Department of Animal Science, Luiz de Queiroz College of Agriculture, University of São Paulo, Piracicaba, São Paulo, Brazil 13418-900.
Department of Animal Production, College of Technology and Agricultural Sciences, São Paulo State University (UNESP), Dracena, São Paulo, Brazil 17900-000.
J Dairy Sci. 2020 Nov;103(11):10083-10098. doi: 10.3168/jds.2020-18514. Epub 2020 Sep 18.
Tropical grass hay feeding is related to improved ruminal health; however, it may decrease energy intake. On the other hand, whole-flint corn grain may be an alternative fiber source in the diet of dairy calves. Forty-two Holstein calves were used in a randomized block design, considering sex, birth date, and weight at 21 d of age, when the supply of whole-flint corn grain or tropical grass hay started. Three component-fed solid diets were compared: (1) starter concentrate only during the preweaning and starter concentrate with free choice of chopped Tifton-85 hay postweaning (SC), (2) starter concentrate with free choice of chopped Tifton-85 hay pre- and postweaning (SCH), and (3) starter concentrate with free choice of whole-flint corn grain pre- and postweaning (SCW). The animals were evaluated from 21 to 84 d of age. Calves were managed equally during the first 21 d, fed with 6 L/d of whole milk and a commercial starter concentrate (46% nonfiber carbohydrates, small particles, and pelleted) ad libitum. After that, milk feeding was reduced to 4 L/d until gradual weaning at 56 d of age. At 56 d of age, 4 animals per treatment were randomly chosen to be slaughtered for digestive tract weight evaluation and to collect tissue for histological analysis of the ruminal wall, duodenum, and cecum, whereas the other 30 animals were weaned and evaluated for a further 22 d when the SC diet also received hay ad libitum. Feed intake was measured daily. Weight gain and metabolic indicators of intermediate metabolism were evaluated weekly. Ruminal fluid was collected at wk 6, 8, 10, and 12 of age. The SCH diet increased the total and starter dry matter intake, and consequently, the average daily gain and body weight at 56 d of age. The SCW diet promoted an increase in propionate and decreased acetate-to-propionate ratio. Morphometric variables were affected by the SCH diet. The postweaning performance was unaffected by solid diets; however, the SCW diet decreased ruminal and fecal pH. Feeding hay, starting at 21 d of age, can stimulate early solid diet intake, promoting better performance and ruminal and intestinal development, when a highly fermentable and small particle pelleted starter is fed.
热带干草的喂养与瘤胃健康的改善有关；然而，它可能会降低能量摄入。另一方面，全粒硬质玉米可能是奶牛犊牛日粮中的一种替代纤维来源。42 头荷斯坦犊牛采用随机分组设计，考虑性别、出生日期和 21 日龄时的体重，此时开始供应全粒硬质玉米或热带干草。比较了三种配合饲料的固体日粮：（1）仅在断奶前提供犊牛代乳料，断奶后可自由选择切碎的提夫顿 85 号干草（SC），（2）断奶前和断奶后均可自由选择切碎的提夫顿 85 号干草（SCH），（3）断奶前和断奶后均可自由选择全粒硬质玉米（SCW）。动物从 21 日龄评估到 84 日龄。在最初的 21 天内，所有动物都平等地进行管理，每天每头动物饲喂 6L 全乳和商业犊牛代乳料（46%非纤维碳水化合物、小颗粒和颗粒状）自由采食。之后，每天的牛奶饲喂量减少到 4L，直到 56 日龄逐渐断奶。在 56 日龄时，每个处理组随机选择 4 头动物进行屠宰，以评估消化道重量，并收集瘤胃壁、十二指肠和盲肠的组织，用于组织学分析，而其余 30 头动物断奶并进一步评估 22 天，此时 SC 日粮也可自由采食干草。每日测量采食量。每周评估体重增加和中间代谢的代谢指标。在 6、8、10 和 12 周龄时收集瘤胃液。SCH 日粮增加了总干物质和犊牛代乳料的采食量，因此，56 日龄的平均日增重和体重增加。SCW 日粮促进了丙酸的增加，并降低了乙酸/丙酸的比值。形态计量学变量受 SCH 日粮的影响。固体日粮对断奶后的表现没有影响；然而，SCW 日粮降低了瘤胃和粪便的 pH 值。21 日龄开始喂干草可以刺激早期固体日粮的摄入，当饲喂高发酵性和小颗粒颗粒状犊牛代乳料时，可促进更好的性能和瘤胃及肠道发育。
