Infection with apicomplexan parasites of the genus Eimeria causes damage to gastrointestinal epithelial cells and increases the malabsorption of nutrients in broiler chickens, resulting in depressed performance and economic loss. The objective of the study was to evaluate the effect of graded Eimeria vaccine challenges on growth performance, oocyst shedding, and plasma carotenoid levels. A total of 140 one-day-old Cobb 500 broiler chicks (55.49 ± 2.55 g BW) were housed in environmentally controlled Petersime battery brooders with modified wire floors, containing 5 birds per pen with 7 replicate pens per treatment. Pens were randomly assigned to 1 of 4 treatments: a negative control and 3 positive treatments that received 15×, 20×, or 25× the recommended vaccination dose. At 10 d of age, positive treatment birds orally received the ADVENT coccidiosis vaccine containing unattenuated strains of Eimeria acervulina, Eimeria maxima, and Eimeria tenella. Body weight, average daily gain, feed intake, and feed conversion ratio were determined after 10, 15, and 20 d of age. On d 15 and 20, one random bird per pen was bled for plasma carotenoid analysis and feces from each pen was collected for oocyst quantification. Body weight, average daily gain, and feed conversion ratio were significantly depressed (P < 0.05) among all positive treatments when compared with the negative control on d 20, but no treatment effect on feed intake was observed. Similarly, birds in positive treatment groups had decreased (P < 0.05) plasma carotenoid levels and greater (P < 0.05) oocysts per gram of feces than the negative control on d 20. No differences were observed in performance, plasma carotenoid levels, and fecal oocysts among treatments on d 15. These results indicate that 15, 20, or 25 doses of the ADVENT vaccine can be used to replicate subclinical coccidiosis in broiler chickens.

中文翻译：

---

PSIII-5 分级艾美球虫疫苗挑战对肉鸡生产性能的影响

感染艾美球虫属的顶复门寄生虫会导致胃肠道上皮细胞受损，并增加肉鸡对营养物质的吸收不良，从而导致生产性能下降和经济损失。该研究的目的是评估分级艾美球虫疫苗攻击对生长性能、卵囊脱落和血浆类胡萝卜素水平的影响。总共 140 只一天大的 Cobb 500 肉鸡（55.49 ± 2.55 g BW）被安置在环境受控的 Petersime 电池育雏器中，该育雏器带有改良的金属丝地板，每栏包含 5 只鸡，每次处理 7 个重复栏。围栏被随机分配到 4 种治疗中的一种：阴性对照和 3 种阳性治疗，接受 15 倍、20 倍或 25 倍推荐的疫苗接种剂量。在 10 天时，阳性治疗的鸡只口服 ADVENT 球虫病疫苗，该疫苗含有未减毒的 Eimeria acervulina、Eimeria maxima 和 Eimeria tenella 菌株。在 10、15 和 20 日龄后测定体重、平均日增重、采食量和饲料转化率。在第 15 天和第 20 天，每栏随机抽取一只鸟进行血浆类胡萝卜素分析，并收集每栏的粪便用于卵囊定量。在第20天，与阴性对照相比，所有阳性处理的体重、平均日增重和饲料转化率均显着降低（P <0.05），但未观察到处理对采食量的影响。同样，在第 20 天，与阴性对照组相比，阳性处理组的鸡只血浆类胡萝卜素水平降低（P < 0.05），每克粪便中的卵囊数量增加（P < 0.05）。