Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad255.
Genetic selection for immune response has the potential to increase the sustainability of the beef industry by breeding cattle that are productive yet with an increased capacity to resist disease. Determining the optimal time to immunophenotype beef cattle is crucial for the accurate prediction of an animal's immune response. The objective of this study was to determine the effect of time of immunophenotyping in relation to weaning on immune responses of beef calves. Antibody- (AMIR) and cell-mediated (CMIR) immune responses were measured on 97 calves on the day of weaning (WEANING, N = 56) or 2 mo post-weaning (POST-WEANING, N = 41). Within each period of immunophenotyping, on day 0, blood was collected, and calves received a 1.0 mL intramuscular injection of type 1 and 2 test antigens. On day 14, blood was collected, and baseline skinfold thickness (SFT) was measured. Calves received an intradermal injection of 0.1 mg of the type 1 antigen suspended in 0.1 mL phosphate buffered saline (PBS) in the right tail fold, and 0.1 mL of PBS in the left. Changes in SFT at 24 h was used to indicate CMIR. To assess AMIR, the titer of type 2 antigen-specific bovine immunoglobulin G in serum from blood collected on day 14 was determined by measuring optical density (OD) using an enzyme-linked immunosorbent assay (ELISA). Among heifers, AMIR was greater for the POST-WEANING group than for the WEANING group (P < 0.01). Among steers, AMIR was not different between the POST-WEANING group and the WEANING group (P = 1.0). Therefore, the AMIR of heifers may be more negatively affected by immunophenotyping at weaning than the AMIR of steers. For steers, CMIR was greater in the POST-WEANING group than the WEANING group (P < 0.001). For heifers, CMIR was not different between the POST-WEANING group and the WEANING group (P = 0.22). The CMIR of steers may be more negatively affected by immunophenotyping at weaning than the CMIR of heifers. Calf age was not associated with AMIR or CMIR for calves phenotyped at weaning or post-weaning. The effect of sire nested within dam age was significant for CMIR for calves in the POST-WEANING group (P < 0.01), but not for calves in the WEANING group (P = 0.67). The results suggest that measuring immunocompetence at weaning may not be representative of a calf's genetic ability to mount an effective immune response, and immunophenotyping should be performed outside the weaning period.
遗传选择免疫反应有可能通过培育生产性能高但对疾病抵抗力增强的牛来提高牛肉行业的可持续性。确定免疫表型的最佳时间对于准确预测动物的免疫反应至关重要。本研究的目的是确定与断奶相关的免疫表型时间对肉牛犊免疫反应的影响。在断奶当天（断奶期，N=56）或断奶后 2 个月（断奶后期，N=41）对 97 头犊牛进行抗体（AMIR）和细胞介导（CMIR）免疫反应测量。在每个免疫表型期间的第 0 天，采集血液，犊牛接受 1.0 mL 肌肉内注射 1 型和 2 型测试抗原。第 14 天，采集血液并测量基线皮褶厚度（SFT）。在右侧尾褶处用 0.1 mL 磷酸盐缓冲盐水（PBS）悬浮的 0.1 mg 1 型抗原对犊牛进行皮内注射，在左侧注射 0.1 mL PBS。24 小时 SFT 的变化用于指示 CMIR。为了评估 AMIR，通过酶联免疫吸附试验（ELISA）测量从第 14 天采集的血液中 2 型抗原特异性牛免疫球蛋白 G 的效价来确定 AMIR。在小母牛中，断奶后期组的 AMIR 大于断奶组（P<0.01）。在公牛中，断奶后期组和断奶组之间的 AMIR 没有差异（P=1.0）。因此，与断奶后免疫表型相比，小母牛的 AMIR 可能受到更大的负面影响。对于公牛，断奶后期组的 CMIR 大于断奶组（P<0.001）。对于小母牛，断奶后期组和断奶组之间的 CMIR 没有差异（P=0.22）。与小母牛相比，断奶后免疫表型对公牛的 CMIR 可能有更大的负面影响。断奶或断奶后期进行免疫表型的犊牛的年龄与 AMIR 或 CMIR 无关。在断奶后期组，母羊年龄嵌套在公羊年龄内对 CMIR 的影响显著（P<0.01），但在断奶组中不显著（P=0.67）。结果表明，在断奶时测量免疫能力可能不能代表犊牛产生有效免疫反应的遗传能力，并且应在断奶期之外进行免疫表型分析。
