No description available.

A metabolism trial was conducted to compare the nutritional value of: 1)"Quickstand" bermudagrass [Cynodon dactylon (L.) Pers.], 2)caucasian bluestem [Bothriochloa caucasia (Trin.) C.E. Hubb], 3)tall fescue (Festuca arundinacea Schreb.), and 4)orchardgrass (Dactylis glomerata L.). The warm-season grasses (bermudagrass and bluestem) were higher (P < .01) in fiber components than the cool-season grasses (tall fescue and orchardgrass). Bluestem was lower (P < .001) in CP, hemicellulose, and ash, and higher in NDF (P < .001), ADF (P < .001), cellulose (P < .001), and lignin (P < .01) than bermudagrass. The warm-season grasses were lower in the apparent digestibility of DM (P < .001), NDF (P < .01), ADF (P < .05), cellulose (P < .05), and hemicellulose (P < .01) than cool-season grasses. Apparent digestibility of NDF (P < .001), ADF (P < .001), cellulose (P < .01), and hemicellulose (P < .01) was higher for bluestem than bermudagrass. Fescue was higher (P < .001) in apparent digestibility of DM and CP and lower (P < .01) in apparent digestibility of NDF, ADF, cellulose, and hemicellulose than orchardgrass. Lambs fed bluestem had lower (P < .05) N retention than those fed bermudagrass, when expressed as g/d. Lambs fed fescue had higher (P < .001) N retention, than those fed orchardgrass. When expressed as a percent of intake or absorption, N retention values were similar among treatments. The results of this study suggest that cool-season grasses are of higher nutritional value than warm-season grasses. / Master of Science

No description available.

No description available.

Characteristics of methionine uptake by brush border membrane vesicles of bovine small intestine were investigated. Alkaline phosphatase marked the brush border membrane fraction obtained through differential centrifugation followed by a sucrose gradient. This preparation yielded a 10-fold enrichment of activity over homogenate. Methionine uptake was found to be into an osmotically active space. A binding constant of 75.4 pmol/mg membrane protein was determined. A significant (p<.05) sodium stimulation of methionine uptake was observed. This indicated active (energy-dependent) transport in addition to the diffusive component of intravesicular mention accumulation. Decreasing the pH of buffer medium significantly (p<.05) depresses methionine transport. A K_m = .114 mM and V_MAX = 56.5 pmol/s/mg membrane protein were ascertained for methionine. / M.S.

Brush border and basolateral membrane vesicles were isolated by subjecting homogenized mucosal cells from bovine small intestine to a divalent cation aggregation followed by a series of differential and density gradient centrifugations. Membrane marker enzyme assays were used to monitor the effectiveness of the fractionation procedure. Enrichments were determined by comparing the enzyme specific activities of the membrane fractions to the homogenate. Sodium-potassium adenosine triphosphatase and alkaline phosphatase served as the enzyme markers for the basolateral and brush border membranes, respectively. Basolateral membrane vesicles enriched 11.1 fold were isolated from the interface of the 31 and 34% sucrose bands of a discontinuous sucrose gradient. Brush border membranes enriched 10.1 fold were isolated from the surface of the 28% sucrose band of a discontinuous sucrose gradient. The use of frozen rather than fresh mucosal tissue in the isolation procedures was found to enhance the purification of basolateral and brush border membrane fractions. The transport capabilities of vesicles were demonstrated by incubating vesicles with radiolabeled substrate, then separating the vesicles and transported substrate from the incubation buffer by filtration. Substrate uptakes were quantified by liquid scintillation counting. Basolateral membrane vesicles were observed to accumulate substrate into an osmotically active space and to have Na⁺-dependent alanine transport capabilities. The use of basolateral and brush border membrane vesicles as tools to investigate nutrient uptake allows the investigator to manipulate both the extravesicular and intravesicular environments, thus making possible the evaluation of the complex interactions which are involved in nutrient transport mechanisms. / M.S.

Studies were conducted to determine the effects of feeding lasalocid and monensin upon mineral status of ruminants, changes in digestive and renal physiology which bring about altered mineral status, and the effects of dietary K upon the actions of ionophores. Two 84-d grazing trials were conducted with steers fed no ionophore, 200 mg lasalocid, or 150 mg monensin. Monensin tended to increase gain of steers, but lasalocid had no effect. Feeding supplemental lasalocid and monensin altered Ca, P, Mg, Na, K, Cu, Fe and Zn status of grazing steers, but effects were not consistent. Twenty-four crossbred steers were individually fed in a 147-d finishing trial to study a possible K x monensin interaction. Steers were fed diets ad libitum containing .4% or 2.3% K, with or without 23 ppm monensin, dry basis. Feeding monensin with low K increased serum Na, Mg, inorganic P, Cu and Zn, but monensin fed with high K had no effect or decreased these serum minerals. Fifteen wethers, fitted with abomasal and ileal cannulae, were fed a basal diet alone or supplemented with 23 ppm lasalocid or monensin; Apparent absorption of Mg, K and Fe increased when ionophores were fed. Magnesium flow through the small and large intestines was decreased by lasalocid and monensin. Effects of lasalocid and monensin differed for metabolism, digestive tract flow and (or) partial absorption of Ca, P, Cu, Fe and Zn. Twelve ewe lambs were used in a renal clearance experiment. Lambs were fed a basal diet with no ionophore, 23 ppm lasalocid, or 23 ppm monensin, dry basis. Ionophores were fed starting on d 1 of the experimental period. Serial collections of blood and urine were made during d 1 and d 5 of the experimental period. Monensin reduced urine flow rate at d 1 and d 5. Feeding monensin lowered serum clearance and urinary excretion rates of Na and K at d 5. Serum clearance and urinary excretion rates of Ca were lower in sheep fed ionophores at d 1. Feeding monensin decreased serum clearance and urinary excretion rates of Cu at d 1. At d 5, urinary excretion rates of Zn were greater when lasalocid was fed, and lower when monensin was fed, compared to feeding no ionophore. These studies indicate that dietary lasalocid and monensin can alter mineral status of ruminants, although their effects may differ. The effects of ionophores may be dependent upon dietary K levels. / Ph. D.

Transport properties of bovine intestinal brush border membranes were investigated. Isolation of brush border membrane vesicles involved magnesium precipitation followed by a sucrose density gradient. Characterization by alkaline phosphatase activity (the brush border marker enzyme) showed 7 fold enrichment over homogenate at the interface between 38 and 42% sucrose. This fraction was employed to study transport of sugars and amino acids. Transport of D-glucose into an osmotically active space, was sodium stimulated, and inhibited by phloridzin, D-galactose, and D-xylose. Transport of L-alanine was sodium stimulated and mediated by at least two systems. Apparent affinities for L-alanine transport were .039, and .943 mM. Maximum velocities were 29.2, and 53.4 pmoles/mg protein/sec, for the two systems. Transport of L-proline, L-lysine, L-methionine, and L-phenylalanine were sodium stimulated. Data indicated sodium independent transport accounted for more influx of L-lysine, L-methionine, and L-phenylalanine than sodium dependent transport. Sodium dependent and sodium independent fluxes were equal for uptake of L-proline. Amino acid inhibition data indicated a common transporter for methionine, alanine, and phenylalanine. There was an additional methionine transport system not shared by alanine or phenylalanine. None of the amino acids effectively inhibited methionine uptake. Data indicated praline was transported by system(s) not shared by the other amino acids. Bovine brush border membranes transported the amino acid analog alpha-methyl-aminoisobutyric acid by sodium stimulated processes. / Ph. D.

Three experiments were conducted to examine the effects of an ionophore, monensin sodium, on digestion in sheep. The first experiment was concerning alterations induced by long-term supplementation and subsequent withdrawal of the ionophore. The diet was a pelleted mixture of 43% native prairie hay, 34% corn grain, and 21% lupin grain plus 100 g wheat straw. Monensin (33 ppm) was added to the diet of four wethers, and four other animals served as controls and consumed an identical diet. without monensin. Monensin supplementation increased (P <.05) ruminal propionate while decreasing (P <.05) acetate levels throughout the 146-d experiment. Withdrawal caused acetate to return to control levels but decreased (P <.05) propionate. During ionophore supplementation, the digestibilities of organic matter (OM) and dry matter (DM) were increased (P <.05) by an average of 8 and 9%, respectively. Apparent digestibility ' of N was increased from 75 to 77% after 19 d of supplementation. There was an augmentation (P <.05) in the flow of bacterial N at the duodenum after 96 d of supplementation. This effect disappeared with ionophore withdrawal. In a second experiment, the effect of monensin on postruminal digestion was examined in three trials with six wethers. There were three treatments: control, dietary monensin, and monensin infused into the duodenum. The diets were the same as in the previous experiment. Dietary monensin caused the same changes in ruminal VFA as in the previous experiment. Infused monensin had no effect on VFA. Dietary monensin increased (P <.05) trypsin activity at the ileum. Dietary ionophore did not alter nutrient digestibilities, but shifted (P <.O5) the site of OM and DM digestion from the cecum to before the terminal ileum by 14 and 10%, respectively. In an in vitro experiment rumen contents from monensin-adapted and nonadapted sheep were compared with and without additional ionophore in a 6 h incubation system. Rumen contents from adapted sheep did not differ from contents of nonadapted sheep in the quantity of microbial N synthesized. With monensin addition to the incubation, microbial synthesis dropped by 49% in nonadapted microorganisms. In adapted contents, the decrease in synthesis was only 9%. Monensin-adapted microbes degraded (P <.O1) more protein substrate than those which were not adapted. / Ph. D. / incomplete_metadata

Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Forages are the main feed components in ruminant production systems for the reason that they are often the major source of energy available to the animal. However, only 10 to 35% of energy intake is available as net energy because the digestion of plant cell walls is not complete. This can significantly affect livestock performance and profits in production systems that use forages as a major source of nutrients of the diet. As a result of low and variable nutritive values of forage feedstuffs, attempts to improve ruminal fibre degradability have been an ongoing research topic. The use of exogenous fibrolytic enzymes (EFE) has been proposed as means to improve forage digestibility. Positive results with regard to rumen forage digestibility and other animal production traits have consequently been obtained due to increased rumen microbial activity following EFE addition in ruminant diets. Two EFE (Abo 374 and EFE 2) and one commercial yeast preparation were firstly identified and selected for their potential to improve the cumulative gas production (GP) at 24 hours of a range of feed substrates using the in vitro GP system as a screening step to identify the superior EFE products. The different feed substrates were lucerne hay, wheat straw, wheat straw treated with urea and a commercial concentrate diet. An in vitro experiment was undertaken on these four different substrates in order to evaluate the two EFE and the yeast preparation. This was to identify the most promising EFE capable of producing a significant effect on feed digestibility using organic matter digestibility (in vitro true digestibility) and fermentation characteristics (in vitro GP system). Results from the in vitro evaluation showed that EFE significantly enhanced in vitro DM degradability and GP profiles (P < 0.05). Abo 374 enzyme showed potential to increase in vitro microbial protein synthesis (MPS) of GP residues of the concentrate diet. In addition, no correlation was found between the in vitro MPS and the 48 hours cumulative GP of all the tested substrates (P < 0.05; R2 < 0.30). Treatments were found to increase in vitro MPS, feed degradability and the cumulative GP of different quality forages and the concentrate diet, with Abo 374 being the best treatment (P < 0.05). However in vitro responses of EFE were variable depending on the energy concentration and chemical composition of different substrates. Variation in MPS was mostly due to the low recovery of purine derivates with the purine laboratory analysis. On the basis of these results, Abo 374 was selected and consequently further tested in another in vitro and in situ trial using a mixed substrate of lucerne hay and wheat straw. Abo 374 significantly improved the cumulative GP, in vitro DM and NDF disappearance of the mixed substrate (P < 0.05). In addition, no correlation was found between the in vitro MPS and the cumulative GP at 48 hours (P = 0.68; R2 < 0.25). The in situ disappearance of feed nutrients (DM, NDF and CP) with Abo 374 was similar to the control. The lack of significance of disappearance was probably due to the small number of sheep used in the study and the relatively high coefficient of variation associated with measuring ruminal digestion. Abo 374 significantly increased the in situ MPS (P = 0.0088) of the mixed substrate of lucerne hay and wheat straw. Evidence of the increased MPS and both in vitro and in situ disappearance of DM and NDF resulted from the Abo 374 activity during either the pre-treatment or the digestion process. The addition of Abo 374 to the mixed substrate of lucerne hay and wheat straw appeared to have been beneficial for microbial colonization of feed particles as a result of the increased rumen activity. It could be speculated that the primary microbial colonization was thus initiated, leading to the release of digestion products that attract in return additional bacteria to the site of digestion. This EFE may be efficient to produce some beneficial depolymerisations of the surface structure of the plant material and the hydrolytic capacity of the rumen to improve microbial attachment and the feed digestibility thereafter. Therefore, the mechanism of action by which Abo 374 improved the feed digestion can be attributed to the increased microbial attachment, stimulation of the rumen microbial population and synergistic effects with hydrolases of ruminal micro-organisms. With regard to these findings, the addition of EFE in ruminant systems can improve the ruminal digestion of DM, NDF and CP to subsequently enhance the supply of the metabolizable protein to the small intestine. Key words: crude protein (CP), exogenous fibrolytic enzymes (EFE), dry matter (DM), gas production (GP), neutral detergent fibre (NDF), microbial protein synthesis (MPS). / AFRIKAANSE OPSOMMING: Ruvoere is die hoof-voerkomponent in herkouer produksiesisteme aangesien dit dikwels die vernaamstebron van energie aan herkouer is. Slegs 10 tot 35% van die energie-inname is beskikbaar as netto-enrgie, omdat die vertering van selwande onvolledig is. Dit kan die prestasie en profyt in produksiesisteme drasties beïnvloed waar ruvoere as ’n hoofbron van nutriënte in die dieet gebruik word. Aangesien die nutriëntwaarde van ruvoere laag is en baie varieer, is navorsing vir verbeterde ruminale veselvertering steeds ’n voorgesette onderwerp. Dit is voorgestel dat eksogeniese fibrolitese ensieme (EFE) gebruik kan word vir verbeterde ruvoervertering. Positiewe resultate in ruminale ruvoerverterig en ander diereproduksie-eienskappe, is verkry as gevolg van toenemende rumen mikrobiese aktiwiteit na EFE aanvulling in herkouerdiëte. Twee EFE’s (Abo 374 en EFE 2) en `n gisproduk is geïdentifiseer en geselekteer vir hul potensiaal om die kumulatiewe gasproduksie (GP) na 24 uur met ’n reeks voersubstrate te verbeter met die gebruik van die in vitro GP sisteem as seleksiemetode om die superieure EFE produkte te identifiseer. Die verskillende ruvoersubstrate was lusernhooi, koringstrooi, ureumbehandelde koringstrooi en ’n kommersiële konsentraatdieet. ’n In vitro eksperiment was onderneem om die vier verskillende substrate te gebruik om die twee EFE’s en gisproduk te evalueer. Hierdeur sou die belowendste EFE’s identifiseer kon word wat ’n betekenisvolle effek op ruvoervertering het. Die vertering van ruvoer sal bepaal word deur organiese materiaal vertering (in vitro ware vertering), asook fermentasie-eienskappe (in vitro GP sisteem). Resultate van die in vitro evaluering het getoon dat EFE’s in vitro DM degradering en GP profiele verbeter. Dit blyk dat die Abo 374 ensiem ’n potensiële toemame in in vitro mikrobiese proteïensintese (MPS), soos bepaal deur die GP oorblyfsels van konsentraat diëte, tot gevolg gehad het. Daar was geen korrelasie tussen die in vitro GP en MPS van al die proefsubstrate nie. Dit blyk dat die behandelings ’n toename in in vitro GP, MPS en ruvoerdegradeerbaarheid van lae kwaliteit ruvoer- en konsentraatdiëte gehad het, waar Abo 374 die beste behandeling was. Die in vitro reaksies van die EFE’s was egter wisselend, afhangende van die energiekonsentrasie en die chemiese samestelling van die verskillende substrate. Variasie van MPS was meestal as gevolg van die lae herwinning van purienderivate tydens die purienanalise. Op grond van dié resultate, is Abo 374 geselekteer om verdere toetse in ander in vitro en in situ proewe te doen. Die substraat wat gebruik is, was ’n 1:1 mengsel van lusernhooi en koringstrooi. Abo 374 het die kumulatiewe RP, in vitro DM en NBV verdwyning van die gemengde substraat verbeter. Boonop is geen korrelasie tussen die MPS en in vitro GP gevind nie. In situ verdwyning van DM, NBV en RP was hoër vir Abo 374, maar nie betekenisvol nie. Die gebrek aan betekenisvolle verdwynings mag die gevolg wees van die klein hoeveelheid skape wat in die proef gebruik is, asook die relatiewe hoë koëffisient van variasie wat gepaard gaan met die bepaling van ruminale vertering. Abo 374 het die in situ MPS betekenisvol verhoog. Verhoogde MPS en in vitro en in situ verdwyning van DM en NBV is waargeneemwaarskynlik as gevolg van die aktiwiteit van Abo 374 gedurende die voorafbehandeling óf die verterings proses. Die byvoeging van Abo 374 tot die gemengde substraat van lusernhooi en koringstrooi blyk om voordelig te wees vir mikrobiese kolonisering van voerpartikels as gevolg van ’n toename in rumenaktiwiteit. Die primêre mikrobiese kolonisering het waaarskynlik gelei tot die vrystelling van verteringsprodukte wat addisionele bakterieë na die plek van vertering lok. Die EFE mag geskik wees vir voordelige depolimerisasie op die oppervlakstruktuur van die plantmateriaal, asook verbeterde hidrolitiese kapasiteit van die rumen om sodoende mikrobiese aanhegting, asook ruvoervertering te verbeter. Dus, Abo 374 se meganisme van aksie wat verbeterde ruvoervertering tot gevolg het, kan toegeskryf word aan `n verhoogde mikrobiese aanhegting, stimulering van die rumen mikrobiese populasie en die sinergistiese effek met hidrolases van rumen mikroörganismes. Ten opsigte van die bevindings, kan die byvoeging van EFE in herkouersisteme ruminale vertering van DM, NBV en RP verbeter, wat dan daaropvolgend die dunderm met meer metaboliseerbare proteïn sal voorsien. Sleutelwoorde: eksogene fibrolitiese ensieme (EFE), droëmaterial (DM), ruproteïen (RP), neutraal bestande vesel (NBV), mikrobiese proteïensintese (MPS), gasproduksie (GP).