The effect of replacing lactose with glucose on the gastrointestinal system of young calves at levels above 20% diet inclusion in milk replacer (MR) is not well described. The aim of this study was to determine tolerance to glucose inclusion at the direct expense of lactose on glucose metabolism, health, and growth performance in Holstein male calves. In total, 110 Holstein male dairy calves (16 ± 2.5 d and 50.3 ± 0.2 kg) were acquired from a commercial collection center. After an adaptation period of 3 d, 100 calves were selected for the study based on health parameters. Calves were blocked based on body weight measured on d 4 after arrival. Within each block, calves were randomly assigned to 1 of 5 levels of glucose inclusion (replacing lactose): 0% (L1, n = 20), 10% (L2, n = 20), 20% (L3, n = 20), 30% (L4, n = 20), and 40% (L5, n = 20), leading to an estimated osmolality range from 417 (L1) to 586 mOsm/kg (L5). Carbohydrates were exchanged based on hexose equivalents, and glucose delivery was standardized across treatments, while the rest of the formula (60%) remained unchanged. Calves received L1 during the adaptation period of 3 d and were then exposed to their respective treatment until d 47 after arrival. Milk replacer was provided daily in 2 equally sized meals. Meal size was 2.0 L during the 3-d adaptation period and gradually increased to 4.0 L until weaning (d 35 after arrival). During weaning, meal size decreased from 4.0 to 2.0 L on d 36, and MR was withdrawn on d 48 after arrival. Straw and concentrates were offered ad libitum from d 25 onward. Calves had ad libitum access to water throughout the study. Measurements included daily feed intakes, weekly body weight, and weekly spot feces sampling in all calves. Blood samples were collected on d 18. Additionally, postprandial responses of insulin and glucose were measured in 6 calves per treatment on d 19, 20, and 21. Increasing glucose inclusion (at the direct expense of lactose) in MR did not affect growth but linearly increased mortality, which was as high as 25% (5/20) in L5. Mortality was primarily associated with gastrointestinal disorders (6/11). At higher glucose levels, calves needed greater serum insulin concentrations to control glycemia, as shown by a linear increase in the area under the curve for insulin. Furthermore, calves needed more time to control glycemia, as indicated by a linear increase in the maximal concentration of insulin. Consequently, there was a linear increase in area under the curve for glucose. Even though calves needed more time and higher insulin concentrations for 30% glucose inclusion and higher, the glucose-to-insulin ratio did not differ across treatments. However, high glucose inclusion levels in MR affected calf mortality and is not a suitable strategy for lactose replacement.

用葡萄糖替代乳糖对年幼犊牛胃肠道系统的影响超过牛奶替代品（MR）中日粮摄入量的20％以上。这项研究的目的是确定直接摄入乳糖对荷斯坦公犊牛的葡萄糖代谢，健康和生长性能造成的葡萄糖包容耐受性。总共从一个商业采集中心获得了110头荷斯坦牛犊（16±2.5 d和50.3±0.2 kg）。经过3天的适应期后，根据健康参数选择了100只犊牛进行研究。根据到达后第4天测得的体重将小牛堵塞。在每个区块中，将小牛随机分配到5种葡萄糖含量水平（代替乳糖）中的1种：0％（L1，n = 20），10％（L2，n = 20），20％（L3，n = 20） ，30％（L4，n = 20）和40％（L5，n = 20），导致渗透压的估计范围为417（L1）至586 mOsm / kg（L5）。碳水化合物根据己糖当量进行交换，并且在各处理之间对葡萄糖的输送进行了标准化，而其余配方（60％）保持不变。小牛在3天的适应期内接受L1，然后接受其各自的治疗，直到到达后第47天。每天提供2份同等大小的餐点牛奶替代品。在3 d适应期间，膳食大小为2.0 L，并逐渐增加至4.0 L，直到断奶（到达后d 35）。在断奶期间，进食后第36天的进餐量从4.0 L降至2.0 L，到达后第48天MR撤回。从第25天起随意提供秸秆和精矿。在整个研究过程中，小牛自由饮水。测量包括每日饲料摄入量，每周体重，以及每周在所有犊牛身上进行粪便采样。在第18天收集血样。另外，在第19、20和21天，在每种治疗的6只犊牛中测量餐后胰岛素和葡萄糖的反应。增加MR中葡萄糖的包涵度（直接消耗乳糖）不会影响生长，但死亡率线性增加，在L5中高达25％（5/20）。死亡率主要与胃肠道疾病有关（6/11）。在较高的葡萄糖水平下，犊牛需要更高的血清胰岛素浓度来控制血糖，如胰岛素曲线下面积的线性增加所示。此外，小牛需要更多的时间来控制血糖，胰岛素最大浓度的线性增加表明了这一点。因此，葡萄糖曲线下的面积线性增加。即使犊牛需要更多的时间和更高的胰岛素浓度（包含30％的葡萄糖和更高浓度），葡萄糖与胰岛素的比例在各治疗之间也没有差异。但是，MR中较高的葡萄糖夹杂物含量会影响小腿死亡率，因此不是适合替代乳糖的策略。