This study aimed to evaluate role of nano-sized zinc (Zn) on lactation performance, health status, and mammary permeability of lactating dairy cows. Thirty multiparous dairy cows with similar days in milk (158 ± 43.2) and body weight (694 ± 60.5 kg) were chosen based on parity and milk production and were randomly assigned to 3 treatment groups: basal diet (control, 69.6 mg/kg of Zn adequate in Zn requirement), basal diet additional Zn-methionine (Zn-Met, providing 40 mg/kg of Zn), and basal diet additional nano-sized Zn oxide (nZnO, providing 40 mg/kg of Zn). The study lasted for 10 wk, with the first 2 wk as adaptation. Feed intake, milk yield and the related variables, and plasma variables were determined every other week. Blood hematological profiles were determined in the 8th week of the study. We found that feed intake, milk yield, and milk composition were similar across the 3 groups. The nZnO- and Zn-Met-fed cows had greater milk Zn concentrations in the milk (3.89 mg/L (Zn-Met) and 3.93 mg/L (nZnO)) and plasma (1.25 mg/L (Zn-Met) and 1.29 mg/L (nZnO)) than the control cows (3.79 mg/L in milk and 1.21 mg/L in plasma). The nZnO-fed cows had higher Zn concentrations in plasma but not in milk compared to Zn-Met-fed cows. The Zn appearance in milk was greater in nZnO-fed (area under curve during the first 4 h post-feeding for milk Zn: 16.1 mg/L) and Zn-Met-fed cows (15.7 mg/L) than in control cows (15.0 mg/L). During the first 4 h post-feeding, milk to blood Zn ratio was greater in nZnO-fed animals but lower in Zn-Met-fed cows compared with control cows. Oxidative stress-related variables in plasma, blood hematological profiles, and mammary permeability related variables were not different across treatments. In summary, lactation performance, Zn concentrations in milk and plasma, hematological profiles, mammary permeability were similar in cows fed nZnO and Zn-Met. We therefore suggested that nZnO feeding can improve Zn bioavailability without impairing lactation performance, health status, and mammary gland permeability in dairy cows.

本研究旨在评估纳米锌 (Zn) 对泌乳奶牛的泌乳性能、健康状况和乳房通透性的作用。根据胎次和产奶量，选择产奶天数（158±43.2）和体重（694±60.5 kg）相似的 30 头经产奶牛，随机分为 3 个处理组：基础日粮（对照组，69.6 mg/kg锌需求量充足），基础饮食添加蛋氨酸锌（Zn-Met，提供 40 毫克/千克锌），基础饮食添加纳米氧化锌（nZnO，提供 40 毫克/千克锌）。研究持续10周，前2周为适应期。每隔一周测定采食量、产奶量和相关变量以及血浆变量。在研究的第 8 周测定血液学特征。我们发现 3 组的采食量、产奶量和乳成分相似。饲喂 nZnO 和 Zn-Met 的奶牛的牛奶中锌浓度更高（3.89 mg/L（Zn-Met）和 3.93 mg/L（nZnO））和血浆（1.25 mg/L（Zn-Met）和比对照奶牛（牛奶中 3.79 毫克/升，血浆中 1.21 毫克/升）高出 1.29 毫克/升（nZnO））。与饲喂 Zn-Met 的奶牛相比，饲喂 nZnO 的奶牛血浆中的锌浓度较高，但牛奶中的锌浓度却没有。与对照奶牛相比，nZnO 喂养的奶牛（奶锌喂养后前 4 小时曲线下面积：16.1 mg/L）和 Zn-Met 喂养的奶牛（15.7 mg/L）牛奶中锌的出现量更大（ 15.0毫克/升）。在饲喂后的前 4 小时内，与对照奶牛相比，nZnO 饲喂动物的乳汁与血液中锌的比例较高，但饲喂 Zn-Met 的奶牛则较低。血浆中氧化应激相关变量、血液学特征和乳腺通透性相关变量在不同治疗中没有差异。总之，饲喂 nZnO 和 Zn-Met 的奶牛的泌乳性能、牛奶和血浆中的锌浓度、血液学特征、乳腺通透性相似。因此，我们建议饲喂 nZnO 可以提高锌的生物利用度，而不损害奶牛的泌乳性能、健康状况和乳腺通透性。