Henderson Jacob A, Genther-Schroeder Olivia N, Hansen Stephanie L, McGill Jodi L
Department of Animal Science, Iowa State University, Ames, IA 50011.
Land O' Lakes, Inc., Gray Summit, MO 63039.
J Anim Sci. 2025 Jan 4;103. doi: 10.1093/jas/skaf218.
Beef-on-dairy crossbred steers are exposed to greater amounts of copper (Cu), which may impact their resiliency to disease. To test this, 26 weaned beef-on-dairy steers (95.2 ± 7.2 kg; ~8 wk old) were blocked by weight to pens, and pens were randomly assigned to two target liver Cu statuses: adequate (ADE) and HIGH. To achieve target statuses, ADE and HIGH were fed diets containing no supplemental Cu and 20 mg Cu/kg diet DM, respectively, for 120 d before enrollment in a 13-d bovine respiratory disease challenge. Liver Cu prior to challenge averaged 279 and 608 mg Cu/kg liver DM for ADE and HIGH, respectively. Steers were infected with 104TCID50 BRSV on day 0 via aerosol inoculation. On day 5 postinfection, steers were intratracheally infected with 5 × 108 CFU Mannheimia haemolytica. A trained observer scored steers for depression, appetite, and respiration from days 0 to 14. On days 0, 5, 7, 10, and 13, thoracic ultrasound was used to score animals based on the degree of lung consolidation and lesions, and jugular blood was collected. Categorical variables (clinical and lung scores) and continuous variables were analyzed using PROC GLIMMIX and PROC MIXED of SAS 9.4 (Cary, NC), respectively. Clinical scores were affected by treatment × day (P = 0.04), where HIGH experienced a sharper increase in clinical scores in response to disease compared to ADE (P < 0.01) and remained higher throughout the remainder of the disease challenge (0.01 < P ≤ 0.08). Over the entire challenge, HIGH steers tended to have greater lung consolidation than ADE (P = 0.08). While no differences in haptoglobin were detected between treatments (P = 0.96), both treatments experienced marked increases in haptoglobin on day 7 postinfection (P < 0.01), indicating inflammation in response to disease. There was a tendency for a treatment × day interaction (P = 0.07) for plasma Cu, where HIGH steers exhibited less dramatic increases in plasma Cu than ADE. Plasma Zn was affected by treatment × day (P < 0.01) where HIGH steers did not change over time and ADE exhibited decreased plasma Zn in response to disease, characteristic of a classical nutritional immunity response. Ferric reducing antioxidant power did not differ by treatment (P = 0.33); however, both treatments decreased on day 7 postinfection (P < 0.01), indicating increased antioxidant demands. In conclusion, these results suggest excessive liver Cu concentrations result in greater disease severity and immune dysfunction in beef-on-dairy steers.
肉牛与奶牛的杂交阉牛接触到更多的铜（Cu），这可能会影响它们对疾病的抵抗力。为了验证这一点，26头断奶的肉牛与奶牛杂交阉牛（95.2±7.2千克；约8周龄）按体重分栏，栏舍被随机分配到两种目标肝脏铜状态：充足（ADE）和高铜（HIGH）。为达到目标状态，在进入为期13天的牛呼吸道疾病挑战试验前120天，ADE组和HIGH组分别饲喂不含补充铜和含20毫克铜/千克日粮干物质的日粮。挑战试验前，ADE组和HIGH组肝脏铜含量平均分别为279毫克铜/千克肝脏干物质和608毫克铜/千克肝脏干物质。在第0天，通过气溶胶接种使阉牛感染104个半数组织培养感染剂量（TCID50）的牛呼吸道合胞病毒（BRSV）。在感染后第5天，给阉牛气管内接种5×108菌落形成单位（CFU）的溶血曼氏杆菌。一名经过培训的观察员在第0天至第14天对阉牛的抑郁、食欲和呼吸情况进行评分。在第0天、第5天、第7天、第10天和第13天，使用胸部超声根据肺实变程度和病变情况对动物进行评分，并采集颈静脉血。分别使用SAS 9.4（北卡罗来纳州卡里）的PROC GLIMMIX和PROC MIXED程序对分类变量（临床和肺部评分）和连续变量进行分析。临床评分受处理×天数的影响（P=0.04），与ADE组相比，HIGH组在疾病反应中临床评分的增加更为明显（P<0.01），并且在疾病挑战的剩余时间内一直较高（0.01<P≤0.08）。在整个挑战试验期间，HIGH组阉牛的肺实变程度往往比ADE组更大（P=0.08）。虽然在处理组之间未检测到触珠蛋白的差异（P=0.96），但在感染后第7天，两组的触珠蛋白均显著增加（P<0.01），表明对疾病产生了炎症反应。血浆铜存在处理×天数的交互作用趋势（P=0.07），其中HIGH组阉牛血浆铜的增加幅度不如ADE组显著。血浆锌受处理×天数的影响（P<0.01），HIGH组阉牛血浆锌随时间没有变化，而ADE组随着疾病的发展血浆锌降低，这是典型的营养免疫反应特征。铁还原抗氧化能力在处理组之间没有差异（P=0.33）；然而，在感染后第7天，两组均下降（P<0.01），表明抗氧化需求增加。总之，这些结果表明，肝脏铜浓度过高会导致肉牛与奶牛杂交阉牛的疾病严重程度增加和免疫功能障碍。
