Secchi Giorgia, Amalfitano Nicolò, Carafa Ilaria, Franciosi Elena, Gallo Luigi, Schiavon Stefano, Sturaro Enrico, Tagliapietra Franco, Bittante Giovanni
Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE) University of Padova (Padua), 35020 Legnaro (PD), Italy; Research and Innovation Centre, Edmund Mach Foundation, San Michele all'Adige, 38010 San Michele all'Adige (TN), Italy.
Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE) University of Padova (Padua), 35020 Legnaro (PD), Italy.
J Dairy Sci. 2023 Jan;106(1):96-116. doi: 10.3168/jds.2022-22449. Epub 2022 Nov 16.
The study of the complex relationships between milk metagenomics and milk composition and cheese-making efficiency as affected by indoor farming and summer highland grazing was the aim of the present work. The experimental design considered monthly sampling (over 5 mo) of the milk produced by 12 Brown Swiss cows divided into 2 groups: the first remained on a lowland indoor farm from June to October, and the second was moved to highland pastures in July and then returned to the lowland farm in September. The resulting 60 milk samples (2 kg each) were used to analyze milk composition, milk coagulation, curd firming, and syneresis processes, and to make individual model cheeses to measure cheese yields and nutrient recoveries in the cheese. After DNA extraction and Illumina Miseq sequencing, milk microbiota amplicons were also processed by means of an open-source pipeline called Quantitative Insights Into Microbial Ecology (Qiime2, version 2018.2; https://qiime2.org). Out of a total of 44 taxa analyzed, 13 bacterial taxa were considered important for the dairy industry (lactic acid bacteria, LAB, 5 taxa; and spoilage bacteria, 4) and for human (other probiotics, 2) and animal health (pathogenic bacteria, 2). The results revealed the transhumant group of cows transferred to summer highland pastures showed an increase in almost all the LAB taxa, bifidobacteria, and propionibacteria, and a reduction in spoilage taxa. All the metagenomic changes disappeared when the transhumant cows were moved back to the permanent indoor farm. The relationships between 17 microbial traits and 30 compositional and technological milk traits were investigated through analysis of correlation and latent explanatory factor analysis. Eight latent factors were identified, explaining 75.3% of the total variance, 2 of which were mainly based on microbial traits: pro-dairy bacteria (14% of total variance, improving during summer pasturing) and pathogenic bacteria (6.0% of total variance). Some bacterial traits contributed to other compositional-technological latent factors (gelation, udder health, and caseins).
本研究旨在探讨室内养殖和夏季高地放牧对牛奶宏基因组学、牛奶成分及奶酪制作效率之间复杂关系的影响。实验设计为对12头瑞士褐牛每月（共5个月）进行一次采样，这些牛分为两组：第一组在6月至10月期间留在低地室内农场，第二组在7月转移到高地牧场，9月再回到低地农场。采集到的60份牛奶样本（每份2千克）用于分析牛奶成分、牛奶凝固、凝乳形成和乳清渗出过程，并制作单个模型奶酪以测量奶酪产量和奶酪中的营养成分回收率。在进行DNA提取和Illumina Miseq测序后，牛奶微生物扩增子还通过一个名为“微生物生态学定量洞察”（Qiime2，2018.2版本；https://qiime2.org）的开源管道进行处理。在总共分析的44个分类单元中，有13个细菌分类单元被认为对乳制品行业（乳酸菌，LAB，5个分类单元；腐败菌，4个）、人类健康（其他益生菌，2个）和动物健康（病原菌，2个）具有重要意义。结果显示，转移到夏季高地牧场的季节性迁移牛群中，几乎所有乳酸菌分类单元、双歧杆菌和丙酸杆菌数量增加，腐败菌分类单元数量减少。当季节性迁移牛群回到永久性室内农场时，所有宏基因组变化均消失。通过相关性分析和潜在解释因子分析，研究了17个微生物特征与30个牛奶成分和工艺特征之间的关系。确定了8个潜在因子，解释了总方差的75.3%，其中2个主要基于微生物特征：有益乳制品细菌（占总方差的14%，在夏季放牧期间增加）和病原菌（占总方差的6.0%）。一些细菌特征对其他成分 - 工艺潜在因子（凝胶化、乳房健康和酪蛋白）有贡献。
