Bartlett J R, Smith M O
Department of Animal Science, The University of Tennessee, Knoxville, Tennessee 37996-4500, USA.
Poult Sci. 2003 Oct;82(10):1580-8. doi: 10.1093/ps/82.10.1580.
Male broilers were used to evaluate the effect of zinc on performance and immune competence during heat stress (HS). Broilers raised in either a thermoneutral (TN, 23.9 degrees C constant) or HS (23.9 to 35 degrees C cycling) environment were fed a low zinc diet (LZ; 34 mg/kg), an adequate zinc diet (AZ; 68 mg/kg), or a supplemental zinc diet (HZ; 181 mg/kg). Humoral immunity was assessed by intravenous injection of 7% SRBC followed by evaluation of serum for antibody titers in primary and secondary responses. Cell-mediated immunity was assessed using a Sephadex stimulation method to recruit abdominal exudate cells (AEC) to evaluate macrophage phagocytic ability. The HS birds consumed 12.5% less feed, gained 24.6% less weight, and had lower feed efficiency when compared to TN birds. Dietary zinc levels did not impact growth performance or plasma zinc concentration. Numbers of AEC, macrophages in AEC, phagocytic macrophages, and internalized opsonized and unopsonized SRBC were increased by HZ. Total, IgM, and IgG antibody titers for primary and secondary responses were significantly increased in birds receiving HZ under TN conditions. Tibia zinc concentration increased with increasing zinc levels but did not change with temperature. Lymphoid organ weights, primary and secondary antibody responses, incidences of macrophages in AEC, phagocytic ability of macrophages, and plasma zinc concentration were all significantly reduced by HS. These results indicate that the immune response of broilers can be influenced by the level of zinc in the diet and by environmental conditions.
雄性肉鸡被用于评估锌对热应激（HS）期间生长性能和免疫能力的影响。在热中性（TN，23.9℃恒温）或热应激（23.9至35℃循环）环境中饲养的肉鸡，分别饲喂低锌日粮（LZ；34毫克/千克）、适宜锌日粮（AZ；68毫克/千克）或高锌日粮（HZ；181毫克/千克）。通过静脉注射7%的绵羊红细胞（SRBC）评估体液免疫，随后在初次和二次应答中检测血清抗体滴度。采用葡聚糖凝胶刺激法评估细胞介导免疫，收集腹腔渗出细胞（AEC）以评估巨噬细胞吞噬能力。与TN组肉鸡相比，HS组肉鸡采食量减少12.5%，体重增加量减少24.6%，饲料效率更低。日粮锌水平对生长性能或血浆锌浓度没有影响。HZ组肉鸡的AEC数量、AEC中的巨噬细胞数量、吞噬性巨噬细胞数量以及内化调理和未调理SRBC的数量均增加。在TN条件下，接受HZ的肉鸡初次和二次应答的总抗体、IgM和IgG抗体滴度均显著增加。胫骨锌浓度随锌水平的升高而增加，但不受温度影响。HS显著降低了淋巴器官重量、初次和二次抗体应答、AEC中巨噬细胞的发生率、巨噬细胞的吞噬能力以及血浆锌浓度。这些结果表明，肉鸡的免疫反应会受到日粮锌水平和环境条件的影响。
