Henningsen Maj Beldring, Denwood Matt, Kirkeby Carsten Thure, Nielsen Søren Saxmose
Animal Welfare and Disease Control, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 1870 Frederiksberg, Denmark.
Animals (Basel). 2023 Aug 4;13(15):2523. doi: 10.3390/ani13152523.
In Denmark, PCR testing of dairy cattle is commonly used to select animals for the antibacterial treatment of intramammary infection (IMI) during the dry-off period. IMI is associated with a high somatic cell count (SCC), routinely recorded for milk quality control for most commercial dairy herds. This study aimed to compare SCC curves over the lactation among dairy cows with positive vs. negative PCR test results for four major IMI pathogens. Data from 133,877 PCR-tested Holstein cows from 1364 Danish conventional dairy herds were used to fit a nonlinear mixed-effects model using a modified four-parameter Wilmink function. We stratified the data into first, second, third or fourth and later parity and fitted Wilmink curves to all SCC observations between 6 and 305 days in milk. The PCR tests were taken before dry-off at the end of the lactation to investigate which animals qualified for selective dry cow therapy. A PCR Ct-value of 37 and below was used to determine if an animal was PCR positive for any of the following IMI pathogens: , , and . Our findings showed that mean SCC curve fits were higher for PCR-positive animals in all four parity groups and across lactations. The use of SCC data fitted to the entire lactation for multiple lactations enabled quantification of overall differences in SCC curves between cattle with and without detected IMI, adjusted for parity group and stage of lactation. These findings are relevant to the use of SCC to support treatment decisions.
在丹麦，奶牛的聚合酶链式反应（PCR）检测通常用于在干奶期选择接受乳房内感染（IMI）抗菌治疗的动物。IMI与高体细胞计数（SCC）相关，大多数商业奶牛场常规记录SCC以进行牛奶质量控制。本研究旨在比较四种主要IMI病原体PCR检测结果为阳性和阴性的奶牛在整个泌乳期的SCC曲线。来自丹麦1364个传统奶牛场的133877头接受PCR检测的荷斯坦奶牛的数据被用于使用修正的四参数威尔明克函数拟合非线性混合效应模型。我们将数据分为头胎、二胎、三胎或四胎及以后胎次，并对产奶6至305天之间的所有SCC观测值拟合威尔明克曲线。在泌乳期末干奶前进行PCR检测，以调查哪些动物有资格接受选择性干奶牛治疗。PCR Ct值为37及以下用于确定动物是否对以下任何一种IMI病原体呈PCR阳性： 、 、 和 。我们的研究结果表明，在所有四个胎次组和整个泌乳期，PCR阳性动物的平均SCC曲线拟合值更高。使用适用于多个泌乳期整个泌乳期的SCC数据能够量化检测到IMI和未检测到IMI的奶牛之间SCC曲线的总体差异，并根据胎次组和泌乳阶段进行调整。这些发现与使用SCC来支持治疗决策相关。
