ABSTRACT The present study was conducted to investigate the effects of two plant extracts as alternatives to dietary antibiotics in broiler chickens exposed to low ambient temperature. A total of 300 one-day-old male broiler chickens were randomly assigned to four dietary treatments (5 replicate pens; 15 broiler chickens each) which consisted of starter (d 0 to 10), and grower (d 10 to 28) diets. Dietary treatments included a basal diet (negative control, NC) and three similar diets that were either supplemented with 200 mg/kg of Prosopis farcta extract (PFE), Rhus coriaria L. extract (RCE) or an antibiotic premix containing oxytetracycline (positive control, PC). In order to simulate low ambient temperature, room temperature was maintained at 32°C during the first 3 d of the trial and afterwards, the temperature was gradually reduced by approximately 1.5°C each day to 14°C on d 21. PFE and PC treatments exerted a significant effect on body weight gain at d 28. Diet PFE was effective in reducing mortality when compared with diet NC (p < 0.05). Furthermore, diet PFE caused increases in ileal digestibility of gross energy, dry matter and organic matter when compared with diet NC (p < 0.05). Diets PFE and PC decreased coliforms, total aerobic bacteria and total anaerobic bacteria loads in the caeca when compared with diet NC (p < 0.05). Moreover, the addition of PFE to the diet improved villous height in all small intestinal segments as well as villous height:crypt depth ratio in the duodenum when compared with diet NC (p < 0.05). The results indicated that PFE is not only a valid alternative to oxytetracycline under cold stress conditions, with no antibiotic resistance, but also has the potential to increase the resistance of broiler chickens against ascites syndrome. Moreover, the addition of RCE at the concentration of 200 mg/kg to the diet was not sufficient to improve the performance of broiler chickens (similar to diet PC) but maybe more effective at higher concentrations.

中文翻译：

---

添加植物提取物作为替代暴露于低环境温度的肉鸡的膳食抗生素的策略

摘要 本研究旨在研究两种植物提取物作为日粮抗生素替代品对暴露于低环境温度的肉鸡的影响。总共 300 只 1 日龄雄性肉鸡被随机分配到四个日粮处理（5 个重复围栏；每个 15 只肉鸡），包括开食日（第 0 天至第 10 天）和生长日粮（第 10 天至第 28 天）。饮食治疗包括基础饮食（阴性对照，NC）和三种类似的饮食，这些饮食补充了 200 mg/kg 的 Prosopis farcta 提取物 (PFE)、Rhus coriaria L.提取物 (RCE) 或含有土霉素的抗生素预混物（阳性对照） ， 个人电脑）。为了模拟低环境温度，在试验的前 3 天和之后，室温保持在 32°C，温度每天逐渐降低约 1.5°C 至第 21 天的 14°C。PFE 和 PC 处理对第 28 天的体重增加产生显着影响。与饮食 NC 相比，饮食 PFE 可有效降低死亡率（p < 0.05)。此外，与饮食 NC 相比，饮食 PFE 导致总能量、干物质和有机物质的回肠消化率增加（p < 0.05）。与饮食 NC 相比，饮食 PFE 和 PC 降低了盲肠中的大肠菌群、总需氧菌和总厌氧菌负荷（p < 0.05）。此外，与饮食 NC 相比，在饮食中添加 PFE 改善了所有小肠段的绒毛高度以及十二指肠中的绒毛高度：隐窝深度比（p < 0.05）。结果表明，PFE不仅是低温胁迫条件下土霉素的有效替代品，无抗生素耐药性，而且有潜力提高肉鸡对腹水综合征的抵抗力。此外，在日粮中添加 200 mg/kg 浓度的 RCE 不足以提高肉鸡的生产性能（类似于日粮 PC），但在更高的浓度下可能更有效。