Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: The use of fungal enzymes as ruminant feed digestibility enhancers was investigated. Currently, ruminants may not digest 38 to 80 % of fibrous forages' content. A renewed interest in the potential of feed enzymes for ruminants was prompted by the high costs of livestock production, together with the availability of newer enzyme preparations. Direct application of enzyme preparations can improve in vitro dry matter (DM) and neutral detergent fibre (NDF) degradation, indicating that direct-fed fibrolytic enzymes may be effective in enhancing in vivo digestion of forages. Two commercial enzyme products, Fibrozyme and Celluclast, and fungal extracellular enzyme extracts from Aureobasidium pullulans, Trichoderma reesei, Aspergillus aculeatus, and Thermomyces lanuginosus were evaluated for enhancing in vitro feed digestibility. Fibrozyme addition to both wheat straw and lucerne hay did not improve their in vitro digestibilities, even after a two hour pre-incubation period. The four fungal enzyme extracts did not enhance wheat straw's digestibility, but marginal increases were evident for lucerne hay. Celluclast addition resulted in marginal increases in the digestibility of both oat hay and oat silage, with no enhanced effect on lucerne hay and NaOH-treated wheat straw. No relationship could be found between the level of enzyme activity and the degree of feed digestion in the in vitro assay. Enzyme hydrolysis with Celluclast, in the absence of rumen fluid, gave more conclusive results. All the feed samples tested showed a positive response to Celluclast addition, even the less digestible feeds, namely sugarcane bagasse and wheat straw. In vitro results show that the assays were unsuccessful, because almost all of the experiments conducted showed inconclusive results. Alternative feed evaluation assays, which include the in vivo, in sacco and in situ methods of analysis, as well as gas production measurement and in vitro analysis with the DAISyII system, should be evaluated. A more detailed study of feed digestibility should be motivated by determining which feeds are hydrolysable, their chemical composition, i.e. how accessible the feeds are, and also evaluation of feed mixtures. The enzyme supplements also need to be evaluated for optimum temperature and pH, as well as the compilation of enzyme cocktails. / AFRIKAANSE OPSOMMING: Die gebruik van swamensieme om die verteerbaarheid van herkouervoere te verhoog, is ondersoek. Tussen 38 en 80 % van veselagtige voere se inhoud is tans onverteerbaar. 'n Hernieude belangstelling in die potensiaal van voerensieme vir herkouers word deur die hoë koste van veeproduksie, asook die beskikbaarheid van nuwe ensiempreparate gedryf Direkte byvoeging van ensiempreparate kan die in vitro droëmateriaal (DM) en neutrale onoplosbare vesel (NOV) vertering verbeter, wat daarop dui dat fibrolitiese ensieme wat direk gevoer word, effektief mag wees tydens die in vivo vertering van voer. Twee kommersiële ensiemprodukte, Fibrozyme en Celluclast, en die vier ekstrasellulêre ensieme van vier swamme, naamlik Aureobasidium pullulans, Trichoderma reesei, Aspergillus aculeatus, en Thermomyces lanuginosus is vir hul vermoë om die in vitro verteerbaarheid van voere te verbeter getoets. Byvoeging van Fibrozyme by beide koringstrooi en lusernhooi het geen verbetering in hulonderskeie in vitro verteerbaarheid tot gevolg gehad nie, selfs nie eens na 'n twee uur vooraf inkubasieperiode nie. Koringstrooi se verteerbaarheid is nie verbeter deur die byvoeging van die vier swam-ensiempreparate nie, maar 'n minimale verbetering is wel waargeneem in die verteerbaarheid van lusernhooi. Byvoeging van Celluclast het 'n minimale verbetering in beide hawerhooi en hawerkuilvoer se verteerbaarheid tot gevolg gehad, maar geen effek op lusernhooi of NaOH-behandelde koringstrooi se verteerbaarheid nie. Geen verwantskap is tussen die vlak van ensiemaktiwiteit en die mate van vertering tydens die in vitro toets gevind nie. Ensiematiese afbraak met Celluclast, in die afwesigheid van rumenvloeistof, het meer konkrete resultate gelewer. Al die voermonsters het 'n positiewe respons op die byvoeging van Celluclast getoon, selfs ook die minder verteerbare voere, nl. suikerrietbagasse en koringstrooi. In die wyer konteks was die resulate van die in vitro verteringstoetse egter onbeduidend as gevolg van groot variasie in die metings. Alternatiewe voerontledingstoetse, wat moontlik beter resultate mag lewer, sluit in in vivo, in sacco en in situ analises, asook die meting van gasproduksie en in vitro analise met die DAISyII sisteem. 'n Meer uitgebreide studie van voerverteerbaarheid wat die bepaling van die afbraak van voere, hul chemiese samestelling, met ander woorde toeganklikheid van voere, en die ondersoek van voermengsels behels, behoort aandag te geniet. Die ensiemmengsels behoort ook ten opsigte van samestelling, optimum temperatuur en pH ondersoek teword.

Thesis (MScAgric) -- Stellenbosch University, 2009. / ENGLISH ABSTRACT: Ruminants have a compound stomach system that enables them to utilize forages more efficiently than monogastric animals. However, forages alone do not contain sufficient nutrients to meet the requirements of high producing dairy cows. Forages are high in fibre and their nutrient availability depends on the degree of cell wall degradability. Improvements in forage fermentation would increase energy intake and subsequently milk production and performance by dairy cows. It is therefore important to find ways to improve forage degradation and utilization in the rumen. The use of different non-fibre carbohydrate (NFC) sources has different effects on animal performance. Supplementing forage based diets with energy sources containing sugar, starch or pectin results in variation in performance measurements such as milk yield, milk composition and dry matter intake (DMI). This thesis reports on two studies in which the effect of energy supplementation on forage fermentation and digestion parameters was investigated. In the first study an in vitro gas production protocol was used to determine the effect of sugar (molasses), starch (maize meal) and pectin (citrus pulp) on total gas production and rate of gas production of different forages. The forage substrates included wheat straw (WS), oat hay, (OH) lucerne hay (LUC), ryegrass (RYE) and kikuyu grass (KIK). The three energy sources, as well as a control (no energy source) were incubated in vitro with each of the above mentioned forages. Rumen fluid was collected from two lactating Holstein cows receiving a diet consisting of oat hay, lucerne, wheat straw and a concentrate mix. Forages alone (0.25 g DM) and/or together (0.125 g DM) with either molasses (0.1412 g DM), citrus pulp (0.1425 g DM) or maize meal (0.125 g DM) were weighed into glass vials and incubated for 72 hours. The weights of the energy sources were calculated on an energy equivalent basis. Blank vials, that contained no substrates, were included to correct for gas production from rumen fluid alone. The substrates were incubated in 40 ml buffered medium, 2 ml of reducing solution and 10 ml rumen fluid. Gas pressure was recorded automatically every five minutes using a pressure transducer system and the method based on the Reading Pressure Technique (Mauricio et al., 1999). Gas pressure was converted to gas volume using a predetermined regression equation. In the first gas production trial, the gas production included gas produced by the energy sources, while in the second gas production trial, the energy source gas production was deducted from the total gas production to determine the effect of energy source on gas production of respective forage substrates per se. Data were fitted to two non-linear models adapted from Ørskov and McDonald (1979). Significant forage x energy interactions were observed for the non-linear parameter gas production (b) in Model 1 and for b and lag phase (L) in Model 2 in both trials. In the first gas production trial, the higher fermentability of the energy sources supplemented to forage substrates, increased b (Model 1 & 2) of the LUC and WS. The gas production rate was affected in different ways for different forages, with the most noticeable effect on WS when it was supplemented with energy sources. All the energy sources increased c of WS irrespective of the model used. Energy sources had no effect on the L of LUC, OH or RYE, but decreased the L of WS and KIK. In the second trial, maize meal had no effect on b for any of the forages (Model 1 & 2), while molasses (Model 1 & 2) decreased b for all forage substrates, and citrus pulp (Model 1 & 2) decreased b of OH and RYE, to lower values than those of the control treatments. Gas production rate was not affected by molasses for any of the forage substrates, while citrus pulp (Model 1 & 2) increased c of OH and maize meal increased c of OH and KIK. Lag phase was only affected by energy sources in WS and KIK, where all the energy sources had lower L values than the control treatment. It was concluded that forage fermentability is affected differently by different energy sources. These observations may have important implications, in practice, on rumen health and milk production, and the data obtained can potentially be used as guidelines in feed formulations. In the second study, in vitro digestibility trials were undertaken to determine the effect of sugar (molasses and sucrose), starch (maize meal and maize starch) and pectin (citrus pulp and citrus pectin) on neutral detergent fibre (NDF) and dry matter (DM) degradability of forages. Forage substrates used included wheat straw, oat hay, lucerne hay, ryegrass and kikuyu grass. Rumen fluid was collected from two lactating Holstein cows receiving a diet consisting of oat hay, wheat straw and a concentrate mix. In vitro degradability was done with an ANKOM Daisy II incubator and forage substrates were incubated with or without the respective energy sources for 24, 48 and 72 hours. The substrates were incubated in 1076 ml buffered medium, 54 ml of reducing solution and 270 ml rumen fluid. The residues were washed, dried and analyzed for NDF. In the study with the applied energy sources (molasses, maize meal and citrus pulp) there were a forage x energy source interactions. Supplementation with the applied energy sources all improved dry matter degradability (DMD) of forages (24 and 72 hours), when compared to the control treatment, except for RYE supplemented with maize meal and citrus pulp at 24 hours. Molasses seemed to have had the biggest effect on DMD in all forage substrates. Supplementation with maize meal had no effect on neutral detergent fibre degradability (NDFD) of any forage substrate, except for an improvement in NDFD of LUC at 72 hours. Molasses improved NDFD of LUC at 24h, but had no effect on the other forage substrates. Citrus pulp improved NDFD of OH (72 hours), as well as LUC and WS (24 and 72 hours). It is postulated that the NDF of the energy sources was more digestible than that of the respective forages, and that the improved NDFD values could be ascribed to the contribution of the energy source NDFD. Overall, pasture grasses had a higher NDFD than the hays and straw, and appear to be more readily fermentable by rumen microbes than the low quality hays and straw explaining the higher NDFD. In the study involving the purified energy sources (sucrose, maize starch and citrus pectin), forage x energy source interactions were observed. In general, supplementation with these energy sources improved DMD at 24 and 72 hours except for RYE and KIK (72 hours). Pasture grasses (RYE and KIK) had a higher NDFD than LUC, OH and WS. At 72 hours, NDFD was 37.1% for LUC, 42.5% for OH and 40.3% for WS, compared to 70.5% for KIK and 64.9% for RYE. A possible explanation is that KIK and RYE samples came from freshly cut material, harvested after a 28d re-growth period. In general, sucrose (24 and 72 hours) and citrus pectin (72 hours) had no effect on NDFD of forage substrates. However, supplementing oat hay (24 hours) with starch and citrus pectin, and wheat straw (24 and 72 hours) with starch lowered NDFD, when compared to the control treatment. It is hypothesized that microbes fermented the easily fermentable energy sources first, before attacking forage NDF. The study suggested that forage NDFD values are not fixed, and may be altered by type of energy supplementation. / AFRIKAANSE OPSOMMING: Die meervoudige maagsisteem van herkouers stel hulle in staat om ruvoer meer effektief te benut as enkelmaagdiere. Ruvoere alleen bevat egter nie genoeg voedingstowwe om die behoeftes van hoogproduserende melkbeeste te bevredig nie. Ruvoere is ryk aan vesel en hul voedingstofbeskikbaarheid word bepaal deur die graad van selwand degradeerbaarheid. ‘n Verhoging in ruvoerfermentasie sal energieinname verhoog en gevolglik ook melkproduksie en prestasie. Dit is dus belangrik om maniere te vind om ruvoerdegradeerbaarheid en -verbruik in die rumen te verbeter. Die gebruik van verskillende nie-vesel koolhidraat (NFC) bronne het verskillende uitwerkings op die prestasie van diere. Energie-aanvullings soos suiker, stysel en pektien tot ruvoer-gebasseerde diëte, beïnvloed prestasiemaatstawwe soos melkproduksie, melksamestelling en droëmateriaalinname (DMI) op verskillende maniere. Hierdie tesis lewer verslag oor twee studies waar die invloed van energie-aanvullings op ruvoerfermentasie en verteringsmaatstawwe ondersoek is. In die eerste studie is ‘n in vitro gasproduksieprotokol gebruik om die invloed van suiker (melasse), stysel (mieliemeel) en pektien (sitruspulp) op totale gasproduksie (b) en tempo van gasproduksie (c) van verskillende ruvoersubstrate te bepaal. Ruvoersubstrate wat gebruik is, was koringstrooi (WS), hawerhooi (OH), lusernhooi (LUC), raaigras (RYE) en kikuyugras (KIK). Die drie energiebronne, sowel as ‘n kontrole (geen energiebron), is in vitro geïnkubeer saam met elk van die genoemde ruvoere. Rumenvloeistof is verkry van twee lakterende Holsteinkoeie, wat ‘n dieet ontvang het bestaande uit hawerhooi, koringstrooi en ‘n kragvoermengsel. Ruvoere is alleen en/of in kombinasie met melasse (0.1412 g DM), sitruspulp (0.1425 g DM) of mieliemeel (0.125 g DM) in glasbottels afgeweeg en vir 72 uur geïnkubeer. Die massas van die energiebronne is op ‘n energie-ekwivalente basis bereken. Leë bottels wat geen substraat bevat het nie, is ingesluit om te korrigeer vir gasproduksie afkomstig vanaf rumenvloeistof alleen. Substrate is in 40 ml van ‘n buffermedium, 2 ml reduserende oplossing en 10ml rumenvloeistof geïnkubeer. Gasdruk is elke vyf minute outomaties aangeteken deur gebruik te maak van ‘n drukmetersisteem en die metode is gebasseer op die Reading gasdruktegniek. Gasdruk is omgeskakel na gasvolume deur gebruik te maak van ‘n voorafbepaalde regressievergelyking. In die eerste proef het totale gasproduksie die gas wat deur die onderskeie energiebronne geproduseer is, ingesluit. In die tweede proef is gasproduksie afkomstig van die energiebronne afgetrek van totale gasproduksie, om sodoende die invloed van die energiebronne per se op die gasproduksie van die onderskeie ruvoersubstrate, te bepaal. Data is met behulp van twee nie-liniëre modelle gepas. Betekenisvolle ruvoer x energie-interaksies is in albei proewe waargeneem vir die nie-liniëre parameter b (gasproduksie) in Model 1, en vir b en L (sloerfase) in Model 2. In die eerste proef het die energiebronne se hoë fermentasie gelei to ‘n verhoging in b (Model 1 & 2) van LUC en WS. Energie-aanvullings het die c-waarde van die onderskeie ruvoere verskillend beïnvloed, met WS wat die mees opvallende effek gehad het. Al die energiebronne het die c-waarde van WS verhoog, ongeag watter model gebruik is. Energiebronne het geen invloed op die L-waarde van LUC, OH of RYE gehad nie, maar het wel die L-waarde van WS en KIK verlaag. In die tweede proef het mieliemeel geen invloed op die b-waarde van enige van die ruvoere gehad nie (Model 1 & 2), terwyl melasse (Model 1 & 2) die b-waarde van alle ruvoere verlaag het, en sitruspulp (Model 1 & 2) OH en RYE se b waardes verlaag het tot laer as die kontroles. Melasse het geen invloed op die c-waarde van die onderskeie ruvoersubstrate gehad nie, terwyl sitruspulp (Model 1 & 2) die c-waarde van OH, en mieliemeel die c-waarde van OH en KIK, verhoog het. Energiebronne het slegs ‘n invloed op die sloerfase in WS en KIK gehad, waar dit L verlaag het tot laer waardes as dié van die kontroles. Daar is gevind dat ruvoer-fermenteerbaarheid verskillend beïnvloed word deur verskillende energiebronne. Bogenoemde resultate kan in die praktyk betekenisvolle invloede hê op rumengesondheid en melkproduksie en die data wat verkry is, kan potensieël gebruik word as riglyne in voerformulerings. In die tweede studie is in vitro verteerbaarheidsproewe gedoen om die effek van suiker (molasse en sukrose), stysel (mieliemeel en mieliestysel) en pektien (sitruspulp en sitrus-pektien) op neutraalonoplosbare vesel (NDF) en droë materiaal (DM) degradeerbaarheid van ruvoere, te bepaal. Ruvoersubstrate wat gebruik is, was WS, OH, LUC, RYE en KIK. Rumen vloeistof is verkry van twee lakterende Holstein koeie, wat ‘n dieet ontvang het bestaande uit hawerhooi, koringstrooi en ‘n konsentraat mengsel. Die in vitro degradeerbaarheidsproef is gedoen met ‘n ANKOM Daisy II inkubator. Ruvoersubstrate is geïnkubeer met of sonder die onderskeie energiebronne vir 24, 48 en 72 uur. Die substrate is geïnkubeer in 1076 ml buffer medium, 54 ml reduserende oplossing en 270 ml rumen vloeistof. Residue is gewas, gedroog en geanaliseer vir NDF. In die proef met toegepaste energiebronne (molasse, mieliemeel en sitruspulp), was daar ruvoer x energiebron interaksies. Toegepaste energiebron aanvullings het almal DMD van ruvoersubstrate (24 en 72 uur) verbeter, uitsluitend vir RYE wat aangevul is met mieliemeel (24 uur) en sitruspulp (24 uur). Van al die ruvoersubstrate het molasse die grootste effek gehad op DMD. Mieliemeel aanvullings het geen effek gehad op neutraal-onoplosbare vesel degradeerbaarheid (NDFD) van ruvoersubstrate nie, behalwe vir ‘n verbetering in NDFD van LUC by 72 uur. Molasse het NDFD van lucern by 24 uur verbeter, maar geen effek gehad op ander ruvoersubstrate nie. Sitruspulp het NDFD van OH (72 uur), asook LUC en WS (24 & 72 uur) verbeter. Daar word beweer dat die NDF van energiebronne meer verteerbaar is as die van ruvoersubstrate, en dat die verbetering in NDFD waardes toegeskryf kan word aan die bydraes van energiebronne se NDFD. Weidingsgrasse (RYE & KIK) het oor die algemeen ‘n hoër NDFD as hooie en strooi gehad. Rumen mikrobes blyk ook om dié grasse vinniger te verteer as lae kwaliteit hooie en strooi, wat gevolglik die hoër NDFD verduidelik. In die proef met suiwer energiebronne (sukrose, mieliestysel en sitrus-pektien) is ruvoer x energiebron interaksies waargeneem. Energiebronaanvullings het DMD by 24 en 72 uur verbeter, buiten vir RYE en KIK (72 uur). Weidingsgrasse het hoër NDFD as LUC, OH en WS. By 72 uur was die NDFD van LUC 37.1%, OH 42.5%, WS 40.3%, in vergelyking met 70.5% vir KIK en 64.9% vir RYE. ‘n Moontlike verklaring vir die hoër NDFD van KIK en RYE, is omdat dit vars gesnyde material is, geoes na slegs 28 dae hergroei. Oor die algemeen het sukrose (24 & 72 uur) en sitrus-pektien (72 uur) geen effek gehad op NDFD van ruvoersubstrate nie, terwyl stysel en pektien aanvullings tot OH (24 uur), en stysel aanvullings tot WS (24 & 72 uur) NDFD verlaag het. Daar word hipotetieseer dat mikrobes eers die vinnig fermenteerbare energiebronne fermenteer, voordat hulle ruvoer NDF aanval. Hierdie studie beweer dat ruvoer NDFD waardes nie vas is nie, en dat dié waardes beïnvloed mag word deur energiebron aanvullings.

Thesis (MScAgric)--Stellenbosch University, 1999. / ENGLISH ABSTRACT: The rate of hydrolysis of urea in the rumen of animals is a major limitation when considering the substitution of natural protein with urea in the formulation of rations. The aim of this study was to evaluate polymer coated urea prills with variable coating thickness and evaluate its potential as a slow-release NPN compound. A new slowrelease urea compound, made by coating prilled feedgrade urea with a co-polymer of urea-formaldehyde resin and a castor-coconut alkyd was initially evaluated for urea-nitrogen concentration in distilled water in order to evaluate its potential as a slow-release urea product for ruminants. Amino/alkyd or polyester blends are among the cheapest of the modern synthetic systems and are considered because it is non-toxic, low-cost, biodegradable and easy to manufacture. A 2 x 2 x 2 x 2 factorial design was used and 16 individual products were made and evaluated. The Wurster method was used to encapsulate urea prills. The slopes of the urea release curves represented the release rate of the encapsulated products and were compared to identify the process variables, which had an effect on release rate. Two of the coating variables, coating weight and alkyd: resin ratio, had a major effect (P = 0.0001) on the release rate of urea. The crushing strength of encapsulated products was significantly (P = 0.0001) higher than that of untreated urea. Results motivated the evaluation of the products in the rumen of sheep in terms of rumen ammonia and blood urea N concentrations. Four slow-release products were made after interpreting results from the first study, and differed on account of the coating weight and the composition of the co-polymer. Fifteen fistulated wethers were randomly allotted into 5 groups and intraruminally received an equivalent of 15g urea. Rumen ammonia and blood ammonia were taken at 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 and 48 h after administration of the various treatments. Slow release urea (SRU) resulted in significantly lower rumen ammonia peaks (P = 0.0001) than untreated urea, while the peaks were also significantly delayed. Untreated urea resulted in the maximum concentration at two hours after administration of the urea (P = 0.0685) while the SRU's reached a maximum at six hours after administration in the rumen. No significant differences between the four different SRU types were found. Responses in blood urea-N was similar to that observed for rumen ammonia nitrogen. The encapsulation was effective in decreasing the rate of ammonia release from the urea for up to six hours after administration. In a third trial four Dehne Merino wethers were used in a 2 x 2 Latin square design. They received a SRU product equivalent to 0.4 g urea per kg body weight orally. Rumen liquor and blood samples were taken at 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 and 48 h after intake. Difficulty was initially experienced with ingestion and palatability of the SRU products due to the strong formaldehyde and butanone odour present in the coating. The maximum rumen ammonia (NH3) concentration for the SRU were lower than that of untreated urea (17.5 mg N/dl vs. 66.9 mg N/dl). The time to reach blood urea levels also differed considerably (6 h vs. 24 h for blood urea nitrogen) between treatments. The encapsulation of urea prills shows potential solutions to reduce the solubility of urea and also reduce the hygroscopic nature of urea and improve the palatability and storage characteristics thereof. Keywords: Slow-release urea, encapsulate, copolymer, urea formaldehyde rumen ammonia, blood urea nitrogen, solubility, palatability, storage characteristics. / AFRIKAANSE OPSOMMING: Die vinnige tempo waarteen ureum in die rumen na ammoniak omgesit word, is die grootste beperking in die optimale benutting van ureum, as vervanging van natuurlike protein in herkouerrantsoene. Die doel van hierdie studie was om 'n stadig vrystellende ureumproduk te ontwikkel wat die rumenammoniakvlak gedurende 'n aansienlike periode van die dag bokant 'n sekere vlak kan hou. 'n Nuwe stadig vrystellende ureumproduk, vervaardig deur ureumkorrels met 'n kopolimeer van ureum-formaldehiedhars en 'n kastor-en klapperalkied te bedek, is geevalueer om die potentiaal as stadig vrystellende nie-protein stikstof (NPN)-produk vir herkouers te ondersoek. Die veiligheid, biodegradeerbaarheid, lae koste en maklike vervaardiging van amino/alkied-kopolimere maak dit een van die goedkoopste sintetiese sisteme om vir stadig vrystellende sisteme te oorweeg. 'n 2 x 2 x 2 x 2 Faktoriale antwerp is gebruik om 16 individuele produkte te vervaardig. Die Wurster-metode is gebruik om individuele korrels te enkapsuleer met die polimeer en die potentiaal van die produkte is aanvanklik geevalueer deur die ureumstikstofvrystelling in gedistilleerde water te meet. Die hellings van die vrystellingsgrafieke is vergelyk om die veranderlikes te bepaal wat die grootste invloed op die vrystellingstempo van ureum uit die ge·inkapsuleerde produkte het. Resultate dui dat twee verandelikes 'n betekenisvolle effek het op die vrystellingstempo, nl. dikte van die omhulsel, en die samestelling van die kopolimeer (P = 0.0001 en P = 0.0135, onderskeidelik) het. Die samedrukbaarheid van die ge ·lnkapsuleerde produkte was ook betekenisvol hoer (P = 0.0001) as die van onbehandelde ureumkorrels, wat lei tot verbeterde bergings- en hanteringseienskappe. lnterpetering van resultate lei tot die vorming van vier stadig vrystellende produkte. Vyf groepe van 3 volwasse rumengefistuleerde Dohnemerinohamels is in 'n proef gebruik om die potentiaal van die produkte verder te ondersoek. 'n Ekwivalent van 15 g ureum is direk in die rumen van elke dier geplaas en ammoniak-en bloed monsters is 0, 1, 2, 4, 6, 8, 12, 16, 20, 24, 36 & 48 ure na dosering geneem. Die stadig vrystellende ureumprodukte het 'n betekenisvol laer maksimum waardes vir beide ammoniak-en bloedstikstofureum getoon (P = 0.0001 ). Onbehandelde ureum het 'n maksimum rumenammoniakstikstof konsentrasie reeds twee ure na toediening bereik in vergelyking met ses ure vir die stadig vrysellende produkte. Geen betekenisvolle verskille in hierdie parameters is tussen die ge·lnkapsuleerde produkte gevind nie, terwyl geen interaksie is tussen hoofeffekte voorgekom het nie. In 'n derde proef is vier Dohnemerinohamels gebruik om die vrystellingstempos, in terme van rumenammoniak-en bloedureumstikstof te bepaal waar die stadig vrystellende produk en onbehandelde ureum direk aan die diere gevoer is . 'n Ekwivalent van 0.4 g ureum/kg liggaamsmassa is gevoer. Aanvanklik is inname- en smaakliksheidprobleme ondervind, moontlik as gevolg van die sterk butanoon-en formaldehiedreuk van die omhulsel. Die rumenammoniakstikstof het 'n laer maksimum (17.5 vs. 66.9 mg N/1 00 ml) as die van onbehandelde ureum gehad terwyl die tyd wanneer maksimum konsentrasie bereik word ook aansienlik later was. Die polimeer inkapsulering van ureumkorrels toon potensiaal as 'n stadig vrystellende ureumproduk deurdat dit die oplosbaarheid van ureum in die rumen verlaag. Bykomende voordele is dat die omhulsel die higroskopisiteit verlaag en die samedrukbaarheid verhoog, beide eienskappe wat die hantering-en bergingseienskappe bevorder. Sleutelwoorde: Stadig vrystellende ureum, enkapsulering, kopolimeer, ureumformaldehied, rumenammoniak, bloed ureum stikstof, oplosbaarheid, smaaklikheid, bergingseienskappe.

Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Statistical analysis was conducted on data from two Elsenburg herds, containing 105 Jersey and 232 Holstein cows. The data was examined for external factors which may affect milk yield and milk composition. The data consisted of 337 first lactation records, taken over a 20 year time period. Breed of cow had an effect on milk yield, butterfat and protein production, as did the year in which the cows were born and the age of the heifer at first calving. There was a significant interaction between the breed and year of birth. There are other external factors, which are difficult to quantify, which may have an effect on production. In the following trials, eight ruminally cannulated dairy cows (four Jerseys and four Holsteins) were used to determine the effect of breed on forage digestibility in the rumen. All cows received a high concentrate mixed ration, with supplementary wheat straw. An in situ rumen degradability trial was conducted with three different forages, viz. lucerne, wheat straw and NaOH-treated wheat straw. The bags were incubated in the rumen for time intervals of 2,4, 8, 12, 16,20,24, 36,48, 72 and 96 hours and samples were analysed for dry matter (DM) and neutral-detergent fibre (NDF). Higher rumen degradability values (P<0.01) ofDM and NDF were observed in Jerseys for all three forages. Differences were more apparent for wheat straw and treated wheat straw than for lucerne. The rate of passage of digesta from the rumen was measured in both breeds by a chromium mordanted wheat straw marker. The Holsteins manifested a higher rate of passage (P<0.05) than the Jerseys, while daily feed intakes were also higher (P<O.Ol) for the Holsteins than for the Jerseys. Daily feed intake, expressed as percentage of body weight was, however, slightly higher for the Jerseys than for the Holsteins. The pH value of the rumen fluid was measured at 0, 4, 8, 10 and 12 hours postfeeding. The only significant difference (P<O.OI)in pH between the breeds was at 4 hours post-feeding, when the ruminal pH dropped more rapidly in the Holsteins than in the Jerseys. The pH in the Holsteins dropped below 6.2, which may have inhibited fibrolytic microbe activity in the rumen, resulting in a lower effective degradability of forages. Total volatile fatty acids were higher in Holsteins from four to 10 hours after feeding, but no differences were observed in acetic acid:propionic acid ratios. It was concluded that Jerseys appear to utilize forages more efficiently than Holsteins and that the differences are more apparent in low quality forages than in high quality forages. / AFRIKAANSE OPSOMMING: Statistiese analises is op data van twee kuddes te Elsenburg uitgevoer, bestaande uit 105 Jersey- en 232 Holsteinkoeie. Die data is ondersoek vir eksterne faktore wat melkproduksie en melksamestelling kan beinvloed. Die data het uit 337 eerste-laktasierekords bestaan, wat oor 'n periode van 20 jaar ingesamel is. Ras van die koei, sowel as die jaar van geboorte en ouderdom met eerste kalwing het 'n invloed op melkproduksie, bottervet- en proteienopbrengs gehad. 'n Betekenisvolle interaksie is tussen ras en jaar van geboorte waargeneem. Ander moeilik kwantifiseerbare faktore mag ook 'n invloed op melkproduksie he. In daaropvolgende proewe is agt rumen-gekannuleerde melkkoeie (vier Jerseys en vier Holsteins) gebruik om die invloed van ras op ruvoerverteerbaarheid in die rumen te bepaal. Al die koeie het 'n hoe-kragvoerdieet ontvang, aangevul met koringstrooi. 'n In situ rumendegradeerbaarheidstudie is met drie verskillende ruvoere, naamlik lusernhooi, koringstrooi en NaOH-behandelde koringstrooi uitgevoer. Die ruvoere is vir tye van 2, 4, 8, 12, 16, 20, 24, 36, 48, 72 en 96 ure in die rumen geinkubeer en monsters is ontleed vir droemateriaal (DM) en neutraal-bestande vesel (NDF). Hoer rumen-degradeerbaarheidswaardes (P<O.Ol) van DM en NDF is in Jerseys waargeneem as in Holsteins vir al drie ruvoere. Verskille was meer opvallend vir koringstrooi en NaOH-behandelde koringstrooi as vir lusem. Uitvloeitempo van digesta uit die rumen is in beide rasse met behulp van chroomgemerkte koringstrooi bepaal. Hoer uitvloeitempo's is in die Holsteins waargeneem as in die Jerseys, terwyl daaglikse voerinnames ook hoer was (P<O.05) by die Holsteins as by die Jerseys. Daaglikse voerinname, uitgedruk as persentasie van liggaamsmassa, was egter effens hoer (P<O.OI)by die Jerseys as by die Holsteins. Die pH van die rumenvloeistof is op 0, 4, 8, 10 en 12 ure na voeding gemeet. Die enigste betekenisvolle verskil (P<O.OI)in pH tussen die rasse het op 4 ure na voeding voorgekom toe die pH van die rumeninhoud vinniger in die Holsteins as in die Jerseys gedaal het. Die pH in die Holsteins het onder 6.2 gedaal, wat moontlik fibrolitiese mikrobe-aktiwiteit in die rumen kon inhibeer, met 'n gevolglike daling in effektiewe degradeerbaarheid van die ruvoere. Vanaf 10 ure na voeding was die totale vlugtige vetsuurkonsentrasies hoer in die Holsteins, maar geen verskille in asynsuur:propionsuurverhoudings is waargeneem nie. Die gevolgtrekking is gemaak dat Jerseys skynbaar meer doeltreffend is om ruvoere te benut as Holsteins en dat die verskil tussen rasse meer opvallend is vir lae kwaliteit ruvoere as vir hoe kwaliteit ruvoere.

Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Six groups each with six Friesian bull calves were used in this investigation and slaughtered at 20 weeks of age. Calves received a low- (LD) or high (HD) degradable protein diet, each with or without rumen inert fat supplementation. Two commercial fat sources were used, Morlae (m) and Golden Flake (gf), included at 2.5% of the diet. A commercial milk replacer (Denkavit) was fed at 4L for 42 days, followed by 2L until weaning at 49 days of age. The starter diets were fed ad lib. from day 14 to 10 weeks of age and finishing diets ad lib. from 11 to 20 weeks of age. There were no significant differences in body mass gain or dry matter intake over the entire 20 week period. The feed conversion ratio (FCR) was improved significantly (P=0.0032) when fat was supplemented to LD, but not to HD diets. The FCR (kg dry matter/ kg gain) ofLD, HD, LDm, HDm, LDgfand HDgfdiets were 3.45,3.44,3.07, 3.81, 3.02 and 3.43, respectively. All 36 calves were used in a digestibility trial, using chromium oxide (Cr203) as a marker, during week 18 of the investigation. Digestibility values (%) for the six diets (LD, HD, LDm, HDm, LDgfand HDgf) were 61.74, 65.91, 75.44, 69.00, 75.54 and 67.15 for dry matter, 61.44, 61.60, 71.33, 68.23, 75.44 and 66.12 for crude protein and 58.56, 66.45, 75.98, 70.92, 78.43 and 70.79 for fat, respectively. The dry matter (P=O.OOOl)and fat (P=O.OOOl) digestibilities were only significantly higher when fat was added to LD diets. The crude protein (CP) digestibilities were significantly higher when fat was added to either the LD (P=0.0001) or the HD (P=0.0488) diets. All the calves were slaughtered at 20 weeks of age and the fatty acid content of the meat (m. longissimus) and subcutaneous fat layer adjacent to the 12th rib as well as the meat colour, was determined. The fatty acid composition of the longissimus muscle was changed by feeding the rumen inert fat sources. The three predominant fatty acids found were palmitic, stearic and oleic acids. The palmitic acid (CI6:0) content of the muscle and diet was 24.44 & 20.47,25.97 & 22.57,31.06 & 33.23, 30.98 & 37.91, 34.94 & 31.77 and 29.71 & 32.88 of the total fat for the LD, HD, LDm, HDm, LDgf and HDgf diets, respectively. The C16:0 content was significantly higher in the muscle of the calves receiving the LD diets supplemented with fat (P=0.0008). There was also a significant interaction between the two fat sources and protein degradability (P=0.0065), but only in the LD diets. The stearic acid (CI8:0) content of the muscle and diet was 14.35 & 5.22, 19.65 & 8.61, 17.29 & 4.68, 22.59 & 5.78, 22.27 & 15.54, and 26.48 & 20.15 of the total fat for the LD, HD, LDm, HDm, LDgfand HDgfdiets, respectively. The C18:0 content was significantly higher in the muscle of calves receiving the HD (P=O.OOOl)compared to LD diets. The stearic acid content was also significantly higher when fat was added to LD (P=0.0042) or HD (P=0.0073) diets. The oleic acid (CI8:1) content of the muscle and diet was 36.06 & 21.51,39.99 & 21.11,32.21 & 23.67, 29.13 & 24.59, 25.23 & 18.68 and 35.93 & 16.02 of the total fat for the LD, HD, LDm, HDm, LDgf and HDgf diets, respectively. The linolenic acid (CI8:3) content of the muscle was significantly higher (P=0.0038) when fat was added to LD diets compared to no fat supplementation (0.87 vs. 0.15). The CIELAB values indicated that LD diets resulted in more pink meat. Mean values ofL* =-32.61, 34.19; a* = 7.08, 7.91 and b* = 3.18 and 4.07 were observed for the LD and HD diets, respectively. Meat from the LD diets had significantly lower L*-(P=0.0252), a*-(P=0.0283) and b*-(P=0.0109) values compared to meat from the HD diets. It was concluded that there was a positive response in CP digestibility when rumen inert fats were supplemented to LD or HD diets, although a greater response was shown in the LD diets. The FCR, dry matter and fat digestibility were only increased when fat was added to the LD and not to the HD diets. Similarly, the fatty acid contents of the longissimus muscle of veal calves can be manipulated with the supplementation of rumen inert fat sources, but only when combined with a low protein degradable diet. The low degradable protein diets also produce a more attractive meat colour for the potential veal consumer. / AFRIKAANSE OPSOMMING: Ses behandelings, lae- (LD) of hoë (HD) degradeerbare diëte, elk met of sonder rumeninerte vetsupplementering, is geëvalueer met ses kalwers in elke groep. Twee kommersiële vetbronne is gebruik, nl. Morlae (m) en Golden Flake (gf) teen 'n 2.5% insluitingspeil. 'n Kommersiële melksurrogaat (Denkavit) is aangebied teen 4L1dag tot 42 dae ouderdom, gevolg deur 2L/dag tot speenouderdom op 49 dae. Aanvangsdiëte is ad lib. aangebied vanaf 14 dae tot 10 weke ouderdom en die groeidiëte ad lib. vanafweek 11 tot 20. Daar was geen betekenisvolle verskille in die totale massatoename of die droëmateriaalinname nie. Die voeromsettingsverhouding is betekenisvol verbeter (P=0.0032) in die behandelings waarin rumeninerte vette by LD diëte ingesluit is, maar nie by die HD diëte nie. Die voeromsettingsverhouding (kg droëmateriaalinname / kg massatoename) van die LD, HD, LDm, HDm, LDgf en HDgf diëte was 3.45, 3.44, 3.07, 3.81, 3.02 en 3.43, onderskeidelik. Al 36 kalwers is in 'n verteringsproef gebruik gedurende week 18 van die proef. Chroomoksied (Cr203) is as merker gebruik. Verteerbaarheidswaardes vir die ses diëte was 61.74, 65.91, 75.44,69.00,75.54 en 67.15 vir droëmateriaal, 61.44, 61.60, 71.33, 68.23, 75.44 en 66.12 vir ruproteïen en 58.56, 66.45, 75.98, 70.92, 78.43 en 70.79 vir vet, onderskeilik. Die droëmateriaal- (P=O.OOOl) en vetverteerbaarheid (P=O.OOOI) was slegs betekenisvol hoër wanneer vet by LD diëte gevoeg is en nie by HD nie. Die ruproteïen (RP) verteerbaarheid Stellenbosch University http://scholar.sun.ac.za VI was betekenisvol hoër (P=0.0002) by LD en HD (P=0.0488) diëte met vet supplementering, teenoor geen vet insluiting. Die kalwers is op 20 weke ouderdom geslag en die vetsuursamestelling van die vleis (m. longissimus) en die subkutane vetlaag teenaan die 12de rib, asook en die vleiskleur, is bepaal. Die vetsuursamestelling van die longissimus spier is deur die supplementering van rumeninerte vet verander. Die drie primêre vetsure wat in die vleis voorgekom het, was palmitiensuur, steariensuur en oleïensuur. Die palmitensuur (CI6:0) inhoud van die spier en diëte was 24.44 & 20.47, 25.97 & 22.57, 31.06 & 33.23, 30.98 & 37.91, 34.94 & 31.77 en 29.71 & 32.88 van die totale vet van die LD, HD, LDm, HDm, LDgf en HDgf diëte, onderskeilik. Die C16:0 was betekinisvol hoër in die spiere van kalwers wat die LD diëte met vet supplementering (P=0.0008) ontvang het. Die steariensuur (CI8:0) inhoud van die spier en diëte was 14.35 & 5.22, 19.65 & 8.61, 17.29 & 4.68, 22.59 & 5.78, 22.27 & 15.54, en 26.48 & 20.15 van die totale vet vir die LD, HD, LDm, HDm, LDgf en HDgf diëte, onderskeidelik. Die C18:0 inhoud was betekinisvol hoër in die spiere van die kalwers wat die HD (P=O.OOOI),teenoor LD diëte ontvang het. Die steariensuur inhoud was ook betekenisvol hoër wanneer vet by LD (P=0.0042) of HD (P=0.0031) diëte gevoeg word. Die oleïensuur (CI8:1) inhoud van die spier en diëte was 36.06 & 21.51, 39.99 & 21.11, 32.21 & 23.67, 29.13 & 24.59, 25.23 & 18.68 en 35.93 & 16.02 van die totale vet vir die LD, HD, LDm, HDm, LDgf en HDgf diëte, onderskeidelik. Die linoleensuur (CI8:3) inhoud van die spier was betekinisvol hoër (P=0.0038) in die LD diëte met vet teenoor LD met geen vet supplementering (0.87 vs. 0.15). Die CIELAB waardes van die LD diëte dui op 'n pienker vleiskleur. Gemiddelde waardes van L* = 32.61 & 34.19, a* = 7.08 & 7.91 en b* = 3.18 & 4.07 is vir die LD en HD diëte, onderskeidelik, waargeneem. Die vleis van die LD diëte het 'n betekenisvol laer L*-(P=0.0252), a*-(P=0.0283) en b*-(P=0.0109) waarde in vergelyking met die HD diëte getoon. Die resultate dui daarop dat daar 'n positiewe respons in die ruproteïenverteerbaarheid by die supplementering van rumeninerte vette by LD en HD diëte voorkom, maar die response op die LD diëte is groter. Die voeromsettingsverhouding, droëmateriaal- en vetverteerbaarheid is egter net bevoordeel in die LD met vet en nie in die HD diëte nie. Die vetsuursamestelling van die longissimus spier in die kalf kan gemanipuleer word met die supplementering van rumeninerte vetbronne, maar slegs wanneer dit gekombineer word met lae degradeerbare proteïen diëte. Die lae degradeerbare proteïen diëte produseer ook die mees aanloklike vleiskleur vir die potensiële kalfsvleisverbruiker.

Nous nous sommes intéressés au rôle des caractéristiques sensorielles des aliments dans les aspects qualitatifs (sélection) et quantitatifs (ingestion) du comportement alimentaire des ovins. Indépendamment des conséquences post-ingestives d'une part, et en interaction avec les conséquences post-ingestives dans les processus d'apprentissage alimentaire d'autre part. A conséquences similaires, les caractéristiques sensorielles n'ont pas influencé l'ingestion journalière mais ont influencé i/ l'ingestion à court-terme via une modification de l'équilibre entre motivation et rassasiement, et ii/ les durées et vitesses d'ingestion. Certaines caractéristiques sensorielles possèdent une valeur hédonique voire une valeur latente potentiellement indicatrice des conséquences, et influencent la sélection. Lors des apprentissages, la valeur hédonique de ces caractéristiques module la propension des animaux à les associer aux conséquences. D'autres ont un rôle d'indicateur des conséquences qui permet aux animaux d'améliorer leurs apprentissages notamment en milieu complexe, via un processus de généralisation, et conforte la validité de la théorie des apprentissages alimentaires dans ces milieux. De part leur rôle d'agent discriminant, leur valeur hédonique voire leur rôle d'indicateur, les caractéristiques sensorielles influencent à différents niveaux le comportement alimentaire des ovins, et devraient être considérées pour améliorer l'utilisation des aliments dans les rations et le bien-être des animaux d'élevage

Four studies were conducted to determine the effect of synchronization of protein and starch degradation on nutrient utilization, microbial protein synthesis and milk production in dairy cows. In Experiment 1, five cereal grains and five protein supplements were compared for extent of solubility and degradability of their starch and nitrogen fractions. Results indicated large differences which permitted their ranking from high to low degradability as follows: grains, oats > wheat > barley > corn > milo protein supplements, soybean meal > cottonseed meal, (CSM) > corn gluten meal > brewers dried grains, (BDG) > blood meal. In Experiment 2, the five grains were incubated for varying times in vitro (with added amylase) or in situ to determine rate and extent of degradation of dry matter, crude protein and starch. Results showed that rate of starch degradation followed a similar, but slightly different trend than in trial 1 (wheat > barley > oats > corn > milo). Rates for DM and CP degradation were similar than those for starch. In Experiment 3, high (barley, HS) and low (milo, LS) degradable starch sources were combined with a high (CSM, HP) and a low (BDG, LP) degradable protein sources to formulate four diets; HSHP, HSLP, LSHP and LSLP. Diets were fed to 32 cows, starting two to four weeks postpartum, for a 60-d milk production and digestibility study. Apparent digestibility was calculated using chromium oxide. Organic matter digestibility was higher (P < .05) was found in nutrient output to the small intestine among diets and microbial CP synthesis was higher (P > .05) for barley diets.

No description available.

Master of Science / Department of Animal Sciences and Industry / Evan C. Titgemeyer / Seven ruminally cannulated heifers approximately 225 kg initial BW were used in a 7 × 4 Youden square design to determine the effects of different levels of limonene on ruminal Fusobacterium necrophorum populations. Treatments included: 1) control, 2) limonene at10 mg/kg diet DM, 3) limonene at 20 mg/kg diet DM, 4) limonene at 40 mg/kg diet DM, 5) limonene at 80 mg/kg diet DM, 6) CRINA-L (a blend of essential oil components) at 180 mg/kg diet DM, 7) tylosin at 12 mg/kg diet DM. Each period included 11 d with 10 d washouts between periods. Samples were collected on d 0 (before treatment initiation), 4, 7, and 10 for measuring F. necrophorum by most probable number (MPN) method using selective culture medium. Results indicate that CRINA-L (P = 0.52) and tylosin (P = 0.19) did not affect ruminal F. necrophorum populations. Limonene linearly decreased (P = 0.03) F. necrophorum populations, and the optimal dietary concentration for limonene was 40 mg/kg DM. Limonene did not affect ruminal degradation rate of lysine, NH3 concentration, or VFA profiles in ruminal fluid. Limonene was useful for reducing ruminal concentrations of F. necrophorum. It may have potential to control liver abscesses, although further research will be needed to assess the effect of limonene under feedlot conditions.

Resumo: Estratégias para reduzir o aquecimento da Terra e aumentar a produção animal requerem novos sistemas, onde devem ser consideradas as emissões de metano e de outros gases que possam provocar danos ao meio ambiente. O objetivo deste trabalho foi a mensuração da produção de metano por arquéias e aplicação da metagenômica para detecção destas na fração sólida do conteúdo ruminal. Para a análise da produção de metano foi colhido o conteúdo ruminal seguido do preparo da solução a ser fermentada e armazenamento dos gases. A amplificação da região 168 rDNA foi obtida por PCR e a seguir foram feitas clonagem, seqüenciamento e análise das seqüências pelos programas "Sequencing Analysis 3.4" e Phred/Phrap/Consed, submetendo-as ao programa BLA8T. Maiores produções de metano e relações acetato:propionato foram observadas nos tratamentos contendo 70% de volumoso. As análises do BLA8T permitiram identificar nos tratamentos com 70% e 30% de feno, 96 seqüências relacionadas à família Methanobacteriaceae, 47 seqüências a arquéias não cultiváveis e 60 seqüências foram de arquéias desconhecidas (T1), 125 seqüências relacionadas à família Methanobacteriaceae, 42 seqüências a arquéias não cultiváveis e 32 seqüências foram de arquéias não conhecidas (T2). Para os tratamentos feitos com 70% e 30% de silagem de milho, foram observadas 30 seqüências referentes à família Methanobacteriacea, 18 seqüências à família Methanomicrobiacea, 43 seqüências a arquéias não cultiváveis e 118 seqüências foram de arquéias desconhecidas (T3) e 173 seqüências referentes à família Methanobacteriacea, 31 seqüências a arquéias não cultiváveis e 25 seqüências foram de arquéias desconhecidas (T4). As análises deste experimento mostraram variação na produção de metano quanto às diferentes proporções V:C e a metagenômic... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Strategies to reduce the Earth worming and raise animal production require new systems, where it must be considered methane and other gases emission that might cause environmental damages. The aim of this work was to evaluate the archaea methane production and the metagenomic evaluation of these bacteria present on the solid phase of the bovine ruminal content. For methane production analysis the ruminar content was collected followed by the proper manipulation for the fermentation process to take place and produced gas storage. The ribosomal 16S rRNA region was obtained by PCR amplification which was followed by cloning and DNA sequencing. The data was later analyzed by the software Sequencing Analysis 3.4, Phred/Phrap/Consed and BLAST. The highest methane production and acetate:propionate ratios were observed for the treatments containing 70% of roughage. The BLAST analysis allowed to identify 96 DNA sequences related to the Methanobacteriaceae family, 47 DNA sequences related to unculturable archaea and 60 DNA sequences were related to unknown archaea (T1), 125 DNA sequences related to Methanobacteriaceae, 42 DNA sequences do unculturable archaea and 32 DNA sequences were considered related to unknown archaea (T2) for the treatments containing 70% and 30% of hay. For those containing 70% and 30% of com silage it was possible to detect 30 DNA sequences related to Methanobacteriaceae, 18 DNA sequences related to Methanomicrobiaceae, 43 sequences related to unculturable archaea, 118 DNA sequences related to unknown archaea (T3) and 173 DNA sequences related to Methanobacteriaceae, 31 sequences related to unculturable archaea, and 25 to unknown archaea (T4). The analysis carried out in this experiment have shown a variation of the methane production as different R:C ratio were used and metagenomic with the rDNA conserved region together with archaea taken from the ruminal content DNA... (Complete abstract click electronic access below) / Orientador: Manoel Victor Franco Lemos / Coorientadora: Jane Maria Bertocco Ezequiel / Banca: Maria Isabel da Silva / Banca: Raul Franzolin Neto / Banca: Janete Apparecida Desidério Sena / Banca: Mauro Dal Secco de Oliveira / Doutor