Effects of ionophore antibiotics on rumen fermentation

用盐霉素（SL）、莫能菌素（MN）和波特霉素（PT）等离子载体抗生素进行了各种实验。得到的主要结果如下：1。添加SL降低了以CO_2和CH_4为主的体外发酵产气量，并短暂提高了绵羊瘤胃液中H_2的产量，而添加适应SL的动物瘤胃液中H_2的产量没有短暂增加。2. 在生长犊牛和阉牛的精料中添加SL、MN或PT均可提高饲料需求，同时瘤胃发酵中丙酸氮和氨基氮含量增加，乙酸、丁酸和氨含量减少。3. 瘤胃发酵的这些变化与淀粉、乳酸和蛋白质可利用菌以及原生动物数量的变化一致。4. 电离层的作用经常波动，可能是由于耐药微生物种群的发展。在补充离子载体之前、期间和之后，绵羊瘤胃原虫的变化表明了这一点。5. 离子载体抑制瘤胃微生物增殖，但对饲料消化率无明显影响。

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.