ABSTRACT: A reliable determination of endogenous phosphorus (P) excretion is required to measure P utilization in chickens accurately. The objective of this study was to investigate phosphorus (P) retention in broilers fed diets formulated with different feed ingredients. Sixty-four 15-d old broiler chicks were fed diets in which part of the dietary P was provided from dicalcium phosphate, maize, barley or soybean. Level of supplementation of each ingredient was calculated to provide two levels of total P (4.5 or 5.0 g kg−1 feed). Birds received a single injection of 3 MBq of 32P to determine endogenous P excretion using the isotope dilution technique. Four days after injection, blood and excreta were collected for analysis of inorganic and radioactive P. There were no differences among diets in total (p = 0.37) or endogenous (p = 0.65) P excretion or in P retention (p = 0.37) regardless of the supplemental feed material used in each diet. Daily P retention was increased (p = 0.004) as P intake increased, but the proportion of P ingested that was retained was not affected (p = 0.23) by the level of dietary P. The use of an isotopic tracer allows for accurate estimation of endogenous P in excreta, ranging from 0.24 to 0.42 mg P g−1 dry matter intake. The retention of P in growing chickens was not changed when 10-20 % of total P was provided by maize, barley or soybean.

Estudou-se o metabolismo de cálcio em eqüinos em crescimento recebendo dietas com diversos níveis desse mineral. Utilizaram-se 12 machos, com média de 12 meses de idade e peso vivo médio de 221,0 kg, mantidos com três dietas com 0,15; 0,45; ou 0,75 de cálcio e 0,23% de fósforo, constituindo um delineamento inteiramente casualizado, com três níveis de cálcio e quatro repetições. Foram injetados em cada animal, via jugular direita, os volumes de uma seringa, correspondentes a 7,4 MBq de 45Ca (CaCl2). Após a injeção, foram colhidas amostras (10 mL) de sangue, via jugular esquerda, aos 5 minutos, 1, 2, 4, 6, 24, 48, 72, 96, 120 e 144 horas. As fezes foram colhidas diariamente pela manhã, a partir de 24 horas após a aplicação do radionuclídeo até o sétimo dia e uma alíquota de 5% do total diário excretado foi colhida e armazenada em congelador para posterior análise. O mesmo procedimento das fezes foi adotado para a urina, quando foram colhidas amostras de 1% do volume total diário. Os níveis de cálcio plasmático, cálcio total na urina e cálcio endógeno nas fezes não diferiram entre os níveis de cálcio com valores médios de 11,76; 5,54 e 20,86 mg/kgPV/dia, respectivamente. A disponibilidade biológica de cálcio (média de 81,71%) também não diferiu entre os níveis de cálcio. As regressões lineares entre níveis de cálcio na dieta e cálcio total ingerido, cálcio absorvido, cálcio total nas fezes e cálcio retido foram expressas, respectivamente pelas equações: y=10,7+2,78x r²=1,0; y=12,41+2,24x r²=0,99; y=5,97+0,92x r²=0,93 e y=6,4+1,70x r²=0,94, com médias de, respectivamente, 135,80; 113,21; 47,37 e 82,90 mg/kgPV/dia.

The objective of this work was to study the calcium metabolism in growing equines receiving diets with different calcium levels. Twelve male were used, with average age of twelve months and average alive weight of 221,0 kg. The treatments consisted of three diets, composed for increasing calcium levels (low = 0.15%-N15; standard = 0.45%-N45; high = 0.75%-N75), and standard phosphorus level (0.23%). Each animal was injected, through the right jugular vein, the volumes of a syringe, which corresponded to about 7.4 MBq of 45Ca (CaCl2). After the injection, blood samples (10 mL) were collected through left jugular vein at five minutes, 1, 2, 4, 6, 24, 48, 72, 96, 120 and 144 hours. The feces were daily collected in the morning, 24 hours after the application of the radionuclide until the seventh day, and an aliquot of 5% of the daily total excreted was collected and stored in freezer for posterior analysis. The same procedure of excrements was adopted for urine, when samples of 1% of the daily total volume had been collected. The experimental techniques used a completely randomized design with three treatments and four replications. No effects were observed on the plasma calcium, total calcium in urine and endogenous calcium in feces, with average values of 11,76; 5,54 and 20,86 mg/kgLW/day, respectively. No effects were observed for the biological calcium availability, with 81.67%, on average. Linear regressions between calcium levels in the diet and total calcium ingested, absorbed calcium, total calcium in feces and restrained calcium have been respectively verified, which were expressed according to the following equations: y=10.7+2.78x r²=1.0; y=12.41+2.24x r²=0.99; y=5.97+0.92x r²=0.93 and y=6.4+1.70x r²=0.94, with averages of 135.80; 113.21; 47.37 and 82.90 mg/kgLW/day, respectively.

Este trabalho foi realizado com o objetivo de estudar, por meio de dois modelos matemáticos, o metabolismo do cálcio (Ca) em ovinos recebendo dietas suplementadas com diferentes fontes de Ca. Foram utilizados 20 cordeiros mestiços Santa Inês (6 a 8 meses de idade) alimentados com uma dieta basal composta de milho, farelo de soja, bagaço de cana hidrolisado, uréia, fosfato monoamônio (MAP) e mistura mineral suplementada com cinco fontes de cálcio: polpa cítrica (PC), feno de alfafa (FA), calcário calcítico (CC), farinha de conchas de ostras (FC) e fosfato bicálcico (FB). Os animais receberam, via jugular, solução contendo 7,7 MBq de 45Ca. Durante sete dias, realizaram-se coletas de fezes, sangue e urina. Após o período de coleta, os animais foram sacrificados para retirada de amostras de tecidos (fígado, rins, coração, músculo e 12ª costela) para análises. O metabolismo de Ca foi avaliado pelos modelos de Vitti et al. (2000) e Fernandez (1995). O delineamento experimental foi o inteiramente casualizado e as médias foram comparadas pelo teste Duncan. Não houve diferença significativa para o consumo de Ca entre os tratamentos. A excreção fecal foi menor para o CC. O balanço de Ca foi negativo para FA e PC. A absorção de Ca pode ter sido prejudicada pela presença de pectina e oxalato na polpa cítrica e no feno de alfafa, respectivamente. Os fluxos entre o compartimento central e o trato digestivo indicaram maior absorção de Ca para o CC. As fontes CC, FB e FC apresentaram maior disponibilidade cálcio, com valores respectivos de 65,38; 34,12 e 32,43%. A comparação entre os modelos comprovou diferenças nos fluxos entre o sangue e os tecidos e ossos, todavia, o balanço entre esses compartimentos foi similar. As diferenças entre os modelos possivelmente foram ocasionadas pela sua estrutura.

This research was conducted to compare the accuracy of two mathematical models to predict calcium (Ca) metabolism in sheep supplemented with different Ca sources. Twenty Brazilian male sheep averaging 7 to 8 months of age were fed a basal diet containing corn, soybean meal, hydrolyzed sugarcane bagasse, urea, mono-ammonium phosphate, mineral mixture and one of the following Ca sources: limestone (LM), alfalfa hay (AH), dicalcium phosphate (DP), oyster shell meal (SM), and citrus pulp (CP). On day 22 each animal received an intravenous injection of 7.7 MBq of radio-calcium (45Ca) followed by collection of blood, feces, and urine every 24 h for 7 days. Total Ca and radioactivity were measured in all samples. At the end of the collection period, animals were slaughtered and samples of liver, heart, kidney, muscles and 12th rib were taken for analysis. Calcium metabolism was evaluated by the models proposed by Vitti et al. (2000) and Fernandez (1995). A completely randomized design was used and means were compared by the Duncan test. No significant differences were observed for Ca intake among treatments. However, total fecal excretion of Ca differed and was lowest in animals fed LM. Calcium balance was negative in sheep receiving AH and CP because Ca absorption might have been compromised by the high contents of pectin and oxalate in these two supplements, respectively. Flows of Ca between the central pool and the digestive tract showed the greatest absorption of Ca on animals fed LM. Diets supplemented with LM, DP, and SM had highest Ca availability with values of 65.38, 34.12 and 32.43%, respectively. The models differed in the predictions of Ca flows among blood, bone and soft tissues but showed similar values for Ca balance in the different compartments. These discrepant results may be explained by structural difference between models.