Abstract: This study aimed to investigate the effects of adding different concentrations of phenyl lactic acid (PLA) at various temperatures on the fermentation quality,abundance changes of antibiotic resistance genes (ARGs),and mobile genetic elements (MGEs) of corn (Zea mays L.) straw silage. A two-factor completely randomized design was employed,with PLA concentration and temperature as the factors. The experimental groups included a control group (CK) and addition groups (0.2%PLA and 0.4%PLA) at temperatures of 20℃ and 30℃. After 30 days,samples were collected for analysis of silage quality. The results revealed that the addition of PLA significantly increased the pH value and the quantity of lactic acid bacteria at both temperatures (P＜0.05). At a storage temperature of 20℃,there was a significant increase in acetic acid content (P＜0.05),while ammonia nitrogen content decreased. Moreover,the number of lactic acid bacteria and butyric acid content were significantly higher at 20℃ compared to 30℃ (P＜0.05). The detected ARGs in this experiment belonged to the macrolide,sulfonamide,and tetracycline classes of resistance genes. After 30 days of fermentation with PLA addition,the absolute abundances of these ARGs and MGEs significantly decreased (P＜0.05). Among them,sul1,sul2,sul3,ermB, tetC,and Tn916/1545 exhibited similar trends in abundance changes,and Pearson correlation analysis revealed a highly significant positive correlation between them (P＜0.01).In conclusion,the addition of PLA to corn straw silage improved the fermentation quality and reduced pollution from ARGs under both temperature conditions.

Key words: Corn straw, Antibiotic resistance genes, Phenyllactic acid, Temperature, Silage

摘要： 本研究旨在探究不同温度下添加不同浓度苯乳酸(Phenyl lactic acid，PLA)对玉米(Zea mays L.)秸秆青贮饲料发酵品质、抗生素抗性基因(Antibiotic resistance genes，ARGs)和可移动遗传元件(Mobile genetic genes，MGEs)丰度变化的影响。采用双因素(苯乳酸×温度)完全随机设计，温度设定20℃和30℃，苯乳酸设置添加组(0.2% PLA和0.4% PLA)和对照组(CK)，30 d后取样分析青贮品质。结果显示，与对照组相比，随着PLA浓度增加，两种温度下的pH值、乳酸菌数量和乙酸含量均显著增加(P＜0.05)。酵母菌数量随着PLA浓度增加而增加，而乳酸和氨态氮含量随之下降。与20℃相比，30℃条件下自然青贮的玉米秸秆饲料pH值显著增加，乳酸菌数量显著下降(P＜0.05)。本试验所检测的ARGs属于大环内脂类、磺胺类和四环素类抗性基因，添加PLA发酵30 d后，与对照组相比，这些ARGs和MGEs绝对丰度均显著下降(P＜0.05)，其中sul1，sul2，sul3，ermB，tetC与Tn916/1545丰度变化趋势相似，Pearson相关性分析发现两者之间具有极显著正相关关系(P＜0.01)。综上，两种温度条件下，添加PLA对玉米秸秆青贮发酵品质均具有改善作用，可以减少ARGs的污染。

关键词: 玉米秸秆, 抗生素抗性基因, 苯乳酸, 温度, 青贮