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Biomedical subjects

R A Leng

Publications and source records attributed to R A Leng.

At least 19 recordsLinked to original sources
PubMed2000

Immunization with Streptococcus bovis protects against lactic acidosis in sheep.

Lactic acidosis is a gastrointestinal disorder resulting from the rapid overgrowth of lactic acid-producing bacteria when ruminants are suddenly introduced to grain feed. The present study has investigated the ability of live and killed bacterial vaccines to reduce lactic acidosis in sheep, via a stimulation of specific antibody production against lactic acid-producing bacteria. Forage-fed sheep were immunized with live or killed Streptococcus bovis Sb-5 vaccine, with or without adjuvant, via intramuscular injection. After the primary immunization, three boosters were given at 2-4 week intervals. Sheep were subsequently challenged by a sudden switch to a grain-based diet. Following challenge, vaccinated sheep maintained significantly higher feed intake, and had higher rumen pH, lower L-lactate concentrations, and less severe diarrhoea scores than non-vaccinated control sheep. Higher rumen pH, lower mortality and less severe diarrhoea were found in the animals immunized with live vaccine compared to the animals immunized with killed vaccines. Significant increases in mucosal and systemic antibody responses were observed after boosting; the S. bovis-specific antibody concentrations were significantly higher in samples of saliva, rumen fluid and serum from sheep immunized with live vaccine than with killed vaccines. These results demonstrate that lactic acidosis can be reduced by immunization against S. bovis, and that live Sb-5 vaccine is effective in invoking mucosal as well as systemic antibody responses.

Acidosis, Lactic↗
PubMed2000

Immunization with a Streptococcus bovis vaccine administered by different routes against lactic acidosis in sheep.

Streptococcus bovis is an important lactic acid bacterium in the rumen, which contributes to the development of lactic acidosis. This study was designed to test the efficacy of immunization with S. bovis primed either intramuscularly (i.m.) or intraperitoneally (i.p. ) against lactic acidosis. Forty-five wethers were allocated to three treatment groups. Two groups were injected with a S. bovis vaccine by either the i.m. or i.p. route for primary immunization; both groups were further immunized by the same route(s) (oral and/or i.m.) for boosters. The third group was not immunized (control). Antibody concentrations were measured in saliva prior to and following animals being fed a grain diet, and also in the rumen fluid, before the animals were suddenly introduced to a grain diet. The average antibody concentration in the animals of the i.m. group was higher than the i.p. group (P< 0.05). The antibody concentration in the rumen fluid of immunized sheep was higher than the control animals (P< 0.01). The difference in the rumen fluid antibody concentration between the i.m. and i.p. groups was not statistically significant (P> 0.05). In the i.m. group, there was a significantly greater feed intake, higher rumen pH, lower diarrhoea scores, and less increase in blood packed cell volume following grain feeding than in the animals of the control group. The severity of diarrhoea and the increase of blood packed cell volume in the animals of the i. p. group were also less than in the animals of the control group. The results suggest that the risk of lactic acidosis can be reduced by immunization against S. bovis, and that the immunization primed i. m. is more effective than the immunization primed i.p.

Acidosis, Lactic↗
PubMed1999

Immunisation against lactic acidosis in cattle.

The present study was designed to investigate the efficacy of control of lactic acidosis by immunisation against lactic acid-producing bacteria, Streptococcus bovis and Lactobacillus. Ten steers were allocated to two treatment groups. One group was immunised with a vaccine containing S. bovis (strain Sb-5) and Lactobacillus (LB-27) cells, and the other was a non-immunised control group. The vaccine, using Freund's complete adjuvant for primary immunisation and Freund's incomplete adjuvant for boosters, was administered intramuscularly. After primary immunisation, boosters were given at 2 to 4 week intervals. Both anti- S. bovis and anti- Lactobacillus IgG levels in saliva increased significantly (P < 0.01) after the 1st booster which were lower (P < 0.05) than the IgG levels after the 2nd and 3rd boosters, but were not significantly different (P > 0.05) from the IgG levels prior to a grain challenge (after the 4th booster). There were positive correlations between the anti- S.bovis and anti- Lactobacillus IgG in serum and saliva. Compared with the control group, steers in the immunised group had higher (P < 0.05) feed intakes, lower (P < 0.05) rumen concentrations of lactate and lower numbers of S. bovis and Lactobacillus. Three of the control animals were withdrawn from the grain challenge due to their rumen pH persisting below 5.2, while only one animal in the immunised group was withdrawn. These results suggest that the risk of lactic acidosis can be reduced by immunisation against S. bovis and Lactobacillus.

Acidosis, Lactic↗
PubMed1995

Roxithromycin 150 mg b.i.d. versus amoxycillin 500 mg/clavulanic acid 125 mg t.i.d. for the treatment of lower respiratory tract infections in general practice.

Two hundred and forty-two patients over 16 years of age with community-acquired lower respiratory tract infection (LRTI), matched for age and sex, were randomised to receive either roxithromycin 150 mg b.i.d. or amoxycillin 500 mg/clavulanic acid 125 mg t.i.d. for 7 days, with a further 7 days if insufficient response was seen. Clinical efficacy at 7 days was 69% for roxithromycin and 56% for amoxycillin/clavulanic acid (p = 0.05) and at study end it was 91% for both antibiotics. There were fewer second treatment courses in the roxithromycin group (26% vs. 38%, p = 0.04) and a shorter treatment duration (8.29 days vs. 9.34 days, p > 0.05). Twelve patients (9.8%) treated with roxithromycin and 19 (17.1%) treated with amoxycillin/clavulanic acid had adverse effects possibly, or probably, related to the antibiotic. Roxithromycin appears to be a more appropriate choice than amoxycillin/clavulanic acid for the treatment of LRTI in the community given its more appropriate in vitro spectrum, efficacy against most common and atypical pathogens, greater cost-effectiveness, more convenient dosage regimen (b.i.d.), and superior tolerability profile.

Adolescent↗
PubMed1991

Acetate clearance rate as a potential index of the availability of glucogenic precursors in ruminants fed on roughage-based diets.

Three experiments were conducted to investigate interactions between acetate and glucose metabolism in sheep fed on roughage-based diets, and to establish whether the clearance rate of an intravenous acetate load would provide a valid index of the dietary acetate:glucogenic precursors ratio. In Expt 1 lambs were fed on a basal diet of wheat straw and supplemented with propionate and protein. Both supplements increased glucose irreversible loss rate (ILR) although not to the same degree. Acetate clearance rates were increased by protein and propionate supplementation and were positively related to glucose ILR irrespective of precursor. In Expt 2 the effects of an increased dietary load of acetate given with or without propionate were investigated. Glucose ILR did not respond to acetate supplementation, but was increased when propionate was fed in addition to acetate. This was reflected in an unchanged ability to clear an intravenous acetate load from the blood when acetate alone was added, but an increased acetate clearance rate when propionate was fed in addition to acetate. In Expt 3 the effects of supplementation with various propionate:acetate ratios were investigated. Acetate clearance was consistently increased by an increased propionate:acetate ratio. These results show that the metabolism of excess acetate is responsive to the dietary supply of glucose precursors, and provide support for the concept that additional glucose precursors are necessary for the efficient utilization of acetate when roughage diets low in protein are fed.

Acetates↗
PubMed1991

Sulphur availability and microbial fermentation in the fauna-free rumen.

The concentration of H2S and rate of feed digestion, VFA and methane production in the rumen were measured in sulphur deficient (-S) and S supplemented (+S) sheep while fauna-free (-P) and after refaunation (+P). The concentration of rumen H2S was increased by S supplementation but was not affected by the presence of protozoa. When fauna-free, -S sheep had reduced rates of feed digestion (30 v 48%/d), acetate synthesis (35 v 115 g/d) and methane synthesis (0.4 v 7.4 g C/d) compared to +S sheep and up to 36% (v/v) of total rumen gas was H2. When these sheep were given a single dose of 8.8 g Na2SO4, the proportion of methane increased and the proportion of H2 in rumen gas decreased. After refaunation of sheep, their rates of feed digestion, VFA production and methane production were higher and were not affected by the level of S. From this differential response to S deficiency by -P and +P sheep, it is concluded rumen protozoa increase the availability of S to other rumen microbes. This is probably because they degrade protein through to peptides and amino acids.

Ammonia↗
PubMed1991

Community acquired pneumonia: aetiology and prognostic index evaluation.

A 10 month prospective study of all adults admitted to Waikato Hospital with community acquired pneumonia was performed to assess aetiology, mortality, hospital stay, and the value of a prognostic index based on that obtained from a British Thoracic Society study. The 92 patients in the survey had a mean age of 56 (range 13-97) years. A microbiological diagnosis was established in 72%; Streptococcus pneumoniae (33%), Mycoplasma pneumoniae (18%), and influenza A virus (8%) were the most common microorganisms. Other causative organisms were Legionella pneumophila (4 cases), Staphylococcus aureus (3), Klebsiella pneumoniae (2), Haemophilus influenzae (2), Nocardia brasiliensis (1), and Acinetobacter calcoaceticus (1). Chlamydia sp, influenza B virus and adenovirus were each found in one case; all were cultured on nasopharygeal aspirates. Aspiration was considered to be the underlying cause in five patients, two with epilepsy and one with pseudobulbar palsy. Five of the six deaths that occurred were in patients over 75 years of age and the other was 69. In four of the six the established causative organisms were Chlamydia sp (1), K pneumoniae (1), and S aureus (2). Patients had a 16 fold increased risk of death if they had two or more of the following on admission: a respiratory rate of 30/minute or more, diastolic blood pressure of 60 mm Hg or less, and either confusion or a plasma urea concentration greater than 7.0 mmol/l.

Adolescent↗
PubMed1989

Sheep productivity in the Ethiopian Highlands on a diet supplemented with urea-molasses block and/or noug cake.

A feeding experiment was carried out in which adult ewes of the Ethiopian Highland Menz breed grazed on meadow pasture were supplemented with urea-molasses block and/or noug cake. There was low consumption of urea-molasses block (67 gd-1) and its contribution to total nitrogen requirement was minimal. Dietary treatment had no significant effect on liveweight changes of ewes, their reproductive performance and performance of the lambs. When there was liver fluke infection, ewes and their lambs which were supplemented with urea-molasses block and/or noug cake had better survival compared to those which did not get any supplements (35% mortality vs 55%). The rumen ammonia-N concentration was significantly lower in the control sheep (11 mg/100 ml) and those that received only urea-molasses (14 mg/100 ml) and highest in sheep receiving the urea-molasses block and noug cake (26 mg/100 ml). The volatile fatty acid proportions were not significantly affected by the diets. Low level of urea-molasses block consumption seemed to be a main factor limiting the usefulness of the urea-molasses block and it is recommended that factors likely to enhance its consumption be investigated.

Animal Feed↗
PubMed1988

Dynamics of protozoa in the rumen of cattle.

1. The dynamics of protozoa were studied in two groups of rumen-fistulated cattle fed on a basal diet of molasses ad lib., with oaten chaff given at 6 or 18 g/kg live weight. This diet resulted in different mixtures of protozoal species in the populations in the rumen. 2. The rumen protozoa were studied by intrarumen injections of protozoa labelled in vitro with [14CH3]choline. An indication of protozoal death and fermentation of protozoal cell residues was obtained by measuring 14C loss via the methane pool. 3. After a single injection of labelled protozoa, the decline in the specific radioactivity (microCi/g nitrogen) of the protozoal pool in the rumen indicated that first-order kinetic processes applied. Conversely the specific radioactivity of protozoa, incubated in rumen fluid, remained constant indicating no growth in vitro, presumably owing to a rapid exhaustion of essential nutrients. 4. The protozoal populations in the rumen of cattle fed on the diet with the low level of oaten chaff were mainly small ciliates; but on the higher level of chaff in the diet, the large ciliates were a higher proportion of the total protozoal population present. 5. The mean pool size of protozoa in the rumen was significantly larger and the protozoal half-life tended to be longer for cattle fed on the higher level of chaff in the diet. The apparent production rate of protozoa in cattle fed on each diet was not significantly different and there were no differences in the production rate of methane. The percentage losses of label from protozoa in the rumen via the methane pool were not significantly different on the two diets and indicated that 74% of the protozoa that were apparently irreversibly lost from the rumen could be accounted for by death and lysis in the rumen and therefore only 26% of protozoa apparently entered the lower digestive tract.

Ammonia↗
PubMed1986

Dynamics of large ciliate protozoa in the rumen of cattle fed on diets of freshly cut grass.

1. The dynamics of large ciliate (holotrich) protozoa (Isotricha and Dasytricha spp.) in the rumen of cattle given cut, fresh ryegrass (Lolium multiflorium Lam) were studied by means of a single intrarumen injection of 14C-labelled protozoa prepared in vitro by adding [Me14C]choline to rumen fluid containing protozoa and incubating at 39 degrees for 2 h. 2. An indication of the lysis rate of protozoa in the rumen was obtained from the radioactivity apparently lost through the methane pool. 3. The turnover time of the holotrich protozoa indicates that these protozoa were extensively retained in the rumen and that only a small proportion of those produced in the rumen flowed out in the digesta. This was supported by the estimation of the rate of lysis which was approximately 85% of the turnover rate in the rumen. 4. The apparent production rate of the larger protozoa indicates that they contribute only about 9% of the predicted net microbial protein synthesis in the rumen.

Animals↗
PubMed1985

Effects of level of dietary protein and exercise on growth rates of horses.

Rates of growth were measured in two-year-old (Experiment 1) and nine-month-old (Experiment 2) horses fed high (12 or 14 per cent) or low (6 or 8 per cent) crude protein diets with one of two levels of exercise (0 or 12 km trotting per day at 12 km/h). In the non-exercised horses feed intakes and growth rates were greater on the high than on the low protein diets. Exercise increased feed intakes and growth rates of horses on the low but not the high protein diets, so that in the exercised groups there were no significant differences in feed intakes or growth rates between the horses on the two dietary protein levels. Exercise increased the apparent digestibility of dry matter, energy and crude protein. There were no differences in skeletal characteristics caused by either dietary protein level or exercise. These results suggest that the growing horse, if exercised regularly, may be given a diet of lower protein concentration than currently recommended without significant reduction in growth rate.

Animal Feed↗
PubMed1985

Effects of exercise and level of dietary protein on digestive function in horses.

Rates of passage of fluid and particulate digesta markers and apparent digestibility estimated by three methods were compared in yearling horses fed high (14 per cent) or low (8 per cent) crude protein diets with one of two levels of exercise (0 or 12 km trotting per day at 12 km/h). Mean retention times (MRT) of the fluid marker (51Cr-EDTA) were shorter than those of the particulate marker (ruthenium-phenanthroline). There were no significant effects of dietary protein level on passage of either marker or on apparent digestibility of dry matter. Exercise increased voluntary feed intake and apparent digestibility and reduced the MRT of the particulate marker but increased the MRT of the fluid marker. Estimates of apparent digestibility based on acid-insoluble ash were similar to those calculated from total faecal collection but those based on chromic oxide were significantly lower.

Animal Feed↗
PubMed1984

Further studies on the effects of the presence or absence of protozoa in the rumen on live-weight gain and wool growth of sheep.

Lambs were given a diet of oaten chaff-sucrose-fishmeal (48:48:4, w/w) and either 60 (diet A) or 120 (diet B) g urea/kg sucrose in the diet. All animals were defaunated and half were refaunated. Each group of lambs (faunated and defaunated) was then divided into two groups and given diet A or diet B. Feed intake, wool growth and live-weight change were monitored over a 182 d period. The level of urea supplementation had no effect on wool growth or live-weight gain. Defaunated lambs gained live weight at a higher rate (9%, P less than 0.06) and grew 37% more wool (P less than 0.01) than the lambs with large populations of protozoa in their rumens.

Animals↗
PubMed1984

Serratia marcescens in a newborn unit--microbiological features.

During a 12 mth period in a newborn unit (NBU), Serratia marcescens was isolated from 3 fatal cases of meningitis, 5 cases of septicemia, 5 of pneumonia, 4 or urinary tract infection and 15 of conjunctivitis. At the peak of the outbreak a 95% incidence of rectal colonization with S. marcescens was observed in the NBU. Polyacrylamide gel electrophoresis of sodium dodecylsulphate disrupted Serratia (SDS-PAGE) established that all isolates were identical.

Bacteriophage Typing↗
PubMed1984

Nitrogen metabolism in the rumen.

Nitrogen metabolism is reviewed with emphasis on methods for quantitating various nitrogen-transactions in the rumen of animals on a variety of diets. Ammonia kinetics, microbial cell synthesis, the inputs of endogenous nitrogen, degradation of dietary protein, and availability to the animal of dietary bypass protein are discussed. The efficiency of microbial protein from the rumen is discussed in relation to the ratio of protein to energy in the nutrients available to meet the requirements of the animal. The ratio is determined largely by the maintenance requirements of microbes and the breakdown of microbial materials, which result in the recycling of microbial nitrogen in the rumen. Emphasis is placed on the role of rumen protozoa in decreasing the ratio of protein to energy in absorbed nutrients in ruminants on diets that are marginally deficient in protein. Recent studies of the dynamics of protozoa in the rumen and their contribution to microbial protein outflow are summarized.

Amino Acids↗
PubMed1982

Dynamics of protozoa in the rumen of sheep.

Protozoa were labelled by incubating 100 ml rumen fluid with [14C]choline for 1 h. The protozoa were concentrated by centrifugation and then washed with rumen fluid. This reduced residual 14C in the fluid medium to insignificant amounts while still retaining the viability of the labelled protozoa. Washing procedures using formal saline (40 g formaldehyde/1 saline (9 g sodium chloride/1)) and saline were developed to isolate protozoa for estimation of specific radioactivity. 2. The protozoal pool in freshly-collected rumen fluid incubated in vitro retained 90% of the radioactivity for up to 6 h following addition of 14C-labelled protozoa produced as indicated previously. The specific radioactivity of protozoa did not change during the incubation period. 3. Protozoa labelled with [14C]choline and then stored until they died rapidly lost 14C to methane when they were incubated in rumen fluid or were injected into the rumen. Some [14C]choline was salvaged under these conditions by the live protozoa present as they apparently incorporated up to 13% of the label from the dead protozoa. However, protozoal debris from the injected solution could also have been present in the isolated protozoa. 4. The in vitro results suggested that the protozoal preparations were viable, and that the incorporated choline did not have a turnover in excess of the turnover of nitrogen (i.e. specific radioactivity remained constant with time in vitro) suggesting that the dilution of specific radioactivity of protozoa following mixing of a 14C-labelled dose of protozoa represented the rate of irreversible loss and also replacement of protozoa in the rumen. 5. 14C-labelled protozoa had a half-life in the rumen which was greater than that of rumen fluid and in six animals the protozoal replacement rate was 1-4.1 mg N/min. 6. Losses of 14C from labelled protozoa in the rumen in methane or via abomasal digesta were 65 and 35% respectively. 7. The results suggest that protozoal growth may be as high as 32% of the total microbial protein synthesis in the rumen but that 65% of the protozoa die and are degraded in the rumen.

Abomasum↗
PubMed1981

Kinetics of large ciliate protozoa in the rumen of cattle given sugar cane diets.

1. Experiments were undertaken to examine the kinetics of large ciliate protozoa in the rumen of cattle on sugar-cane diets. 2. Three Zebu bulls were fed once daily on a diet of sugar cane and wheat bran. The diurnal patterns of volatile fatty acids and ammonia concentrations, and the numbers of protozoa in rumen fluid were determined. The numbers of protozoa reached values of 5 X 10(4)/ml for holotrichs (large ciliates) mainly Isotricha and Dasytricha spp and 4 X 10(5) for smaller protozoa, mainly Entodinia (small ciliates). 3. A method was developed which allowed large ciliate protozoa in rumen fluid to be separated from plant material and bacteria and concentrated in a relatively uncontaminated form. Analysis of these protozoa indicated that 1.8 X 10(5) large ciliates contained 1 mg nitrogen and approximately 32 mg dry matter. 4. A labelled preparation consisting mainly of large ciliates (principally Isotricha spp.) was obtained by incubating isolated protozoa in rumen fluid (free of plant materials) containing [14C-methyl]choline and then isolating them by sedimentation and differential centrifugation. 5. A portion of the preparation containing labelled protozoa was incubated in vitro with rumen fluid to determine the turnover of 14C-labelled metabolites. There was no apparent dilution of the label in the protozoa over a 22 h period. 6. A major portion of the preparation containing labelled protozoa was returned to the rumen of each of the donor cattle as a single injection. The specific radioactivity in the large protozoa (microCi/mg N) was monitored frequently for over 30 h, and thereafter daily for a further 12 d. The kinetics of tracer dilution were analyzed to give estimates of the size of the pool of these large ciliates in the rumen (24-46 g N), and of their apparent rate of turnover. 7. In contrast to the slow turnover of the large ciliates, the rate of turnover of the rumen fluid pool (approximately 54 1), estimated from the rate of dilution of polyethylene glycol, was considerably faster. Large ciliates were therefore selectively retained within the rumen.

Ammonia↗