Calves are born immunologically immature and are highly susceptible to infectious diseases. For these reasons, suitable handling practices that favor health conditions and improve performance are necessary at this phase of life. The aim of this study was to evaluate whether the inclusion of Schizochytrium sp. microalgae for Holstein calves at different ages would improve dry matter intake (DMI), performance and health. Twenty-four newborn Holstein calves (34.0 ± 1.5 kg of BW) were allocated in a completely randomized design and were individually housed over 45 days. Starter and ryegrass hay and water were offered separately and ad libitum after the third day of life. Calves were daily fed five liters of whole milk divided in two equal meals. Treatments were as follows: whole milk without addition of microalgae (CON); addition of 6 g of microalgae/day over 45 days (ENT); addition of 6 g of microalgae/day from the 15th day of life until weaning (A15); and addition of 6 g of microalgae/day from the 30th day of life until weaning (A30). Calves that received microalgae (ENT, A15 and A30) had greater intake of starter in grams per day (P = 0.01) and metabolic weight (P = 0.02), and they tended (P = 0.07) to increase total DMI when compared with CON, without a difference in terms of feed efficiency (P = 0.20). Higher weaning thoracic perimeter (P = 0.03) for supplemented animals were observed. Serum lipid peroxidation (LPO) and reactive oxygen species (ROS) were reduced (P = 0.029 and P < 0.001, respectively) with the addition of microalgae, regardless of the time of supplementation. The inclusion of 6 gs of Schizochytrium spp. microalgae increased starter intake and reduced oxidative reactions regardless of supplementation time, which justifies microalgae supplementation only in the final 15 days of suckling.

小牛天生免疫不成熟，对传染病高度敏感。由于这些原因，在生命的这一阶段，必须采取有利于健康状况并改善性能的适当处理方法。这项研究的目的是评估是否包含裂殖壶菌sp。不同年龄的荷斯坦犊牛微藻将改善干物质摄入量（DMI），性能和健康。将二十四只新生的荷斯坦犊牛（34.0±1.5千克体重）分配到完全随机的设计中，并分别放置45天。开胃菜和黑麦草的干草和水分开提供，并在生命的第三天后随意提供。每天给小牛喂五升全脂牛奶，分成两等份。处理方法如下：不加微藻类（CON）的全脂牛奶；在45天内每天添加6克微藻（ENT）；从生命的第15天到断奶，每天添加6克微藻（A15）；从生命的30天到断奶，每天添加6克微藻（A30）。 与CON相比，接受微藻类（ENT，A15和A30）的犊牛每天摄入的起动剂以克计（P  = 0.01）和代谢重量（P  = 0.02）更多，它们倾向于（P = 0.07）增加总DMI。 ，但进给效率没有差异（P  = 0.20）。 观察到补充动物的较高的断奶胸围（P = 0.03）。不论补充时间如何，添加微藻均可降低血清脂质过氧化（LPO）和活性氧（ROS）（分别为P  = 0.029和P <0.001）。包含6 g的裂殖壶菌spp。无论补充时间如何，微藻都会增加起动剂的摄入量并减少氧化反应，这仅在哺乳的最后15天才有理由补充微藻。