Université Clermont Auvergne, INRA, VetAgro Sup, UMR Herbivores, F-63122 Saint-Genès-Champanelle, France.
Lallemand SAS, F-31702 Blagnac, France.
Animal. 2020 Feb;14(2):388-398. doi: 10.1017/S1751731119001629. Epub 2019 Jul 16.
High-starch diets (HSDs) fed to high-producing ruminants are often responsible for rumen dysfunction and could impair animal health and production. Feeding HSDs are often characterized by transient rumen pH depression, accurate monitoring of which requires costly or invasive methods. Numerous clinical signs can be followed to monitor such diet changes but no specific indicator is able to make a statement at animal level on-farm. The aim of this pilot study was to assess a combination of non-invasive indicators in dairy cows able to monitor a HSD in experimental conditions. A longitudinal study was conducted in 11 primiparous dairy cows fed with two different diets during three successive periods: a 4-week control period (P1) with a low-starch diet (LSD; 13% starch), a 4-week period with an HSD (P2, 35% starch) and a 3-week recovery period (P3) again with the LSD. Animal behaviour was monitored throughout the experiment, and faeces, urine, saliva, milk and blood were sampled simultaneously in each animal at least once a week for analysis. A total of 136 variables were screened by successive statistical approaches including: partial least squares-discriminant analysis, multivariate analysis and mixed-effect models. Finally, 16 indicators were selected as the most representative of a HSD challenge. A generalized linear mixed model analysis was applied to highlight parsimonious combinations of indicators able to identify animals under our experimental conditions. Eighteen models were established and the combination of milk urea nitrogen, blood bicarbonate and feed intake was the best to detect the different periods of the challenge with both 100% of specificity and sensitivity. Other indicators such as the number of drinking acts, fat:protein ratio in milk, urine, and faecal pH, were the most frequently used in the proposed models. Finally, the established models highlight the necessity for animals to have more than 1 week of recovery diet to return to their initial control state after a HSD challenge. This pilot study demonstrates the interest of using combinations of non-invasive indicators to monitor feed changes from a LSD to a HSD to dairy cows in order to improve prevention of rumen dysfunction on-farm. However, the adjustment and robustness of the proposed combinations of indicators need to be challenged using a greater number of animals as well as different acidogenic conditions before being applied on-farm.
高淀粉日粮（HSD）用于高生产性能的反刍动物往往会导致瘤胃功能障碍，并可能损害动物的健康和生产性能。饲喂 HSD 的特点通常是暂时性的瘤胃 pH 降低，准确监测需要昂贵或侵入性的方法。可以通过许多临床症状来监测这种饮食变化，但没有特定的指标能够在农场层面上对动物水平做出声明。本初步研究的目的是评估奶牛中能够在实验条件下监测 HSD 的非侵入性指标的组合。对 11 头初产奶牛进行了一项纵向研究，这些奶牛在三个连续时期内分别饲喂两种不同的日粮：低淀粉日粮（LSD；13%淀粉）的 4 周对照期（P1）、高淀粉日粮（P2，35%淀粉）的 4 周期和再次饲喂 LSD 的 3 周恢复期（P3）。在整个实验过程中监测动物行为，并在每个动物中每周至少采集一次粪便、尿液、唾液、牛奶和血液进行分析。通过逐步的统计方法筛选了总共 136 个变量，包括：偏最小二乘判别分析、多变量分析和混合效应模型。最后，选择了 16 个指标作为 HSD 挑战的最具代表性指标。应用广义线性混合模型分析来突出能够在我们的实验条件下识别动物的简洁指标组合。建立了 18 个模型，其中牛奶尿素氮、血液碳酸氢盐和采食量的组合是检测挑战不同时期的最佳组合，特异性和敏感性均达到 100%。其他指标，如饮水量、牛奶、尿液和粪便 pH 的脂肪：蛋白质比值，在提出的模型中使用最多。最后，所建立的模型突出了动物在 HSD 挑战后需要 1 周以上的恢复期日粮才能恢复到初始对照状态的必要性。本初步研究表明，使用非侵入性指标组合来监测从 LSD 到 HSD 的奶牛饲料变化是有意义的，这有助于改善农场中瘤胃功能障碍的预防。然而，在将这些组合的指标应用于农场之前，需要使用更多的动物和不同的产酸条件来挑战和调整这些组合的指标的适应性和稳健性。
