Orientador: Renato de Mello Prado / Banca: Aguinaldo José Freitas Leal / Banca: Manoel Evaristo Ferreira / Resumo: A escória de siderurgia surgiu na agricultura como fonte alternativa de material corretivo da acidez do solo, trazendo em sua composição o silício, considerado um elemento benéfico para as plantas. O objetivo do presente trabalho foi avaliar o efeito da aplicação de nitrogênio em cobertura associado ao uso da escória de siderurgia e calcário sobre as propriedades químicas do solo, o estado nutricional, o acúmulo de N e Si nas folhas e colmos, a produção de colmos e a qualidade tecnológica da terceira soqueira de cana-de-açúcar. O experimento foi desenvolvido em sistema de colheita sem despalha a fogo em um Latossolo Vermelho distrófico, textura média. O delineamento foi de blocos ao acaso, com tratamentos dispostos em esquema fatorial 5x2, cinco doses de nitrogênio (0; 40; 80; 120 e 160 kg ha-1) e dois materiais corretivos, escória de siderurgia 0,9 t ha-1 e calcário 1,0 t ha-1, com quatro repetições. Foram avaliados os atributos químicos do solo, o desenvolvimento, o estado nutricional, a produção de matéria seca, a produção de colmos e a qualidade tecnológica da cana-de-açúcar. Aplicação dos corretivos afetou os teores de H+Al e a saturação por bases aos 12 meses. Houve interações dos corretivos, doses de N e profundidades aos 6 e 12 meses. Os tratamentos não afetaram o estado nutricional e o desenvolvimento da cultura, apesar de interação para acúmulo de matéria seca nas folhas. As doses de nitrogênio, independentemente do corretivo aplicado, não afetaram a produção de colmos e a qualidade tecnológica da cana-de-açúcar / Abstract: The slag appeared in agriculture as an alternative source of corrective material soil acidity, bringing in its composition silicon, considered a beneficial element for plants. The objective of this study was to evaluate the effect of nitrogen application in coverage associated with the use of slag and limestone on the chemical properties of the soil, nutritional status, the accumulation of N and Si in the leaves and stems, producing stems and the technological quality of the third ratoon of sugarcane. The experiment was carried on without fire husking harvesting system in an Oxisol, medium texture. The design was a randomized block, with treatments arranged in a 5x2 factorial scheme, five nitrogen rates (0, 40, 80, 120 and 160 kg ha- 1) and two corrective materials, slag 0,9 t ha-1 and limestone 1,0 t ha-1, with four replications. They evaluated the soil chemical properties, development, nutritional status, the production of dry matter production of stems and the technological quality of sugarcane. Liming affected the H+Al contents and base saturation at 12 months. There were interactions corrective, N rates and depths at 6 and 12 months. The treatments did not affect the nutritional status and the development of culture, although interaction for dry matter accumulation in the leaves. Nitrogen rates, regardless of the correction did not affect the production of stems and the technological quality of sugarcane / Mestre

Para comparar o risco de intoxicação por uréia granulada (G) e extrusada (E) 24 garrotes, nunca alimentados com uréia, foram distribuídos em quatro grupos de seis animais, onde foi administrada, de uma só vez, (G) ou (E) em duas diferentes doses: alta (A; 0,5 g/kg PV) ou padrão (B; 0,22 g/kg PV). Em seguida, foram acompanhados o pH e os teores de amônia no rúmen, as concentrações sangüíneas de amônia, uréia, creatinina, glicose, lactato-L, potássio, as atividades de gama glutamiltransferase, aspartato aminotransferase e creatina quinase, perfil hemogasométrico e hematócrito, além de acompanhamento quadro clínico no decorrer de 240 min após as administrações de G ou E. Alguns animais dos grupos GB e EB tiveram um discreto quadro de intoxicação, se recuperando sem quaisquer tratamentos. Por outro lado, cinco garrotes de ambos grupos GA e EA tiveram severo quadro tóxico que exigiram tratamento, sendo que um animal GA sucumbiu. A velocidade de hidrólise ruminal da uréia G e E foi semelhante, embora as manifestações clínicas tenha sido iniciadas mais tardiamente no grupo EA. Quanto mais intensa foi a hiperamoniemia mais destacada foi o grau de acidose metabólica, desidratação, a glicólise anaeróbica e a gliconeogênese. Pela análise das atividades enzimáticas comprovou-se que os danos bioquímicos foram intensos na musculatura, mas não nos hepatócitos. Concluiu-se que tanto a uréia G como E quando oferecidas subitamente, em especial em doses altas, podem oferecer igual risco de intoxicação por amônia. / To compare the toxicity potential of prilled urea (G) and extruded grain with urea (E), both were administered all at once in two different doses, high (A; 0,5 g/kg BW) or standard (B; 0,22 g/kg BW), to 24 steers divided into four groups of six animals, which had never been fed nonprotein nitrogen compounds. For 240 min after the administration of urea the following variables were determined: rumen fluid pH and ammonia level, blood ammonia, urea, creatinine, glucose, L-lactate, potassium, and activities of gama glutamiltranspeptidase, aspartate aminotransferase and creatine kinase, haemogasometric profile and hematocrit. The clinical picture was also followed. Some steers from groups GB and EB showed slight signs of ammonia toxicity, overcoming it without treatment. On the other hand, five steers from either groups GA and EA showed severe signs of ammonia toxicity that required treatment; even though one animal from group GA succumbed. The speed of ruminal urea hydrolysis of G and E was similar, although the clinical signs started later in group EA. The higher the hyperammonemia, the higher the metabolic acidosis, dehydration, anaerobic glycolysis and gluconeogenesis. The enzymatic profile showed that biochemical damage occurred in the striated muscular tissue, but not in the hepatocytes. The results showed that both G and E had similar potential to cause ammonia poisoning, principally when high doses were administered all at once.

A utilização de uréia na alimentação de fêmeas bovinas pode prejudicar o desempenho reprodutivo destes animais, provavelmente decorrente do aumento do teor de nitrogênio uréico plasmático (NUP). O objetivo deste estudo foi avaliar se alimentação com uréia por curto prazo oferecida a novilhas, e conseqüente aumento de NUP, exerce influência sobre a quantidade, qualidade e competência dos complexos cumulus-oócito (CCO). O experimento teve duração de 62 dias, dividido em oito semanas e dois períodos. Foram utilizadas 40 novilhas mestiças mantidas a pasto, alocadas a dois tratamentos, utilizando-se delineamento \"cross-over\": dieta sem uréia (SU): 5 kg (matéria original) de silagem de milho e 1 kg de concentrado/animal/dia ou dieta com uréia (U): 5 kg de silagem de milho e 1 kg de concentrado contendo 75 g de uréia/animal/dia. Os animais selecionados a cada semana receberam as dietas por seis dias, uma única vez ao dia. No sexto dia de oferecimento das dietas, foram realizadas aspiração folicular (OPU) e colheita de sangue, em jejum e 3 horas após a alimentação. Imediatamente após a OPU, foi realizada contagem total de CCO recuperados e classificação dos mesmos em viáveis e inviáveis. Apenas os viáveis foram destinados à produção In vitro de embriões. Em relação ao teor de NUP, houve efeito de interação entre tratamento e tempo de colheita (P=0,04) e dentro de cada tempo foi observado aumento significativo (P<0,01) para os animais do tratamento U. Não foi observado efeito de tratamento em relação ao número total de CCO recuperados por animal (média ± EPM: SU=9,15 ± 0,82 vs. U=8,82 ± 0,95), nem sobre a porcentagem de CCO viáveis sobre total de CCO recuperados por animal (SU=73,61% ± 2,47 vs. U=70,26% ± 2,31). A taxa de clivagem obtida no dia 3 após a inseminação In vitro (IIV) e as taxas de blastocisto nos dias 6, 7 e 9 após a IIV, não foram influenciadas pelo tratamento. Porém, no 11º pós IIV, houve diminuição (P=0,04) da taxa de blastocistos eclodidos para o tratamento U (SU=82,50% ± 0,05 vs. U=64,33% ± 0,07). Apesar do aumento do teor de NUP observado nas novilhas do tratamento U, a quantidade, qualidade e competência dos CCO durante as primeiras clivagens até atingirem o estádio de blastocisto In vitro não foram influenciadas pelo oferecimento de 75 g de uréia na dieta, durante seis dias. Porém, foi observada redução da taxa de eclosão dos blastocistos das novilhas do tratamento U. / Urea feeding offered to bovine dams may damage their reproductive performance, probably due to an increase in levels of plasmatic urea nitrogen (PUN). The aim of this study was evaluate if short-term urea feeding of heifers, following high PUN levels, would have an influence on the quantity, quality and competence of cumulus-oocyte complexes (COC). Trial lasted 62 days, divided into eight weeks and two periods. Forty crossbred grazing heifers were allocated to one of two treatments, using a cross-over design: diet without urea (WU): 5 kg (as fed) of corn silage and 1 kg of concentrated/animal/day, or diet with urea (U): 5 kg of corn silage and 1 kg of concentrated with 75 g of urea/animal/day. Heifers selected in each week received these diets once a day, for six days. On the sixth day of diets? offer, ovum pick-up (OPU) and blood sampling at fasting and 3 hours after feeding were carried out. Immediately after OPU, total COC recovered was counted and classified as either viable or unviable. Only viable were destined to In vitro embryo production. In relation to PUN level, there was a significant interaction between treatment and sampling time (P=0.04) and a significant (P<0.01) increase in animals undergoing U treatment for each of the test times. No significant effect was observed relative to either the total number of recovered COC per animal (mean ± SEM: WU=9.15 ± 0.82 vs. U=8.82 ± 0.95), or the viable COC as a percentage of total recovered COC per animal (WU=73.61% ± 2.47 vs. U=70.26% ± 2.31). Cleavage ratio assessed on day 3 post In vitro insemination (IVI) and blastocyst ratio on days 6, 7 and 9 post IVI were not influenced by treatments. However, there was a significant treatment effect (P=0.04) in relation to hatched blastocysts on day 11 after IVI (WU=83% ± 0.05 vs. U=64% ± 0.07). Even though higher PUN levels were observed in animals from treatment U, quantity, quality and competence of the COC during first cleavages until reaching the blastocyst stage In vitro were not influenced by adding 75 g of urea on the diet offered to heifers, during six days. Neverthless, a decline in hatched blastocysts rate was observed in heifers of treatment U.

No presente experimento os efeitos de adicionar-se enxofre, nas formas inorgânica e orgânica (quelatada) em rações ricas em uréia (nitrogênio não protéico), nos tecidos reprodutivos de ovinos e as conseqüências advindas desta suplementação sobre as características seminais destes animais foram estudados num delineamento em blocos incompletos equilibrados. Doze carneiros machos adultos de mesma idade, mestiços Santa Inês e de porte semelhante foram empregados em dois períodos experimentais de 60 dias cada para avaliar três tratamentos: A. 100% das exigências em proteína degradável no rúmen (controle); B. 100% das exigências em proteína degradável no rúmen + 3% de uréia + enxofre (99% S) e C. 100% das exigências em proteína degradável no rúmen + 3% de uréia + enxofre quelatado (21,5% S). Colheitas semanais de sêmen foram realizadas em vagina artificial durante ambos períodos experimentais, cada um correspondente a um ciclo espermático, totalizando nove colheitas por animal em cada período experimental. Colheitas de sangue foram realizadas semanalmente para determinação da concentração de nitrogênio (N) uréico. Peso vivo e circunferência escrotal também foram aferidos semanalmente. No sêmen foram analisados: volume, turbilhonamento, vigor espermático, motilidade espermática, concentração espermática, total de espermatozóides no ejaculado, total de espermatozóides viáveis no ejaculado, integridade de membrana espermática, integridade de acrossoma e concentração de nitrogênio uréico no plasma seminal. Os tratamentos com suplementação de uréia apresentaram níveis de N-uréico no plasma sanguíneo e seminal significativamente maiores que os níveis encontrados no tratamento controle (p&lt;0,05). Não houve diferença significativa entre as fontes de enxofre utilizadas. Os tratamentos avaliados não diferiram (p&gt;0,05) quanto às características do sêmen estudadas. O aumento dos níveis de Nuréico no sangue e sêmen não provocou prejuízos nas características seminais de carneiros mestiços Santa Inês, nas condições deste experimento. / In this research the addiction of inorganic and organic sulphur to diets with urea over the reproductive tissues of rams and its consequences on seminal characteristics were studied in a balanced incomplete block design. Twelve adult Santa Inês crossbred rams with similar weight and age were employed in two 60 days periods to evaluate three treatments: A. 100% of degradable protein requirement (control); B. 100% of degradable protein requirement + 3% urea + inorganic sulphur (99% S) and C. 100 % of degradable protein requirement + 3% urea + organic sulphur (21,5% S). Seminal collections were made weekly through artificial vagina over both experimental periods, corresponding each one to spermatic cycle, getting at an amount of nine collections by animal by period. Blood collections were made weekly to analyze plasma Nureic levels. Live weight and scrotal circumference were measured also weekly. In semen samples were studied volume, microscopic waves, vigor, motility, concentration, total sperm per ejaculate, total feasible sperm per ejaculate, membrane sperm integrity, acrosomal integrity and N-ureic level in seminal plasma. Treatments with urea presented blood and seminal plasma Nureic levels higher than the ones of control treatment (p&lt; 0,05). There was no significant difference between organic and inorganic sources of sulphur. The treatments did not affect semen characteristics (p&gt;0,05). Increased blood and semen N-ureic levels did not evoke damages on seminal characteristics of Santa Inês crossbred rams, under the conditions studied during this experiment.

No presente experimento os efeitos de adicionar-se enxofre, nas formas inorgânica e orgânica (quelatada) em rações ricas em uréia (nitrogênio não protéico), nos tecidos reprodutivos de ovinos e as conseqüências advindas desta suplementação sobre as características seminais destes animais foram estudados num delineamento em blocos incompletos equilibrados. Doze carneiros machos adultos de mesma idade, mestiços Santa Inês e de porte semelhante foram empregados em dois períodos experimentais de 60 dias cada para avaliar três tratamentos: A. 100% das exigências em proteína degradável no rúmen (controle); B. 100% das exigências em proteína degradável no rúmen + 3% de uréia + enxofre (99% S) e C. 100% das exigências em proteína degradável no rúmen + 3% de uréia + enxofre quelatado (21,5% S). Colheitas semanais de sêmen foram realizadas em vagina artificial durante ambos períodos experimentais, cada um correspondente a um ciclo espermático, totalizando nove colheitas por animal em cada período experimental. Colheitas de sangue foram realizadas semanalmente para determinação da concentração de nitrogênio (N) uréico. Peso vivo e circunferência escrotal também foram aferidos semanalmente. No sêmen foram analisados: volume, turbilhonamento, vigor espermático, motilidade espermática, concentração espermática, total de espermatozóides no ejaculado, total de espermatozóides viáveis no ejaculado, integridade de membrana espermática, integridade de acrossoma e concentração de nitrogênio uréico no plasma seminal. Os tratamentos com suplementação de uréia apresentaram níveis de N-uréico no plasma sanguíneo e seminal significativamente maiores que os níveis encontrados no tratamento controle (p&lt;0,05). Não houve diferença significativa entre as fontes de enxofre utilizadas. Os tratamentos avaliados não diferiram (p&gt;0,05) quanto às características do sêmen estudadas. O aumento dos níveis de Nuréico no sangue e sêmen não provocou prejuízos nas características seminais de carneiros mestiços Santa Inês, nas condições deste experimento. / In this research the addiction of inorganic and organic sulphur to diets with urea over the reproductive tissues of rams and its consequences on seminal characteristics were studied in a balanced incomplete block design. Twelve adult Santa Inês crossbred rams with similar weight and age were employed in two 60 days periods to evaluate three treatments: A. 100% of degradable protein requirement (control); B. 100% of degradable protein requirement + 3% urea + inorganic sulphur (99% S) and C. 100 % of degradable protein requirement + 3% urea + organic sulphur (21,5% S). Seminal collections were made weekly through artificial vagina over both experimental periods, corresponding each one to spermatic cycle, getting at an amount of nine collections by animal by period. Blood collections were made weekly to analyze plasma Nureic levels. Live weight and scrotal circumference were measured also weekly. In semen samples were studied volume, microscopic waves, vigor, motility, concentration, total sperm per ejaculate, total feasible sperm per ejaculate, membrane sperm integrity, acrosomal integrity and N-ureic level in seminal plasma. Treatments with urea presented blood and seminal plasma Nureic levels higher than the ones of control treatment (p&lt; 0,05). There was no significant difference between organic and inorganic sources of sulphur. The treatments did not affect semen characteristics (p&gt;0,05). Increased blood and semen N-ureic levels did not evoke damages on seminal characteristics of Santa Inês crossbred rams, under the conditions studied during this experiment.

As moléculas orgânicas podem ser a principal entrada de nitrogênio para plantas em ambientes onde as fontes inorgânicas de nitrogênio são limitadas, como o ambiente epífitico. Estudos recentes têm mostrado que plantas de Vriesea gigantea, uma bromélia epífita formadora de tanque, possuem alta capacidade de absorver ureia, fazendo dela um excelente modelo para estudar o metabolismo de ureia. Entretanto, os processos de absorção e assimilação de ureia estão pouco caracterizados nessas plantas. Várias aquaporinas de plantas têm mostrado ser capazes de facilitar a difusão de ureia através das membranas. Três genes que codificam para aquaporina foliares, VgPIP1;2, VgPIP1;5 e VgTIP2, recentemente foram clonados a partir de plantas V. gigantea tratadas com ureia, sendo que as expressões de VgPIP1,5 e VgTIP2, foram induzidas por essa fonte nitrogenada. No entanto, não tinha sido testado funcionalmente se, de fato, essas aquaporinas seriam capazes de transportar ureia, amônio ou água através das membranas. Uma vez absorvida, a ureia precisa ser metabolizada. Sugere-se que a assimilação do N ocorra por meio da via GS/GOGAT, com prévia hidrólise da ureia pela enzima urease, fornecendo amônio e CO2. Contudo, nunca se analisou a relevância da urease nesse processo em V. gigantea. Dessa maneira, no presente trabalho o transporte de ureia, amônio e água através de VgPIP1;2, VgPIP1;5 e VgTIP2 foi determinado por meio de ensaios de absorção em ovócitos de Xenopus laevis (água e ureia) e de estudos de complementação em Saccharomyces cerevisiae (NH4+/NH3). Os resultados mostraram que, enquanto VgTIP2 facilita o transporte de água quando expresso isoladamente em ovócitos, VgPIP1;2 e VgPIP1;5 precisaram de ser co-expressos com aquaporinas do tipo PIP2 para serem corretamente transportadas para a membrana plasmática e atuem como canais de água. Além disso, VgTIP2 foi a única aquaporina capaz de facilitar a difusão de ureia através das membranas, enquanto que VgPIP1;2 parece ser capaz de transportar NH4+/NH3. Adicionalmente, a relevância da urease no processo de assimilação de ureia foi analisada por meio do perfil isotópico dos aminoácidos em plantas de V. gigantea tratadas com um inibidor da urease (cloranil) antes de fornecer ureia duplamente marcada com C13 e N15. Os experimentos foram conduzidos em plantas nas fases ontogenéticas, atmosférica e adulta-tanque devido a existência de diferenças metabólicas e morfológicas. Os resultados sugeriram que a atividade da urease é um passo limitante na conversão do N da ureia em amônio para sua assimilação. Adicionalmente, foi visto que a diminuição na atividade da urease afeta principalmente a formação de glutamina (Gln) em plantas atmosféricas, enquanto que em plantas adultas-tanque a transaminação é o principal processo prejudicado. A diferença de assimilação de ureia entre as fases ontogenéticas podem ser consequência de diferenças morfológicas associadas com estratégias para captar nutrientes. Além disso, apesar da diminuição da atividade da urease pela ação do inibidor, processos de assimilação direta (sem prévia hidrólise da ureia anterior) em plantas V. gigantea parecem improváveis de acontecer / Organic molecules can be the main input of nitrogen for plants in environments where inorganic nitrogen sources are limited, such as the epiphytic habitat. Recent studies have shown a high capacity of Vriesea gigantean, an epiphytic tank-forming bromeliad, to absorb urea by their leaves, making this bromeliad an excellent model to study urea metabolism. Nevertheless, urea uptake and assimilation processes are little characterized in these plants. Several plant aquaporins from different species are able to facilitate the diffusion of urea through the membranes. Three foliar aquaporin genes, VgPIP1;2, VgPIP1;5 and VgTIP2, have been recently cloned from urea-treated V. gigantea plants. The expression of VgPIP1;5 and VgTIP2 was specifically up-regulated by urea in the basal part of the leaves. Nevertheless, it had not been tested whether these aquaporins were in fact capable of facilitating the membrane diffusion of either urea, ammonium or water. Moreover, it was suggested that after urea absorption, this organic N compound is hydrolyzed by the urease enzyme into CO2 and NH4+ prior to NH4+ assimilation by the GS/GOGAT pathway. In the present project, urea, NH4+/NH3 and water diffusion through VgPIP1;2, VgPIP1;5 and VgTIP2 were determined by uptake studies in Xenopus laevis oocytes (urea and water)and complementation assay in Saccharomyces cerevisiae (NH4+/NH3). The results showed that while VgTIP2 facilitates water transport when expressed alone in oocytes, VgPIP1;2 and VgPIP1;5 needed to be co-expressed with a PIP2 aquaporin to be targeted to the plasma membrane and act as water channels. Moreover, VgTIP2 was the only aquaporin able to facilitate the diffusion of urea through the membrane, while VgPIP1;2 seems to be capable of transporting NH4+/NH3. Additionally, the urease relevance in the urea assimilation process was investigated through the analysis of the amino acid profile in V. gigantea plants kept under a urease inhibitor (chloranil) and supplied with labeled [13C]-[ 15N]2-urea. The experiments were conducted in atmosphheric and adult-tank ontogenetic stages of V. gigantea due to their metabolic and morphological differences. The results suggested that urease activity may be a limiting step in the conversion of N from urea to ammonium. Moreover, decreases in urease activity by chloranil impared the first steps in N assimilation, droping the pool of glutamine (Gln) in atmospheric plants. In adult-tank plants the transamination appeared to be adversely affected. Those differences in urea assimilation might be due to differences in the morphology and the nutrient capture strategies of the ontogenetic phases. Finally, direct urea assimilation process (without previous urea hydrolysis) in V. gigantea plants seems unlikely to occur

Background: Soil transmitted helminth infections (STHI) are important Neglected Tropical Diseases (NTD). The three main STHI are infections with Ascaris lumbricoides, Trichuris trichiura and hookworms. STHI have a significant effect on the growth and development of children. A national survey for STHI in El Salvador by Pan American Health Organization and Ministry of Health in 2012 in school children aged 8years to 10 years. The survey collected data on age, gender, behavioral habits, and source of drinking water, type of toilet facility used and ecological zone of residence. A) We did an analyses of the data with an aim to determine the prevalence of STHI in El Salvador, assess the risk factors and risk interactions. B) We also aimed to determine the efficacy of urea as a potential additive for inactivation of Ascaris suum in solar toilets. Methods: A) Data from 1310 subjects was analysed for determination of prevalence of STHI in El Salvador. Risk factor assessment was done by chi-square test, unadjusted logistic regression and fully adjusted logistic regression. Risk factor interactions was tested on multiplicative and additive scale. B) Urea was tested for efficacy in inactivation of Ascaris suum ova in 20 solar toilets. Under conditions of controlled pH and moisture, concentration of gas ammonia, peak temperature were measured along with duration of treatment with urea to determine viability of Ascaris suum samples placed in the solar toilets. Results: I) The prevalence of Ascaris lumbricoides in 8-10 year old school children is 2.75%, Trichuris trichiura is 4.1% and hookworm is 1.83%. A) For Ascaris lumbricoides infection: Significant risk in individuals from volcanic chains and central depression compared to those from the mountains. Spring or well water when used as source of drinking water was associated with higher risk of infection when compared with piped water. Higher infection was also associated with open air defecation compared to use of septic tank or flush toilet. Use of sandals or no footwear was associated with a higher risk of infection when compared to use of closed footwear at all times. B) For Trichuris infection: Coastal plains were associated with a higher risk of infection compared to the mountains while rural status was protective against infection. Spring or well water when used as source of drinking water was associated with higher risk of infection when compared with piped water. Use of sandals or no footwear was associated with a higher risk of infection when compared to use of closed footwear at all times. C) For hookworm infection: Risk of infection was higher in individuals from urban regions. Spring or well water when used as source of drinking water was associated with higher risk of infection when compared with piped water. Use of sandals or no footwear was associated with a higher risk of infection when compared to use of closed footwear at all times. Poor handwashing was shown to be protective against infection with hookworm. Significant risk factor interactions were identified for infection with each of the three soil transmitted helminths. II) Urea as an additive at 1%w/w to feces tested in solar toilets showed an inactivation rate of nearly half the Ascaris suum ova samples. Fifty percent or higher inactivation rates were associated with ammonia gas concentrations of 109.5 ppm or higher and duration of treatment of 72 hours or higher. Conclusions: Prevalence of STHI in 8-10 year old school children for 2012 in El Salvador is low. Significant risk factors for STHI in El Salvador are eco-epidemiologic zone, source of drinking water, type of sanitation, use of shoes behavior and urban status of place of residence. Use of urea for inactivation of soil transmitted helminth ova in feces is a possible intervention for environmental control of STHI.

No description available.

Bibliography: leaves 132-147 / ix, 147 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1987

Data is limited evaluating infrequent supplementation of urea or biuret to ruminants consuming low-quality forage (<6% crude protein). Therefore, a series of experiments were designed to compare the effects of daily (D) and alternate day (2D) supplementation of two non-protein nitrogen (NPN) sources (urea or biuret) to ruminants consuming low-quality forage. Experiment 1 was a N balance study using five wethers in an incomplete 5 x 4 Latin square design (five treatments; four 24-d periods) with a 2 x 2 factorial arrangement of treatments (two sources of NPN and two supplementation frequencies) and an unsupplemented control. Supplements, consisting of urea or biuret mixed with ground soy hulls and dried molasses, were isonitrogenous (approximately 26% crude protein; dry matter basis) and offered D or 2D. The 2D supplemented lambs received double the quantity of supplemental N on their supplementation day compared with D lambs; therefore, all D and 2D treatments received the same amount of supplemental N over a 2-d period. Experiment 2 was a 70-d cow performance study using 80 spring-calving cows during the last third of gestation. Cows were stratified by age, body condition score, and expected calving date, and assigned randomly within stratification to one of the five treatments described in Experiment 1 above. They were then sorted by treatment and randomly assigned to 1 of 20 pens (4 cows/pen, 4 pens/treatment). Experiment 3 was a site of digestion study using five ruminally and duodenally fistulated steers to compare D and 2D supplementation of urea or biuret on forage intake, ruminal fermentation, site and extent of nutrient digestion, and rumen microbial efficiency. Five ruminally and duodenally fistulated steers were used in an incomplete 5 x 4 Latin square design with the same treatments described in Experiment 1. The results for Experiment 1 reported that DM, OM, and N intake, DM, OM, and N digestibility, N balance, and digested N retained were greater (P<0.03) for supplemented wethers compared with CON with no difference (P>0.05) because of NPN source or SF. Supplemented lambs had increased plasma urea N (PUN) compared with CON (P<0.01) and urea treatments had greater PUN compared with biuret (P<0.01). Also, PUN was increased (P=0.02) for D compared with 2D treatments. In addition, data suggest that PUN exhibited less fluctuation on the day of a supplementation event for biuret compared with urea. Experiment 2 demonstrated that pre- and post- calving (within 14 d and 24 h of calving, respectively) cow weight and body condition score changes were more positive (P<0.05) for supplemented groups compared with the CON. In Experiment 3, forage OM intake and OM digestibility were not affected (P>0.05) by NPN supplementation, NPN source, or SF. However, total OM and N intake were increased (P<0.01) with supplementation. Duodenal flow of OM tended (P=0.08) to increase with NPN supplementation while N flow was greater (P=0.04) with NPN supplementation compared with the control. In addition, duodenal bacterial N flow was increased with NPN supplementation (P=0.04) and for biuret compared with urea (P<0.01). Bacterial efficiency (g bacterial N/kg OM truly digested in the rumen) was greater for the control compared with NPN treatments (P<0.01) while biuret had greater true N disappearance compared with urea (P=0.01). Intestinal disappearance (% of duodenal flow) of OM and N was not affected by NPN supplementation, NPN source, or SF. However, apparent total tract N digestibility was increased with NPN supplementation (P<0.01) and not affected by NPN source or SF. In addition, ruminal NH���-N increased (P<0.04) on the day all supplements were provided and the day only daily supplement were provided with supplemental NPN. However, an NPN source x SF interaction (P=0.03) on the day all supplements were provided indicated NH���-N increased at a greater rate for urea as SF decreased compared with biuret. Ruminal NH���-N on the day only daily supplements were provided was greater for D compared with 2D (P=0.02). This data suggests that ruminal degradation of biuret to NH���-N was more moderate and prolonged compared with urea, possibly improving use by ruminal microflora. On the day all supplements were provided, D treatments had increased (P=0.05) ruminal indigestible acid detergent fiber passage rate and ruminal liquid volume compared with 2D treatments. Overall, NPN supplementation when feeding low-quality forage (<6% CP) was more beneficial than compared to a negative control, for increasing efficiency of forage digestion, N use, and animal performance. While at the same time indicating that the infrequent supplementation of urea or biuret was not detrimental to forage nutrient utilization, N efficiency or cow performance. This research will provide researchers and ruminant livestock producers with original information that can be used in designing winter supplementation strategies that decrease supplementation costs. Keywords: Urea, Biuret, Forage, Non-Protein Nitrogen, Supplementation, Frequency / Graduation date: 2003