GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, F-31326, France; Interactions Hôtes-Agents Pathogènes (IHAP), Université de Toulouse, ENVT, Toulouse, F-131076, France.
GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, F-31326, France.
J Dairy Sci. 2018 Mar;101(3):2248-2259. doi: 10.3168/jds.2017-13479. Epub 2018 Jan 10.
During the transition from late gestation to early lactation ruminants experience a negative energy balance (NEB), which is considered to increase susceptibility to mammary infections. Our previous study in 2 divergent lines of sheep selected for high and low somatic cell score (SCS) suggested an association between the response to NEB and genetic susceptibility to mastitis. Forty-eight early-lactation primiparous dairy ewes from the 2 SCS genetic lines were allocated to 2 homogeneous subgroups-an NEB group, which was energy restricted and received 60% of the energy requirements for 15 d, and a control-fed group-to obtain 4 balanced groups of 12 ewes: high-SCS positive energy balance, low-SCS positive energy balance, high-SCS NEB, and low-SCS NEB. High-SCS ewes showed greater weight loss and increased plasmatic concentrations of β-hydroxybutyrate and nonesterified fatty acids than low-SCS ewes when confronted with an induced NEB. The aim of this study was to further characterize this interaction by combining transcriptomic and phenotypic data with a generalized partial least squares discriminant analysis using mixOmics package framework. A preliminary analysis using 3 blocks of phenotypes (fatty acids, weight and production, blood metabolites) revealed a high correlation between fat-to-protein ratio, β-hydroxybutyrate, and nonesterified fatty acids concentrations with milk long-chain fatty acid yields. These phenotypes allowed good discrimination of the energy-restricted high-SCS ewes and confirmed a high level of adipose tissue mobilization in this group. A second analysis, which included RNA-seq data, revealed high correlations between the long-chain fatty acid yields in milk and PDK4, CPT1A, SLC25A20, KLF10, and KLF11 expression, highlighting the relationship between mobilization of body reserves and enhanced fatty acids utilization for energy production in blood cells. Finally, analysis of milk composition measured in 1,025 ewes from the 2 genetic lines over 10 yr confirmed significant higher fat-to-protein ratio in high-SCS ewes in early lactation. Altogether, our results strongly confirmed a genetic link between susceptibility to mastitis and metabolic adaptation to energy shortage. Improving genetic resistance to mastitis using SCS should be accompanied by a favorable effect on the response to metabolic stress, especially in highly stressful early lactation. Moreover, this study suggests that the fat-to-protein ratio could be used as a low-cost tool for monitoring energy balance and ketosis during this critical phase of lactation.
在妊娠后期到泌乳早期的过渡期间，反刍动物经历负能量平衡（NEB），这被认为会增加乳房感染的易感性。我们之前在选择高体细胞评分（SCS）和低体细胞评分（SCS）的 2 个绵羊品系中的研究表明，NEB 反应与乳房炎易感性的遗传易感性之间存在关联。48 只来自 2 个 SCS 遗传系的泌乳初期初产母羊被分配到 2 个同质亚组-能量限制组，接受 15 天 60%的能量需求，和对照组-以获得 4 个平衡组的 12 只母羊：高 SCS 正能量平衡，低 SCS 正能量平衡，高 SCS NEB 和低 SCS NEB。与低 SCS 母羊相比，高 SCS 母羊在面临诱导性 NEB 时表现出更大的体重减轻和血浆 β-羟丁酸和非酯化脂肪酸浓度升高。本研究的目的是通过使用 mixOmics 软件包框架结合转录组学和表型数据与广义偏最小二乘判别分析进一步描述这种相互作用。使用 3 个表型块（脂肪酸、体重和产奶量、血液代谢物）的初步分析显示，脂肪-蛋白质比、β-羟丁酸和非酯化脂肪酸浓度与牛奶长链脂肪酸产量之间高度相关。这些表型可以很好地区分能量限制的高 SCS 母羊，并证实该组中有高水平的脂肪组织动员。第二次分析包括 RNA-seq 数据，揭示了牛奶中长链脂肪酸产量与 PDK4、CPT1A、SLC25A20、KLF10 和 KLF11 表达之间的高度相关性，突出了动员身体储备与增强血液细胞中脂肪酸的能量利用之间的关系。最后，对来自 2 个遗传系的 1025 只母羊在 10 年内测量的牛奶成分的分析证实，在泌乳早期，高 SCS 母羊的脂肪-蛋白质比显著更高。总之，我们的结果强烈证实了乳房炎易感性与对能量短缺的代谢适应之间的遗传联系。使用 SCS 提高对乳房炎的遗传抗性应该伴随着对代谢应激的有利影响，特别是在高度应激的泌乳早期。此外，这项研究表明，脂肪-蛋白质比可以作为监测泌乳期这一关键阶段能量平衡和酮症的低成本工具。
