Search PubMed⌕ Search

Biomedical subjects

J V Nolan

Publications and source records attributed to J V Nolan.

At least 37 records · Page 2Linked to original sources
PubMed1988

The effect of haemonchosis and blood loss into the abomasum on digestion in sheep.

1. An experiment was conducted to determine the effect of the abomasal parasite, Haemonchus contortus, on the pattern of digestion and nutrient utilization in Merino sheep. There were three groups of sheep: infected with H. contortus (300 larvae/kg live weight) (n 5), sham-infected by transferring blood from the jugular vein to the abomasum, and uninfected (control) sheep (n 9) which were fed daily rations equal to amounts consumed by 'paired' animals in the two other treatment groups. A diet containing (g/kg): lucerne (medicago sativa) chaff 490, oat chaff 480, ground limestone 10, urea 10, and sodium chloride 10, was given in equal amounts at 3-h intervals. 2. Continuous intrarumen infusions (8 d) of chromium and ytterbium were made in order to measure the flow of digesta through the rumen, duodenum and ileum with 15NH4Cl included in the infusate for the final 3 d. The loss of blood into the gastrointestinal tract was measured using 51Cr-labelled erythrocytes and the rate of irreversible loss of plasma urea was measured with reference to a single intravenous injection of [14C]urea. Samples of rumen fluid were taken for analysis of volatile fatty acid (VFA) concentrations. 3. The infected and sham-infected sheep developed severe anaemia during the period over which digestion and metabolism measurements were made (packed cell volume 0.118 (SE 0.0042) and 0.146 (SE 0.0073) respectively). The corresponding rates of blood loss into the gastrointestinal tracts were 253 (SE 23) and 145 (SE 17) ml/d. 4. The proportions of VFA in rumen fluid were altered (P less than 0.05) in the infected group with a decrease in the ratio, acetate: propionate (control 3.28, infected 2.58, standard error of difference (SED) 0.21). There was also an increase in rumen fluid outflow rate (P less than 0.01) from 4.05 litres/d in the control group to 5.53 litres/d in the infected group (SED 0.43). Water intake was higher (P less than 0.05) in the infected than in the control animals (2.25 and 5. There was a decrease (P less than 0.05) in apparent digestion of organic 5. There was a decrease (P less than 0.05) in apparent digestion of organic matter in the forestomachs of infected sheep (0.32 compared with 0.39 in the control, SED 0.02). There was also a decrease (P less than 0.05) in the apparent digestion of organic matter across the whole digestive tract (0.65 control, 0.61 infected, SED 0.013).(ABSTRACT TRUNCATED AT 400 WORDS)

Abomasum↗
PubMed1986

Nitrogen and carbon flows between the caecum, blood and rumen in sheep given chopped lucerne (Medicago sativa) hay.

1. Experiments involving 15N and 14C tracers were made in sheep consuming 800 g air-dry chopped lucerne (Medicago sativa) hay/d and providing 20.4 g N/d to study N and C flows within the caecal digesta and between the caecum, blood and rumen. 2. Continuous infusions of 15N tracers were made into the caecal ammonia, blood urea and rumen NH3 pools. The concentration and enrichment of caecal digesta NH3-N, caecal microbial N, caecal digesta non-urea, non-ammonia-N (NU-NAN), faecal NU-NAN, blood urea-N, rumen digesta NH3-N and rumen bacterial N were estimated at intervals during the infusions. A three-pool open-compartment model was solved to estimate N flows between the caecal digesta NH3-N, blood urea-N and rumen digesta NH3-N pools. 3. The rate of irreversible loss from the caecal digesta NH3-N pool was 2.17 (SE 0.623) g N/d. On average 0.9 (SE 0.56) g N/d of caecal digesta NH3-N was derived from blood urea and 0.1 (SE 0.08) g caecal digesta NH3-N/d was apparently derived from the fermentation of undigested rumen microbes in the caecum. The amount of NH3-N produced by proteolysis and deamination of dietary and endogenous N was 1.1 (SE 0.13) g/d. 4. There was net incorporation of 0.56 (SE 0.306) g caecal digesta NH3-N/d into caecal microbes. The microbial N synthesized de novo in the caecum was not determined, but 2.9 (SE 0.52) g microbial N/d of both rumen and caecal origin flowed out of the caecum and constituted 0.48 of the NU-NAN flow. The majority (mean 0.83 (SE 0.044] of this microbial N was excreted in faeces. 5. On average 1.8 (SE 0.80) g caecal digesta NH3-N/d were absorbed. Of this NH3-N, 0.92 (SE 0.054) was converted to blood urea, contributing 0.10 (SE 0.031) of blood urea-N. Only 0.012 (SE 0.0041) of rumen digesta NH3-N and 0.005 (SE 0.0009) of rumen bacterial N were derived from caecal digesta NH3-N. 6. Infusions of 14C tracers were made into the caecal digesta bicarbonate, blood bicarbonate, rumen digesta bicarbonate and blood urea pools, and samples were obtained at intervals to determine the specific radioactivity of each pool. A four-pool open-compartment model was solved to estimate C flows between these pools. 7. The rate of irreversible loss of blood urea estimated with [14C]urea (17.1 (SE 1.18) g N/d) was greater (P less than 0.01) than that estimated with [15N]urea (14.0 (SE 0.87) g N/d).(ABSTRACT TRUNCATED AT 400 WORDS)

Ammonium Sulfate↗
PubMed1985

Nitrogen digestion and metabolism in sheep consuming diets containing contrasting forms and levels of N.

Nitrogen kinetics were studied in six sheep (45-55 kg live weight) consuming either a high-N grass silage or a low-N dried grass made from swards of perennial ryegrass (Lolium perenne). The diets were fed hourly at a level of 600 g dry matter/d and supplied 19.5 and 11.0 g N/d respectively. The amounts of organic matter (OM) consumed and flowing at the duodenum and ileum and excreted in the faeces were similar (P greater than 0.05) with both diets. Each diet supplied 23 g digestible OM/d per kg live weight 0.75, which was sufficient to maintain body-weight. There were no differences (P greater than 0.05) between diets in rumen fluid volume, fractional outflow rate of fluid from the rumen, total concentration of volatile fatty acids or molar proportion of acetate in the rumen. The pH and molar proportion of propionate in rumen fluid were higher (P less than 0.01), and molar proportion of butyrate lower (P less than 0.001) when the silage was given. There was a net loss of N (4.0 g/d) between mouth and duodenum when the silage was consumed but a net gain (5.5 g/d) when the dried grass was consumed. As a result, total non-ammonia-N (NAN) flow at the duodenum did not differ (P greater than 0.05) between diets. Rumen microbial NAN flow at the duodenum, based on 15N as the marker, also did not differ (P greater than 0.05) between diets but the efficiency of microbial N synthesis in the rumen (g/kg OM apparently digested) was higher (P less than 0.05) with the dried grass. When the sheep were consuming silage they had a higher concentration of ammonia in rumen fluid (P less than 0.01), a higher rate of irreversible loss of ammonia from the rumen (P less than 0.05) and a higher rate of absorption of ammonia across the rumen wall (P less than 0.01). The rate of absorption was found to be more closely related to the unionized ammonia concentration in rumen fluid (r2 0.85) than to the total ammonia concentration (r2 0.36). Endogenous N entry into the forestomachs was calculated to be 5.5 g/d when the silage was given and 9.4 g/d when the dried grass was given, of which 1.7 and 3.5 g/d respectively were in the form of urea. Thus, approximately 4-6 g N/d were derived from non-urea materials.(ABSTRACT TRUNCATED AT 400 WORDS)

Absorption↗
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↗
PubMed1983

Studies of the large intestine of sheep. 3. Nitrogen kinetics in sheep given chopped lucerne (medicago sativa) hay.

A study was made of nitrogen kinetics in the large intestine of sheep given 800 g chopped lucerne (Medicago sativa) hay/d. Four sheep were continuously infused with (15NH4)2SO4 into the caecum and three other sheep were infused intravenously with [15N]urea. A digesta marker, 51Cr complexed with EDTA (51Cr-EDTA), was infused into the rumen of each sheep to allow estimation of the rates of digesta constituents. Infusions were continued until tracer concentrations reached plateaux in digesta and blood pools, after which the sheep were anaesthetized and slaughtered. Pre-infusion samples and samples on plateau were obtained before slaughter for subsequent analysis to give plasma urea and rumen ammonia-N concentration and enrichment. At slaughter, digesta were obtained from the ileum and segments of the large intestine. These were analysed for 51Cr-EDTA content and concentration and enrichment of ammonia-N, microbial N and non-urea non-ammonia-N (NU-NAN). N flows in segments of the large intestine were calculated and represented in a quantitative eight-pool model. Transfer of plasma urea across the wall of the caecum and proximal colon was negligible but there was an input of 0.8 g endogenous NU-NAN/d. Flow of urea plus ammonia-N in digesta from the ileum into the caecum contributed 1.0 g N/d to the caecal ammonia pool. Proteolysis and deamination produced a further 3.0 g ammonia-N/d in the caecum and proximal colon. The net absorption of N between the ileum and the rectum was 2.8 g N/d but 3.0 g ammonia-N/d was absorbed from the caecum and proximal colon and, in addition, at least 0.9 g ammonia-N/d from the distal colon and rectum. Ammonia-N was incorporated into caecal microbes (0.6 g N/d) and approximately 57% of the NU-NAN in caecal digesta was microbial N. The majority of the microbial N flowing from the caecum was excreted in faeces. The rate of irreversible loss of urea-N from plasma, measured by intravenous infusion of [15N]urea, was 13.6 g/d. On average 83 (SE 6.8)% of the 15NH3 apparently absorbed from the caecum was incorporated into plasma urea; caecal ammonia contributed 9-19% of the N in plasma urea and 0.2-3.1% of the N in rumen ammonia.

Ammonia↗
PubMed1982

Studies of the large intestine of sheep. 1. Fermentation and absorption in sections of the large intestine.

1. Fermentation and absorption of constituents of digesta in segments of the large intestine of sheep given different diets were studied by analysis of gut contents obtained at slaughter after a period during which the sheep had been administered a non-absorbable gut marker. 2. In sheep given chopped, dried lucerne (Medicago sativa) there was net absorption of water throughout the large intestine with concomitant increases in the proportion of dry matter (DM) and organic matter (OM). There was net disappearance of 62 g OM, 1.66 g non-urea non-ammonia-nitrogen (NU-NAN) and 0.6 g (urea + NH3(-N in the caecum and proximal colon. There was no significant change in OM and NU-NAN flow through the remainder of the large intestine but there was a net disappearance of 0.3 g NH3-N. There was also net appearance of volatile fatty acids (VFA) in the caecum, most of which was apparently absorbed before the rectum. 3. Metabolism in the caecum was also studied in sheep grazing fresh pasture or consuming one of three sugar cane-bagasse-based diets, or barley pellets. In the lucerne- and pasture-fed sheep there was a net disappearance of approximately 0.5 g NH3-N/d from the caecum, while in sheep fed on bagasse plus urea, 1.4 g NH3-N/d was apparently absorbed from this region. The addition of fish meal to this latter diet resulted in apparent disappearance of 5.3 g NH3-N/d from the caecum and proximal colon. 4. There was apparent loss of NU-NAN from the caecum of sheep on all diets except the barley diet. With the latter diet there was a net gain of 1 g NU-NAN/d which was associated with relatively high VFA concentration and production; taken together these results indicate that microbial fermentation in the caecum was more extensive in the sheep fed on the barley diet than in those fed on the other diets. 5. The proportions of individual VFA in digesta from the rumen and caecum of lucerne-fed and pasture-fed sheep and in digesta from the caecum of sheep given the bagasse-based or barley diets are also reported and discussed. 6. In general the results indicate that the caecum and to a lesser extent the proximal colon were the major regions of fermentation and absorption of the components of the digesta in the large intestine.

Ammonia↗
PubMed1982

A comparison of methods for the estimation of microbial nitrogen in duodenal digesta of sheep.

1. Six sheep, each fitted with a rumen cannula and re-entrant cannulas in the proximal duodenum and distal ileum, were given two diets (600 g dry matter (DM)/d) consisting of either grass silage (32.1 g nitrogen/kg DM) or dried grass (18.3 g N/kg DM). A net loss of N occurred between mouth and duodenum with the silage diet, indicating extensive ruminal degradation of dietary N, compared with a net gain on the dried-grass diet. Consequently, despite higher N intakes when silage was given, N flow at the duodenum was similar for both diets. 2. The proportion of microbial N in duodenal digesta N was estimated using diaminopimelic acid (DAPA), [35S]methionine (35S), 15N-enriched non-ammonia-N (15NAN) and amino acid profiles (AAP) as microbial markers. Isotopic labelling of rumen micro-organisms was achieved by intraruminal infusions of Na2 35SO4 and (15NH4)2SO4. 3. A comparison of all methods was made based on the marker concentrations in microbial fractions isolated by differential centrifuagation of strained rumen contents. With both diets, DAPA gave the highest estimates and AAP the lowest. Estimates based on 35S and 15NAN were intermediate and did not differ significantly (P greater than 0.05). 4. For the 15NAN, 35S and AAP methods, the effect of site of sampling of the microbial fraction, i.e. from rumen contents or duodenal digesta, was examined and in all instances mean estimates based on duodenally-derived microbes were higher. However, the differences were significant for only 15NAN with both diets (P less than 0.001), for 35S with the dried grass (P less than 0.05), and for AAP with the silage (P less than 0.05). Estimates based on duodenally-derived microbes were higher (P less than 0.05) using 15 NAN than those obtained using 35S with both diets. 5. Depending on the method used for estimating microbial N, estimates of the efficiency of microbial N synthesis in the rumen (g microbial N flow at duodenum/kg organic matter apparently digested in the rumen) ranged between 16 and 38 for the silage diet and 10 and 46 for the dried grass diet. Similarly, estimates of feed N degradability in the rumen ranged between 0.62 and 0.97 for the silage and 0.00 and 0.93 for the dried grass.

Amino Acids↗
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↗
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

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↗
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

Simulation of the dynamics of nitrogen metabolism in sheep.

1. The results of isotope tracer studies of the dynamics of nitrogen metabolism in mature sheep were used to construct a seven-pool mathematical model. 2. The model was extended to a nine-pool model, which incorporates lags describing the time taken for the passage of digesta through the gut of sheep. 3. Simulation studies using these models satisfactorily predicted results of independent experiments. 4. The dynamics of N metabolism in sheep appear to be best approximately by first-order kinetics; that is, many of the important N transport processes are substantially linear or concentration-dependent.

Amino Acids↗