A revised model for studying phosphorus and calcium kinetics in growing sheep1

Dias, R. S.; Kebreab, E.; Vitti, Dorinha Miriam Silber Schmidt; Roque, Ana Paula; Bueno, Ives Cláudio da Silva

doi:10.2527/jas.2006-082

Cited by 31 publications

(27 citation statements)

References 31 publications

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“…Several models have been created to examine changes in P metabolism with dietary changes (Vitti et al, 2000;Bravo et al, 2003;Dias et al, 2006). However, these models have been created to interpret in vivo tracer kinetic data from small ruminants.…”

Section: Introductionmentioning

confidence: 99%

A Model of Phosphorus Digestion and Metabolism in the Lactating Dairy Cow

Hill

Knowlton

Kebreab

et al. 2008

Journal of Dairy Science

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A dynamic, mechanistic, compartmental model of phosphorus (P) digestion and metabolism was constructed in the Advanced Continuous Simulation Language using conservation of mass principles and mass action kinetics. Phosphorus was assumed to exist in 3 forms: inorganic (Pi), phytic acid (Pp), and organic (excluding phytic acid; Po). All 3 forms were assumed to be present in the digestive tract with absorption of Pi into blood. Inputs to the model were total P intake; Pp, Po, and Pi as proportions of total P; milk yield; rate of salivation (fixed at 239 L/d); and rate of liquid passage from the rumen (fixed at 198 L/d). The model was fitted to 2 experiments from the literature. Derived parameters were well defined by the data. With a mean observed P intake of 75 g/d, total tract P digestibility was 38%. Phytic acid P digestibility in the rumen was 74%, with no additional Pp digestion in the lower tract. Inorganic P and Po digestibility in the lower tract were 48 and 89%, respectively. Flows of Po and Pi from the rumen were 2.4 and 3.0 times greater than intake, respectively. The increase in Po was apparently due to microbial growth. The increase in Pi arose primarily from secretion of Pi into the rumen via salivation where 65% of absorbed P was recycled to the rumen. Milk synthesis used 30% of absorbed Pi, and 1% was excreted in urine. This research suggested that the primary regulation points for maintaining blood P were bone deposition and resorption and absorption from the intestine. However, because bone P balance was related to both dietary P intake and ruminal phytase activity, it is critical to achieve a better understanding of phytate digestibility across several feeds if dietary P is to be reduced below current requirements.

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Section: Introductionmentioning

confidence: 99%

A Model of Phosphorus Digestion and Metabolism in the Lactating Dairy Cow

Hill

Knowlton

Kebreab

et al. 2008

Journal of Dairy Science

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“…Vitti et al (2000), utilizando dados de experimentos de balanço e cinética de P em caprinos, propuseram modelo matemático contendo quatro compartimentos (trato, sangue, ossos e tecidos moles) para o estudo do efeito de níveis crescentes de P nos animais em crescimento. Este modelo foi recentemente revisado (Dias et al, 2006) para o estudo da cinética de P em caprinos e da cinética de Ca em ovinos.…”

Section: Introductionunclassified

Efeitos de diferentes níveis de cálcio dietético na cinética de cálcio e fósforo em eqüinos

Vitti¹,

Furtado

Quadros

et al. 2008

R. Bras. Zootec.

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RESUMO -Objetivou-se estudar o metabolismo de cálcio (Ca) e fósforo (P) nos eqüinos em crescimento que receberam diferentes níveis de suplementação de Ca: 0,15; 0,45 e 0,75% na dieta, utilizando-se o modelo determinístico e compartimental. Foram utilizadas informações sobre o estudo de metabolismo e cinética de Ca e P em tecidos, obtidas pela técnica da diluição isotópica. Constatou-se que os níveis dietéticos de Ca tiveram influência na absorção real do Ca, sendo menor para o nível 0,15% (4,97 g Ca/dia). As trocas de Ca entre o sangue e o trato digestivo foram menores para o nível 0,15%. A mobilização entre o sangue e os ossos e sangue e tecidos moles não foi influenciada pelos tratamentos, mas o balanço nos ossos e tecidos foi menor para o nível 0,15%. Os níveis de Ca dietéticos tiveram influência no P eliminado através da urina, sendo este valor maior para o tratamento 0,15% (2,49 g/animal/dia). A absorção real média do P foi de 83%, não havendo diferenças para os tratamentos. Verificou-se deposição óssea média de 9,69 g P/animal/dia, indicando que a quantidade de P fornecida foi adequada em relação à tolerância permissível à amplitude na relação Ca:P para a espécie na categoria animal estudada. Não houve diferenças significativas entre os fluxos de P nos diversos compartimentos, por intermédio do modelo de metabolismo. A ingestão de níveis crescentes de Ca afetou o metabolismo e a cinética deste elemento, entretanto, a proporção Ca:P é o fator predominante para determinar a excreção, retenção e absorção de Ca.A deposição de Ca no osso foi influenciada pela quantidade ingerida deste mineral. O metabolismo de P em eqüinos em crescimento não foi afetado pelos teores de Ca. O fornecimento de 13,4 g P/animal/dia foi suficiente para manter o metabolismo de P nos padrões considerados normais. Palavras-chave: fluxo de minerais, macrominerais, potros, radioisótopos Effects of different levels of dietary calcium on calcium and phosphorus kinetics in horsesABSTRACT -This experiment was carried out to study calcium (Ca) and phosphorus (P) kinetics of growing horses fed diets with different Ca levels: 0.15%, 0.45, and 0.75%, using a deterministic and compartmental model. The information on metabolism and kinetic of Ca and P in tissues was obtained by the isotopic dilution technique. Dietary Ca levels influenced Ca true absorption, showing lower value (4.97 g Ca/day) for the Ca level of 0.15%. The changes of Ca between the blood and digestive tract were lower for 0,15% Ca. The flows between the blood and bone and blood and soft tissues did not show differences between treatments, but bone and tissue balance was lower for the level of 0.15%. Dietary Ca levels influenced on P in urine and values were higher for 0.15% (2.49 g P/anim.day). The mean true P absorption was of 83%, with no differences among treatments. Bone deposition of 9.69g P/anim.day was observed, showing that the amount of P fed was adequate in relation to the allowed amplitude for Ca:P ratio for the specie in the studied animal category. No differences betw...

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“…If we consider the indications of other authors (23)(24)(25)(26)(27) in relation to the coefficients of absorption of Ca and P, there are still aspects that could cause differences in the determination of dietary requirements.…”

Section: Discussionmentioning

confidence: 99%

Nutrient absorption in lambs fed diets containing different amounts of phosphorus

Silva²,

Filho

et al. 2013

Rev MVZ Córdoba

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Objective. Evaluate the effect of increasing P intake on nutrient digestibility, and compare the true and apparent absorption coefficients of P and Ca in lambs. Materials and methods. Twenty-four Santa Ines sheep, with an average weight of 33.6 ± 1.6 kg, were distributed into four treatments (0, 2, 4 and 6 g/day of supplementary P) with forage: concentrate ratio of 70:30. The study of apparent nutrient digestibility was conducted during the first week, using the total feces collection method. During the second week, after injection of 7.4 MBq of 32 P and 7.7 MBq of 45 Ca, apparent (AAC) and true (TAC) absorption coefficients of P and Ca were determined. The lambs were kept in metabolic cages. Results. The increase in P intake did not affect (p>0.05) dry matter, crude protein, NDF or ADF digestibility, but the TAC of P and Ca and mineral matter digestibility decreased. The AAC was not affected (p=0.10). A cubic relationship was observed between P intake and TAC (TAC=2.16-1.95X+0.55X 2 -0.04X 3 ; R 2 =0.38) and linear relationship with the TAC of Ca (TAC=0.559-0.03X; R 2 =0.26). TAC and AAC values were different (p<0.001). Conclusions. The increase in P intake doesn't impact organic matter digestibility, but does affect P and Ca absorption. Apparent digestibility is not a reliable parameter to determine the efficiency of P and Ca absorption.

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A revised model for studying phosphorus and calcium kinetics in growing sheep1

Cited by 31 publications

References 31 publications

A Model of Phosphorus Digestion and Metabolism in the Lactating Dairy Cow

A Model of Phosphorus Digestion and Metabolism in the Lactating Dairy Cow

Efeitos de diferentes níveis de cálcio dietético na cinética de cálcio e fósforo em eqüinos

Nutrient absorption in lambs fed diets containing different amounts of phosphorus

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