Indirect quantification of IgG using a digital refractometer, and factors associated with colostrum quality in Norwegian Red Cattle
Indirect quantification of IgG using a digital refractometer, and factors associated with colostrum quality in Norwegian Red Cattle
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DOI：
10.1186/s13028-019-0494-9
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发表时间：
2019-12-05
影响因子：
2.1
通讯作者：
Holmoy, Ingrid Hunter
中科院分区：
文献类型：
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作者：
Johnsen, Julie Foske;Sorby, Johanne;Holmoy, Ingrid Hunter
背景：人们对使用数字折光仪间接评估奶牛初乳质量的兴趣越来越大，但对挪威红奶牛的诊断准确性缺乏了解。最近的研究表明，挪威奶牛和奶牛群的初乳质量有很大的差异。本研究的目的是评价数字折光仪（Brix折光仪）在Brix%的不同截止值下检测金标准单径向免疫扩散（IgG g/L）定义的高质量（> 50 g/L）初乳的诊断试验灵敏度和特异性。此外，我们旨在确定选定的牛群和奶牛水平管理因素与挪威红奶牛初乳igg水平之间可能存在的关联。结果：19个畜群167头奶牛初乳IgG水平中位数为35.0 g/L，范围为5 ~ 129 g/L。平均Brix% （+/- SD）为19.7 +/- 4.12%，范围为10.1 ~ 30.5。大多数样品（72.5%）的质量低于50 g/L的国际标准。初乳Brix%与IgG呈极显著相关（r = 0.71, P < 0.001）。目前推荐的Brix截止值为22%，对于鉴别高质量（> 50 g/L）的初乳，灵敏度（95% CI）为69.4%(54.6-81.7)，特异性为83.1%（75.0-89.3）。发现与低初乳质量有关的唯一因素是胎次。具体来说，与四胎及以后胎次的奶牛相比，第二胎次的奶牛生产的初乳质量较低。结论：初乳IgG与Brix%吻合较好。然而，诊断测试评估表明，在识别高和低初乳质量方面，这一人群的表现不理想，可能与IgG < 50 g/L的样品比例高有关。发现与低初乳质量有关的唯一因素是胎次。具体来说，第二胎的奶牛生产的初乳质量较低。未来的研究应调查初乳和血清IgG水平，以最好地预防小牛疾病在挪威条件下。
Background: There is an increased interest in using digital refractometers to indirectly assess colostrum quality of dairy cattle, but knowledge on diagnostic accuracy for Norwegian Red dairy cows is lacking. Recent research has indicated a profound variability in the colostrum quality among dairy cows and herds in Norway. The aim of this study was to evaluate the diagnostic test sensitivity and specificity of a digital refractometer (Brix refractometer) at different cut-offs in Brix% for detection of colostrum of high quality (> 50 g/L) defined by the gold standard single radial immunodiffusion (IgG g/L). Furthermore, we aimed to identify possible associations between selected herd and cow-level management factors and colostrum IgG-levels in Norwegian Red dairy cows.Results: Median colostrum IgG level across 167 cows from 19 herds was 35.0 g/L, ranging from 5 to 129 g/L. Mean Brix% (+/- SD) was 19.7 +/- 4.12%, ranging from 10.1 to 30.5. Most samples (72.5%) had inferior quality as compared to the international standard of 50 g/L. Brix% and IgG in colostrum were strongly correlated (r = 0.71, P < 0.001). A Brix cut-off of 22%, which is currently recommended, yielded a sensitivity of (95% CI) 69.4% (54.6-81.7) and a specificity of 83.1% (75.0-89.3) for identifying colostrum with high quality (> 50 g/L). The only factor found to be associated with low colostrum quality was parity. Specifically, cows in the second parity were found to produce colostrum with low quality compared to cows in parities four and later.Conclusions: The agreement between colostrum IgG and Brix% is good. However, the diagnostic test evaluation indicates suboptimal performance in identifying high vs. low colostrum quality in this population, possibly related to a high proportion of the samples with < 50 g/L IgG. The only factor found to be associated with low colostrum quality was parity. Specifically, cows in the second parity were found to produce colostrum with lower quality. Future research should investigate colostrum and serum IgG levels which best prevent calf illness under Norwegian conditions.