Institute of Animal Nutrition and Functional Plant Compounds, University of Veterinary Medicine, 1210 Vienna, Austria.
Christian Doppler Laboratory for Innovative Gut Health Concepts of Livestock, 1210 Vienna, Austria.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae041.
First-lactation cows are particularly prone to subacute ruminal acidosis (SARA) during transition. Besides common risk factors of SARA, such as feeding of starch-rich diets, an individual severity of SARA in cows has been recently evidenced. Yet, the factors that play a role in SARA severity have not been elucidated. The main goal of this research was to evaluate the factors of SARA severity in first-lactation cows during transition and early lactation, which go beyond high-grain feeding, and to explore their impact on behavior, health, and fermentation in the rumen and hindgut. Twenty-four first-lactation Holstein cows with the same feeding regime were used starting from 3 wk before the expected calving day until 10 wk postpartum. Cows received a close-up diet (32% concentrate) until calving and were then transitioned to a lactation diet (60% concentrate) within 1 week. The SARA severity was assessed by cluster analysis of several rumen pH metrics, which revealed exceptionally longer and more severe SARA in cows denominated as high (n = 9), as compared to moderate (n = 9) and low (n = 6) SARA severity cows (P < 0.01). The logistic analysis showed that the length of close-up feeding, age at parturition, and the level of dry matter intake (DMI) were the main factors that influenced the cows' odds for high SARA severity (each P ≤ 0.01). Moreover, the ANOVA hinted differences in the metabolic activity of the ruminal microbiome to promote SARA severity, as indicated by highest ruminal propionate proportions (P = 0.05) in high SARA severity cows, also with similar DMI. The distinct SARA severity was marginally reflected in behavior and there were no effects of SARA severity or high-grain feeding on blood inflammation markers, which peaked at parturition regardless of SARA severity (P < 0.01). Still, ongoing high-grain feeding increased liver enzyme concentrations from 6 wk postpartum on, compared to weeks before (P < 0.01), yet irrespectively of SARA severity. In conclusion, first-lactation cows differed in SARA severity under the same feeding regime, which was ascribed to management factors and differences in ruminal fermentation. Further research is warranted to validate these findings and to understand the mechanisms behind differences in the metabolic function of rumen microbiome, in particular in terms of evaluating markers for various SARA severity, as well as to evaluate potential long-term effects on health, performance, fertility, and longevity of dairy cows.
初产奶牛在过渡期特别容易发生亚急性瘤胃酸中毒（SARA）。除了 SARA 的常见风险因素，如饲喂富含淀粉的日粮外，最近还证明了奶牛 SARA 的个体严重程度。然而，在 SARA 严重程度中起作用的因素尚未阐明。本研究的主要目的是评估初产奶牛在过渡期和早期泌乳期除高谷物喂养以外的 SARA 严重程度的因素，并探讨其对瘤胃和后肠发酵、行为、健康的影响。从预计产犊前 3 周开始，24 头荷斯坦初产奶牛在同一饲养制度下被用于研究，直至产后 10 周。奶牛在产犊前接受紧密饲养（32%浓缩饲料），然后在 1 周内过渡到泌乳期饲料（60%浓缩饲料）。通过聚类分析几个瘤胃 pH 指标来评估 SARA 严重程度，结果表明，与中度（n = 9）和低度（n = 6）SARA 严重程度的奶牛相比，被称为高度（n = 9）SARA 严重程度的奶牛的 SARA 严重程度异常延长且更为严重（P < 0.01）。逻辑分析显示，紧密饲养的时间、分娩时的年龄和干物质采食量（DMI）水平是影响奶牛发生高度 SARA 严重程度的主要因素（每项 P ≤ 0.01）。此外，方差分析表明，瘤胃微生物组的代谢活性存在差异，以促进 SARA 严重程度，这表现为高度 SARA 严重程度的奶牛瘤胃丙酸比例最高（P = 0.05），同时 DMI 也相似。不同的 SARA 严重程度在行为上略有反映，并且 SARA 严重程度或高谷物喂养对血液炎症标志物没有影响，这些标志物在分娩时达到峰值，与 SARA 严重程度无关（P < 0.01）。尽管如此，从产后 6 周开始，持续的高谷物喂养会增加肝脏酶的浓度，与前几周相比（P < 0.01），但与 SARA 严重程度无关。总之，在相同的饲养制度下，初产奶牛的 SARA 严重程度存在差异，这归因于管理因素和瘤胃发酵的差异。需要进一步的研究来验证这些发现，并了解瘤胃微生物组代谢功能差异的机制，特别是在评估各种 SARA 严重程度的标志物方面，以及评估对奶牛健康、性能、繁殖力和寿命的潜在长期影响方面。
