The objective of this study was to investigate the effects of calf starters with different starch content on rumen and blood properties in calves fed under a high plane of nutrition program. Twenty‐seven Holstein calves (14 female, 13 male) were assigned to one of three starter treatment groups in a randomized block design: high‐starch (41.8%) (n = 9), H; medium‐starch (31.9%) (n = 9), M; low‐starch (22.0%) (n = 9), L. Milk replacer on powder basis was fed up to 1.2 kg/day as fed, gradually reduced from 6 weeks of age; calves were weaned at 8 weeks of age. Each starter (up to 3.5 kg/day as fed) and chopped hay were provided ad libitum from 5 days of age. Blood was collected from 4 to 13 weeks of age. Rumen fluid was collected at 6, 8, 10, and 13 weeks of age. Serum urea nitrogen concentration after weaning was the lowest in H. Plasma IGF‐1 concentrations were higher in H than in L. Ruminal pH was not different, but the molar proportion of ruminal propionate was higher in H than in L throughout the study period. In summary, a high‐starch starter may increase propionate production and microbial protein synthesis in the rumen, inducing higher plasma IGF‐1 concentrations.

中文翻译：

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高平面饲喂犊牛发酵剂淀粉含量对奶牛瘤胃特性及代谢物和激素血液浓度的影响

本研究的目的是研究不同淀粉含量的犊牛开胃菜对高水平营养计划下饲喂的犊牛瘤胃和血液特性的影响。27 头荷斯坦犊牛（14 头雌性，13 头雄性）被分配到随机区组设计中的三个起始治疗组之一：高淀粉组（41.8%）（n= 9), H; 中等淀粉 (31.9%) (n= 9), M; 低淀粉 (22.0%) (n= 9), L. 粉状代乳粉按饲喂量至1.2公斤/天，从6周龄开始逐渐减少；小牛在8周龄时断奶。从 5 日龄开始，每份开食料（最多 3.5 公斤/天）和切碎的干草均提供。从 4 周龄到 13 周龄期间采集血液。在 6、8、10 和 13 周龄时收集瘤胃液。断奶后血清尿素氮浓度在 H 组中最低。血浆 IGF-1 浓度在 H 组中高于 L 组。瘤胃 pH 值没有差异，但在整个研究期间，H 组瘤胃丙酸的摩尔比例高于 L 组。总之，高淀粉发酵剂可能会增加瘤胃中丙酸的产生和微生物蛋白质的合成，从而诱导更高的血浆 IGF-1 浓度。