Am J Vet Res. 2024 Jul 15;85(10). doi: 10.2460/ajvr.24.02.0035. Print 2024 Oct 1.
To develop an accessible ruminant immune challenge model for rapid in vivo assessments of feed additives.
60 hair-breed ram lambs.
Sheep were randomly assigned to 1 of 4 treatments: treatment 1, not immunosuppressed, control fed (n = 12); treatment 2, immunosuppressed, supplemented with a yeast and botanical extract (n = 18); treatment 3, immunosuppressed, supplemented with a blend of natural aluminosilicates and yeast components (n = 18); and treatment 4, immunosuppressed, control fed (n = 12). Twice-daily injections of dexamethasone (Dex; 0.1 mg/kg bodyweight, SC) were used to induce immunosuppression throughout the study (from September 25, 2020, to November 2, 2020). All sheep were immunized with keyhole limpet hemocyanin (KLH) on days 0 and 14 and injected with heat-aggregated KLH, ID, to induce a skin induration on day 15. Measurements included body weight (BW), average daily gain (ADG), CBC, and skin induration diameter.
Dex treatment resulted in reduced BW and ADG that was not mitigated by either feed additive. Dex reduced lymphocyte percentage, RBC count, hemoglobin, hematocrit, and skin induration diameter and increased concentrations of granulocytes and granulocyte percentage. Effects on hematocrit, hemoglobin, RBC, and skin induration diameter were mitigated with the addition of feed additives.
The described model is a tool to evaluate the ability of feed additives to mitigate the immunosuppressive effects of Dex.
开发一种易于操作的反刍动物免疫挑战模型，用于快速进行体内饲料添加剂评估。
60 只毛发品种公羊羔羊。
羊随机分为 4 种处理之一：处理 1，未免疫抑制，对照喂养（n=12）；处理 2，免疫抑制，补充酵母和植物提取物（n=18）；处理 3，免疫抑制，补充天然铝硅酸盐和酵母成分混合物（n=18）；处理 4，免疫抑制，对照喂养（n=12）。在整个研究过程中（从 2020 年 9 月 25 日至 2020 年 11 月 2 日），每天两次通过皮下注射地塞米松（Dex；0.1mg/kg 体重）以诱导免疫抑制。所有羊在第 0 天和第 14 天接受血蓝蛋白（KLH）免疫接种，并在第 15 天注射热凝聚 KLH，ID，以诱导皮肤硬结。测量包括体重（BW）、平均日增重（ADG）、CBC 和皮肤硬结直径。
Dex 处理导致 BW 和 ADG 降低，而这两种饲料添加剂均不能缓解。Dex 降低了淋巴细胞百分比、红细胞计数、血红蛋白、红细胞压积和皮肤硬结直径，并增加了粒细胞和粒细胞百分比。添加饲料添加剂可减轻对红细胞压积、血红蛋白、红细胞和皮肤硬结直径的影响。
所描述的模型是评估饲料添加剂减轻 Dex 免疫抑制作用的能力的工具。
