Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, Australia 3010; CSIRO Agriculture and Food, Werribee, Victoria, Australia 3030.
CSIRO Agriculture and Food, Black Mountain, Canberra, Australia 2601.
J Dairy Sci. 2020 Feb;103(2):1920-1930. doi: 10.3168/jds.2019-16775. Epub 2019 Nov 20.
This study compared cows that consistently produce milk with small (volume-weighted mean diameter of 2.92-3.83 µm, with an average diameter of 3.29 µm) or large (volume-weighted mean diameter of 4.58-5.67 µm, with an average diameter of 4.92 µm) milk fat globule (MFG) size distributions in terms of the fatty acid (FA) composition of the MFG core. Selected cows fell into the respective size group over at least 3 independent measurements, including an observation period before the experiment. Further selection criteria were similar milk production traits between cows (milk yield, fat yield, fat/protein ratio) and established lactation (>50 d in milk). However, the selected groups differed in parity (parity 1-3 and 3-5 in the small and large MFG groups, respectively), and the small MFG group was an average of 25 d in milk later in their lactation period. All cows were under the same nutritional management and environmental conditions. Here, we show that cows with the small or large MFG phenotype differed in their lipid metabolism in terms of the FA composition of the MFG core. Our results indicate that cows with the small MFG phenotype produced milk with higher concentrations of unsaturated FA despite being fed the same diet. We suggest that this characteristic of the small MFG phenotype is the result of increased uptake of long-chain FA from the blood circulation. A relationship between the degree of unsaturation and MFG size was also identified in preliminary studies across other species-namely, camels, sheep, and goats. These findings show the potential for on-farm selection of cows (and potentially other dairy species) based on MFG size to produce milk with improved nutrient composition. This could lead to purpose-specific separation of milk based on MFG size and FA profile, both known to alter the technological properties of milk.
本研究比较了产奶量始终保持较小（体积加权平均直径为 2.92-3.83μm，平均直径为 3.29μm）或较大（体积加权平均直径为 4.58-5.67μm，平均直径为 4.92μm）乳脂球（MFG）大小分布的奶牛，其 MFG 核心的脂肪酸（FA）组成。选定的奶牛在至少 3 次独立测量中（包括实验前的观察期）归入相应的大小组。进一步的选择标准是奶牛之间相似的产奶性状（产奶量、脂肪产量、脂肪/蛋白质比）和已建立的泌乳期（>50 天）。然而，选择的组在胎次（小 MFG 组为 1-3 胎，大 MFG 组为 3-5 胎）和泌乳期（小 MFG 组晚 25 天）方面存在差异。所有奶牛都处于相同的营养管理和环境条件下。在这里，我们表明，在 MFG 核心的 FA 组成方面，具有小或大 MFG 表型的奶牛在其脂质代谢方面存在差异。我们的结果表明，尽管喂食相同的饮食，具有小 MFG 表型的奶牛所产牛奶中不饱和 FA 的浓度更高。我们认为，小 MFG 表型的这一特征是其从血液循环中吸收长链 FA 增加的结果。在跨其他物种（即骆驼、绵羊和山羊）的初步研究中，也发现了不饱和程度与 MFG 大小之间的关系。这些发现表明，基于 MFG 大小在农场中选择奶牛（可能还有其他乳用动物）生产具有改善营养成分的牛奶的潜力。这可能导致基于 MFG 大小和 FA 分布对牛奶进行有针对性的分离，这两种特性都已知会改变牛奶的技术特性。
