Beaudeau François, Belliard Maud, Joly Alain, Seegers Henri
Unit of Animal Health Management, Veterinary School-INRA, BP 40706, 44307 Nantes Cedex 03, France.
Vet Res. 2007 Jul-Aug;38(4):625-34. doi: 10.1051/vetres:2007021. Epub 2007 Jun 13.
To assess the profitability of control schemes for Mycobacterium avium subspecies paratuberculosis (Map)-infection implemented in dairy herds, accurate estimates of its production effects are needed. This study aimed at quantifying the variation in milk yield of dairy cows according to their Map-infection status. The cow-status was determined by combining (i) its testing(s)-result(s) (serum ELISA, faecal culture (FC), PCR, Ziehl staining), (ii) the Map-status of its herd, and (iii) its possible vaccination against Map. A total of 15 490 cows in 569 herds located in western France was considered. The effect on test-day milk yield (TDMY) of the cow-status to Map was assessed separately in parity 1, 2 and 3 or more, using mixed linear models, after adjustment for herd-season (random), days in milk and breed. Average TDMY was significantly lower in cows from herds with at least one Map-infected cow (defined as positive herds). Individual TDMY showed a reduction ranging from 1.58 to 3.30, 2.03 to 2.51, 5.36 to 7.20 kg/day (P < 0.001) depending on parity for unvaccinated cows and testing ELISA-positive, PCR- or FC-positive, and Ziehl-positive, respectively, compared to cows in Map-free herds. The loss in milk yield increased with increased parity in ELISA-positive and Ziehl-positive cows. Cows that were both tested ELISA-positive and vaccinated had a smaller loss in TDMY than those that were unvaccinated. The estimates from this study can be used to further assess the economic impact associated with Map-infection in dairy herds or to help in the culling decisions regarding infected cows.
为评估奶牛群中实施的副结核分枝杆菌（Map）感染控制方案的盈利能力，需要准确估计其生产效应。本研究旨在量化奶牛根据其Map感染状况的产奶量变化。通过结合（i）其检测结果（血清ELISA、粪便培养（FC）、PCR、齐-尼氏染色）、（ii）其所在牛群的Map感染状况以及（iii）其可能的Map疫苗接种情况来确定奶牛状态。共考虑了法国西部569个牛群中的15490头奶牛。在调整牛群季节（随机因素）、泌乳天数和品种后，使用混合线性模型分别评估第1胎、第2胎和第3胎及以上胎次中奶牛状态对Map的检测日产奶量（TDMY）的影响。来自至少有一头Map感染奶牛的牛群（定义为阳性牛群）中的奶牛，其平均TDMY显著较低。与无Map感染牛群中的奶牛相比，未接种疫苗且ELISA检测呈阳性、PCR或FC检测呈阳性以及齐-尼氏染色呈阳性的奶牛，其个体TDMY分别减少1.58至3.30、2.03至2.51、5.36至7.20千克/天（P < 0.001），具体取决于胎次。ELISA检测呈阳性和齐-尼氏染色呈阳性的奶牛，其产奶量损失随着胎次增加而增加。ELISA检测呈阳性且接种了疫苗的奶牛，其TDMY损失比未接种疫苗的奶牛小。本研究的估计结果可用于进一步评估与奶牛群中Map感染相关的经济影响，或帮助做出关于感染奶牛的淘汰决策。
