Vitti D M, Kebreab E, Lopes J B, Abdalla A L, De Carvalho F F, De Resende K T, Crompton L A, France J
Animal Nutrition Laboratory, Centro de Energia Nuclear na Agricultura, Piracicaba, SP, Brazil.
J Anim Sci. 2000 Oct;78(10):2706-12. doi: 10.2527/2000.78102706x.
The effect of increasing phosphorus (P) intake on P utilization was investigated in balance experiments using 12 Saanen goats, 4 to 5 mo of age and weighing 20 to 30 kg. The goats were given similar diets with various concentrations of P, and 32P was injected to trace the movement of P in the body. A P metabolism model with four pools was developed to compute P exchanges in the system. The results showed that P absorption, bone resorption, and excretion of urinary P and endogenous and fecal P all play a part in the homeostatic control of P. Endogenous fecal output was positively correlated to P intake (P < .01). Bone resorption of P was not influenced by intake of P, and P recycling from tissues to the blood pool was lesser for low P intake. Endogenous P loss occurred even in animals fed an inadequate P diet, resulting in a negative P balance. The extrapolated minimum endogenous loss in feces was .067 g of P/d. The minimum P intake for maintenance in Saanen goats was calculated to be .61 g of P/d or .055 g of P/(kg(.75) x d) at 25 kg BW. Model outputs indicate greater P flow from the blood pool to the gut and vice versa as P intake increased. Intake of P did not significantly affect P flow from bone and soft tissue to blood. The kinetic model and regressions could be used to estimate P requirement and the fate of P in goats and could also be extrapolated to both sheep and cattle.
在平衡实验中，研究了增加磷（P）摄入量对磷利用的影响。实验使用了12只4至5月龄、体重20至30千克的萨能山羊。给山羊喂食含不同磷浓度的相似日粮，并注射32P以追踪磷在体内的移动。建立了一个具有四个库的磷代谢模型来计算系统中的磷交换。结果表明，磷吸收、骨吸收以及尿磷、内源性磷和粪磷的排泄均参与了磷的稳态控制。内源性粪磷排出量与磷摄入量呈正相关（P <.01）。磷的骨吸收不受磷摄入量的影响，低磷摄入量时从组织到血库的磷再循环较少。即使给动物喂食磷含量不足的日粮，也会发生内源性磷损失，导致磷平衡为负。推算出的粪便中最低内源性损失为0.067克磷/天。计算得出，体重25千克的萨能山羊维持所需的最低磷摄入量为0.61克磷/天或0.055克磷/（千克（0.75）×天）。模型输出结果表明，随着磷摄入量增加，从血库到肠道以及从肠道到血库的磷流量更大。磷摄入量对从骨骼和软组织到血液的磷流量没有显著影响。该动力学模型和回归分析可用于估计山羊的磷需求量以及磷的去向，也可外推至绵羊和牛。
