Yue Xiaomei, Wu Jingyi, van der Voort Mariska, Steeneveld Wilma, Hogeveen Henk
Business Economics Group, Department of Social Sciences, Wageningen University, Wageningen, Netherlands.
Department of Population Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Utrecht, Netherlands.
Front Vet Sci. 2022 Jul 7;9:892928. doi: 10.3389/fvets.2022.892928. eCollection 2022.
More and more European countries have implemented a bovine viral diarrhea virus (BVDV) control program. The economic effects of such programs have been evaluated in simulations, but empirical studies are lacking, especially in the final stage of the program. We investigated the economic (gross margin) and production effects (milk yield, somatic cell count, and calving interval) of the herds obtaining BVDV-free certification based on longitudinal annual accounting and herd performance data from Dutch dairy herds between 2014 and 2019, the final stages of the Dutch national BVDV-free program. This study was designed as a case-control study: two types of case herds were defined for two analyses. The case herds in the first analysis are herds where the BVDV status changed from "BVDV not free" to "BVDV free" during the study period. The not-free status refers to a herd that participated in the BVDV-free program but had not yet obtained the BVDV-free certification. In the second analysis, the case herds started participating in the Dutch BVDV-free program during the study period and obtained the BVDV-free certification. Control herds in both analyses were BVDV-free during the entire study period. Potential bias between the covariates of the two herd groups was reduced by matching case and control herds using the propensity score matching method. To compare the differences between case and control herds before and after BVDV-free certification, we used the time-varying Difference-in-Differences estimation (DID) methodology. The results indicate that there was no significant change in milk yield, somatic cell count, calving interval, and gross margin upon BVDV-free certification. There are several possible explanations for the non-significant effects observed in our study, such as the final stage of the BVDV control program, not knowing the true BVDV infection situation in case herds and not knowing if control measures were implemented in case herds prior to participating in the BVDV-free program. In our study, the effects of BVDV-free certification might have been underestimated, given that the Dutch BVDV control program became mandatory during the study period, and some of the case herds might have never experienced any BVDV infection. The results of this study suggest that in the final stage of the BVDV control program, the program may no longer have a clear benefit to the herd performance of participating dairy herds. When designing national programs to eradicate BVDV, it is therefore important to include incentives for such farms to motivate them to join the program.
越来越多的欧洲国家实施了牛病毒性腹泻病毒（BVDV）控制计划。此类计划的经济影响已在模拟中进行了评估，但缺乏实证研究，尤其是在该计划的最后阶段。我们基于2014年至2019年荷兰奶牛场的纵向年度会计和畜群性能数据，调查了获得BVDV无疫认证的畜群的经济（毛利润）和生产影响（产奶量、体细胞计数和产犊间隔），这是荷兰国家BVDV无疫计划的最后阶段。本研究设计为病例对照研究：为两项分析定义了两种类型的病例畜群。第一次分析中的病例畜群是在研究期间BVDV状态从“非BVDV无疫”变为“BVDV无疫”的畜群。非无疫状态是指参与BVDV无疫计划但尚未获得BVDV无疫认证的畜群。在第二次分析中，病例畜群在研究期间开始参与荷兰BVDV无疫计划并获得了BVDV无疫认证。两项分析中的对照畜群在整个研究期间均为BVDV无疫。通过使用倾向得分匹配方法匹配病例和对照畜群，减少了两个畜群组协变量之间的潜在偏差。为了比较病例畜群和对照畜群在获得BVDV无疫认证前后的差异，我们使用了随时间变化的差分估计（DID）方法。结果表明，获得BVDV无疫认证后，产奶量、体细胞计数、产犊间隔和毛利润没有显著变化。对于我们研究中观察到的无显著影响，有几种可能的解释，例如BVDV控制计划的最后阶段、不了解病例畜群中真正的BVDV感染情况以及不知道病例畜群在参与BVDV无疫计划之前是否实施了控制措施。在我们的研究中，BVDV无疫认证的影响可能被低估了，因为荷兰BVDV控制计划在研究期间成为强制性的，并且一些病例畜群可能从未经历过任何BVDV感染。本研究结果表明，在BVDV控制计划的最后阶段，该计划可能对参与的奶牛场的畜群性能不再有明显益处。因此在设计根除BVDV的国家计划时，重要的是要为这些农场提供激励措施，以促使它们加入该计划。
