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Biomedical subjects

M J Ulyatt

Publications and source records attributed to M J Ulyatt.

15 recordsLinked to original sources
PubMed1988

The digestion of perennial ryegrass (Lolium perenne cv. Melle) and white clover (Trifolium repens cv. Blanca) by grazing cattle.

1. Pure swards of perennial ryegrass (Lolium perenne cv. Melle) as a primary growth (May), trimmed primary growth (early June) and regrowth (late June), and white clover (Trifolium repens cv. Blanca) as a mature primary growth (July) and vegetative regrowth (August), were grazed by twelve Friesian steers (mean body-weights throughout experiment 152-231 kg) at daily allocation rates of forage which provided dry matter (DM) intakes ranging from 28 to 36 g/kg body-weight). 2. Total nitrogen contents of the three ryegrasses declined with season (37-20 g/kg DM), but in vitro organic matter (OM) digestibilities were relatively constant (0.76-0.79). The clovers had higher N (average 36.6 g/kg DM) and lower fibre and water-soluble carbohydrate contents than the grasses, and in vitro OM digestibilities of 0.70 and 0.76 respectively. 3. Duodenal digesta samples were obtained, using a portable sampling apparatus from the animals grazing the pasture, and estimates of the flow of nutrients into the small intestine were derived using two indigestible markers which were continuously infused into the rumen using a portable infusion apparatus. Forage intakes were calculated from estimates of faecal output of indigestible OM and the predicted in vivo OM digestibilities of the forages consumed. Coefficients of variation for OM flow to the small intestine and OM intake were 11.8 and 10.9% respectively. 4. The apparent digestion of OM in the rumen ranged from 722 to 741 g/kg digestible OM intake and from 681 to 711 g/kg digestible OM intake for the grass and clover diets respectively. Substantial losses of ingested N before the small intestine were measured on all diets except the regrowth ryegrass. Losses were 0.30 and 0.40 g/g N intake on the primary growth ryegrass and the regrowth clover respectively; N contents were 37 and 39 g/kg DM respectively. 5. Comparison of the values obtained at pasture with that obtained when similar diets were offered to housed cattle (Beever et al. 1985) indicated that combined relations relating duodenal OM and non-ammonia-N (NAN) flows to OM and N intakes respectively could be established for each diet. For two diets (primary-growth grass and regrowth clover) the relations were curvilinear; for the remaining diets, the derived relations were linear.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Nutritional Physiological Phenomena↗
PubMed1987

The effect of condensed tannins on the site of digestion of amino acids and other nutrients in sheep fed on Lotus corniculatus L.

Sheep were used to evaluate the nutritional consequences of a low condensed-tannin concentration (22 g/kg dry matter (DM)) in lotus (Lotus corniculatus L.) (control group) compared with lotus given to sheep receiving intraruminal polyethylene glycol (PEG) infusion (PEG group). PEG selectively binds to tannins and prevents tannins from binding proteins. DM intakes (1430 (SE 28) g/d) and digestibility of energy (663 (SE 4.5) kJ/MJ intake) were similar for both groups but the apparent digestion of nitrogen was lower in the control sheep (0.70) than in the PEG sheep (0.78; P less than 0.001). The proportion of N apparently digested before the abomasum (i.e. in the rumen) was lower (P less than 0.05) in control sheep (0.12) than in PEG sheep (0.21; P less than 0.05). Rumen ammonia concentrations were lower (P less than 0.001) in control sheep than in PEG sheep. The proportion of neutral-detergent fibre (NDF) digested in the rumen was similar for both groups (0.48 (SE 0.012)) but less energy was digested in the rumen of the control (0.42) than of the PEG sheep (0.47; P less than 0.05). The flux of essential amino acids (EAA) through the abomasum of control sheep was 50% greater than that in PEG sheep; flux of non-essential amino acids (NEAA) was 14% higher in control than in PEG sheep. Apparent digestibility of EAA in the small intestine was similar for both treatments (0.67), but NEAA were less well digested in the control (0.55) than in the PEG sheep (0.69). The presence of tannins in the control group increased net apparent absorption of threonine (57%), valine (89%), isoleucine (94%), leucine (30%), tyrosine (41%), phenylalanine (93%), histidine (90%) and lysine (59%), and reduced NEAA absorption by 10%, compared with PEG sheep.

Abomasum↗
PubMed1986

An update of a dynamic model of ruminant digestion.

The progressive development of a dynamic model of ruminant digestion for evaluation of factors affecting nutritive value of feedstuffs is outlined. Significant changes have been introduced in many of the interactive subunits that accommodate the digestion of 12 chemical constituents (soluble carbohydrate, organic acids, starch, pectin, hemicellulose, cellulose, lipids, soluble protein, insoluble protein, nonprotein N, lignin and ash), microbial growth, animal interactions and summary computations. Explicit consideration of soluble carbohydrates, organic acids and pectins has been replaced by an aggregate fraction. A section has been added to follow dynamic aspects of volatile fatty acid metabolism in the rumen. Evaluations of the model were made by comparing its behavior with that observed experimentally for sheep fed a number of diets. These included an alfalfa diet fed at two intake levels either hourly or once daily, a dried subterranean clover diet fed hourly, a forage oat diet fed every 3 h and an 80% concentrate diet fed twice daily. For frequently fed diets, model estimates, in general, agreed very well with experimental estimates. Although changes in representations of protein metabolism were helpful, the pool size of ruminal ammonia N was not simulated well. Digestion and passage in the model occurred more rapidly than was observed when animals were fed high-quality forages once daily and rates of particle size reduction, fermentation and passage were lower than observed when low-quality diets were fed. It was concluded that the model can serve as a useful and adaptable tool for analyzing factors affecting nutritive value. Particle size reduction and passage from the rumen, dynamics of protein metabolism and utilization, and water dynamics were identified as areas requiring further research.

Animals↗
PubMed1985

The digestion of fresh perennial ryegrass (Lolium perenne L. cv. Melle) and white clover (Trifolium repens L. cv. Blanca) by growing cattle fed indoors.

1. Pure swards of perennial ryegrass (Lolium perenne L. cv. Melle) or white clover (Trifolium repens L. cv. Blanca) were harvested daily at three and two stages of growth respectively, and offered to housed cattle. The grass diets comprised primary growth (May) and two later regrowths of contrasting morphology (i.e. leaf: stem values of 1.54 and 2.84 respectively), and were characterized by high contents of water-soluble carbohydrate and neutral-detergent fibre and comparable in vitro dry matter (DM) digestibilities (mean 0.80). Total nitrogen content was higher on primary growth grass (34 g/kg DM) than on regrowths (23 g/kg DM) but lower than values obtained for the two clover diets (38 and 43 g/kg DM, respectively). The clover diets had lower water-soluble carbohydrate contents than the grasses, comparable cellulose, but lower neutral-detergent fibre contents and in vitro DM digestibilities of 0.70 and 0.77 respectively. 2. The experiment lasted from May until August, during which time a total of twenty-one young Friesian steers (initial average live weight 130 kg) were used to determine both nutrient supply to the small intestine (twelve animals) and apparent digestibility (nine animals). Each diet was offered at three levels of DM intake (i.e. 18, 22 and 26 g/kg live weight). A further six steers, all fed at the rate of 22 g DM/kg live weight, were used to determine the metabolizable energy contents of the five diets by means of open-circuit calorimetry. 3. The three grass diets and the later-cut clover had, as intended, quite similar in vivo organic matter digestibilities, but that of the earlier-cut clover was lower, and this was associated with a large number of flower heads in this crop at the time of feeding. 4. On the clover diets, proportionately less of the ingested organic matter appeared to be digested in the rumen (0.40) compared with the grass diets (0.58) (P less than 0.001). On the high-N primary grass and the clover diets, substantial rumen losses of N were detected (P less than 0.01) compared with regrowth grasses. 5. The metabolizable energy content of the primary growth of grass was 12.2 MJ/kg DM, whilst the values for the other two grass diets were lower (11.6 MJ/kg DM), despite no marked decline in overall energy digestibility. Values for the two clover diets (mean 10.5 MJ/kg DM) were considerably lower than all values noted for the grasses.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed1980

The effect of level of food intake on the incorporation of acetate into lipids and its distribution among various tissues in sheep.

1. Romney wethers were infused intravenously with [2-14C]acetate for 5 d during which time they were given, three/group, different amounts of lucerne (Medicago sativa L.) chaff. The groups and the amounts fed were: MS, 700 g but starved during the infusion period; M, 700 g throughout; 1.3 M, 950 g throughout; AL, ad lib. throughout. 2. On day 4 of the infusion, the oxygen consumption, and production rate of expired 14CO2 were measured. At the end of the infusion, the sheep were killed and the amounts of radioactivity in the lipids of various tissues were determined. 3. Significant differences were present between the specific activities of the tissues. The internal adipose tissues generally had higher specific activities than subcutaneous or intermuscular adipose depots. Although the intramuscular lipid also was highly labelled, the liver had the greatest specific activity. 4. Food intake did not significantly affect this pattern of specific activity of labelling of the tissues. 5. While most of the total lipid radioactivity was present in adipose tissue, the proportion in the liver increased to 40% during starvation.

Acetates↗
PubMed1979

The metabolism of methionine in silage-fed sheep.

1. L-[U-14C]methionine was used to study methionine metabolism in sheep fed on untreated silage, silage treated with formaldehyde and untreated silage plus intraperitoneal infusion of L-methionine. 2. Over-all the values ranged from 0.43 to 0.86 mmol/h for methionine turnover rate, from 13.3 to 19.9 for the percentage of methionine oxidized to carbon dioxide and from 245 to 1089 mumol for methionine pool size.

Animal Feed↗
PubMed1975

Iterative computation of metabolic flux and stoichiometric parameters for alternate pathways in rumen fermentation.

A model is presented which has been derived to compute the end-products of rumen fermentation from knowledge of the input of feedstuff. The model comprises a set of algebraic equations for the fermentation of each of the following feedstuff components: soluble sugars, starch, cellulose, hemicellulose and protein. The equations were derived from known biochemical stoichiometric relationships. A iterative, non-linear least sqares method (steepest descent) was used to estimate parameter values. In a sample run the inputs used were from an experiment where eight sheep were fed white clover. The model predicted values were in good agreement with the experimental values.

Animals↗