Potential protein supplements to grazing cattle were evaluated in two projects. In the first project, Karanja seedcake samples were prepared and ruminally incubated using the in situ method to measure nutrient disappearance in cattle consuming low-quality forage. Organic matter and CP were fractionated by degradability into A, B, and C fractions. Organic matter fraction A degradability ranged from 59.6 to 89% (P < 0.05) for all the karanja seedcake samples. Fraction A of CP ranged from 61.6 to 96.2% degradability for all the samples (P < 0.05). Karanja seedcake samples were observed to contain highly degradable nutrients and our results indicate karanja seedcake may possibly be utilized in grazing cattle protein supplements, consequently increasing economic sustainability of biofuel production. In the second experiment, four non-protein nitrogen supplements were ruminally infused in steers consuming low-quality forage. Supplements included a 40% CP mineral mix (40MM), 60% CP mineral mix (60MM), 25% CP liquid (25L), or 35% CP liquid (35L). Protein provision stimulated forage OM intake and total OM intake for both liquid supplements. Forage OM intake tended to be greater for the liquid supplements; 25L (P = 0.06) and 35L (P = 0.08), then control. Total OM intake significantly increased (P < 0.01) for both liquid supplements, when compared to the control treatment. Total digestible OM intake was greater (P < 0.01) for 25L (3.4 kg/d) and 35L (3.36 kg/d) than control (2.94 kg/d). Forage and total OM intake were not significantly affected by 40MM or 60MM treatments. Total tract digestions (OM and NDF) were not observed to be significantly different (P ≥ 0.11) between supplements and control. Ruminal ammonia was greater (P < 0.01) for all supplements then control and total ruminal VFA concentrations increased from 84.7 to 98.7 mM for control versus supplemented. Supplementation with liquids had a significant effect on intake. Our results indicate of the four supplements, liquid supplements improved the utilization of low-quality forage by cattle, thus improving nutrient stewardship.

Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: South Africa, like many other developing countries throughout the world, has a rapidly growing human population, resulting in a consequent increased demand for food. Ironically, this increased food supply has to be produced on a smaller area of available agricultural land, which means that agricultural production processes have to become more efficient. Furthermore, the majority of the people in these countries are unschooled and poverty is a common phenomenon. Therefore, animal scientists are faced with the challenge and the responsibility to provide affordable, high quality food to these people. One way of reaching this objective is to improve the utilisation of low-quality, high roughage feedstuffs like crop residues and dry natural grass pastures. In the winter rainfall area of South Africa alone, about 460 000 ha of wheat straw are annually available. The ruminant animal has the ability to utilise the relatively unavailable energy (cellulose, hemi-cellulose and pectin) in the fibre component of these low-quality forages. Unfortunately, various factors, of which a N deficiency is the pre-dominant one, limit the utilisation of these feedstuffs. If the ability of the ruminant to utilise low-quality, fibrous energy sources is improved, these abundantly available and relatively inexpensive crop residues and natural pastures can be converted into high quality protein food for human consumption. Therefore, in order to rectify the N deficiency caused by these low-quality forages, the supplemental N requirement to optimise the fermentation and digestive processes of the ruminant animal has to be determined. The first study was conducted to determine the supplemental rumen degradable protein (RDP) requirement, to maximise the digestible organic matter intake (DOMI) of Dohne Merino sheep fed wheat straw. Keeping the high cost of natural protein supplementation in mind, the purpose of the second study was to determine the amount of true protein that can be replaced by nonprotein nitrogen (NPN) in RDP supplements fed to Dohne Merino sheep consuming wheat straw. In both trials animals had ad libitum access to low-quality wheat straw (3.2% CP; 74.2% NDF) and water. In the first trial, RDP (calsium caseinate: 90% CP; 100% rumen degradable) was intraruminally administered at 07hOOand 19hOO,at the following levels: 0, 40,80, 120 and 160 gld. Intake, fermentation and digestion were monitored to determine the RDP requirement to maximise DOM!. Digestible organic matter (OM) intake displayed a quadratic increase with elevated amounts of RDP (P < .01), and was maximised at an estimated 3.15 g RDPlkg BW·75 or 11.6% of DOM. Forage OM intake tended to increase quadratically (P = .15) with higher RDP levels. Microbial nitrogen (MN) flow to the duodenum and microbial efficiency increased quadratically (P ~ .04) and fluid dilution rate tended to increase in a quadratic manner (P = .15) with increased RDP supplementation levels. Rumina! ammonia nitrogen (NH3-N) and total volatile fatty acid (VFA) concentrations increased linearly (P ~ .07), while rumen pH exhibited a variable response to increased RDP levels (cubic; P = .08). Increasing RDP supplementation to Dohne Merino wethers consuming wheat straw, generally enhanced forage utilisation and DOM!. In the second trial, urea replaced different levels of casein N on an isonitrogenous basis, ranging from 0 - 100%. Since true protein is much more expensive than urea, the purpose of this study was to determine the maximum natural protein level that can be replaced by urea in RDP supplements, without adversely affecting intake and/or fermentation and digestive processes. The control treatment provided all of the RDP in the form of calcium caseinate (90% CP; 100% rumen degradable). The percentages of supplemental RDP from urea in the other treatments were 25, 50, 75 and 100%. The 100% urea treatment was balanced with maize starch to contain 40% CP and all other treatments received the same amount (150 gld) of starch. Intake of forage OM showed a weak decreasing trend (linear; P = .16) with increasing urea levels. Ruminal digestibilities of OM and NDF were not affected (P ;;::.:18) by urea level. Increasing urea levels resulted in linearly reduced total tract OM and NDF digestibilities (P ~ .10). As a result, DOMI declined (linear; P < .01) with increasing proportions of urea. Effects of increasing urea proportions on duodenal N flow, microbial efficiency and fluid dilution rate were minimal. Ruminal NH3-N tended to increase quadratically with increasing urea levels (P = .l4). Total VFA concentration decreased linearly (P = .03), while rumen pH increased in a linear manner (P = .08) with increasing urea proportions. Branched-chain volatile fatty acids (BCVFA's) and valerate decreased linearly (P ~ .05) with increasing urea levels, while other VFA's and the acetate:propionate ratio were generally not affected by treatment (P ;;:::.16). It appears as though ruminal and total tract OM and NDF digestibility criteria, as well as DOMI reached maximum values at substituting 25% of casein for urea. It is therefore concluded that replacing 25% of casein with urea in RDP supplements, will maintain effective utilisation of low-quality forages by sheep. / AFRIKAANSE OPSOMMING: Ontwikkelende lande, insluitend Suid-Afrika, word gekenmerk deur 'n vmmge bevolkingsaanwas. Dit lei tot 'n verhoogde vraag na voedsel, wat op 'n gevolglik kleinerwordende beskikbare kommersiële lanbbou-area geproduseer moet word. Die doeltreffendheid van produksieprosesse in die landbousektor moet dus noodgedwonge verbeter word. Die oorgrootte meerderheid van die bevolkings in ontwikkelende lande is ongeletterd en armoede en hongersnood is soms 'n algemene verskynsel. Veekundiges word dus gekonfronteer met die uitdaging en verantwoordelikheid om bekostigbare, hoë kwaliteit voedsel aan hierdie mense te voorsien. Een van die mees doeltreffende metodes om hierdie probleem aan te spreek, is om die benutting van lae kwaliteit, hoë-vesel voerbronne, bv. oesreste en droë grasweidings te verhoog. In die winterreënstreek van Suid-Afrika alleen, is 460 000 ha koringstrooi jaarliks beskikbaar. Herkouers beskik oor die besondere vermoë om die relatief onbeskikbare energie (sellulose, hemi-sellulose en pektien) in die veselkomponent van hierdie lae kwaliteit voere te benut. Verskeie faktore, waarvan 'n N-tekort die mees prominente is, beperk egter die benutting van hierdie voerbronne. Die uitdaging is dus om die herkouer se vermoë om hierdie voere te benut, te optimaliseer. Sodoende word 'n geredelik beskikbare, onderbenutte en relatief goedkoop voerbron omgeskakel in hoë kwaliteit proteïen vir menslike gebruik. Die N-aanvullingsbehoefte om die fermentasie- en verteringsprosesse van die herkouerdier te optimaliseer moet dus bepaal word, sodat die N-tekort in herkouers, wat soortgelyke weidings benut, reggestel kan word. Gevolglik was die doel met die eerste proef om die behoefte aan rumen degradeerbare proteïen-(RDP)-aanvulling, vir die maksimum inname van verteerbare organiese materiaal (VOM) van Dohne Merino skape wat koringstrooi ontvang, te bepaal. Weens die hoë koste van natuurlike proteïenaanvulling, was die doel met die tweede proef om die hoeveelheid ware proteïen in RDP-aanvullings, vir Dohne Merino skape wat koringstrooi ontvang, wat met nie-proteïen stikstof (NPN) vervang kan word, te bepaal. In beide eksperimente het die diere ad libitum toegang tot koringstrooi (3.2% RP; 74.2% NBV) en water gehad. In die eerste proefis RDP (kalsiumkaseïnaat; 90% RP; 100% rumen degradeerbaar) teen 07hOOen 19hOOintraruminaal toegedien, teen die volgende peile: 0, 40, 80, 120 en 160 gld. Inname, fermentasie en vertering is gemonitor om die RDP behoefte vir die maksimum inname van VOM te bepaal. Verteerbare OM-inname het 'n stygende kwadratiese tendens (P < .01) getoon met verhoogde RDP-peile en het 'n maksimum bereik by 'n aanvullingspeil van 3.15 g RDPlkg metaboliese liggaamsmassa (LM·75 ) of 11.6% van VOM. Organiese materiaalinname vanaf koringstrooi het geneig om kwadraties toe te neem (P = .15) met verhoogde RDP-peile. Mikrobiese stikstof-(MN)-vloei na die duodenum en mikrobiese effektiwiteit het kwadraties toegeneem (P :::;.;04) en vloeistof deurvloeitempo het 'n neiging vir 'n kwadratiese toename (P = .15) met verhoogde RDPpeile getoon. Rumen-ammoniakstikstof (NH3-N) en vlugtige vetsuur-(VVS)-konsentrasies het lineêr toegeneem (P :::;.;07), terwyl rumen pH 'n wisselende reaksie (kubies; P = .08) met stygende RDP-peile getoon het. Verteerbare OM-inname en benutting van koringstrooi is verbeter deur stygende peile van RDP aanvulling by Dohne Merino hamels. In die tweede proef is kaseïen op 'n iso-stikstof basis met verskillende ureumpeile, vanaf o - 100%, vervang. Omdat ureum baie goedkoper is as natuurlike proteïen, was die doel van die tweede proef om die hoeveelheid natuurlike proteïen in RDP-aanvullings te bepaal wat met ureum vervang kan word, sonder om inname, fermentasie en vertering te benadeel. Die kontrolebehandeling het 100% van die RDP in die vorm van kalsiumkaseïnaat (90% RP; 100% rumen degradeerbaar) voorsien, terwyl ureum in die ander behandelings onderskeidelik 25, 50, 75 en 100% van die kaseïen-N vervang het. Die 100% ureumbehandeling is met mieliestysel tot 40% RP gebalanseer en dieselfde hoeveelheid stysel (150 gld) is by al die ander behandelings ingesluit, om moontlike effekte van stysel op rumenfermentasie te elimineer. Organiese materiaalinname vanafkoringstrooi het 'n swak dalende tendens getoon met stygende ureum insluitingsvlakke (lineêr; P = .16). Rumenverteerbaarheid van OM en neutraal bestande vesel (NBV) is nie deur die ureumpeil beïnvloed nie (P ;;:: .18). Toenemende ureumpeile het gelei tot 'n lineêre afname in totale kanaal OM en NBVverteerbaarheid (P ~ .10). Gevolglik het VOM inname lineêr afgeneem (P < .01) met stygende ureum insluitingspeile. Die effek van behandeling op duodenale N-vloei, mikrobiese effektiwiteit en vloeistof deurvloeitempo was minimaal. Rumenammoniakstikstof-( NH3-N)-konsentrasie het 'n stygende kwadratiese tendens getoon (P = .14) met toenemende ureum peile. Totale vlugtige vetsuur-(VVS)-konsentrasies het lineêr gedaal (P = .03), terwyl rumen pH lineêr toegeneem het (P = .08) met stygende ureum insluitingsvlakke. Vertakte ketting VVS' e en valeriaansuurkonsentrasies het lineêr gedaal (P ~ .05) met stygende ureumpeile, terwyl die ander VVS' e en die asynsuur:propioonsuurverhouding oor die algemeen nie deur behandeling beïnvloed N; nie (P ;;:: .16). Dit blyk asof VOM inname, sowel as rumen- en totale kanaal verteerbaarheidsmaatstawwe, by 25% vervanging van kaseïen-N met ureum-N 'n maksimum bereik het. Die gevolgtrekking is gemaak dat die doeltreffende benutting van lae kwaliteit ruvoere deur skape, gehandhaaf sal word deur 25% van die ware proteïen in RDP-aanvullings met ureum te vervang.

Capítulo 2: Estudos vêm sendo realizados na tentativa de se avaliar os efeitos da manipulação da nutrição protéica, devido à sua importância no metabolismo e desempenho de bovinos. O presente estudo teve como objetivo identificar a melhor fonte de nitrogênio não-proteico (uréia, uréia de liberação lenta ou a combinação destas) em substituição parcial ao farelo de soja sobre o desempenho, características de carcaça e qualidade da carne de novilhos Nelore em terminação. Quarenta e seis novilhos Nelore (313,30 ± 22,62 kg) foram distribuídos em um delineamento em blocos e confinados em baias individuais por 74 dias. As dietas foram formuladas isoproteicas e isoenergéticas, com os seguintes tratamentos: 1)Controle: composta por 12% de farelo de soja, 2)Uréia: com a substituição de 6 % da proteína do farelo de soja por uréia, 3)Optigen: com a substituição de 6 % da proteína do farelo de soja por uréia de liberação lenta e 4)Uréia e Optigen: com a substituição de 6 % da proteína do farelo de soja por uréia e uréia de liberação lenta, tendo como volumoso o bagaço e a silagem de cana totalizando 21,5% da MS. Não foram verificados efeitos das dietas (P&gt;0,05) no peso vivo final, ganho médio diário, consumo de matéria seca, eficiência alimentar, características de carcaça e qualidade de carne. A substituição parcial do farelo de soja pelas fontes de NNP (uréia e uréia de liberação lenta) proporcionou desempenho, características de carcaça e qualidade da carne semelhantes. -- Capítulo 3: O objetivo deste trabalho foi identificar a melhor fonte de nitrogênio não protéico (NNP), (uréia, uréia de liberação lenta ou a combinação destas) para a substituição parcial ao farelo de soja, avaliando seus efeitos na fermentação ruminal, digestibilidade aparente total, produção de proteína microbiana, contagem de microrganismos ruminais e parâmetros sanguíneos de bovinos Nelore. Para tanto, quatro novilhos Nelore com cânulas ruminais (PV 407,1 ± 11,7 kg) foram distribuídos em um quadrado latino (4×4) durante quatro períodos de 21 dias. As dietas foram formuladas isoproteicas e isoenergéticas, com os seguintes tratamentos: 1)Controle (CTL): composta por 12% de farelo de soja, 2)Uréia (U): com a substituição de 6 % da proteína do farelo de soja por uréia, 3)Optigen (O): com a substituição de 6 % da proteína do farelo de soja por uréia de liberação lenta e 4)Uréia e Optigen (UO): com a substituição de 6 % da proteína do farelo de soja por uréia e uréia de liberação lenta, tendo como volumoso o bagaço e a silagem de cana totalizando 21,5% da MS. Não foi observado efeito das dietas experimentais (P&gt;0,05) no consumo de nutrientes e digestibilidade aparente total, com exceção do consumo de extrato etéreo que foi maior nos animais alimentados com as fontes de NNP (U:0,19, O:0,20 e UO:0,19 kg/d) em relação a dieta CTL (0,17 kg/d). A concentração de nitrogênio amoniacal, proporção molar, porcentagem e total de ácidos graxos de cadeia curta no líquido ruminal foram semelhantes entre as dietas. No entanto, os animais alimentados com a dieta CTL apresentaram maior (P=0,017) pH ruminal (6,81) em relação as fontes de NNP (U:6,64, O:6,63 e UO:6,76). A quantidade de todos os gêneros de protozoários ciliados foram aumentados no conteúdo ruminal dos animais alimentados com as fontes de NNP em relação à dieta controle (P&lt;0,001). Foi observada maior produção de proteína microbiana para as dietas com NNP, devido aos maiores valores de alantoina (P=0,074), purinas totais (P=0,090), purinas microbianas absorvidas (P=0,091), nitrogênio microbiano (P=0,091) e proteína bruta microbiana (P=0,091) observados quando comparadas a dieta CTL. A concentração plasmática de glicose, uréia no plasma e nitrogênio ureico no soro foram maiores na dieta CTL (P=0,012; 0,017 e 0,017, respectivamente) em relação as fontes de NNP. A substituição parcial de farelo de soja por uréia, uréia de liberação lenta ou a combinação de uréia e uréia de liberação lenta, resultou em melhor eficiência de utilização protéica pelos animais, entretanto, a uréia e a uréia de liberação lenta foram semelhantes nas variáveis analisadas. / Chapter 1: Several studies have been performed to evaluate the effects of protein nutritional manipulation due to its importance to ruminant metabolism and performance. This study aimed to identify the best source of non protein nitrogen (urea, slow releasing urea and their combination) for the partial replacement of soybean meal, and its effect on the animal performance, carcass traits and meat quality. Forty-six Nellore steers (BW 313.30 ± 22.62 kg) were allotted in a randomized block design and fed in individual pens for 74 days. Steers were fed isoproteic and isoenergetic diets as follows: 1)Control (CTL): 12% of soybean meal 2)Urea (U): the replacement of 6% of soybean meal protein for urea, 3)Optigen (O): the replacement of 6% of soybean meal protein for slow releasing urea and 4)Urea and Optigen (UO): the replacement of 6% of soybean meal protein for urea and slow releasing urea, with 21.5% of the total DM of sugarcane silage and bagasse as roughage. No differences (P&gt;0,05) in final body weight, average daily gain, dry matter intake, feed efficiency, carcass traits and meat quality were found among steers fed with the dietary treatments. The partial replacement of soybean meal by NPN sources (urea and slow releasing urea) had animal performance, carcass traits and meat quality similar to the control. -- Chapter 2: This study aimed to identify the best source of non protein nitrogen (urea, slow releasing urea and their combination) for the partial replacement of soybean meal, and its effect on the ruminal fermentation, total apparent digestibility, microbial protein production, ruminal microorganisms and blood parameters in Nelore steers. Four Nelore steers (BW 407,1 ± 11,7 kg) with ruminal canulas were alloted in a (4×4) square design for four 21 days periods. Steers were fed isoproteic and isoenergetic diets as follows: 1)Control (CTL): 12% of soybean meal 2)Urea (U): the replacement of 6% of soybean meal protein for urea, 3)Optigen (O): the replacement of 6% of soybean meal protein for slow releasing urea and 4)Urea and Optigen (UO): the replacement of 6% of soybean meal protein for urea and slow releasing urea, with 21.5% of the total DM of sugarcane silage and bagasse as roughage. There was no effect of experimental diets (P&gt;0.05) on nutrient intake and total apparent digestibility, but ether extract intake was higher in animals fed NPN diets (U:0.19, O:0.20 e UO:0.19 kg/d) when compared to the CTL diet (0.17 kg/d). The ruminal ammonia N concentration and the ruminal short-chain fatty acid concentrations were similar among the diets. Therefore, the animals fed the CTL diet had increased (P=0.017) ruminal pH (6.81) when compared to the NPN diets (U:6.64, O:6.63 e UO:6.76). The NPN diets provided more protozoa than the CTL diet. (P&lt;0.001). It was observed an increase production of microbial protein to the NPN diets due to the higher values of allantoin (P=0.074), total purine (P=0.090), microbial purine absorbed (P=0.091), microbial N (P=0.091) and microbial crude protein (P=0.091) observed when compared to the CTL diet. The CTL diet had higher blood concentration of glucose (P=0.012) plasma urea (P=0.017) and serum urea nitrogen (P=0.017) when compared with the NPN sources. The partial replacement of soybean meal for urea, slow releasing urea or their combination resulted in better efficiency on protein utilization by the animals.

Capítulo 2: Estudos vêm sendo realizados na tentativa de se avaliar os efeitos da manipulação da nutrição protéica, devido à sua importância no metabolismo e desempenho de bovinos. O presente estudo teve como objetivo identificar a melhor fonte de nitrogênio não-proteico (uréia, uréia de liberação lenta ou a combinação destas) em substituição parcial ao farelo de soja sobre o desempenho, características de carcaça e qualidade da carne de novilhos Nelore em terminação. Quarenta e seis novilhos Nelore (313,30 ± 22,62 kg) foram distribuídos em um delineamento em blocos e confinados em baias individuais por 74 dias. As dietas foram formuladas isoproteicas e isoenergéticas, com os seguintes tratamentos: 1)Controle: composta por 12% de farelo de soja, 2)Uréia: com a substituição de 6 % da proteína do farelo de soja por uréia, 3)Optigen: com a substituição de 6 % da proteína do farelo de soja por uréia de liberação lenta e 4)Uréia e Optigen: com a substituição de 6 % da proteína do farelo de soja por uréia e uréia de liberação lenta, tendo como volumoso o bagaço e a silagem de cana totalizando 21,5% da MS. Não foram verificados efeitos das dietas (P&gt;0,05) no peso vivo final, ganho médio diário, consumo de matéria seca, eficiência alimentar, características de carcaça e qualidade de carne. A substituição parcial do farelo de soja pelas fontes de NNP (uréia e uréia de liberação lenta) proporcionou desempenho, características de carcaça e qualidade da carne semelhantes. -- Capítulo 3: O objetivo deste trabalho foi identificar a melhor fonte de nitrogênio não protéico (NNP), (uréia, uréia de liberação lenta ou a combinação destas) para a substituição parcial ao farelo de soja, avaliando seus efeitos na fermentação ruminal, digestibilidade aparente total, produção de proteína microbiana, contagem de microrganismos ruminais e parâmetros sanguíneos de bovinos Nelore. Para tanto, quatro novilhos Nelore com cânulas ruminais (PV 407,1 ± 11,7 kg) foram distribuídos em um quadrado latino (4×4) durante quatro períodos de 21 dias. As dietas foram formuladas isoproteicas e isoenergéticas, com os seguintes tratamentos: 1)Controle (CTL): composta por 12% de farelo de soja, 2)Uréia (U): com a substituição de 6 % da proteína do farelo de soja por uréia, 3)Optigen (O): com a substituição de 6 % da proteína do farelo de soja por uréia de liberação lenta e 4)Uréia e Optigen (UO): com a substituição de 6 % da proteína do farelo de soja por uréia e uréia de liberação lenta, tendo como volumoso o bagaço e a silagem de cana totalizando 21,5% da MS. Não foi observado efeito das dietas experimentais (P&gt;0,05) no consumo de nutrientes e digestibilidade aparente total, com exceção do consumo de extrato etéreo que foi maior nos animais alimentados com as fontes de NNP (U:0,19, O:0,20 e UO:0,19 kg/d) em relação a dieta CTL (0,17 kg/d). A concentração de nitrogênio amoniacal, proporção molar, porcentagem e total de ácidos graxos de cadeia curta no líquido ruminal foram semelhantes entre as dietas. No entanto, os animais alimentados com a dieta CTL apresentaram maior (P=0,017) pH ruminal (6,81) em relação as fontes de NNP (U:6,64, O:6,63 e UO:6,76). A quantidade de todos os gêneros de protozoários ciliados foram aumentados no conteúdo ruminal dos animais alimentados com as fontes de NNP em relação à dieta controle (P&lt;0,001). Foi observada maior produção de proteína microbiana para as dietas com NNP, devido aos maiores valores de alantoina (P=0,074), purinas totais (P=0,090), purinas microbianas absorvidas (P=0,091), nitrogênio microbiano (P=0,091) e proteína bruta microbiana (P=0,091) observados quando comparadas a dieta CTL. A concentração plasmática de glicose, uréia no plasma e nitrogênio ureico no soro foram maiores na dieta CTL (P=0,012; 0,017 e 0,017, respectivamente) em relação as fontes de NNP. A substituição parcial de farelo de soja por uréia, uréia de liberação lenta ou a combinação de uréia e uréia de liberação lenta, resultou em melhor eficiência de utilização protéica pelos animais, entretanto, a uréia e a uréia de liberação lenta foram semelhantes nas variáveis analisadas. / Chapter 1: Several studies have been performed to evaluate the effects of protein nutritional manipulation due to its importance to ruminant metabolism and performance. This study aimed to identify the best source of non protein nitrogen (urea, slow releasing urea and their combination) for the partial replacement of soybean meal, and its effect on the animal performance, carcass traits and meat quality. Forty-six Nellore steers (BW 313.30 ± 22.62 kg) were allotted in a randomized block design and fed in individual pens for 74 days. Steers were fed isoproteic and isoenergetic diets as follows: 1)Control (CTL): 12% of soybean meal 2)Urea (U): the replacement of 6% of soybean meal protein for urea, 3)Optigen (O): the replacement of 6% of soybean meal protein for slow releasing urea and 4)Urea and Optigen (UO): the replacement of 6% of soybean meal protein for urea and slow releasing urea, with 21.5% of the total DM of sugarcane silage and bagasse as roughage. No differences (P&gt;0,05) in final body weight, average daily gain, dry matter intake, feed efficiency, carcass traits and meat quality were found among steers fed with the dietary treatments. The partial replacement of soybean meal by NPN sources (urea and slow releasing urea) had animal performance, carcass traits and meat quality similar to the control. -- Chapter 2: This study aimed to identify the best source of non protein nitrogen (urea, slow releasing urea and their combination) for the partial replacement of soybean meal, and its effect on the ruminal fermentation, total apparent digestibility, microbial protein production, ruminal microorganisms and blood parameters in Nelore steers. Four Nelore steers (BW 407,1 ± 11,7 kg) with ruminal canulas were alloted in a (4×4) square design for four 21 days periods. Steers were fed isoproteic and isoenergetic diets as follows: 1)Control (CTL): 12% of soybean meal 2)Urea (U): the replacement of 6% of soybean meal protein for urea, 3)Optigen (O): the replacement of 6% of soybean meal protein for slow releasing urea and 4)Urea and Optigen (UO): the replacement of 6% of soybean meal protein for urea and slow releasing urea, with 21.5% of the total DM of sugarcane silage and bagasse as roughage. There was no effect of experimental diets (P&gt;0.05) on nutrient intake and total apparent digestibility, but ether extract intake was higher in animals fed NPN diets (U:0.19, O:0.20 e UO:0.19 kg/d) when compared to the CTL diet (0.17 kg/d). The ruminal ammonia N concentration and the ruminal short-chain fatty acid concentrations were similar among the diets. Therefore, the animals fed the CTL diet had increased (P=0.017) ruminal pH (6.81) when compared to the NPN diets (U:6.64, O:6.63 e UO:6.76). The NPN diets provided more protozoa than the CTL diet. (P&lt;0.001). It was observed an increase production of microbial protein to the NPN diets due to the higher values of allantoin (P=0.074), total purine (P=0.090), microbial purine absorbed (P=0.091), microbial N (P=0.091) and microbial crude protein (P=0.091) observed when compared to the CTL diet. The CTL diet had higher blood concentration of glucose (P=0.012) plasma urea (P=0.017) and serum urea nitrogen (P=0.017) when compared with the NPN sources. The partial replacement of soybean meal for urea, slow releasing urea or their combination resulted in better efficiency on protein utilization by the animals.

<p>A large amount of non-protein nitrogen, in the form of urea and ammonium, is present in human breastmilk; however its physiological role in the infant is as yet not fully understood. It has been hypothesized that an insufficient enteric metabolism of urea could play a role in the sudden infant death syndrome (SIDS). This thesis was undertaken to study the enteric metabolism of non- protein nitrogen in healthy infants, in comparison with those who had succumbed to SIDS.</p><p>Aerobic and anaerobic faecal microflora, were studied in healthy infants from birth to 6 months of age. They were found to appear in faeces within 3 days of birth and were present throughout the first 6 months of life. The effect of nitrate, nitrite and nitric oxide on faecal urease activity was investigated and found to be inhibitory in action. The sigmoid faecal urease activity and sigmoid faecal urea content of SIDS infants were compared to those of control infants; significantly lower sigmoid faecal urease activity and greater sigmoid faecal urea content were found in the SIDS infants. The total number of SIDS cases occurring in Sweden during the period 1990 through 1996 was analysed regarding geographical and seasonal distribution, in relation to the nitrate concentration in drinking water and changes in the groundwater level. The northernmost parts of the country had its highest incidence when the rest of the country had its lowest incidence, and the occurrence of individual deaths was associated with the recharge of groundwater, which is known to increase its nitrate content. The effect of ingested ammonium on carbon dioxide production was determined in healthy infants using the doubly labelled water technique. No change in carbon dioxide production was observed.</p><p>An insufficient enteric metabolism of urea in infants and peak or greatly varying nitrate concentrations in drinking water are associated with the occurrence of SIDS. Ingested ammonium supplements in the given doses did not influence carbon dioxide production in healthy infants.</p>

A large amount of non-protein nitrogen, in the form of urea and ammonium, is present in human breastmilk; however its physiological role in the infant is as yet not fully understood. It has been hypothesized that an insufficient enteric metabolism of urea could play a role in the sudden infant death syndrome (SIDS). This thesis was undertaken to study the enteric metabolism of non- protein nitrogen in healthy infants, in comparison with those who had succumbed to SIDS. Aerobic and anaerobic faecal microflora, were studied in healthy infants from birth to 6 months of age. They were found to appear in faeces within 3 days of birth and were present throughout the first 6 months of life. The effect of nitrate, nitrite and nitric oxide on faecal urease activity was investigated and found to be inhibitory in action. The sigmoid faecal urease activity and sigmoid faecal urea content of SIDS infants were compared to those of control infants; significantly lower sigmoid faecal urease activity and greater sigmoid faecal urea content were found in the SIDS infants. The total number of SIDS cases occurring in Sweden during the period 1990 through 1996 was analysed regarding geographical and seasonal distribution, in relation to the nitrate concentration in drinking water and changes in the groundwater level. The northernmost parts of the country had its highest incidence when the rest of the country had its lowest incidence, and the occurrence of individual deaths was associated with the recharge of groundwater, which is known to increase its nitrate content. The effect of ingested ammonium on carbon dioxide production was determined in healthy infants using the doubly labelled water technique. No change in carbon dioxide production was observed. An insufficient enteric metabolism of urea in infants and peak or greatly varying nitrate concentrations in drinking water are associated with the occurrence of SIDS. Ingested ammonium supplements in the given doses did not influence carbon dioxide production in healthy infants.

Os efeitos da substituição da uréia tradicional por uréia de liberação lenta (ULL) e de dois níveis de nitrogênio não-protéico (NNP) na fração proteína bruta (PB) em suplementos oferecidos a 0,6% do peso vivo (PV) de novilhos Nelore alimentados ad libitum com feno de Brachiaria brizantha foram avaliados. Foram utilizados oito animais com 374,40kg (&plusmn; 42Kg) de PV, dotados de cânulas ruminais, em um delineamento Quadrado Latino 4 x 4 replicado, cujos períodos foram compostos por cinco dias de adaptação dos animais às dietas e 7 dias de coletas de amostras. Os suplementos foram confeccionados de forma a conterem 40% (0; 50 ou 100% de uréia de liberação lenta em substituição à uréia tradicional) ou 80% da PB como fonte de NNP (100% de uréia de liberação lenta). Os dados foram analisados utilizando-se contrastes ortogonais para avaliar os efeitos de substituição da uréia tradicional e de percentagem da PB oriunda de fonte de NNP. Quando houve efeitos significativos de substituição da uréia, foi utilizada análise de regressão polinomial. Para o estudo dos parâmetros de fermentação ruminal, foi considerado adicionalmente o delineamento em parcelas sub-divididas, a fim de se avaliar a interação entre tratamentos e tempo de coleta. A substituição da uréia tradicional não teve efeitos sobre o consumo de matéria seca e matéria seca digestível. O aumento na percentagem de NNP na fração proteína bruta dos suplementos diminuiu a digestibilidade da matéria seca e o consumo de matéria seca digestível em percentagem do peso vivo e em gramas por quilo de peso metabólico. A digestibilidade da proteína bruta foi maior, à medida que ULL foi inclusa no suplemento, porém nenhum efeito foi verificado sobre a digestibilidade da, fibra em detergente ácido (FDA) e neutro (FDN), carboidratos não-fibrosos (CNF) e matéria orgânica (MO). O suplemento com 80% da PB como NNP oriundo de ULL diminuiu a digestibilidade das frações PB, FDA e FDN. A substituição de uréia tradicional por ULL diminuiu linearmente a concentração total de ácidos graxos voláteis no rúmen, mas não afetou as concentrações de ácidos acético, propiônico e butírico, assim como a relação acético:propiônico. O aumento de 40% para 80% da PB como fonte de NNP aumentou a concentração de ácido acético e diminuiu a concentração de ácido butírico, sendo que não foi verificado nenhum efeito sobre as concentrações de AGVs totais e de ácido propiônico e na relação acético:propiônico. O pH e as concentrações de nitrogênio amoniacal ruminal não foram afetados pela inclusão de ULL ou pelos níveis de NNP do suplemento. A substituição de uréia tradicional por uréia de liberação lenta apresentou poucos efeitos no padrão de fermentação ruminal e na disponibilidade dos nutrientes de dietas à base de forragem de baixa qualidade. O aumento no teor de NNP da PB dietética pode comprometer a disponibilidade de nutrientes de bovinos alimentados com forragens. / The effects of traditional urea replacement for slow-release urea (SRU) and of two levels of non-protein nitrogen (NPN) in crude protein (CP) fraction of supplements fed at 0.6% of body weight (BW) to Nellore steers consuming Brachiaria brizantha hay (ad libitum) were evaluated. Eight animals, with 374,40kg (&plusmn; 42Kg) of BW and fitted with rumen cannulas were used in a replicated 4 x 4 Latin Square design, composed by 5-day adjustment-periods and 12-day sampling periods. Supplements were prepared with the purpose to contain: 40% (0; 50 and 100% of SRU replacing traditional urea) or 80% of CP as a NPN source (100% of SRU). Data were analyzed using ortogonal contrasts in order to evaluate the effects of traditional urea replacement and NPN levels. Polynomial regression was used when effects of urea replacement levels were significant. To ruminal fermentation parameters evaluation, additional split-plot design was considered to assess treatments and time for sampling interaction. Replacement of traditional urea for SRU had no effects on dry matter and digestible dry matter intakes. Increasing NPN percentage of CP fraction decreased dry matter digestibility and digestible dry matter intakes as percentage of BW and in grams per kilogram of metabolic weight (MW). Crude protein digestibility was increased as SRU was included in the supplement, but had no effect on acid (ADF) and neutral detergent fiber (NDF), ether extract (EE), non-fiber carbohydrates (NFC) and organic matter (OM) digestibility. Supplement with 80% of CP as SRU NPN decreased CP, ADF and NDF digestibility. Replacement of urea for SRU decreased linearly ruminal total volatile fatty acids (VFA) concentration, but had no effect on acetic, propionic and butyric acids concentration, as well as acetic to propionic ratio. Increasing 40% to 80% of CP as NPN source increased acetic acid and decreased butyric concentrations. Ruminal pH and amnoniacal nitrogen concentration were not affected by SRU inclusion or NPN levels. Replacement of traditional urea for slow-release urea showed few effects on rumen fermentation patterns and on nutrients availability of low quality forage based diets. Increasing NPN percentage of diet CP fraction may compromise nutrients availability of cattle fed forage.

An improved understanding of nitrogen metabolism in the gastrointestinal tract of the pig is required in order to provide accurate estimates of nitrogen and amino acid (AA) bioavailability in feed ingredients and for adequate diet formulation. Research objectives were to estimate the extent of fermentative AA catabolism (FAAC) in the upper gut of pigs. Further objectives were to determine the impact of lower gut nitrogen absorption on measures of apparent ileal digestibility of AA and nitrogen, whole-body nitrogen balance, and urea kinetics in pigs fed a valine-limiting diet. It was determined that simple isotope dilution calculations are inappropriate for determining ileal ammonia flux and FAAC from a continuous infusion of labelled ammonia and urea. A static model with two-pools (blood urea and digesta ammonia) was then developed to determine possible value ranges for FAAC in the upper gut of pigs. Maximum estimated FAAC based on this model was lower when dietary protein content was decreased (P < 0.001). The model presented is limited to minimum and maximum estimates of FAAC due to the sampling and isotope infusion protocol used. Refinements to the model and experimental protocol could allow for more accurate estimates of FAAC. Infusion of casein or urea into the lower gut of pigs did not affect measures of apparent ileal digestibility of AA or nitrogen. These results further validate the methodology available for determination of ileal digestibility and the use of ileal digestibility to estimate bioavailability of AA and nitrogen. Infusion of casein or urea into the lower gut resulted in an increase in nitrogen balance and urea flux in growing pigs fed a valine-limiting diet. Nitrogen absorbed from the lower gut of pigs is likely in the form of ammonia which is converted to urea. Lower gut nitrogen can contribute to whole-body protein deposition via urea recycling and microbial AA production in the upper gut. Lower gut nitrogen absorption should be accounted for when estimating bioavailability of nitrogen in feeds and foods. / Ontario Ministry of Agriculture, Food, and Rural Affairs (OMAFRA); Ontario Pork; Canadian Swine Research and Development Cluster; Natural Sciences and Engineering Research Council of Canada (NSERC); Evonik Industries AG

Os efeitos da substituição da uréia tradicional por uréia de liberação lenta (ULL) e de dois níveis de nitrogênio não-protéico (NNP) na fração proteína bruta (PB) em suplementos oferecidos a 0,6% do peso vivo (PV) de novilhos Nelore alimentados ad libitum com feno de Brachiaria brizantha foram avaliados. Foram utilizados oito animais com 374,40kg (&plusmn; 42Kg) de PV, dotados de cânulas ruminais, em um delineamento Quadrado Latino 4 x 4 replicado, cujos períodos foram compostos por cinco dias de adaptação dos animais às dietas e 7 dias de coletas de amostras. Os suplementos foram confeccionados de forma a conterem 40% (0; 50 ou 100% de uréia de liberação lenta em substituição à uréia tradicional) ou 80% da PB como fonte de NNP (100% de uréia de liberação lenta). Os dados foram analisados utilizando-se contrastes ortogonais para avaliar os efeitos de substituição da uréia tradicional e de percentagem da PB oriunda de fonte de NNP. Quando houve efeitos significativos de substituição da uréia, foi utilizada análise de regressão polinomial. Para o estudo dos parâmetros de fermentação ruminal, foi considerado adicionalmente o delineamento em parcelas sub-divididas, a fim de se avaliar a interação entre tratamentos e tempo de coleta. A substituição da uréia tradicional não teve efeitos sobre o consumo de matéria seca e matéria seca digestível. O aumento na percentagem de NNP na fração proteína bruta dos suplementos diminuiu a digestibilidade da matéria seca e o consumo de matéria seca digestível em percentagem do peso vivo e em gramas por quilo de peso metabólico. A digestibilidade da proteína bruta foi maior, à medida que ULL foi inclusa no suplemento, porém nenhum efeito foi verificado sobre a digestibilidade da, fibra em detergente ácido (FDA) e neutro (FDN), carboidratos não-fibrosos (CNF) e matéria orgânica (MO). O suplemento com 80% da PB como NNP oriundo de ULL diminuiu a digestibilidade das frações PB, FDA e FDN. A substituição de uréia tradicional por ULL diminuiu linearmente a concentração total de ácidos graxos voláteis no rúmen, mas não afetou as concentrações de ácidos acético, propiônico e butírico, assim como a relação acético:propiônico. O aumento de 40% para 80% da PB como fonte de NNP aumentou a concentração de ácido acético e diminuiu a concentração de ácido butírico, sendo que não foi verificado nenhum efeito sobre as concentrações de AGVs totais e de ácido propiônico e na relação acético:propiônico. O pH e as concentrações de nitrogênio amoniacal ruminal não foram afetados pela inclusão de ULL ou pelos níveis de NNP do suplemento. A substituição de uréia tradicional por uréia de liberação lenta apresentou poucos efeitos no padrão de fermentação ruminal e na disponibilidade dos nutrientes de dietas à base de forragem de baixa qualidade. O aumento no teor de NNP da PB dietética pode comprometer a disponibilidade de nutrientes de bovinos alimentados com forragens. / The effects of traditional urea replacement for slow-release urea (SRU) and of two levels of non-protein nitrogen (NPN) in crude protein (CP) fraction of supplements fed at 0.6% of body weight (BW) to Nellore steers consuming Brachiaria brizantha hay (ad libitum) were evaluated. Eight animals, with 374,40kg (&plusmn; 42Kg) of BW and fitted with rumen cannulas were used in a replicated 4 x 4 Latin Square design, composed by 5-day adjustment-periods and 12-day sampling periods. Supplements were prepared with the purpose to contain: 40% (0; 50 and 100% of SRU replacing traditional urea) or 80% of CP as a NPN source (100% of SRU). Data were analyzed using ortogonal contrasts in order to evaluate the effects of traditional urea replacement and NPN levels. Polynomial regression was used when effects of urea replacement levels were significant. To ruminal fermentation parameters evaluation, additional split-plot design was considered to assess treatments and time for sampling interaction. Replacement of traditional urea for SRU had no effects on dry matter and digestible dry matter intakes. Increasing NPN percentage of CP fraction decreased dry matter digestibility and digestible dry matter intakes as percentage of BW and in grams per kilogram of metabolic weight (MW). Crude protein digestibility was increased as SRU was included in the supplement, but had no effect on acid (ADF) and neutral detergent fiber (NDF), ether extract (EE), non-fiber carbohydrates (NFC) and organic matter (OM) digestibility. Supplement with 80% of CP as SRU NPN decreased CP, ADF and NDF digestibility. Replacement of urea for SRU decreased linearly ruminal total volatile fatty acids (VFA) concentration, but had no effect on acetic, propionic and butyric acids concentration, as well as acetic to propionic ratio. Increasing 40% to 80% of CP as NPN source increased acetic acid and decreased butyric concentrations. Ruminal pH and amnoniacal nitrogen concentration were not affected by SRU inclusion or NPN levels. Replacement of traditional urea for slow-release urea showed few effects on rumen fermentation patterns and on nutrients availability of low quality forage based diets. Increasing NPN percentage of diet CP fraction may compromise nutrients availability of cattle fed forage.

A produção de metano entérico está entre as principais fontes de emissão de gases de efeito estufa dentre as atividades agropecuárias, além de gerar perda energética ao animal de até 12% da energia bruta consumida. Assim, o objetivo deste trabalho foi avaliar o uso de nitrato de cálcio encapsulado na alimentação de ruminantes como estratégia nutricional a mitigação de metano entérico. O experimento consistiu de duas fases. Fase I: Foram testadas dietas suplementadas com produto comercial de nitrato de cálcio encapsulado utilizando a técnica semiautomática de produção de gases in vitro. Meio grama de substrato com 50 mL de meio de incubação e 25 mL de inóculo ruminal foram incubados em frascos de vidro (160 mL) à 39 ºC por 24 horas para determinação da melhor dieta a ser testada in vivo. O primeiro ensaio testou a associação entre a monensina (dietas com e sem adição de monensina) e doses de nitrato encapsulado (0; 1,5 e 3% da matéria seca (MS)) para mitigação de metano in vitro. Não foi observada interação entre monensina e nitrato para as variáveis testadas. O segundo ensaio in vitro testou a interação do tipo de dieta com duas relações concentrado:volumoso, 20:80 e 80:20, e a inclusão de doses de nitrato encapsulado (0; 1,5; 3 e 4,5% MS). Embora não foi observado efeito associativo entre dieta e nitrato para redução de metano, foi observada mudança nos produtos da fermentação ruminal, com redução de propionato, em decorrência da concorrência de nitrato e propianogênicas por hidrogênio mais escasso em dietas com menor fermentação. Fase II: Conforme os resultados obtidos na Fase I, na segunda fase foi avaliado o efeito associativo da relação de concentrado:volumoso da dieta e a dose de nitrato sobre a emissão de metano, constituintes ruminais e toxicidade do nitrato in vivo. Utilizou-se seis borregos canulados no rúmen, distribuídos em delineamento experimental quadrado latino 6 x 6, em fatorial 2 x 3. Os fatores foram tipo de dieta (relação concentrado:volumoso 20:80 e 80:20) e inclusão de doses de nitrato encapsulado na dieta (0; 1,5 e 3% MS) em substituição gradual ao farelo de soja, totalizando seis tratamentos. Os teores de substituição do farelo de soja pelo nitrato foram em equivalente proteico de maneira a deixar as dietas isonitrogenadas. Os animais foram adaptados gradualmente a oferta de nitrato dietético para evitar problemas com toxidez. A análise de toxicidade foi avaliada pela taxa de metahemoglobina no sangue dos ovinos 3 horas após a alimentação. Nitrato reduziu a produção de metano em ambas as dietas. Os níveis de metahemoglobina no sangue dos animais não foram alterados pela adição de nitrato. Foi observado efeito associativo entre o tipo de dieta e nitrato para os produtos da fermentação ruminal, como acetato, que aumentou linearmente nas dietas com 80% de concentrado quando nitrato foi adicionado. Concluí-se que nitrato, utilizado de forma segura, é uma promissora estratégia para redução de metano entérico independentemente do tipo de dieta com que está sendo suplementado / Production of enteric methane is among the leading sources of greenhouse gas emissions from agricultural activities and generate energy loss to the animal up to 12% of gross energy consumption. The objective of this study was to evaluate the use of calcium nitrate encapsulated in ruminant feed as a nutritional strategy for mitigation of enteric methane. The experiment consisted of two phases. Phase I: tested diets were supplemented with encapsulated calcium nitrate using a semi-automatic in vitro gas production technique Half gram of substrate with 50 mL of incubation medium, and 25 mL of rumen fluid were incubated in glass bottles (160 ml) at 39 °C for 24 hours to determine the best diets to be tested in vivo. The first trial tested the association between monensin (diets with and without monensin) and encapsulated nitrate levels (0, 1.5 and 3% of dry matter (DM)) for in vitro methane mitigation. There was no interaction between monensin and nitrate for the tested variables. The second in vitro assay tested the interaction of diet type with two concentrate:forage ratios, 20:80 and 80:20, and the inclusion of encapsulated nitrate levels (0, 1.5, 3 and 4.5% DM). Although it was not observed associative effect between diet and nitrate for reduction of methane, it was observed change in the ruminal fermentation products. Phase II: According to the results obtained in Phase I, in the second phase we evaluated the associative effect of concentrate: forage ratio of diet and the dose of nitrate on the methane emission, ruminal constituents and nitrate toxicity in vivo. We used six lambs cannulated in the rumen, distributed in Latin square design 6 x 6 in factorial 2 x 3. The factors were type of diet (concentrate:forage ratios 20:80 and 80:20) and inclusion of encapsulated nitrate doses in the diet (0, 1.5 and 3% DM) in the gradual replacement of soybean meal, a total of six treatments. The replacement levels of soybean meal by nitrate were in protein equivalent so as to leave the diets isonitrogenous. The animals were gradually adapted to dietary nitrate supply to avoid problems with toxicity. The analysis of toxicity were evaluated by the rate of methemoglobin in the blood of sheep 3 hours after feeding. Methemoglobin levels in blood of animals were not changed by the addition of nitrate. Associative effect was observed between the type of diet and nitrate for ruminal fermentation products such as acetate, which decreased linearly in the diets with 80% forage when nitrate was added. It can be concluded that nitrate used securely is a promising strategy for reducing enteric methane independently of the type of diet being supplemented