Butler J A, Sickles S A, Johanns C J, Rosenbusch R F
Veterinary Medical Research Institute, College of Veterinary Medicine, Iowa State University, Ames 50011, USA.
J Dairy Sci. 2000 Oct;83(10):2285-8. doi: 10.3168/jds.S0022-0302(00)75114-9.
Discard milk from sick or antibiotic-treated cows is often used as an economical alternative to milk replacer at dairy farms. This practice poses a health risk to calves if the discard milk is from cows with mycoplasma mastitis. Mycoplasma bovis, Mycoplasma californicum, and Mycoplasma canadense are among the agents known to cause contagious mastitis in cattle and occasionally pneumonia, otitis media, or arthritis in calves. This report describes a recent outbreak of calf polyarthritis and respiratory disease on a midwest dairy farm. The farm fed discard mycoplasma mastitic milk to its calves. On-the-farm pasteurization of the discard milk to 65 degrees C for 1 h before feeding prevented additional illness in the calves. Discard milk samples were collected before and after heating and tested for mycoplasma by culture. Only samples collected before pasteurization yielded live cultures. Common mastitic mycoplasma agents were also tested for sensitivity to heat. It was determined that 65 degrees C killed M. bovis and M. californicum after 2 min of exposure, while M. canadense remained viable for up to 10 min. Exposure to 70 degrees C inactivated M. bovis and M. californicum after 1 min, but M. canadense samples were positive for up to 3 min. Thus, M. canadense appears to be more heat resistant than M. bovis and M. californicum. Heat treatment that results in the destruction of M. canadense should be used for the pasteurization of discard mycoplasma mastitic milk.
患病或经抗生素治疗的奶牛所产的废弃奶，在奶牛场常被用作代乳品的一种经济替代品。如果废弃奶来自患有支原体乳腺炎的奶牛，这种做法会对犊牛构成健康风险。牛支原体、加利福尼亚支原体和加拿大支原体是已知可引起牛传染性乳腺炎的病原体，偶尔也会导致犊牛肺炎、中耳炎或关节炎。本报告描述了中西部一个奶牛场最近爆发的犊牛多关节炎和呼吸道疾病。该农场将患有支原体乳腺炎的奶牛的废弃奶喂给犊牛。在喂食前将废弃奶在农场进行巴氏杀菌，加热到65摄氏度并保持1小时，可防止犊牛出现更多疾病。在加热前后采集废弃奶样本，通过培养检测支原体。只有巴氏杀菌前采集的样本培养出了活的培养物。还对常见的乳腺炎支原体病原体进行了热敏感性测试。结果发现，暴露于65摄氏度2分钟后，牛支原体和加利福尼亚支原体被杀死，而加拿大支原体在长达10分钟内仍保持活力。暴露于70摄氏度1分钟后，牛支原体和加利福尼亚支原体失活，但加拿大支原体样本在3分钟内仍呈阳性。因此，加拿大支原体似乎比牛支原体和加利福尼亚支原体更耐热。对于患有支原体乳腺炎的奶牛的废弃奶进行巴氏杀菌时，应采用能杀死加拿大支原体的热处理方法。
