The objective of this study was to estimate the prevalence of failure of passive transfer of immunity (FPTI) in dairy calves in the south-west region of Western Australia herds. A cross-sectional study was conducted in 26/140 dairy farms and serum samples were collected from 495 healthy 2–7 day-old calves. A radial immunodiffusion (RID) test was used to determine the concentration of serum IgG and calves were classified as having FPTI if the IgG concentration was less than 10 mg/mL. Estimation of FPTI was also assessed using two indirect methods using serum total protein (STP) and a brix refractometer. The estimated prevalence of FPTI was found to be 8.7% (43 calves out of 495) by RID with the concentration of IgG ranging between 0 and 6.2 mg/ml. The STP was found to vary from 46 to 96 mg/mL and using a cut-off point of 55 mg/mL the calf level prevalence was estimated as 7.1% (33 calves). Using the brix refractometer, the prevalence was found to be 13.1% (65 calves) with the refractometer reading ranging 6–14% of IgG. In the present study there was no association between calf-level factors (age, sex and breed) and FPTI. There was a higher correlation of the RID test results and the STP results compared to the RID and brix refractometer results. It is concluded that the prevalence of FPTI in dairy calves in the south-west region of Western Australia is low (8.7%) and the brix refractometer is not a reliable indirect method for determining passive transfer of immunity to calves.

本研究的目的是估计西澳大利亚牛群西南地区奶牛犊被动免疫转移 (FPTI) 失败的发生率。在 26/140 的奶牛场进行了一项横断面研究，并从 495 头 2-7 日龄的健康小牛中收集了血清样本。使用径向免疫扩散 (RID) 测试来确定血清 IgG 的浓度，如果 IgG 浓度低于 10 mg/mL，则将小牛归类为 FPTI。还使用血清总蛋白 (STP) 和白利糖度折光仪使用两种间接方法对 FPTI 的估计进行了评估。通过 RID 发现 FPTI 的估计患病率为 8.7%（495 头小牛中的 43 头），IgG 的浓度范围在 0 和 6.2 毫克/毫升之间。发现 STP 从 46 到 96 毫克/毫升不等，使用 55 毫克/毫升的分界点，小牛水平流行率估计为 7.1%（33 头小牛）。使用白利糖度折射计，发现流行率为 13.1%（65 头小牛），折射计读数范围为 IgG 的 6-14%。在本研究中，犊牛水平因素（年龄、性别和品种）与 FPTI 之间没有关联。与 RID 和白利糖度折光仪结果相比，RID 测试结果和 STP 结果之间的相关性更高。得出的结论是，西澳大利亚西南地区奶牛犊的 FPTI 流行率较低（8.7%），并且白利糖度折光仪不是确定免疫被动转移到犊牛的可靠间接方法。1%（65 头小牛），折射计读数范围为 IgG 的 6-14%。在本研究中，犊牛水平因素（年龄、性别和品种）与 FPTI 之间没有关联。与 RID 和白利糖度折光仪结果相比，RID 测试结果和 STP 结果之间的相关性更高。得出的结论是，西澳大利亚西南地区奶牛犊的 FPTI 流行率较低（8.7%），并且白利糖度折光仪不是确定免疫被动转移到犊牛的可靠间接方法。1%（65 头小牛），折射计读数范围为 IgG 的 6-14%。在本研究中，犊牛水平因素（年龄、性别和品种）与 FPTI 之间没有关联。与 RID 和白利糖度折光仪结果相比，RID 测试结果和 STP 结果之间的相关性更高。得出的结论是，西澳大利亚西南地区奶牛犊的 FPTI 流行率较低（8.7%），并且白利糖度折光仪不是确定免疫被动转移到犊牛的可靠间接方法。