Effects of ionophore antibiotics on rumen fermentation

用离子载体抗生素如盐霉素(SL)、莫能菌素(MN)和门霉素(PT)进行了各种实验。主要研究结果如下：1.在绵羊瘤胃液的体外发酵中，添加SL降低了以CO_2和CH_4为主的产气量，瞬时增加了H_2的产生量，但对适应SL的动物瘤胃液的H_2产生量没有一过性的增加。2.在生长犊牛精料中添加SL、MN或PT均可提高饲料需要量，瘤胃发酵过程中丙酸态氮和氨基态氮含量增加，醋酸盐、丁酸盐和氨含量降低。3.瘤胃发酵的这些变化与利用淀粉、乳酸盐和蛋白质的细菌数量以及原生动物数量的变化是一致的。4.离子载体的作用常常起伏不定，可能是由于耐药微生物种群的发展所致。这从绵羊瘤胃中添加离子载体前后瘤胃原虫的变化可以看出这一点。5.离子载体对瘤胃微生物增殖有抑制作用，但对饲料消化率影响不大。

Various experiments were conducted with ionophore antibiotics such as salinomycin(SL), monensin(MN) and portomycin(PT). The principal results obtained are as follows: 1. Addition of SL reduced gas production consisting mainly of CO_2 and CH_4, and transiently increased H_2 production in in vitro fermentation with sheep rumen fluid, but with rumen fluid from animals adapted to SL there were no transient increases in H_2 production. 2. Addition of either SL, MN or PT to concentrate feeds for growing calves and steers improved feed requirement, with concomitant changes in rumen fermentation towards more propionate and -amino nitrogen, and less acetate, butyrate and ammonia. 3. These alterations in rumen fermentation were in good agreement with those in numbers of starch-, lactateand protein-utilizable bacteria and of protozoa. 4. Effects of ionophore often fluctuated, presumably due to the development of resistant microbial population. This was shown by variations of rumen protozoa before, during and after ionophore supplement in sheep rumen. 5. Ionophore depressed microbial proliferation in the rumen, but did not affect digestibility of feeds appreciably.