Darabi Mahin, Hozhabri Fardin, Piray Alihossein, Foroutanifar Saheb
Department of Animal Science, College of Agriculture and Natural Resources, Razi University, PO Box 6,715,685,418, Kermanshah, Iran.
Biol Trace Elem Res. 2025 Jul 10. doi: 10.1007/s12011-025-04669-z.
The effects of dietary zinc (Zn) supplementation on lambs fed diets without added Zn remain controversial, and the precise nature and extent of the associations between Zn administration and lamb responses are not fully understood. To address this, a comprehensive systematic review and dose-response meta-analysis was conducted to explore the effects of Zn supplementation on growth performance, mineral metabolism, and nutrient digestibility. Initially, 3169 studies were identified through comprehensive database searches using relevant keywords. Following a two-stage screening process, 30 eligible articles were selected based on predefined criteria and used in the current meta-analysis. The one-stage random-effects model was utilized in this meta-analysis, with sensitivity analyses conducted to evaluate the robustness of the derived effect sizes. The results showed nonlinear relationships between Zn supplementation and performance parameters. Optimal Zn levels were identified: approximately 28.51 mg/kg DM for maximum dry matter intake, 37.84 mg/kg DM for highest weight gain, and 42.00 mg/kg DM for best feed conversion ratio. Linear increases in fecal and urinary Zn, and a decrease in apparent Zn absorption, were observed with increasing Zn supplementation (P < 0.05). Zinc supplementation up to 53 mg/kg DM enhanced Zn retention, and up to 107 mg/kg DM, increased liver Zn concentration, with the highest concentration at 50.59 mg/kg DM. Zinc supplementation also affected copper and iron concentrations in various tissues. Specifically, it decreased pancreatic copper up to 22 mg/kg DM but increased it above 50 mg/kg DM. In kidney tissue, copper concentration increased linearly with Zn supplementation from 76 to 150 mg/kg DM, while in liver tissue, it decreased from 42 to 150 mg/kg DM. Heart tissue iron concentration increased up to 24 mg/kg DM but decreased from 41 to 150 mg/kg DM, with the highest concentration at 16.31 mg/kg DM. Zinc supplementation at 28.28 and 20.88 mg/kg DM increased total concentration of rumen volatile fatty acids and dry matter digestibility, respectively. However, final weight, carcass weight, nitrogen metabolism, Zn levels in heart, pancreas, and kidney tissues, copper levels in heart tissue, iron levels in pancreas and liver tissues, and the digestibility of most dietary fractions (organic matter, crude protein, NDF, and ADF) were not affected (P > 0.05). In summary, the findings of this meta-analysis generally align with NRC guidelines; this study underscores the necessity of precise Zn supplementation to optimize lamb productivity and mitigate potential adverse effects.
在不添加锌的日粮中添加锌对羔羊的影响仍存在争议，锌的添加与羔羊反应之间关联的确切性质和程度尚未完全明确。为解决这一问题，我们进行了一项全面的系统综述和剂量反应荟萃分析，以探讨锌添加对生长性能、矿物质代谢和养分消化率的影响。最初，通过使用相关关键词进行全面的数据库检索，共识别出3169项研究。经过两阶段筛选过程，根据预先设定的标准选择了30篇符合条件的文章，并用于当前的荟萃分析。本荟萃分析采用单阶段随机效应模型，并进行敏感性分析以评估所推导效应量的稳健性。结果表明，锌添加量与性能参数之间存在非线性关系。确定了最佳锌水平：最大干物质采食量约为28.51mg/kg干物质，最高体重增加量为37.84mg/kg干物质，最佳饲料转化率为42.00mg/kg干物质。随着锌添加量的增加，粪便和尿液中的锌呈线性增加，表观锌吸收率降低（P<0.05）。锌添加量高达53mg/kg干物质可提高锌的保留率，高达107mg/kg干物质可增加肝脏锌浓度，最高浓度为50.59mg/kg干物质。锌添加还会影响各种组织中的铜和铁浓度。具体而言，锌添加量高达22mg/kg干物质时会降低胰腺中的铜含量，但超过50mg/kg干物质时会增加。在肾脏组织中，锌添加量从76mg/kg干物质增加到150mg/kg干物质时，铜浓度呈线性增加，而在肝脏组织中，锌添加量从42mg/kg干物质增加到150mg/kg干物质时，铜浓度降低。心脏组织中的铁浓度在锌添加量高达24mg/kg干物质时增加，但在锌添加量从41mg/kg干物质增加到150mg/kg干物质时降低，最高浓度为16.31mg/kg干物质。锌添加量为28.28mg/kg干物质和20.88mg/kg干物质时，分别增加了瘤胃挥发性脂肪酸的总浓度和干物质消化率。然而，最终体重、胴体重量、氮代谢、心脏、胰腺和肾脏组织中的锌水平、心脏组织中的铜水平、胰腺和肝脏组织中的铁水平以及大多数日粮成分（有机物、粗蛋白、中性洗涤纤维和酸性洗涤纤维）的消化率均未受到影响（P>0.05）。总之，本荟萃分析的结果总体上与美国国家研究委员会（NRC）的指南一致；本研究强调了精确添加锌以优化羔羊生产性能并减轻潜在不良影响的必要性。
