Milk replacer (MR) feeding programs have traditionally fed at less than ad libitum amounts to promote calf starter (CS) intake and allow early weaning. More recently, increased amounts of MR preweaning have been shown to increase preweaning ADG, although postweaning growth may be reduced. Several studies suggest that limited postweaning digestion of nutrients in CS may contribute to postweaning growth impairment. It is not clear whether CS formulation might also contribute to differences in postweaning nutrient digestion when calves are fed different MR programs. A 56-d feeding and digestion trial was conducted to compare growth and digestion in 2- to 3-d-old male Holstein calves (n = 48; initially 41.9 kg of body weight) fed a moderate (MRM) or high (MRH) MR program and either a pelleted CS containing 9.9% starch or a texturized CS containing 41.3% starch. Programs were 0.66 kg of dry matter (DM)/d of MR to d 46, then 0.33 kg/d to d 49 (MRM) and 0.85 kg of DM/d to d 5, then 1.07 kg/d to d 42, then 0.53 kg/d to d 49 (MRH). The MR contained 25% crude protein and 18.6% fat and was reconstituted to 13 (MRM) or 15% (MRH) solids. Calves were also assigned randomly to receive a pelleted CS (9.9% starch, 36.9% NDF) or a textured CS (41.3% starch, 13.3% NDF) and water for ad libitum intake for 56 d. During d 31 to 35 and 52 to 56, fecal samples were collected from 5 calves per treatment for estimates of digestibility. Selected nutrients and chromic oxide (d 31–35) or acid-insoluble ash (d 52–56) were analyzed in feed and feces to estimate digestibility. Data were analyzed as a completely randomized design. Repeated measures analysis was performed when data were measured by week. Calves fed MRH gained more body weight (but not hip width) and were more efficient to weaning compared with calves fed MRM, although fecal scores and days treated with medications were greater. We found no effect of CS on animal performance, although calves fed textured CS had higher fecal scores. Digestibilities of nutrients were affected by treatment and time of sampling (5 or 8 wk). At 5 wk, digestion of DM, organic matter, crude protein, and fat were lower and digestion of acid detergent fiber, neutral detergent fiber, and starch were higher in calves fed MRM and reflected greater CS intake. Also, digestion of DM, organic matter, acid detergent fiber, starch, crude protein, and fat were greater in calves fed textured CS at 5 wk. By 8 wk, when CS was the only source of nutrients, digestion of DM, organic matter, acid detergent fiber, and neutral detergent fiber were greater in calves fed MRM and digestion of DM and organic matter were greater, and acid detergent fiber and neutral detergent fiber digestion were lower in calves fed textured CS. Formulation of CS as well as amount of MR offered to young calves influenced animal performance and digestion in this study.

传统上，代乳品（MR）喂养计划的饲喂量少于自由采食量，以促进犊牛初学者（CS）的摄入并允许早期断奶。最近，已显示出增加的MR断奶前剂量可增加断奶前ADG，尽管断奶后生长可能会降低。几项研究表明，断奶后CS中营养物质的有限消化可能会导致断奶后生长受损。尚不清楚当犊牛饲喂不同的MR程序时，CS配方是否也可能会导致断奶后营养物质消化的差异。进行了56天的饲喂和消化试验，以比较饲喂中度（MRM）或高水平（MRH）的2至3天大雄性荷斯坦犊牛（n = 48；最初体重为41.9 kg）的生长和消化MR程序以及包含9.9％淀粉的粒化CS或包含41的膨化CS。3％淀粉。程序是将MR干物质（DM）/ d设为第46天，然后是0.63 kg / d至第49 d（MRM），然后将d / d设为0.85 kg d / d至第5天，然后是1.07 kg / d至d 42，然后0.53 kg / d至d 49（MRH）。MR包含25％的粗蛋白和18.6％的脂肪，并重构为13（MRM）或15％（MRH）固体。还随机分配犊牛以接收粒状CS（9.9％淀粉，36.9％NDF）或网纹CS（41.3％淀粉，13.3％NDF）和水，自由采食56天。在第31至35天和52至56天期间，从每种处理的5头小牛收集粪便样品，以估计消化率。在饲料和粪便中分析了选定的养分和氧化铬（d 31–35）或酸不溶性灰分（d 52–56），以估计消化率。数据作为完全随机设计进行分析。当按周测量数据时，进行重复测量分析。与饲喂MRM的犊牛相比，饲喂MRH的犊牛增加了体重（但没有增加髋部宽度），并且断奶效率更高，尽管粪便评分和用药治疗的天数都更长。尽管饲喂带纹理的小牛的粪便得分更高，但我们发现CS对动物的生长性能没有影响。营养物质的消化率受处理和采样时间（5或8周）的影响。在5周时，饲喂MRM的犊牛的DM，有机物，粗蛋白和脂肪的消化率较低，而酸性洗涤剂纤维，中性洗涤剂纤维和淀粉的消化率较高，反映了CS摄入量增加。同样，在5 wk饲喂带纹理的CS的犊牛中，DM，有机物，酸性洗涤剂纤维，淀粉，粗蛋白和脂肪的消化更大。到了8周，当CS是唯一的养分来源时，就消化了DM，有机物，酸性洗涤剂纤维，饲喂MRM的犊牛的中性洗涤剂纤维和中性洗涤剂纤维较多，DM和有机物的消化较大; 在这项研究中，提供给小牛犊的CS以及MR的量影响了动物的生产和消化。