Effects of partial substitution of barley with maize and beet pulp (BP) on animal performance, rumen fermentation and rumen microbial populations were evaluated in thirty-nine newly weaned calves transitioned from a milk and pasture regime to a high-concentrate ration. Diets were: a barley-based growing diet (C); and two diets in which barley was partially replaced with maize and 10% BP (BP10) or 22% BP (BP22) on as fed basis. Wheat straw was offered ad libitum in all cases. Three adaptation protocols were followed: in Protocol 1 animals were abruptly shifted to the C diet, whereas calves in Protocols 2 and 3 were gradually adapted and received diets BP10 and BP22, respectively, for 10d; thereafter a 50:50 mixture of their diet and diet C until day 14, and finally, from day 15, diet C. All animals were slaughtered at a target live weight (LW) of ca. 500 kg. The experiment had then three phases (Ph): Ph1 (0-10d), Ph2 (11-14d) and Ph3 (15d-slaughter). Concentrate intake and proportion of straw in the diet were affected (P<0.01) by the interaction dietary protocol by phase, showing animals in Protocol 3 the lowest concentrate intake and the highest straw proportion in Ph2. Daily gains, LW at the end of each phase, dressing percentage (59 ± 0.4%, on average) and total concentrate intake along the experiment (995 ± 21.3 kg DM, on average) were similar (P>0.05) among adaptation protocols. Daily rumen pH, and concentrations of lactate and volatile fatty acids were not affected by protocol. At the end of the trial, protozoa persisted in the rumen of all calves with an average concentration of 5.89 log cells/mL. Diversity dropped throughout the study; most protozoa belonged to genera Entodinium (97.5%) and Isotricha (1.7%), with minor presence of Dasytricha (0.05%), Epidinium (0.43%) and Subfamily Diplodiniinae (0.23%). Adaptation protocol had no effect on rumen bacterial population or diversity; however, both were affected by day of sampling indicating a shift in bacterial community in response to the concentrate inclusion. Although diversity dropped with concentrate inclusion, there was an increase after d10. In conclusion, the application of different protocols to adapt beef cattle to high-concentrate diets had no effect on animal performance and rumen fermentation which were not negatively affected by the abrupt transition to the high-concentrate diet. This suggests that calves might cope with those feeding conditions probably due to the microbial adaptions to a new rumen environment.

在从奶牛和牧草方式向高浓度配比过渡的三十九只新断奶小牛中，评估了用玉米和甜菜粕（BP）替代大麦对动物生产性能，瘤胃发酵和瘤胃微生物种群的影响。饮食是：基于大麦的生长饮食（C）；两种日粮中的大麦部分用玉米和10％BP（BP10）或22％BP（BP22）代替（饲喂）。随意提供麦秸在所有情况下。遵循三种适应方案：在方案1中，动物突然转变为C型饮食，而逐渐对方案2和3中的犊牛进行适应，分别接受BP10和BP22日粮，持续10天。此后他们的饮食和饲料C的直到14天的50:50混合物，最后，从第15天，饮食C.所有动物在的目标活重（LW）屠宰CA。500公斤 然后，实验分为三个阶段（Ph）：Ph1（0-10d），Ph2（11-14d）和Ph3（15d-屠宰）。饮食中秸秆的摄入量和比例受到影响（P<0.01）（按阶段互动饮食方案），显示方案3中的动物在Ph2中的最低浓缩物摄入量和最高秸秆比例。在适应方案中，实验的日增重，每个阶段结束时的LW，选矿百分比（平均59±0.4％）和实验中的精矿总摄入量（平均995±21.3 kg DM）相似（P > 0.05）。每日瘤胃pH值，乳酸和挥发性脂肪酸的浓度不受方案的影响。在试验结束时，所有小牛的瘤胃中都存在原生动物，平均浓度为5.89 log细胞/ mL。整个研究过程中多样性下降；多数原生动物属于Entodinium（97.5％）和Isotricha（1.7％）属，而Dasytricha则很少（0.05％），淫羊din（0.43％）和梁龙亚科（0.23％）。适应方案对瘤胃细菌种群或多样性没有影响；但是，两者都受到采样日的影响，表明响应于浓缩物的加入，细菌群落发生了变化。尽管随着浓缩物的加入，多样性下降了，但在d10之后有所增加。总之，采用不同的方案使肉牛适应高浓度日粮对动物的生产性能和瘤胃发酵没有影响，而不受突然过渡到高浓度日粮的负面影响。这表明，由于微生物对新瘤胃环境的适应性，犊牛可能会适应那些饲养条件。