Allen P C
U.S. Department of Agriculture, Livestock and Poultry Sciences Institute, Beltsville, Maryland 20705.
Avian Dis. 1992 Oct-Dec;36(4):852-7.
Virginiamycin (Stafac 20) was mixed with feed at three levels recommended for chickens--5.5, 11, and 22 mg/kg (respectively 5, 10 and 20 g/ton)--and fed to broiler chicks. When fed from 1 day through 2 weeks of age, the drug appeared to retard infection of the lower small intestine by long, segmented, filamentous organisms (LSFOs), and at 2 weeks of age serum carotenoids in treated chicks were significantly higher than levels found in unmedicated chicks. However, as chicks were grown out to 4 and 6 weeks of age, the drug did not completely prevent eventual LSFO infection, even at the highest dose, and mean serum carotenoid levels in treated chicks were not significantly different from levels in control chicks. However, chicks fed at the level of 22 mg/kg had fewer LSFOs. Withdrawal of virginiamycin from treated chicks at 4 weeks of age allowed LSFO infection to occur but did not significantly affect serum carotenoid levels. When the drug was fed for 2 weeks at 22 mg/kg to 2-week-old chicks already infected with LSFOs, the bacteria could no longer be detected, suggesting that virginiamycin may aid the natural decline in LSFO population. Coincident with this treatment, serum carotenoids were higher, but not significantly so. Virginiamycin did not significantly increase the mean body weights of chicks in any of these experiments.
维吉尼亚霉素（Stafac 20）以推荐给鸡的三个剂量水平与饲料混合——5.5、11和22毫克/千克（分别为5、10和20克/吨）——并喂给肉仔鸡。从1日龄到2周龄饲喂时，该药物似乎能抑制长的、分段的丝状生物（LSFOs）对小肠下段的感染，并且在2周龄时，经处理的雏鸡血清类胡萝卜素水平显著高于未用药雏鸡。然而，随着雏鸡生长到4周龄和6周龄，即使在最高剂量下，该药物也不能完全预防最终的LSFO感染，并且经处理的雏鸡血清类胡萝卜素平均水平与对照雏鸡的水平没有显著差异。然而，以22毫克/千克水平饲喂的雏鸡LSFOs较少。在4周龄时从经处理的雏鸡中撤掉维吉尼亚霉素会使LSFO感染发生，但对血清类胡萝卜素水平没有显著影响。当以22毫克/千克的剂量将该药物喂给已经感染LSFOs的2周龄雏鸡2周时，细菌不再被检测到，这表明维吉尼亚霉素可能有助于LSFO数量的自然下降。与此处理同时，血清类胡萝卜素较高，但差异不显著。在任何这些实验中，维吉尼亚霉素都没有显著增加雏鸡的平均体重。
