Plants, Soils, and Climate Department, Utah State University, Logan 84322-4820.
Forage and Range Research Laboratory, USDA Agricultural Research Service, Logan, UT 84322-6300.
J Dairy Sci. 2023 Jun;106(6):3918-3931. doi: 10.3168/jds.2022-22858. Epub 2023 Apr 25.
Insufficient dry matter intake (DMI) of pasture by dairy cattle is a major factor limiting growth and milk production; however, it has been hypothesized that some dairy breeds may be more efficient grazers than others. This study was conducted to determine whether dairy breed types differ in DMI and feed efficiency when grazing either grass monoculture or grass-legume mixed pastures. The experiment compared 4 different dairy breed types (Jersey, Holstein, Holstein-Jersey crossbreds, and Montbéliarde-Swedish Red-Holstein 3-breed crossbreds) and 2 levels of pasture type [grass monoculture (MONO) and grass-birdsfoot trefoil (BFT) mixture (MX)] for a total of 8 treatments. Pastures were rotationally stocked with groups of 4 prepubertal heifers for 105 d for 3 yr, and DMI was determined from herbage disappearance. Feed conversion efficiency (FCE) and residual feed intake (RFI) were then derived from DMI, and heifer body weights (BW) and normalized to animal units (AU) as 40% metabolic mature BW of the corresponding dairy breed type to account for inherent differences in size and growth rates. We observed differences in DMI and feed efficiency among breed types and between pasture types. On average, Holsteins had the greatest overall DMI (4.4 kg/AU), followed by intermediate DMI by the crossbreds (4.0 kg/AU), and Jerseys had the least DMI (3.6 kg/AU). Heifers grazing MX pastures had on average 22% greater DMI than those grazing MONO, but heifers on grass monocultures were more efficient in converting DMI to BW gain (i.e., RFI/AU of 0.27 and -0.27, respectively; more negative RFI numbers indicate less DMI to achieve the expected gains). Overall, Jerseys had the most favorable feed efficiency; however, ranking of Holsteins and crossbreds depended upon the feed efficiency metric. This study is one of the first to compare the interaction of dairy breed and pasture quality on grazing efficiency. However, the lack of a breed type × pasture type interaction for DMI, FCE, or RFI indicated that none of these dairy breed types were better adapted than another breed type to pastures with contrasting levels of nutritive value.
奶牛对牧场干物质摄入量（DMI）不足是限制其生长和产奶量的主要因素；然而，有人假设某些奶牛品种可能比其他品种更善于放牧。本研究旨在确定当放牧单一草牧场或草豆科混合牧场时，不同奶牛品种类型在 DMI 和饲料效率方面是否存在差异。该实验比较了 4 种不同的奶牛品种类型（泽西、荷斯坦、荷斯坦-泽西杂交品种和蒙贝利亚德-瑞典红牛 3 品种杂交品种）和 2 种牧场类型[单一草牧场（MONO）和草-三叶草混合牧场（MX）]，共 8 种处理。在 3 年内，用 4 组处于初情期前的小母牛轮流放牧 105 天，从牧草消失量中确定 DMI。然后从 DMI 中得出饲料转化效率（FCE）和剩余饲料摄入量（RFI），并将小母牛体重（BW）归一化为动物单位（AU），作为相应奶牛品种类型的 40%代谢成熟 BW，以考虑大小和生长率的固有差异。我们观察到品种类型和牧场类型之间在 DMI 和饲料效率方面存在差异。平均而言，荷斯坦牛的总 DMI 最高（4.4kg/AU），其次是杂交品种（4.0kg/AU），而泽西牛的 DMI 最低（3.6kg/AU）。放牧 MX 牧场的小母牛的 DMI 平均比放牧 MONO 的小母牛高 22%，但在草单牧场饲养的小母牛在将 DMI 转化为 BW 增加方面效率更高（即，RFI/AU 分别为 0.27 和-0.27；负的 RFI 数字表示达到预期收益所需的 DMI 较少）。总体而言，泽西牛的饲料效率最有利；然而，荷斯坦牛和杂交品种的排名取决于饲料效率指标。本研究是首次比较奶牛品种和牧场质量对放牧效率的相互作用的研究之一。然而，DMI、FCE 或 RFI 均不存在品种类型与牧场类型的相互作用，这表明这些奶牛品种类型都没有比其他品种类型更适应具有不同营养价值的牧场。
