Department of Physiology, University of Veterinary Medicine Hannover, Bischofsholer Damm 15/102, 30173 Hannover, Germany.
Br J Nutr. 2011 Jun;105(11):1619-26. doi: 10.1017/S0007114510005350.
In goats, the combination of dietary N and Ca reduction caused hypocalcaemia and further changes in Ca homeostasis. The aim of the present study was to characterise the effects of dietary N reduction under normocalcaemia on mineral and bone metabolism in young goats. Young male goats of the Saanen breed were fed a diet reduced in N (8 %) for about 7 weeks (ten animals per group) and were compared with goats fed with an adequate N (14 %) diet. When N intake was reduced in young goats, plasma urea concentrations as well as renal elimination of urea were reduced. This was inversely related to creatinine in plasma and urine, which increased during a dietary N reduction as a function of reduced renal activity to save urea during N scarcity. During this decrease in renal function, associated with declined insulin-like growth factor 1 concentrations, a reduction in calcidiol and calcitriol concentrations could be observed. Meanwhile, carboxyterminal cross-linked telopeptide of type I collagen values and activity of total alkaline phosphatase were both elevated, indicating some bone remodelling processes taking place during a reduced N diet in young goats. The concentrations of inorganic phosphate (Pi) and total Ca were changed in several body fluids, indicating that Pi and Ca homeostasis was perturbed in goats fed a reduced N diet. Therefore, more research is needed to find the balance between reduction of environmental N pollution by reducing dietary N in ruminant feeding and maintaining the animal's health.
在山羊中，饮食中 N 和 Ca 的减少会导致低钙血症和进一步的 Ca 稳态变化。本研究的目的是描述在正常血钙水平下减少饮食 N 对年轻山羊矿物质和骨代谢的影响。用减少 N（8%）的饮食喂养大约 7 周的萨能种雄性山羊（每组 10 只），并与用适当 N（14%）饮食喂养的山羊进行比较。当年轻山羊的 N 摄入量减少时，血浆尿素浓度以及尿素的肾脏排泄都会减少。这与血浆和尿液中的肌酐呈反比，在饮食 N 减少期间，肌酐增加，这是由于肾脏活动减少，以在 N 缺乏时保存尿素。在此肾功能下降期间，与胰岛素样生长因子 1 浓度下降相关，可观察到 calcidiol 和 calcitriol 浓度降低。同时，I 型胶原羧基端交联肽的价值和总碱性磷酸酶的活性都升高，表明在年轻山羊的低 N 饮食期间发生了一些骨重塑过程。几种体液中的无机磷（Pi）和总 Ca 浓度发生变化，表明 Pi 和 Ca 稳态在低 N 饮食喂养的山羊中受到干扰。因此，需要进一步研究以找到减少反刍动物饲养中饮食 N 来减少环境 N 污染与维持动物健康之间的平衡。
