

Animals↗
PubMed1979

Protein nutrition of growing lambs. 2. Effect on nitrogen digestion of supplementing a low-protein-cellulosic diet with either urea, casein or formaldehyde-treated casein.

1. Lambs with cannulas in the duodenum and ileum were allowed free access to one of four diets: a basal diet of oat hulls and solka floc, or the basel diet supplemented with either urea, urea plus casein or urea plus formaldehyde-treated (HCHO)-casein. Mean nitrogen intake was 1.9 g N/d for the basal diet and 15.0. 32.4 and 36.9 g N/d respectively for the other diets. 2. The rate of irreversible loss of ammonia from the rumen pool estimated using 15NH4+ was highest on the casein diet (33 g NH3-N/d) by comparison with 18 g NH3-N/d for the urea and HCHO-casein diets and 7 g NH3-N/d for the basal diet. 3. The proportions of bacterial and protozoal N in the rumen derived from rumen ammonia did not differ significantly between the supplemented diets and were 0.66 and 0.52 respectively. 4. Estimation of 15N flowing to the duodenum during continuous infusions of 15NH4+ into the rumen indicated considerable ammonia absorption from the rumen on all the diets. Greatest absorption of ammonia (21 gN/d) apparently occurred in animals on the diet supplemented with urea and casein. 5. The estimated microbial non-ammonia-N (NAN) flowing out of the rumen per unit organic matter fermented in the rumen (FOM) was similar on all diets, i.e. 21.3 (+/- 1.09) g N/kg Fom. the requirement for dietary fermentable N for microbial N production on these diets was 1.2 (+/- 0.07) g N/MJ ME. 6. The flow of NAN into the duodenum and through the ileum, and total N in the faeces was significantly influenced by the form of N supplementation. The flow of NAN into the duodenum for the HCHO-casein diet (27 g N/d) was more than twice that for the other diets (11 g N/d). The flow of NAN through the ileum and excretion of total N in the faeces was also greater with the HCHO-casein diet than with all other diets. The apparent digestibility of NAN in the small intestine ranged between 0.62--0.66 for all diets. 7. Urea and casein supplements were apparently completely degraded in the rumen. In contrast, the HCHO-casein was almost completely resistant to degradation in the rumen and only 65% of the HCHO-casein was digested in the small intestine. 8. Protein absorbed : energy absorbed (expressed as NAN digested in the small intestine/MJ ME) was calculated to be 5.5 (+/- 0.70) for the basal, urea and urea-plus-casein diets, and 11.6 (+/- 1.71) for the urea-plus-HCHO-casein diet.

Animals↗
PubMed1978

Methane production in the rumen and lower gut of sheep given lucerne chaff: effect of level of intake.

1. Methane production rates were estimated simultaneously in the rumen and caecum of sheep given 200, 400, 600, 800 and 1000 g lucerne (Medicago sativa) chaff/d using isotope dilution techniques. Estimates were also made of volatile fatty acid (VFA) production in the rumen at each level of feeding. In all studies three to four animals were used at each level of intake. 2. Production of VFA and of methane were both related to digestible energy (DE) intake. Regression lines for both VFA production and methane production v. DE intake had significant intercepts indicating an input of endogenous, fermentable organic matter into the rumen in excess of 50 g/d. 3. The values obtained for rates of methane production were compared with those calculated from stoicheiometric equations relating rates of methane and VFA production. Comparisons of methane production with that predicted from DE intake were also made. 4. Balances for digestion of food determined for the rumen indicated that the energies in the end-products were more than 100% of the DE intakes of lucerne chaff. Correction for fermentation of apparent endogenous materials resulted in more realistic values. Endogenous materials appeared to make a significant contribution to VFA and methane production, particularly at low levels of intake.

Animals↗
PubMed1978

The effects of defaunation of the rumen on the growth of cattle on low-protein high-energy diets.

1. The effects of defaunation of the rumen of cattle on low-protein diets was studied using animals given free access to a basal diet of liquid molasses and 1500 g oaten straw/head per d. These diets induced moderate numbers of protozoa in the rumen. 2. Nonyl phenol ethoxylate (trade name teric GN9) was used for defaunation; 100 g teric GN9 was found to be sufficient to eliminate protozoa from the rumen. 3. In cattle given the basal diet without bypass protein supplementation, defaunation had no effect on growth rates. Addition of 240 g of a feed pellet containing bypass protein increased growth rate significantly. Growth rates were significantly increased by 43% in cattle on the higher protein intake and where protozoa were removed. Intake of molasses was apparently stimulated by a protein supplementation but not by defaunation and this finding is discussed. 4. The results demonstrate that in cattle given a molasses-based diet, low in bypass protein, growth rates can be stimulated by defaunation without an effect on feed intake, the main effect apparently arising through an increased efficiency of utilization of feed.

Animals↗
PubMed1977

Listeria monocytogenes meningitis: case report.

A case of Listeria monocytogenes septicaemia with meningitis is described. Predisposing factors in this case included chronic liver disease, diabetes mellitus and liver malignancy. The infection responded poorly to ampicillin.

Aged↗
PubMed1977

Studies of fatty liver and kidney syndrome in chickens: dynamics of glucose metabolism.

1. Fatty liver and kidney syndrome (FLKS) was induced in a proportion of a group of 4-week-old chickens by giving a diet of meat meal and wheat; inclusion in the diet of animal tallow for 54 h substantially reduced the occurrence of FLKS. 2. Measurements of dynamic aspects of glucose metabolism were made with single injections of [2-3H]glucose which indicated that birds given the 'FLKS-inducing' diet and showing physical symptoms of FLKS had significantly lower rates of synthesis of glucose than birds given either the same diet supplemented with tallow or a commercial diet. 3. In a second series of experiments glucose metabolism was studied in birds (1) with or without physical symptoms that were given the 'FLKS-inducing' diet and (2) birds given the same diet supplemented with tallow or biotin. Affected birds fed the 'FLKS-inducing' diet had significantly lower plasma glucose concentrations, pool sizes and synthesis rates than birds fed the same diet and not showing symptoms, or birds fed the supplemented diets. 4. It is suggested that the cause of death in birds with FLKS is a low rate of gluconeogenesis during periods without feed which results in a lack of glucose to meet essential functions.

Animals↗
PubMed1976

Methane production and digestibility measurements in the grey kangaroo and sheep.

Three grey knagaroos and three sheep were given a diet of lucerne chaff and measurements were made of feed intake, digestibility coefficients, methane production rate and volatile fatty acid content of the "stomach" and caecum for each animal. The kangaroos had lower intakes of digestible dry matter and organic matter than the sheep; this was related to lower intakes of dry matter and lower apparent digestibility coefficients particularly of the crude fibre fraction. Methane production in the sheep (collected in respired air through a mask) was 0-81 litre/h; no methane was collected in the respired air from kangaroos. Anal release of methane in sheep and kangaroos indicated that some methane was produced in the hind gut of kangaroos and that all of this methane was lost via the anus. This finding was different to the sheep which apparently excreted 80-90% of the hind gut methane via the lungs. Thus in both sites of apparent high microbial growth in the gut of kangaroos methane production is negligible or lower than in the same sites in sheep. Possible explanations for the absence of measurable methane production in the kangaroo fore-stomachs are discussed.

Anal Canal↗
PubMed1976

Further studies of the dynamics of nitrogen metabolism in sheep.

1. A study of ammonia and urea metabolism in sheep was made using isotope dilution techniques with (15NH4)2SO4,[15N]urea and [14C]urea in order to determine quantitatively the movements of urea-N and NH3-N throughout the body of normal, feeding sheep. 2. Single injections of 15N-labelled compounds were made into the rumen fluid NH3, caecal fluid NH3 and the blood urea pools, in order to estimate the rates of flux through, and the transfer of N between, these and other nitrogenous pools in the body. 51CrEDTA was injected into the rumen and caecum with (15NH4)2SO4 to allow estimation of fluid volumes and to provide an indication of mixing, and of times of transit of isotopes between different sampling sites in the digestive tract. 3. The sheep ate approximately 22 g lucerne chaff/h and the mean dietary N intake was 16-3 g/d. 4. The rate of flux of NH3 through the rumen NH3 pool was 15-0 g/d (i.e. 90% of the dietary N ingested; however, this amount also included N from plasma urea (1-1 g/d) and other endogenous sources including NH3 derived from caecal NH3 (0-4 g/d). 5. Only 40% of the N in isolated rumen bacteria was derived from NH3, indicating that a considerable proportion of their N requirements were obtained from compounds other than NH3 (e.g. peptides and amino acids). 6. There was evidence of recycling of N between nitrogenous pools in the rumen, probably through rumen NH3 leads to microbial N leads to NH3. 7. It was estimated that 5-3 g blood urea-N/d entered the digestive tract; 20% of this urea was degraded in the rumen, 25% in the caecum and the remainder was apparently degraded elsewhere; there was evidence of urea degradation in the large intestine posterior to the caecum and it is suggested that urea degradation and absorption of the resultant NH3 may occur in the ileum. 8. Of the 4-8 g N/d entering the caecal NH3 pool, 4-2 g N/d left and did not return and the difference (0-6 g N/d) was recycled, possibly through caecal NH3 leads to microbial N leads to NH3. 9. A large proportion of the NH3 entering the caecal NH3 pool (70% or 3-2 g N/d) was apparently derived from degradation of nitrogenous products, other than urea, including rumen microbial N (1-0 g N/d) passing undigested from the small intestine. 10. Less than half the NH3-N of caecal origin entering the rumen passed through the blood urea pool; the remainder was apparently transported as other nitrogenous compounds in the blood or body fluids. 11. The results of the three experiments were combined in a general three-pool, open-compartment model which formally recognizes an unlimited number of other unspecified, interconnected pools together comprising the whole-animal system. Rates of flux through, and transfer of N between these and other nitrogenous pools in the body were calculated by solving this model and the information derived has been applied to whole-animal models with a view to subsequently using these models in computer simulation studies.

Ammonia↗
PubMed1976

Rates of production of methane in the rumen and large intestine of sheep.

1. An isotope tracer method for estimating methane production in sheep is described. 2. The technique was used to estimate methane produced in both the upper and lower digestive tract and to determine the routes by which it was excreted. 3. Four Merino ewes given lucerne chaff (33 g every hour) were used. 4. Total methane production rate was 21 +/- 1-1 (SE) ml/min; production in the rumen accounted for 87 +/- 1-2% of the total production; 95 +/- 1-4% of the methane produced in the rumen was excreted by eructation. 5. Of the methane produced in the lower digestive tract, 89 +/- 2-3% was excreted through the lungs and 11% through the anus.

Anal Canal↗