This study evaluated the influence of feeding low and high preweaning allowances of unpasteurized whole milk (MA) on intake, selected blood metabolites, antibody response, mammary gland growth, and growth of New Zealand (NZ) dairy heifers to 7mo of age. At 10 ± 2d of age (study d0), group-housed (6/pen) heifer calves (Holstein-Friesian×Jersey) were allocated to low (4L whole milk -1calf -1d; n = 7 pens) or high (8L whole milk -1calf -1d; n = 7 pens) MA for the next 63d. Calves were gradually weaned between d63 ± 2 and 73 ± 2. Calves in each pen had ad-libitum access to clean water, pelleted calf starter, and chopped grass hay from d1 to 91 ± 2d. At 92 ± 2d, all calves were transferred to pasture, grazed in a mob, and their growth and selected blood metabolites were measured until d209. All animals were weighed weekly during the indoor period (to d91) and then at d105, 112, 128, 162, 184, and 209. Skeletal growth measurements and blood samples to analyze selected metabolites were collected at the start of the experiment, weaning, and then postweaning on d91, and d201. Specific antibodies against Leptospira and Clostridia were quantified in wk7, 13, and 27. Mammary glands were scanned using ultrasonography at the start of the experiment, weaning, and d201. Feeding high versus low amounts of MA increased the preweaning growth in heifer calves (P = 0.02) without negatively affecting postweaning Average Daily Gain (ADG) (P = 0.74). Compared with heifers fed low MA, high MA fed heifers had greater increase in antibodies against Leptospira and Clostridia by 13wk of age (P = 0.0007 and P = 0.06, respectively). By 27wk of age, the antibody response was the same in heifers offered low or high MA. There was no effect of MA on the total size of the mammary gland, measured by ultrasonography, at weaning and 7mo of age. However, the greater MA was associated with more mammary parenchyma (P = 0.01) and less mammary fat pad (P = 0.03) in back glands at 7mo of age compared with heifers fed lower MA. In conclusion, feeding a high versus a low amount of unpasteurized whole milk increased the preweaning growth of New Zealand replacement heifers without negatively affecting their ADG during postweaning under grazing conditions. Feeding more (8 vs. 4L/d) unpasteurized whole milk positively affected antibody responses early in life and mammary gland composition by 7mo of age in dairy heifers reared for pasture-based dairy systems.

中文翻译：

---

饲喂少量或大量未经高温消毒的全脂牛奶的新西兰奶牛替代小母牛的生长性能、抗体反应和乳腺发育

本研究评估了饲喂低和高断奶前未巴氏杀菌全脂牛奶 (MA) 对采食量、选择的血液代谢物、抗体反应、乳腺生长和新西兰 (NZ) 奶牛到 7 个月龄的生长的影响。在 10 ± 2 日龄（研究 d0），群养（6 只/栏）小牛犊（Holstein-Friesian × Jersey）被分配到低（4L 全脂牛奶 -1 小牛 -1d；n = 7 栏）或高（8L全脂牛奶 -1calf -1d；n = 7 笔）接下来 63 天的 MA。犊牛在 d63 ± 2 和 73 ± 2 天之间逐渐断奶。从 d1 到 91 ± 2 天，每个围栏中的犊牛都可以随意饮用干净的水、颗粒状的小牛起子和切碎的干草。在 92 ± 2 天，所有小牛都被转移到牧场，成群地放牧，并测量它们的生长和选定的血液代谢物，直到第 209 天。在室内期间（至第 91 天）每周对所有动物称重，然后在第 105、112、128、162、184 和 209 天称重。在实验开始时收集骨骼生长测量值和血液样本以分析选定的代谢物，断奶，然后在 d91 和 d201 断奶。在第 7 周、第 13 周和第 27 周对钩端螺旋体和梭状芽胞杆菌的特异性抗体进行了量化。在实验开始、断奶和第 201 天使用超声检查了乳腺。饲喂高量和低量 MA 增加了小母牛断奶前的生长 (P = 0.02)，而不会对断奶后平均日增重 (ADG) (P = 0.74) 产生负面影响。与饲喂低 MA 的小母牛相比，饲喂高 MA 的小母牛在 13 周龄时针对钩端螺旋体和梭状芽胞杆菌的抗体增加更多（分别为 P = 0.0007 和 P = 0.06）。到 27 周岁时，提供低或高 MA 的小母牛的抗体反应是相同的。在断奶和 7 个月时，通过超声测量，MA 对乳腺的总大小没有影响。然而，与饲喂较低 MA 的小母牛相比，较大的 MA 与 7 个月龄时背部腺体中更多的乳腺实质 (P = 0.01) 和较少的乳腺脂肪垫 (P = 0.03) 相关。总之，在放牧条件下，饲喂大量与少量未经巴氏消毒的全脂牛奶可增加新西兰后备小母牛的断奶前生长，而不会对其断奶后的 ADG 产生负面影响。饲喂更多（8 对 4 升/天）未经巴氏消毒的全脂牛奶对以牧场为基础的奶牛系统饲养的奶牛在生命早期的抗体反应和 7 个月龄时的乳腺成分产生积极影响。