Department of Diagnostic Medicine and Pathobiology, Kansas State University, 1600 Denison Avenue, Manhattan, KS 66502, USA.
Vet Rec. 2011 Jan 8;168(1):21. doi: 10.1136/vr.c5965. Epub 2010 Dec 17.
A longitudinal cross-sectional time-series study was carried out to determine the prevalence of nasal mycoplasma carriage, serostatus and seroconversion, and to evaluate the associations between these parameters and health and performance in weaned beef calves during a 42-day feeding period. Nasal swabs and serum were collected on days 0 (arrival), 10, 42 and at the first incidence of bovine respiratory disease complex. The samples were evaluated for Mollicutes (by culture), Mycoplasma bovis (by PCR) and serum antibody to M. bovis. On day 0, 90.4 per cent of the calves were Mollicutes nasal culture-positive. The seroprevalence of M. bovis was 26.6 per cent on day 0 and 98.2 per cent by day 42 (P<0.05). Seroconversion to M. bovis between days 0 and 42 was significantly associated (P=0.04) with lower weight gain. Weight gain was greater in calves that were PCR-negative for M. bovis on day 10 (P=0.01). The percentage of calves seropositive to M. bovis increased throughout the study, indicating exposure and an immunological response to the organism. Although associations with health outcomes were not identified, seroconversion to M. bovis was associated with a decreased rate of weight gain during the study period.
一项纵向的、横断面的时间序列研究旨在确定鼻腔支原体携带率、血清学状态和血清学转换率，并评估这些参数与断奶肉牛在 42 天饲养期间的健康和性能之间的关系。在 0 天（到达）、10 天、42 天和牛呼吸道疾病复合体首次发生时采集鼻腔拭子和血清。对样品进行密螺旋体（通过培养）、牛支原体（通过 PCR）和血清抗体牛支原体评估。在 0 天，90.4%的犊牛鼻腔培养呈密螺旋体阳性。M. bovis 的血清阳性率在第 0 天为 26.6%，第 42 天为 98.2%（P<0.05）。在第 0 天和第 42 天之间发生 M. bovis 血清学转换与较低的体重增加显著相关（P=0.04）。在第 10 天 M. bovis PCR 检测为阴性的犊牛体重增加更大（P=0.01）。在整个研究过程中，牛支原体血清阳性率增加，表明暴露于该病原体并产生免疫反应。尽管与健康结果没有关联，但 M. bovis 血清学转换与研究期间体重增加率下降有关。
