Department of Production Animal Health, University of Calgary Faculty of Veterinary Medicine, Calgary, Alberta, Canada.
Department of Animal Medicine, Division of Infectious Diseases, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
J Vet Intern Med. 2020 Jul;34(4):1662-1673. doi: 10.1111/jvim.15805. Epub 2020 May 28.
Brix refractometry can be used to assess colostral immunoglobulin G (IgG) concentration, but studies identifying Brix percentages to detect high- and low-IgG colostrum are lacking for beef cows and interlaboratory agreement is unknown.
Evaluate Brix refractometer performance and interlaboratory agreement for assessing beef cow colostrum IgG concentration, including determination of thresholds to identify colostrum containing IgG concentrations <100 g/L and ≥150 g/L.
Beef cows (n = 416) from 11 cow-calf operations in Alberta, Canada.
Colostral IgG concentrations were measured using radial immunodiffusion (RID) and estimated by Brix refractometry for this retrospective study. Spearman correlation coefficients were assessed between RID and Brix refractometry. Likelihood ratios and misclassification cost-term analysis were used to determine optimal Brix percentages for detecting colostrum containing IgG concentrations <100 g/L and ≥150 g/L. Concordance correlation coefficient (CCC) and Bland-Altman analyses were performed for Brix percentages obtained at 3 different laboratories.
Brix percentages obtained at 3 laboratories were positively correlated with IgG results (r = 0.72, 0.68, and 0.76, respectively). Colostrum Brix percentages of <24% and ≥30% were optimal for indicating IgG concentrations of <100 g/L and ≥150 g/L, respectively. Interlaboratory agreement was substantial, with CCC ranging from 0.89 to 0.96 and Bland-Altman analysis showing small mean differences (-1.2% to 0.09% Brix) and narrow limits of agreements (-4.8% to 2.4% Brix) among laboratories.
Brix refractometry shows good potential for reliably estimating IgG concentrations in beef cow colostrum across multiple laboratories and can be recommended to aid colostrum management decisions on farms.
Brix 折射计可用于评估初乳免疫球蛋白 G（IgG）浓度，但针对肉牛且缺乏确定高和低 IgG 初乳的 Brix 百分比的研究，其实验室间一致性也尚不清楚。
评估 Brix 折射计评估肉牛初乳 IgG 浓度的性能和实验室间一致性，包括确定识别 IgG 浓度<100 g/L 和≥150 g/L 的初乳的阈值。
来自加拿大艾伯塔省 11 个奶牛场的 416 头奶牛。
本回顾性研究使用放射免疫扩散（RID）测量初乳 IgG 浓度，并通过 Brix 折射计进行估计。评估 RID 和 Brix 折射计之间的 Spearman 相关系数。使用似然比和误分类成本项分析确定用于检测 IgG 浓度<100 g/L 和≥150 g/L 的最佳 Brix 百分比。在 3 个不同实验室获得的 Brix 百分比进行了一致性相关系数（CCC）和 Bland-Altman 分析。
3 个实验室获得的 Brix 百分比与 IgG 结果呈正相关（r = 0.72、0.68 和 0.76）。Brix 百分比<24%和≥30%分别为指示 IgG 浓度<100 g/L 和≥150 g/L 的最佳值。实验室间一致性较高，CCC 范围为 0.89 至 0.96，Bland-Altman 分析显示实验室间平均差异较小（-1.2%至 0.09%Brix）和协议界限较窄（-4.8%至 2.4%Brix）。
Brix 折射计在多个实验室中具有可靠估计肉牛初乳 IgG 浓度的良好潜力，可以推荐用于帮助农场进行初乳管理决策。
