Carmichael-Wyatt Remy N, Genther-Schroeder Olivia N, Hansen Stephanie L
Department of Animal Science, Iowa State University, Ames, IA.
Transl Anim Sci. 2020 Nov 14;4(4):txaa207. doi: 10.1093/tas/txaa207. eCollection 2020 Oct.
The objective of this study was to determine the effects of increased supplemental Zn from differing sources on growth performance of steers fed diets differing in net energy. Angus steers ( = 72, 324 ± 2.1 kg) with Genemax gain scores of 3, 4, or 5 were blocked by BW and stratified by Genemax gain score into 12 pens of 6 steers each for 158 d. Pens were randomly assigned to 1 of 3 Zn treatments (ZNTRT): 1) control (no supplemental Zn, analyzed 33 mg Zn/kg DM; CON); 2) inorganic Zn (CON + 120 mg supplemental Zn/kg DM as ZnSO for entire trial; INZN); or 3) 120 mg supplemental Zn/kg DM as Zn-amino acid complex (Availa-Zn; Zinpro, Eden Prairie, MN) for first 60 d, then a blend of ZnSO and Zn-AA complex (CON + 60 mg supplemental Zn/kg DM as ZnSO + 60 mg supplemental Zn/kg DM as Zn-amino acid complex) for the remainder of the trial (ZNBLD). Two dietary energy strategies (ENERGY) were formulated to reach ADG rates of 1) 1.6 kg/d (LE) or 2) 2.0 kg/d (HE) utilizing a 3 × 2 factorial arrangement (12 steers/treatment). All steers were fed LE for a 60 d growing period, then pens were randomly assigned to ENERGY treatments fed the remaining 91 d. Day 60 BW tended to be greater ( = 0.07) in steers receiving supplemental Zn vs. CON. Liver Cu was decreased in Zn supplemented steers vs. CON ( = 0.02). Liver Zn concentrations on d 56 did not differ for Zn vs. CON ( = 0.22) nor were there differences due to Zn source ( = 0.98). There were or tended to be ZNTRT × ENERGY effects for d 67-90 ADG and G:F ( ≤ 0.01), and d 122 BW and d 90-122 G:F ( ≤ 0.10) driven by improved performance for ZNBLD-HE over ZNBLD-LE, while ENERGY within CON and INZN did not differ. Day 90-122 ADG, overall ADG and overall G:F was greater ( ≤ 0.02) and d 67-90 G:F tended to be greater ( = 0.10) for HE vs. LE. No ZNTRT × ENERGY or ZNTRT effects were detected for HCW, REA, BF, KPH, MS, or YG ( ≥ 0.37) while HE increased HCW, BF, MS, and YG compared with LE ( ≤ 0.05). In the liver, ZNTRT affected d 97 MT1A expression ( = 0.03) where INZN was greater than ZNBLD or CON ( ≤ 0.02), while ZIP14 was unaffected due to ZNTRT, ENERGY, or the interaction ( ≥ 0.39). Supplying supplemental Zn as ZNBLD during the transition period appeared to improve performance measures, but no final performance advantages were noted due to increased supplemental Zn, regardless of source. Additionally, differences in liver MT1A expression may indicate differing post-absorptive metabolism between Zn sources.
本研究的目的是确定来自不同来源的增加的锌补充剂对采食净能量不同的日粮的阉牛生长性能的影响。将Genemax生长评分分别为3、4或5的安格斯阉牛（n = 72，体重324 ± 2.1 kg）按体重进行分组，并按Genemax生长评分分层，分成12个栏，每个栏6头阉牛，试验期为158天。将栏随机分配到3种锌处理（ZNTRT）中的1种：1）对照（不补充锌，分析得出锌含量为33 mg/kg干物质；CON）；2）无机锌（在整个试验期内，CON + 120 mg补充锌/kg干物质，以硫酸锌形式添加；INZN）；或3）在试验的前60天，补充120 mg锌/kg干物质，以锌氨基酸络合物（Availa-Zn；Zinpro公司，明尼苏达州伊甸草原）形式添加，然后在试验剩余时间内，补充硫酸锌和锌氨基酸络合物的混合物（CON + 60 mg补充锌/kg干物质，以硫酸锌形式添加 + 60 mg补充锌/kg干物质，以锌氨基酸络合物形式添加；ZNBLD）。制定了两种日粮能量策略（ENERGY），以达到如下平均日增重率：1）1.6 kg/d（低能量组，LE）或2）2.0 kg/d（高能量组，HE），采用3×2析因设计（每个处理12头阉牛）。所有阉牛在60天的生长阶段饲喂低能量日粮LE，然后将栏随机分配到能量处理组，在剩余的91天饲喂相应日粮。与CON组相比，接受锌补充剂的阉牛在第60天的体重有增加趋势（P = 0.07）。与CON组相比，补充锌的阉牛肝脏铜含量降低（P = 0.02）。在第56天，锌处理组与CON组的肝脏锌浓度没有差异（P = 0.22），锌源之间也没有差异（P = 0.98）。在第67 - 90天的平均日增重和料重比方面存在或有ZNTRT×ENERGY效应（P≤0.01），在第122天的体重和第90 - 122天的料重比方面存在或有ZNTRT×ENERGY效应（P≤0.10），这是由于ZNBLD - HE组相对于ZNBLD - LE组性能提高所致，而CON组和INZN组内的ENERGY处理之间没有差异。与低能量组相比，高能量组在第90 - 122天的平均日增重、总体平均日增重和总体料重比更高（P≤0.02），在第67 - 90天的料重比有增加趋势（P = 0.10）。对于热胴体重、眼肌面积、背膘厚度、肌内脂肪含量、大理石花纹评分或胴体等级，未检测到ZNTRT×ENERGY或ZNTRT效应（P≥0.37），而与低能量组相比，高能量组的热胴体重、背膘厚度、大理石花纹评分和胴体等级增加（P≤0.05）。在肝脏中，ZNTRT影响第97天金属硫蛋白1A（MT1A）的表达（P = 0.03），其中INZN组大于ZNBLD组或CON组（P≤0.02），而锌转运蛋白14（ZIP14）不受ZNTRT、ENERGY或交互作用的影响（P≥0.39）。在过渡期以ZNBLD形式供应补充锌似乎能改善性能指标，但无论锌源如何，增加补充锌并未带来最终的性能优势。此外，肝脏MT1A表达的差异可能表明锌源之间吸收后代谢的差异。
