Phillips C J C, Chiy P C, Omed H M
Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, UK.
J Anim Sci. 2004 Aug;82(8):2489-502. doi: 10.2527/2004.8282489x.
The effects of feeding Cd to sheep at a level that is typical of polluted regions were investigated, as well as possible amelioration by adding Zn to the diet. Welsh Mountain ewes (n = 24) were fed herb-age and concentrate in metabolism crates, with four supplement treatments in a two-factor factorial design: no supplement, Cd supplement only, Zn supplement only, and a combination of both the Cd and Zn supplement. Cadmium (286 microg/kg of feed DMI) and Zn (8.6 mg/kg feed DMI) were added as sulfates. Food and water intakes and element balances were recorded over 20 d after 7 d dietary adaptation, and element concentrations were determined in wool samples. Neither metal affected DMI or digestibility (P > 0.15), but water intake (P = 0.001) and urine output (P = 0.03) were decreased when only the Zn supplement was added. Water retention was increased by the Cd supplement (P = 0.04). In wool, the Cd supplement greatly increased the K concentration if no Zn supplement was fed (P = 0.02), and the Zn supplement decreased Mn concentration (P = 0.02). Cadmium in feed increased the Cd balance and produced several mineral disturbances, in particular a decrease in Na balance that is typical of renal tubular disorders. Adding Zn as well as Cd to feed returned the Cd balance to a level similar to that of sheep receiving neither Cd nor Zn, which suggests that Zn status is critical in determining whether Cd in feed increases the Cd balance in sheep. Feeding Cd also increased urinary K, Fe, Mo, Cr, B, and Ca concentrations, even when supplementary Zn was fed. It is concluded that low levels of Cd in sheep feed can increase the Cd balance if adequate Zn is not provided, which can lead to subclinical mineral disturbances and changes in the mineral concentrations in wool.
研究了以污染地区典型水平向绵羊投喂镉的影响，以及通过在日粮中添加锌进行可能的改善。将24只威尔士山地母羊置于代谢笼中饲喂牧草和精饲料，采用两因素析因设计进行四种补充处理：不补充、仅补充镉、仅补充锌以及同时补充镉和锌。以硫酸盐形式添加镉（286微克/千克饲料干物质摄入量）和锌（8.6毫克/千克饲料干物质摄入量）。在7天日粮适应期后，记录20天内的食物和水摄入量以及元素平衡，并测定羊毛样品中的元素浓度。两种金属均未影响干物质摄入量或消化率（P>0.15），但仅添加锌时，水摄入量（P=0.001）和尿量（P=0.03）减少。补充镉增加了水分潴留（P=0.04）。在羊毛中，如果不补充锌，补充镉会显著增加钾浓度（P=0.02），补充锌会降低锰浓度（P=0.02）。饲料中的镉增加了镉平衡并导致多种矿物质紊乱，尤其是钠平衡降低，这是肾小管疾病的典型表现。在饲料中同时添加锌和镉可使镉平衡恢复到与既不摄入镉也不摄入锌的绵羊相似的水平，这表明锌状态对于确定饲料中的镉是否会增加绵羊的镉平衡至关重要。即使补充了锌，投喂镉也会增加尿中钾、铁、钼、铬、硼和钙的浓度。得出的结论是，如果不提供足够的锌，绵羊饲料中低水平的镉会增加镉平衡，这可能导致亚临床矿物质紊乱以及羊毛中矿物质浓度的变化。
