Department of Animal Sciences, Colorado State University, Fort Collins, CO.
North Carolina State University, Raleigh, NC.
J Anim Sci. 2019 Mar 1;97(3):1286-1295. doi: 10.1093/jas/skz016.
Four hundred crossbred steers were used in a randomized complete block design to investigate the effects of supplemental Zn source and concentration, and dietary Cr on performance and carcass characteristics of feedlot steers fed a steam-flaked corn-based finishing diet. Steers were blocked by initial BW within cattle source (3 sources) and randomly assigned within block to 1 of 5 treatments. Before the initiation of the experiment, trace mineral supplement sources were analyzed for Zn and Cr. Zinc and Cr concentrations of the Zn sources were used to balance all dietary treatments to obtain correct Zn and Cr experimental doses. Treatments were the addition of: 1) 90 mg Zn/kg DM from ZnSO4 and 0.25 mg Cr/kg DM from Cr propionate (90ZS+Cr); 2) 30 mg Zn/kg DM from Zn hydroxychloride and 0.25 mg Cr/kg DM from Cr propionate (30ZH+Cr); 3) 90 mg Zn/kg DM from Zn hydroxychloride and 0.25 mg Cr/kg DM from Cr propionate (90ZH+Cr); 4) 60 mg Zn/kg DM from ZnSO4 and 30 mg Zn/kg DM from Zn methionine (90ZSM); and 5) 90 mg Zn/kg DM from Zn hydroxychloride (90ZH). Steers were individually weighed on d-2 and on 2 consecutive days at the end of the experiment. Initial liver biopsies were obtained from all steers at processing. Equal numbers of pen replicates per treatment were slaughtered at a commercial abattoir on day 162, 176, and 211; individual carcass data and final liver samples were collected. Total finishing dietary Zn and Cr concentrations were 118.4, 58.2, 114.2, 123.0, and 108.2 mg Zn/kg DM and 0.740, 0.668, 0.763, 0.767, and 0.461 mg Cr/kg DM, for treatments 1 to 5, respectively. Data were analyzed statistically using preplanned single degree of freedom contrasts. Steers receiving 90ZH+Cr had greater final BW (P < 0.04) and ADG (P < 0.03) when compared with steers receiving 90ZH. Additionally, hot carcass weight was 8.5 kg greater (P < 0.03) for 90ZH+Cr compared with 90ZH supplemented steers. Steers receiving 90ZH+Cr had greater longissimus muscle area when compared with steers receiving 90ZSM. Dry matter intake, G:F, morbidity and mortality, and all other carcass measurements were similar across treatments. These data indicate that under the conditions of this experiment, Zn source and concentration had no impact on live performance, liver Zn and Cu concentrations, and carcass characteristics. Supplemental Cr in diets containing 90 mg of supplemental Zn/kg DM from ZH improved final BW, ADG, and hot carcass weights.
四百头杂交牛被用于随机完全区组设计，以研究补充锌源和浓度以及日粮铬对饲喂蒸汽压片玉米基础育肥日粮的肥育牛的性能和胴体特性的影响。牛按初始体重（3 个来源）分为块，然后按块内随机分配到 5 种处理中的 1 种。在实验开始前，对微量元素补充剂来源进行了锌和铬分析。利用锌源的锌和铬浓度来平衡所有日粮处理，以获得正确的锌和铬实验剂量。处理方法是：1）每公斤干物质添加 90 毫克硫酸锌和 0.25 毫克丙酸盐中的铬（90ZS+Cr）；2）每公斤干物质添加 30 毫克氧化锌和 0.25 毫克丙酸盐中的铬（30ZH+Cr）；3）每公斤干物质添加 90 毫克氧化锌和 0.25 毫克丙酸盐中的铬（90ZH+Cr）；4）每公斤干物质添加 60 毫克硫酸锌和 30 毫克蛋氨酸中的锌（90ZSM）；5）每公斤干物质添加 90 毫克氧化锌（90ZH）。牛在第-2 天和实验结束后的连续 2 天分别进行个体称重。在加工过程中从所有牛身上采集初始肝脏活检样本。在第 162、176 和 211 天，商业屠宰场对每个处理的等数量的畜栏重复进行屠宰；收集个体胴体数据和最终肝脏样本。处理 1 至 5 的总育肥日粮中锌和铬的浓度分别为 118.4、58.2、114.2、123.0 和 108.2 毫克锌/千克干物质和 0.740、0.668、0.763、0.767 和 0.461 毫克铬/千克干物质。使用预先计划的单自由度对比对数据进行了统计分析。与接受 90ZH 的牛相比，接受 90ZH+Cr 的牛的最终体重（P<0.04）和 ADG（P<0.03）更高。此外，与接受 90ZH 补充的牛相比，接受 90ZH+Cr 的牛的热胴体重高 8.5 公斤（P<0.03）。与接受 90ZSM 的牛相比，接受 90ZH+Cr 的牛的背最长肌面积更大。干物质采食量、增重效率、发病率和死亡率以及所有其他胴体测量在处理之间相似。这些数据表明，在本实验条件下，锌源和浓度对活性能、肝脏锌和铜浓度以及胴体特性没有影响。日粮中添加 90 毫克补充锌/千克干物质的铬可提高最终体重、ADG 和热胴体重。
