Hematological and immunological development from birth to six months of age in Holstein calves

ABSTRACT The hematological and immunological development of calves from birth to 6 months of age was performed by hemogram and cellular phenotype. Ten male Holstein calves were assessed in 13 moments: before colostrum intake (D0), every 2 days until the 10th day of life (D2 to D10), at the 15th day after birth (D15), and then monthly up to 6 months (D180). Calves presented hemoconcentration on day (D) 0 and showed a gradual decrease in hematimetric rates until D180. The inversion of the neutrophilic for lymphocytic profile was observed on D4. The percentage of CD3+ cells on D10 was higher than D30 up to D180. The number of CD4+ and CD8+ cells did not change between time points. The number of CD21+ lymphocytes was significantly higher at early time points of D0 up to D15, compared on D30 until D150. In conclusion, the neonatal period was marked by stress leukogram in the first 4 days, and low number of B lymphocytes. These might be risk factors for bacterial infections responsible for navel inflammation and diarrhea. The increase in the number of B cells from 30 days of age demonstrated that the calves were functional and able to generate an immune response.摘要 本研究采用血常规（hemogram）检测与细胞表型（cellular phenotype）分析方法，探究了犊牛从出生至6月龄的血液学与免疫学发育规律。研究纳入10头雄性荷斯坦犊牛，共设置13个采样时间点：初乳（colostrum）摄入前（D0）、出生后前10天每2天采样1次（D2至D10）、出生后第15天（D15），之后每月采样1次直至6月龄（D180）。检测结果显示，犊牛在D0时出现血液浓缩现象，血液学指标呈逐步下降趋势直至D180；在D4时观察到中性粒细胞与淋巴细胞谱的倒置现象。D10时的CD3阳性细胞（CD3+）比例高于D30至D180的所有采样时间点。CD4阳性细胞（CD4+）与CD8阳性细胞（CD8+）的数量在各采样时间点间无显著变化。相较于D30至D150的采样时间点，D0至D15的早期采样点中CD21阳性淋巴细胞（CD21+）数量显著更高。综上，新生期前4天呈现应激性白细胞象，且B淋巴细胞数量较低，这可能是引发脐炎与腹泻的细菌性感染的潜在风险因素。从30日龄起B细胞数量的上升表明，犊牛免疫系统已具备功能，能够产生免疫应答。