An extended model of phosphorus metabolism in growing ruminants

Autor(es)

Dias, R. S. ^[1] ; Lopez, S. ^[2] ; Patino, R. M. P. ^[3] ; Silva, T. S. ^[4] ; Silva Filho, J. C. ^[5] ; Vitti, D. M. S. S. ^[4] ; Pecanha, M. R. S. R. ^[4] ; Kebreab, E. ^[6] ; France, J. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Guelph, Ctr Nutr Modelling, Guelph, ON N1G 2W1 - Canada

^[2] Univ Leon, Dept Anim Prod, CSIC, IGM, E-24071 Leon - Spain

^[3] Univ Sucre, Fac Ciencias Agr, Sincelejo, Sucre - Colombia

^[4] Univ Sao Paulo, Ctr Energia Nucl Agr, BR-13400970 Sao Paulo - Brazil

^[5] Univ Fed Lavras, Dept Zootecnia, BR-37200000 Lavras, MG - Brazil

^[6] Univ Calif Davis, Dept Anim Sci, Davis, CA 95616 - USA

• Tipo de documento: Artigo Científico
• Fonte: JOURNAL OF ANIMAL SCIENCE; v. 89, n. 12, p. 4151-4162, DEC 2011.
• Citações Web of Science: 3

Resumo

A major objective of this study was to extend the Vitti-Dias model used to describe P metabolism in ruminants, by adding 2 new pools to the original model to represent the rumen and saliva. An experiment was carried out using 24 male sheep, initial BW of 34.5 kg, aged 8 mo, fed a basal diet supplied with increasing amounts of dicalcium phosphate to provide 0.14, 0.32, 0.49, and 0.65% P in the diet. Sheep were individually housed indoors in metabolic cages and injected with a single dose of 7.4 MBq of (32)P into a jugular vein. Feed intake and total fecal and urinary outputs were recorded and sampled daily for 1 wk, and blood samples were obtained at 5 min, and 1, 2, 4, 6, 24, 48, 72, 96, 120, 144, and 168 h after (32)P injection. Saliva and rumen fluid samples were taken on d 6, 7, and 8. Then, animals were slaughtered and samples from liver, kidney, testicle, muscle, and heart (soft tissue) and bone were collected. Specific radioactivity and inorganic P were then determined in bone, soft tissue, plasma, rumen, saliva, and feces, and used to calculate flows between pools. Increased P intake positively affected total P (r = 0.97, P < 0.01) and endogenous P excretion in feces (r = 0.85, P < 0.01), P flow from plasma to saliva (r = 0.73, P < 0.01), from saliva to rumen (r = 0.73, P < 0.01), and from lower gastrointestinal tract to plasma (r = 0.72, P < 0.01). Urinary P excretion was similar for all treatments (P = 0.35). It was, however, related to plasma P (r = 0.63, P < 0.01) and to net P flow to bone (accretion - resorption; r = -0.64, P < 0.01). Phosphorus intake affected net P flow to soft tissue (P = 0.04) but not net P flow to bone (P = 0.46). Phosphorus mobilized from bone was directed toward soft tissue, as suggested by the correlations between P flow from bone to plasma and net P flow to soft tissue (r = 0.89, P < 0.01), and P flow from plasma to soft tissue and net P flow to bone (r = -0.76, P < 0.01). The lack of effect of dietary P on net P accretion in bone suggests that P demand for bone formation was low and surplus P was partially used by soft tissue. In conclusion, the model resulted in appropriate biological description of P metabolism in sheep and added knowledge of the effects of surplus dietary P on P metabolism. Additionally, the model can be used as a tool to assess feeding strategies aiming to mitigate P excretion into the environment. (AU)

• Processo FAPESP: 04/14532-5 - Impacto ambiental das perdas fecais de nutrientes pelos animais domésticos: análise quantitativa do fluxo de fósforo através de modelos biomatemáticos
• Beneficiário: Dorinha Miriam Silber Schmidt Vitti
• Modalidade de apoio: Auxílio à Pesquisa - Temático