Towne G, Nagaraja T G, Brandt R T, Kemp K E
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-1600.
Appl Environ Microbiol. 1990 Oct;56(10):3174-8. doi: 10.1128/aem.56.10.3174-3178.1990.
Fluctuations in ciliated protozoan concentrations were monitored in 40 individually fed crossbred heifers that were stepped up to an 85% concentrate diet either slowly (12 days) or rapidly (3 days), with or without monensin (30 ppm). Ruminal fluid was withdrawn from all animals by stomach tube at the start of the study, after each group reached full feed, and at 14-day intervals thereafter throughout the finishing period until termination (day 119). Neither monensin nor speed of step-up affected (P greater than 0.10) total protozoan concentrations, ruminal pH, or lactic acid concentrations. Average protozoan concentrations peaked on day 5, progressively declined until day 56, and then increased (P less than 0.05), suggesting an adaptation to ruminal conditions. Concentrations of Isotricha spp. were higher (P less than 0.05) on the final two sampling dates than at any other time. After day 28, Entodinium, Isotricha, and Polyplastron were the only surviving genera. Protozoa were not detected in 11 heifers on day 42 and day 56, but only two animals were defaunated on day 119, indicating either exogenous or endogenous refaunation. Average protozoan concentrations were not different (P greater than 0.25) between ruminal samples collected by stomach tube the day before slaughter (2.8 x 10(5)/g) and digesta samples collected the next day (1.6 x 10(5)/g). In feedlot cattle, defaunation apparently is transitory and individual animals harbor a dynamic protozoan population that fluctuates in response to changing ruminal conditions.
在40头单独饲养的杂交小母牛中监测纤毛虫原生动物浓度的波动情况，这些小母牛分别以缓慢（12天）或快速（3天）的方式逐步过渡到85%精料日粮，且分别添加或不添加莫能菌素（30 ppm）。在研究开始时、每组达到全量采食后、育肥期此后每隔14天直至试验结束（第119天），通过胃管从所有动物采集瘤胃液。莫能菌素和过渡速度均未影响（P>0.10）原生动物总浓度、瘤胃pH值或乳酸浓度。原生动物平均浓度在第5天达到峰值，随后逐渐下降直至第56天，然后升高（P<0.05），表明对瘤胃环境产生了适应性。在最后两次采样日期，等毛虫属的浓度高于其他任何时间（P<0.05）。第28天后，内毛虫属、等毛虫属和复毛虫属是仅存的属。在第42天和第56天，11头小母牛未检测到原生动物，但在第119天只有2头动物去原虫化，表明存在外源性或内源性的再殖。屠宰前一天通过胃管采集的瘤胃样本（2.8×10⁵/g）和第二天采集的消化物样本（1.6×10⁵/g）中的原生动物平均浓度无差异（P>0.25）。在饲养场牛中，去原虫化显然是暂时的，个体动物体内的原生动物群体动态变化，会随着瘤胃条件的改变而波动。
