RESUMO
Four experiments were performed to study the kinetics of purine metabolism and urinary excretion in Zebu crossbred cattle. Fasting excretion was established in Expt 1, using eighteen male Bos indicus x Bos taurus crossbred cattle (261 (SE 9.1) kg body weight), six of each of the following genotypes: 5/8 Bos indicus, 1/2 Bos indicus and 3/8 Bos indicus. No significant differences were observed among genotypes in fasting purine derivative excretion (277.3 (SE 35.43) micromol/metabolic body weight). In a second experiment we measured the xanthine oxidase activity, which was higher in liver than in duodenal mucosa (0.64 and 0.06 (SE 0.12) units/g wet tissue per min respectively; P>0.05) being in plasma 0.60 (SE 0.36) units/l per min. The kinetics of uric acid were measured by intravenous pulse dose of [1,3-15N]uric acid (Expt 3). The cumulative recovery of the isotope in urine was 82 (SE 6.69) %, and uric acid plasma removal, pool size and mean retention time were 0.284 (SE 0.051) per h, 5.45 (SE 0.823) mmol and 3.52 (SE 0.521) h, respectively. Allantoin was removed from plasma at an estimated fractional rate of 0.273 (SE 0.081) per h and mean retention was 3.66 (SE 1.08) h. In Expt 4, the relationship between urinary purine derivative excretion (Y; mmol/d) and digestible organic matter intake (X, kg/d) was defined by the equation: Y=7.69 (SE 4.2)+5.69 (SE 1.68) X; n 16, Se 1.31, r 0.67.
Assuntos
Bovinos/metabolismo , Purinas/metabolismo , Animais , Bovinos/urina , Duodeno/enzimologia , Ingestão de Alimentos/fisiologia , Jejum/metabolismo , Jejum/urina , Intestinos/enzimologia , Fígado/enzimologia , Masculino , Purinas/urina , Ácido Úrico/urina , Xantina Oxidase/sangue , Xantina Oxidase/metabolismoRESUMO
In this experiment four Holstein heifers fitted with rumen and duodenum canulae were utilized to evaluate the rumen parameters as pH, passage rate (%/h), volume (L) and ciliated protozoa concentration, when fed diets with four levels of rumen degradable protein. This was achieved supplementing 0, 25, 50 or 75 grams of degradable protein per kg of concentrate as a urea and casein (98.2% OM and 93.2% CP). The diets had 25% of barley straw without treatment and 75% concentrate formulated to contain different proportions (25/75 and 75/25) of corn and barley and also 5% of wheat residue and 5% of mineral and vitamin supplement. A continuous infusion of Cr-EDTA was used as a liquid phase marker. A cross-over design with 8 treatments (2 diets and 4 degradable protein levels) were utilized in 8 balance periods in a factorial arrangement. The level of degradable protein significantly affected the mean pH values that decreased as the supplementation increased (P 0.05) mainly in the corn based diet. The passage rate of the liquid phase, similar for the diets, was lower in the first experimental period (8.65 vs. 10.56%/h) and decreased as the level of degradable protein increased. Ciliated protozoa had higher concentration (P 0.01) in the corn diet (79.1 x 103/mL) than in the barley diet (59.5 x 103/mL). The Entodinium genus represented 87.8% of the total population. The genus Ep
Em um ensaio de controle de parâmetros ruminais (pH, ritmo de trânsito (%h), volume ruminal (l), e concentração de protozoários ciliados), foram utilizadas quatro novilhas Holstein, canuladas no rúmen e duodeno, recebendo dietas com 4 níveis de proteína degradável, sem suplementar ou suplementadas com 25, 50 e 75 gramos de proteína degradável por quilo de concentrado em forma de uréia e caseína (98,2 e 93,2% de matéria orgânica e proteína bruta, respectivamente). As rações experimentais foram compostas por 25% de palha de cevada sem tratar e 75% de concentrado formulado em base a diferentes proporções (25/75 e 75/25) de milho/cevada, com 5% de resíduo de trigo e 5% de suplemento vitamínico mineral. Uma contínua infusão de marcador de fluxo de fase líquida (Cr-EDTA) foi executada. Os oito tratamentos experimentais (2 dietas x 4 níveis de infusão) foram administrados em 8 períodos de balanço em um delineamento cross-over, em esquema fatorial. O nível de infusão de N degradável afetou de forma significativa os valores médios ponderados de pH, que decresceram ao aumentar a suplementação (p 0,05), e o efeito foi mais concreto na dieta de milho. O ritmo de trânsito da fase líquida ruminal, similar entre ambas dietas, foi aparentemente inferior durante o primeiro período experimental (8,65 vs. 10,56%/h) e decresceu com o nível de suplementação (10,16 vs. 9,20%/h). Ciliados encont
RESUMO
In this experiment four Holstein heifers fitted with rumen and duodenum canulae were utilized to evaluate the rumen parameters as pH, passage rate (%/h), volume (L) and ciliated protozoa concentration, when fed diets with four levels of rumen degradable protein. This was achieved supplementing 0, 25, 50 or 75 grams of degradable protein per kg of concentrate as a urea and casein (98.2% OM and 93.2% CP). The diets had 25% of barley straw without treatment and 75% concentrate formulated to contain different proportions (25/75 and 75/25) of corn and barley and also 5% of wheat residue and 5% of mineral and vitamin supplement. A continuous infusion of Cr-EDTA was used as a liquid phase marker. A cross-over design with 8 treatments (2 diets and 4 degradable protein levels) were utilized in 8 balance periods in a factorial arrangement. The level of degradable protein significantly affected the mean pH values that decreased as the supplementation increased (P 0.05) mainly in the corn based diet. The passage rate of the liquid phase, similar for the diets, was lower in the first experimental period (8.65 vs. 10.56%/h) and decreased as the level of degradable protein increased. Ciliated protozoa had higher concentration (P 0.01) in the corn diet (79.1 x 103/mL) than in the barley diet (59.5 x 103/mL). The Entodinium genus represented 87.8% of the total population. The genus Ep
Em um ensaio de controle de parâmetros ruminais (pH, ritmo de trânsito (%h), volume ruminal (l), e concentração de protozoários ciliados), foram utilizadas quatro novilhas Holstein, canuladas no rúmen e duodeno, recebendo dietas com 4 níveis de proteína degradável, sem suplementar ou suplementadas com 25, 50 e 75 gramos de proteína degradável por quilo de concentrado em forma de uréia e caseína (98,2 e 93,2% de matéria orgânica e proteína bruta, respectivamente). As rações experimentais foram compostas por 25% de palha de cevada sem tratar e 75% de concentrado formulado em base a diferentes proporções (25/75 e 75/25) de milho/cevada, com 5% de resíduo de trigo e 5% de suplemento vitamínico mineral. Uma contínua infusão de marcador de fluxo de fase líquida (Cr-EDTA) foi executada. Os oito tratamentos experimentais (2 dietas x 4 níveis de infusão) foram administrados em 8 períodos de balanço em um delineamento cross-over, em esquema fatorial. O nível de infusão de N degradável afetou de forma significativa os valores médios ponderados de pH, que decresceram ao aumentar a suplementação (p 0,05), e o efeito foi mais concreto na dieta de milho. O ritmo de trânsito da fase líquida ruminal, similar entre ambas dietas, foi aparentemente inferior durante o primeiro período experimental (8,65 vs. 10,56%/h) e decresceu com o nível de suplementação (10,16 vs. 9,20%/h). Ciliados encont