Abstract

There are few published data on the accurate on-farm diagnosis of failure of transfer of passive immunity (FTPI) in beef–suckler calves. This observational study aimed to evaluate the diagnostic performance and differences among four types of refractometers for assessing FTPI in Chianina beef–suckler calves. Blood samples were collected from 85 Chianina calves aged 2–7 days. The serum immunoglobulin G (IgG) concentration was measured using radial immunodiffusion (RID), digital and optical serum total protein (STP) refractometers, and digital and optical serum refractometers. The diagnostic performance of the refractometers was determined based on the serum IgG threshold of 16 g/L (measured by RID). A receiver operating characteristic (ROC) curve was used to identify the optimal cutoff values for all refractometers. The RID IgG concentration was positively correlated with all four refractometers (correlation coefficient: 0.75–0.84). ROC analysis yielded optimal cutoff values for predicting FTPI of 51 g/L (sensitivity (Se)=0.63 and specificity (Sp)=0.96) and 52 g/L (Se = 0.69 and Sp = 0.90) for the digital and optical STP refractometers, respectively. At the threshold of 8.3% Brix, the Se and Sp were 0.66 and 0.92 for the optical Brix and 0.77 and 0.92 for the digital Brix refractometer, respectively. All four refractometers were useful for assessing FTPI in Chianina calves. However, the digital Brix had the highest combined diagnostic accuracy for FTPI. The on-farm use of refractometers to assess FTPI can become part of routine monitoring of the colostrum management program in beef–suckler calf herds.

• Highlights

• The cutoff values were 51 and 52 g/L for the digital and optical serum total protein refractometers, respectively.

• The digital Brix refractometer was the most accurate for the detection of calves with inadequate transfer of passive immunity.

摘要

关于牛-牛犊牛的被动免疫（FTPI）转移失败的准确农场诊断，很少有公开的数据。这项观察性研究旨在评估四种类型的折光仪的诊断性能和差异，以评估基安纳纳牛-牛犊牛的FTPI。从2-7天龄的85株Chianina小牛收集血液样本。使用放射免疫扩散（RID），数字和光学血清总蛋白（STP）折光仪以及数字和光学血清折光仪测量血清免疫球蛋白G（IgG）的浓度。折光仪的诊断性能是根据16 g / L的血清IgG阈值（通过RID测量）确定的。接收器工作特性（ROC）曲线用于确定所有折光仪的最佳截止值。RID IgG浓度与所有四个折光仪呈正相关（相关系数：0.75–0.84）。ROC分析得出用于数字和光学STP折光仪的FTPI预测为51 g / L（灵敏度（Se）= 0.63和特异性（Sp）= 0.96）和52 g / L（Se = 0.69和Sp = 0.90）的最优临界值， 分别。在白利糖度为8.3％的阈值下，光学白利糖度的Se和Sp分别为0.66和0.92，数字白利糖度折射计的Se和Sp分别为0.77和0.92。所有四个折光仪都可用于评估基阿尼纳犊牛的FTPI。但是，数字白利糖度对FTPI的综合诊断准确性最高。在场上使用折光仪评估FTPI可能成为例行的牛乳母牛初乳管理计划的一部分。

• 强调

• 数字和光学血清总蛋白折光仪的截断值分别为51和52 g / L。

• 数字式Brix折光仪对于被动免疫传递不足的小牛的检测最为准确。