此外，不同形式的添加铜对植酸酶的影响也不同。

　　Lu 等[9]检测了鸡饲粮在储存过程中，不同剂量硫酸铜和碱式氯化铜对植酸酶酶活性影响，结果表明添加添加200 mg·kg-1铜的处理组植酸酶活性都明显低于无添加铜对照组，并且各添加水平的硫酸铜组植酸酶酶活显著低于碱式氯化铜组。Lu 等[10]报道，断奶仔猪饲粮中添加200 mg·kg-1硫酸铜和碱式氯化铜都显著降低了植酸酶在体外的酶活性，并且硫酸铜组的降低幅度大于碱式氯化铜组。以上结果可能与碱式氯化铜较硫酸铜稳定，解离的铜离子较少有关。提示，不同形式的铜对植酸酶的干扰强度不同，其达到干扰植酸酶的“阈值”可能也不同。

　　一些研究认为高剂量铜具有杀菌作用，可以预防仔猪腹泻[33]。但本试验中120 mg·kg-1 铜+植酸酶组仔猪腹泻频率低于180 mg·kg-1 铜+植酸酶组，显著低于180 mg·kg-1 铜无植酸酶组。郭彤等[34]报道，Cu2+在微摩尔水平时就能有效抑制微生物的呼吸代谢途径。

　　Ball 和Aherne[35]认为，早期断奶仔猪消化道及其酶系尚未发育健全，消化力差是导致腹泻的重要原因。本试验结果可能与“120 mg·kg-1 铜+植酸酶”组营养物质消化利用率较高有关。

　　4 结论

　　现有试验表明，在添加植酸酶的玉米-豆粕型饲粮中，将铜（硫酸铜形式）添加量从180 mg·kg-1 减少到120 mg·kg-1 可以显著提高钙、磷表观消化率，降低粪铜和粪磷含量。

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