Department of Animal Sciences, College of Agriculture, 210 Upchurch Hall, Auburn University, Alabama, USA.
Theriogenology. 2012 Oct 15;78(7):1508-16. doi: 10.1016/j.theriogenology.2012.05.031.
The reproductive impact following controlled introduction of animals persistently infected (PI) with bovine viral diarrhea virus (BVDV) was evaluated in BVDV-naive heifers. Heifers were randomly allocated into two groups: an unexposed control herd (n = 34) and a herd exposed to five persistently infected (PI) animals for 7 mo, beginning 50 days before the breeding season (n = 34). Initiation of the BVDV-challenge was timed to mimic either direct contact with PI calves born in the previous calving season or accidental introduction of PI herd additions prior to the breeding season. The PI animals represented BVDV Types 1a (n = 3), 1b (n = 1) and 2 (n = 1). Two BVDV-free, seropositive bulls were used in each group for 78 days breeding seasons. In both groups, 33 of 34 heifers became pregnant, with similar distribution of fetal ages. Two heifers in each group aborted (etiology undetermined). In addition, one calf was born dead and one calf died 3 days post-partum in the BVDV-exposed group. One calf in the unexposed group died 4 mo post-partum. No calves, including the stillborn calf and the two calves that died prior to weaning, were persistently infected with BVDV. In summary, introduction of PI cattle to a group of BVDV-naive heifers 50 days prior to the breeding season did not negatively impact reproductive performance. To the contrary, the active immunity that developed following field exposure to BVDV provided effective reproductive and fetal protection during the breeding season and subsequent gestations, despite continuous exposure to PI animals until approximately midgestation. Although BVDV can have potentially devastating reproductive effects, timing of infection is a critical determinant in the outcome of a BVDV infection. A controlled breeding season with introduction of herd additions at less critical reproductive time points can mitigate the negative reproductive health consequences of BVDV.
将持续感染牛病毒性腹泻病毒（BVDV）的动物引入 BVDV 无感染牛群后对其繁殖性能的影响进行了评估。将牛群随机分为两组：未暴露组（n = 34）和暴露组（n = 34）。暴露组在配种季节前 50 天接触 5 头持续感染（PI）动物，持续 7 个月。启动 BVDV 挑战以模拟与上一季出生的 PI 犊牛直接接触或在配种季节前意外引入 PI 牛群添加物。PI 动物代表 BVDV 1a 型（n = 3）、1b 型（n = 1）和 2 型（n = 1）。每组使用 2 头 BVDV 阴性、血清阳性公牛进行 78 天的配种季节。两组中，34 头母牛中有 33 头怀孕，胎儿年龄分布相似。每组中有两头母牛流产（病因不明）。此外，暴露组中有一头犊牛出生时死亡，一头犊牛产后 3 天死亡。未暴露组中有一头犊牛产后 4 个月死亡。除死产犊牛和断奶前死亡的两头犊牛外，没有犊牛持续感染 BVDV。总之，在配种季节前 50 天将 PI 牛引入一组 BVDV 无感染牛群不会对繁殖性能产生负面影响。相反，在配种季节和随后的妊娠期间，通过现场接触 BVDV 产生的主动免疫为繁殖和胎儿提供了有效保护，尽管在妊娠中期之前持续接触 PI 动物。尽管 BVDV 可能对繁殖产生潜在的破坏性影响，但感染时间是 BVDV 感染结果的关键决定因素。在繁殖时间不太关键的情况下进行有控制的配种季节并引入牛群添加物，可以减轻 BVDV 对繁殖健康的负面影响。
