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Biomedical subjects

E R Orskov

Publications and source records attributed to E R Orskov.

At least 37 records · Page 2Linked to original sources
PubMed1991

Effect of different volatile fatty acids mixtures on energy metabolism in cattle.

Four Friesian steers (mean BW = 282 kg) were given mixtures of VFA and casein by intragastric infusion to give a total energy input of 675 kJ/kg BW.75. Casein supplied 16.3% of the energy and 777 mg N/kg BW.75. The molar proportion of butyric acid was held constant at 8 mol/100 mol, and the acetic and propionic acids varied inversely. Acetic acid was varied in 12 increments from 11 to 91 mol/100 mol and propionic acid proportion varied inversely. Heat production, blood (urea, insulin, beta-hydroxybutyrate, free fatty acids) and urine metabolites (urea, N, VFA) were measured. There were no differences (P greater than .05) in heat production until the acetic acid proportions exceeded approximately 90 mol/100 mol, at which point there was a decrease in heat production (P less than .05) accompanied by a considerable excretion of acetic acid in the urine. Above 80 mol/100 mol acetic acid, beta-hydroxybutyrate was greatly elevated, accompanied by a small decrease in blood glucose and blood insulin together with an increase in blood free fatty acid concentration. There was also an elevation of N excretion in the urine. When the proportion of propionic acid exceeded 76 mol/100 mol there were some metabolic disturbances resulting in blood hemolysis, an increase in N excretion in the urine, and nervous disposition of the animals. It is concluded that differences in heat production between roughage and concentrate diets are not likely to be a result of differences in the energetic response to different proportions of VFA. Differences in activity during standing, feeding, and ruminating may, therefore, be more important.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Excretion of purine derivatives by ruminants: endogenous excretion, differences between cattle and sheep.

The endogenous urinary excretion of the purine derivatives allantoin, uric acid and xanthine plus hypoxanthine were measured in twenty-nine lambs, ten cattle (six steers, one cow and three preruminant calves) and four pigs. The sheep and mature cattle were nourished by intragastric infusion and the calves were given a milk-substitute. The pigs were fed on a purine-free diet. The excretion of total purine derivatives was substantially greater by the cattle, being 514 (SE 20.6) mumol/kg live weight (W)0.75 per d compared with 168 (SE 5.0) mumol/kg W0.75 per d by the sheep and 166 (SE 2.6) mumol/kg W0.75 per d by the pigs. Plasma from normally fed sheep, cows and pigs was incubated with either xanthine or uric acid. Sheep and pig plasma had no xanthine oxidase (EC 1.2.3.2) activity whereas plasma from cattle did. Uricase (EC 1.7.3.3) was not present in plasma of cattle and pigs and appeared to be present in trace amounts only in sheep plasma. It is suggested that the species differences in endogenous purine derivative excretion were probably due to the different profiles of xanthine oxidase activity in tissues and particularly in the blood. This is because a high xanthine oxidase activity would reduce the chance to recycle purines, by increasing the probability of degradation to compounds which could not be salvaged.

Allantoin↗
PubMed1990

Excretion of purine derivatives by ruminants: effect of exogenous nucleic acid supply on purine derivative excretion by sheep.

The present study examined the relationship between the supply of exogenous nucleic acid (NA) purines and their recovery as the derivatives hypoxanthine, xanthine, uric acid and allantoin in urine. Six lambs, totally nourished by intragastric infusions of volatile fatty acids (VFA) and casein (i.e. no rumen fermentation), were given by abomasal infusion a microbial NA concentrate at six levels (from zero to 24.5 mmol purines/d). The true digestibility between the abomasum and terminal ileum of the NA purines was measured in a separate experiment using three lambs. The relative proportion of urinary allantoin increased, and that of other derivatives decreased, as the amount of NA infused was increased. The relationship between total excretion of purine derivatives (Y; mmol/d) and exogenous purines absorbed (X; mmol/d) was Y = 0.84X + 0.150W0.75 e-0.25X, where W is body-weight (kg). This implies that the endogenous contribution to the total excretion of derivative decreased as the supply of exogenous purines increased, with an associated progressive replacement of de novo synthesis by exogenous purines. The model also implies that 0.16 of the purines were eliminated through routes other than derivative excretion in urine. Once excretion exceeded 0.6 mmol/kg W0.75 per d, endogenous excretion was effectively zero and thus Y = 0.84 X. In normally fed sheep, derivative excretion should therefore relate to the microbial purines and, hence, microbial protein absorbed according to these models. The changing proportions of allantoin and other derivatives in urine were probably due to changes in the relative importance of endogenous and exogenous purines as precursors.

Allantoin↗
PubMed1990

Excretion of purine derivatives by ruminants: recycling of allantoin into the rumen via saliva and its fate in the gut.

The saliva of sheep was shown to contain significant concentrations of uric acid (16(SD 4.5) mumol/l) and allantoin (120(SD 16.4) mumol/l), sufficient to recycle purine derivatives equivalent to about 0.10 of the normal urinary excretion. When allantoin was incubated in vitro in rumen fluid, it was degraded at a rate sufficient to ensure complete destruction of recycled allantoin. In a series of experiments in which allantoin was infused into the rumen of sheep fed normally, or into the rumen or abomasum of sheep and the rumen of cattle completely nourished by intragastric infusion of volatile fatty acids and casein, no additional allantoin was recovered in the urine. These losses were probably due to the degradation of allantoin by micro-organisms associated with the digestive tract. It is concluded that all allantion and uric acid recycled to the rumen via saliva will be similarly degraded. Therefore, the use of urinary excretion of purine derivatives as an estimator of the rumen microbial biomass available to ruminants will need to be corrected for such losses.

Allantoin↗
PubMed1990

Urea metabolism in sheep given conventional feeds or nourished by intragastric infusion.

A comparison has been made of the kinetics of urea metabolism in sheep given conventional feeds or maintained wholly by intragastric infusions of volatile fatty acids, buffer, mineral and casein solutions. Daily nitrogen supply was 13.2 g/day in 'fed' sheep and 6.0 g/day in 'infusion' sheep. On each feeding system measurements were made at the basal (maintenance) level of intake and when the basal level was supplemented with infusions of urea into the abomasum (125 mmol/day) or into the rumen (300 mmol/day). Additional measurements were made when ammonium carbonate (100 mmol/day) was infused into the rumen, when cassava (150 g/day) was added to the diet of 'fed' sheep or when the input of casein to 'infusion' sheep was reduced by half. Urea kinetics were measured by means of a single intravenous injection of [14C]urea. Urea irreversible loss rate, urea pool size, urinary urea excretion, plasma urea concentrations and rumen ammonia concentrations were all significantly higher in sheep given conventional feeds than in those nourished by infusion but urea degradation in the gastrointestinal tract did not differ between the two methods of feeding. Regression analysis indicated only minor differences between the two feeding systems in the relationships between the various indices of urea metabolism. It is concluded that most of these findings can be attributed to differences in the quantity and nature of the nitrogen supplied in the basal diets and that the sheep nourished by infusion would be a suitable model for the study of factors involved in the control of urea recycling.

Ammonia↗
PubMed1990

Adhesion of cellulolytic ruminal bacteria to barley straw.

Adhesion of the cellulolytic ruminal bacteria Ruminococcus flavefaciens and Fibrobacter succinogenes to barley straw was measured by incubating bacterial suspensions with hammer-milled straw for 30 min, filtering the mixtures through sintered glass filters, and measuring the optical densities of the filtrates. Maximum adhesion of both species occurred at pH 6.0 and during mid- to late-exponential phase. Adhesion was saturable at 33 and 23 mg (dry weight) g of straw for R. flavefaciens and F. succinogenes, respectively. Methyl cellulose and carboxymethyl cellulose inhibited adhesion by 24 to 33%. Competition between species was determined by measuring characteristic cell-associated enzyme activities in filtrates of mixtures incubated with straw; p-nitrophenyl-beta-d-lactopyranoside hydrolysis was used as a marker for F. succinogenes, while either beta-xylosidase or carboxymethyl cellulase was used for R. flavefaciens, depending on the other species present. R. flavefaciens had no influence on F. succinogenes adhesion, and F. succinogenes had only a minor (<20%) effect on R. flavefaciens adhesion. The noncellulolytic ruminal bacteria Bacteroides ruminicola and Selenomonas ruminantium had no influence on adhesion of either cellulolytic species, although these organisms also adhered to the straw. We concluded that R. flavefaciens and F. succinogenes have separate, specific adhesion sites on barley straw that are not obscured by competition with non-cellulolytic species.

Journal Article↗
PubMed1988

Comparison of estimates of ruminal protein degradation by in vitro and in situ methods.

Ruminal degradation of eight soluble proteins and 10 protein meals was determined using three methods: 1) an inhibitor in vitro system (IIV), to which inhibitors are added to prevent metabolism of protein degradation products, 2) in situ incubations in nylon bags and 3) in vitro NH3 production in typical ruminal inoculum. In vitro NH3 production rate from different proteins was not related to in situ or IIV degradation rate. Degradation rates for soluble proteins by IIV ranged from .103 to .813/h, yielding estimated extents of degradation that ranged from 73 to 94% (assuming ruminal passage of .05/h). For seven of the protein meals, degradation rates measured by IIV were threefold greater than in situ rates. However, mean degraded fractions estimated from zero-time intercepts were twofold greater using the in situ method, and calculated extents of degradation averaged 83% of IIV values. Extents of degradation estimated (assuming ruminal passage of .05/h) for fish meal, soybean meal, linseed meal, sunflower meal, rapeseed meal, copra meal and meat and bone meal were, respectively; 55, 79, 84, 59, 75, 54 and 58% (IIV) and 46, 63, 69, 51, 52, 43 and 55% (in situ). These values were generally similar to those reported in the literature. The extent of degradation of feather meal was 28% by in situ determination. Neither the IIV nor in situ method gave significant regressions for blood meal; neither method yields reliable data for very slowly degraded proteins. The IIV procedure has the advantage over the in situ method because it can yield degradation estimates for soluble as well as insoluble proteins.

Animals↗
PubMed1987

Undernutrition in sheep. Nitrogen repletion by N-depleted sheep.

Wether lambs of 29-44 kg live-weight, totally nourished by the infusion of volatile fatty acids (VFA) into the rumen and casein into the abomasum, were given five treatments in consecutive periods. The treatments were (daily amounts per kg live weight (W)0.75): (a) high-protein for 7 d (2500 mg nitrogen, 650 kJ VFA); (b) low-protein for 7-15 d (525 mg N, 650 kJ VFA); (c) N-free for 7 d (no N, 450 kJ VFA); (d) very-low-protein for 24-28 d (300 mg N, 400 kJ VFA); (e) high-protein for 40 d (2500 mg N, 650 kJ VFA). Nine lambs were subjected to treatments (a), (b) and (c) (Expt 1) and four of the lambs additionally received treatments (d) and (e) (Expt 2). In Expt 1 all nine lambs had a positive N retention on treatment (a) but abrupt change to treatment (b) resulted in substantial negative N balances initially, and a period of approximately 5 d adaptation was required before N equilibrium was re-established. Animals again exhibited negative N balances when the N-free infusion (treatment c) was introduced and during that period there was no evidence of adaptation. Basal urinary N excretion was estimated to be 356 (SE 12) mg N/kg W 0.75. In Expt 2 all four lambs were depleted of N when receiving the very-low-protein treatment (d). The progressively decreasing N losses recorded during days 1 to 12 of the treatment period were slightly greater than those recorded during days 13 to 28 but the difference between the means was not significant (P greater than 0.05). There was no evidence of an adaptation in N retention between days 13 and 28 of the treatment. As assessed during days 13 to 28 of the treatment the efficiency of utilization of infused casein N was 1.0; this compared with a value of 0.66 recorded during treatment (b) in Expt 1. Live weight loss during the period of N depletion was 101 (SE 27) g/d. When lambs were given treatment (e) during the last period of Expt 2, N repletion was rapid and complete within a few days. Ten days after the introduction of the treatment the rate of N retention was estimated to be 1019 (SE 38) mg/kg W 0.75 per d and this value declined at a rate of 9.5 (SE 1.9) mg N/kg W 0.75 per d for the following 30 d.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Biological↗
PubMed1987

Use of particle-bound microbial enzyme activity to predict the rate and extent of fibre degradation in the rumen.

A method was developed for extracting enzymes from micro-organisms closely associated with ammonia-treated straw (NH3-S) that had been incubated in nylon bags in the rumen. Incubation of washed straw with 125 ml carbon tetrachloride/l and 20 micrograms lysozyme/ml for 3 h at 37 degrees gave carboxymethylcellulase (EC 3.2.1.4; CMCase) and NAD-linked glutamate dehydrogenase (EC 1.4.1.2; GDH) activities greater than those extracted by sonication. GDH associated with NH3-S increased with incubation time and was highest in sheep receiving a high-barley diet. Particle-bound CMCase activity reached a peak between 16 and 24 h and declined thereafter. Particle-bound GDH activity showed no correlation with dry matter (DM) degradation in the rumens of sheep fed on a range of diets. In contrast, CMCase activity after 24 h was highly correlated with DM degradability of the same samples at 24 h (r 0.98) and 48 h (r 0.94). It was concluded that GDH and CMCase can be used as indices of the total population of colonizing rumen micro-organisms and of the fibre-degrading population respectively, and that these enzymes can therefore be used to assess rapidly and with great sensitivity variations in the rumen environment that affect the rate of fibre breakdown.

Ammonia↗
PubMed1987

Effects on plasma insulin of intermittent infusions of propionic acid, glucose or casein into the alimentary tract of non-lactating cows maintained on a liquid diet.

1. An experiment was conducted using three non-lactating cows completely maintained by infusions of volatile fatty acids into the rumen, and casein into the abomasum. Plasma insulin responses to propionic acid, glucose or casein were recorded. Further information was obtained using protein-free infusions. 2. When part of the propionic acid was infused into the rumen in a twice-daily 3 h dose and the remainder infused continuously with acetic and butyric acids and casein, there were large increases in the concentrations of propionic acid and insulin in the jugular blood. When glucose, corresponding in energy to that supplied by the intermittent propionic acid infusions was similarly infused, the plasma levels of glucose and insulin were increased. Glucose appeared to stimulate a greater increase in insulin than did propionic acid. Casein infused into the abomasum in intermittent doses produced a rise in plasma insulin, but smaller than that observed with propionic acid or with glucose. 3. The protein-free infusion was characterized by a lower concentration of insulin in the blood plasma, a reduction in plasma urea and free amino nitrogen and unchanged plasma glucose.

Abomasum↗
PubMed1986

The nitrogen and energy metabolism of lactating cows given abomasal infusions of casein.

1. Four cows in early lactation were given continuous infusion into the abomasum of 0, 200, 400 or 600 g lactic casein/d according to a Latin-square design. Each period was of 14 d and the Latin square was followed by 7 d in which an infusion of 800 g glucose/d was given. The basal diet was given at a level which provided sufficient nitrogen and energy for 10 kg milk yield/d. 2. Infusion of casein resulted in significant increases in milk yield, milk N yield and milk energy yield; milk N increased progressively but milk energy reached a maximum at 400 g casein/d. Milk yields and composition when glucose was infused resembled those seen on the zero casein treatment. 3. N-balance measurements indicated a severe deficit (-20 g/d) on the zero casein treatment and a progressive increase to +7 g/d as casein increased; N equilibrium was achieved at about 400 g casein/d. The regression of net productive N on N intake (P less than 0.001) indicated that the efficiency of utilization of dietary N did not differ between treatments. 4. Heat production increased with increase in casein infused (P less than 0.05) but remained a constant proportion of the metabolizable energy (ME) intake. Energy balances were negative and did not differ significantly between treatments but calculation of the protein and fat components indicated a threefold increase in body fat mobilization in response to the first increment of casein. Milk yield adjusted to zero energy balance was significantly related to ME intake (P less than 0.001) but the efficiency of energy utilization was not affected by the level of casein infusion. 5. The concentrations of glucose, beta-hydroxybutyrate and non-esterified fatty acids in plasma did not differ between treatments but the concentration of urea in plasma increased markedly (P less than 0.05) at the highest level of casein addition. Insulin concentrations increased and growth hormone decreased (both P less than 0.05) with increase in casein infusion. 6. The concentration of total amino acids (AA) in plasma increased up to 400 g casein/d and then declined. Changes in concentration and in the ratio of essential:total AA indicated a very high extraction rate of essential AA at the lower levels of casein infusion. 7. The observed lactational responses are discussed in relation to the ratio of protein:energy in the absorbed nutrients.(ABSTRACT TRUNCATED AT 400 WORDS)

Abomasum↗
PubMed1986

Flow of nitrogen from the rumen and abomasum in cattle and sheep given protein-free nutrients by intragastric infusion.

1. Three experiments were conducted to determine the flow of nitrogen through the rumen and abomasum when cows, steers and lambs were totally nourished on volatile fatty acids infused into the rumen. 2. In two dairy cows (650-700 kg) and two large steers (370-405 kg) the daily flow of non-ammonia-N (NAN) from the rumen was 50.7 and 58 mg/kg live weight (W)0.75 respectively. 3. The flows of NAN through the rumen and abomasum in four young steers (240-315 kg) were 85.0 (SE 21.0) and 195 (SE 7.0) mg/kg W 0.75 respectively. 4. In the third experiment the effects of altering rumen pH and osmotic pressure on flow of NAN through the rumen and abomasum were investigated in lambs. While rumen pH and osmotic pressure influenced rumen volume and outflow they had no significant effect on NAN flow. The mean values for NAN outflow from the rumen and abomasum were 76 and 181 mg N/kg W 0.75 respectively. 5. Abomasal NAN flow increased with increasing abomasal pH. When osmotic pressure was greater than about 330 mosmol/l in the rumen there was a net inflow of water, while below this value there was net loss of water. 6. For all experiments the flow of N both from the rumen and abomasum was highly variable; this has to be considered if a constant value is used for endogenous N in estimating dietary N in the abomasum. 7. With N-free infusion the rumen NH3 concentration varied from 50 to 120 mg NH3-N/l. 8. The amino acid composition of rumen and abomasal N was also determined. Relative to tissue N it contained a higher proportion of cysteine.

Abomasum↗
PubMed1986

Starch digestion and utilization in ruminants.

For most grain, except corn and sorghum, 90% or more of starch is normally fermented in the rumen. With corn, up to 30% or more could escape ruminal fermentation; most of the starch escaping fermentation would be digested in the small intestine or fermented in the large intestine. The capacity for digestion of raw starch in the small intestine is limited to 100 to 200 g/d in sheep. Gelled starch could be digested in quantities up to 200 to 300 g/d. The capacity would ultimately be limited by lack of enzymes involved in hydrolysis of short chain di- and oligosaccharides and also by capacity for absorption of glucose. Starch fermented in the cecum leads to an increase of N loss in the feces. In some instances, the high propionic acid proportion arising from fermentation of starch exceeds the capacity of the liver for metabolism. In growing lambs and goats, this creates problems of synthesis of branched-chain fatty acids in adipose tissue and, in dairy cows, problems of low milk yield and milk fat production. The low ruminal pH that often occurs when starchy grain is included in diets for ruminants can cause depression in fiber digestion. Some of these problems can be overcome by reducing extent of cereal processing and other methods that prevent low ruminal pH. It is concluded that due to limited capacity for starch digestion postruminally and high animal variability, deliberate attempts to increase postruminal digestion of starch are unlikely to be beneficial and are likely to create potential digestive problems.

Animal Feed↗
PubMed1985

Use of by-products and supplementary protein in dairy cow nutrition.

The new systems of protein evaluation distinguish clearly between the requirement of the rumen microbes and the need of the host animal. While the requirement of the rumen microbes and the production of microbial protein is related to fermented energy, the need of the host animal varies with type and level of productivity. In dairy cows microbial protein is insufficient for the host animal, particularly when the animals are in negative energy balance, and in order to efficiently utilise body energy reserves undegraded protein must be given. Several experiments are discussed in which dairy cows have been given ammonia treated straw as the only source of roughage and where milk yields have been maintained. It is emphasised that increased use of high roughage diets in early lactation increases the demand for undegraded proteins. The converse is also true: that undegraded protein increases the proportion of roughage that can be used for high yielding dairy cows.

Animal Feed↗
PubMed1985

The effect of intragastric infusion of glucose, lipids or acetate on fasting nitrogen excretion and blood metabolites in sheep.

Two experiments are reported in which the effect of the intragastric infusion of non-protein energy on fasting nitrogen losses was studied. Expt 1 was a preliminary trial with two 35 kg lambs given 0, 144, 288 or 432 kJ/kg live weight (W)0.75 per d as lipid or glucose infused into the abomasum for periods of 3 d. Expt 2 was of a 4 X 4 Latin square design with four sheep of about 30 kg live weight. The four treatments were control (fasted with water infusion), or the infusion of 144 kJ/kg W0.75 per d as glucose or lipid into the abomasum or as acetic acid into the reticulo-rumen. Compared with the fasted control, glucose infusion reduced (P less than 0.05) N excretion to about 0.6 of that of the control, increased (P less than 0.05) plasma glucose, decreased (P less than 0.05) plasma urea and beta-hydroxybutyrate, and was without effect on plasma amino-N or creatinine excretion. Lipid and acetate infusions were without statistically significant effect on N or creatinine excretion or any of the blood indices measured, with the exception of plasma glucose which was reduced (P less than 0.05) with acetate infusion.

Abomasum↗
PubMed1984

Undernutrition in sheep. The effect of supplementation with protein on protein accretion.

In a comparative-slaughter experiment, individually rationed wether lambs initially of 42 kg were given 235, 362 or 456 kJ metabolizable energy (ME)/kg live weight (LW)0.75 per d as sodium hydroxide-treated barley straw with urea (six lambs per treatment), or NaOH-treated barley straw with urea plus 125 g/d white-fish meal to give 307 or 488 kJ ME/kg LW0.75 per d (seven lambs per treatment) for 92 d. All unsupplemented lambs lost both fat and body protein. The changes in fat were -3.53, -2.75 and -1.40 (SE 0.59) kg (initial value 8.6 kg), and the changes in body protein were -0.47, -0.09 and -0.14 (SE 0.13) kg (initial value 4.9 kg) for the three unsupplemented groups respectively. When supplemented with fish meal, fat was again lost as -1.53 and -0.93 (SE 0.55) kg, but wool-free body protein was increased, and gains were 0.48 and 0.89 (SE 0.12) kg for the two supplemented groups respectively. All animals lost wool-free body energy, total changes being -150, -111, -59 and -49 and -16 MJ respectively. When corrected to an equal ME intake the supplemented lambs, when compared with the unsupplemented lambs, gained (instead of losing) body protein (P less than 0.001) and lost less fat (P less than 0.05). Wool growth did not respond to supplemental protein, but was related to ME intake with an increase of 0.78 g wool fibre for each additional MJ ME. The maintenance requirements of the unsupplemented and supplemented groups respectively were estimated by regression analysis to be 554 and 496 kJ ME/kg LW0.75 per d. The apparent utilization of ME below energy equilibrium (km) was 0.31 (SE 0.08) for the unsupplemented animals, and 0.12 (SE 0.10) for the supplemented animals, well below a km of 0.70 which current UK standards (Agricultural Research Council, 1980) would predict. Most of these differences could be reconciled if basal metabolism was assumed not to be constant. It is concluded that lambs in negative energy balance can continue lean body growth at the expense of body fat, provided sufficient dietary protein is available. It is also concluded that since the animals at the lowest ME intakes required less ME than predicted by current feeding standards, the effect was that it would have been difficult to distinguish between the apparent utilization of ME for maintenance (km) and for fattening (kf).

Animals↗