Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada T6G 2P5.
The Research Center for Animal Science, Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, Japan 739-8528.
J Dairy Sci. 2020 Dec;103(12):11461-11471. doi: 10.3168/jds.2020-18768. Epub 2020 Oct 1.
The objective of this study was to evaluate the effects of starch concentration of close-up diets on plasma concentrations of energy metabolites and rumen pH of dairy cows after calving. Eighteen multiparous Holstein dairy cows (mean parity = 2.78; mean body weight = 708 kg; mean body condition score = 3.08) fitted with ruminal cannulas were assigned to treatment balanced for parity, body condition score, and expected calving date. Cows were enrolled in the study at d 28 ± 3 before the expected calving date and fed either a low-starch (LS; 14.0% starch) or high-starch (HS; 26.1% starch) diet until parturition. All cows were fed a common diet after calving (25.1% starch). A grain challenge was performed on d 7 ± 2 and 21 ± 2 after calving by dosing 6.35 kg (dry matter basis) of finely ground barley and wheat grain (1:1) into the rumen via cannula. Feeding the HS diet before calving increased the duration (369 vs. 49 min/d) and area of pH below 5.8 (85.1 vs. 5.2 pH × min/d) during d -10 to -8. In addition, even though all cows were fed a common diet after calving, HS cows tended to have longer duration (177 vs. 76 min/6 h) and greater area of pH below 5.8 (67.8 vs. 20.3 pH × min/6 h) during a grain challenge on d 7. Plasma concentration of insulin tended to be greater in cows fed the HS diet (1.40 vs. 1.09 ng/mL), whereas plasma free fatty acid concentration was not different between treatments during the grain challenge on d 7. During the grain challenge on d 21, neither rumen pH nor blood metabolites were different between the HS and LS cows. These findings suggested that feeding an HS diet during the close-up period does not mitigate rumen pH depression but may exacerbate it after calving compared with feeding an LS diet.
本研究旨在评估临产前高淀粉（26.1%）和低淀粉（14.0%）日粮对奶牛产后血浆能量代谢物浓度和瘤胃 pH 的影响。选择 18 头荷斯坦奶牛（胎次平均值=2.78；体重平均值=708kg；体况评分平均值=3.08），通过瘤胃瘘管进行评估。根据胎次、体况评分和预期产犊日期进行平衡分组。奶牛于预期产犊日期前 28±3d 进入研究，分娩前分别饲喂低淀粉（LS）或高淀粉（HS）日粮。所有奶牛在产后均饲喂相同的日粮（25.1%淀粉）。在产后第 7±2 和 21±2d 进行谷物挑战，通过瘘管向瘤胃内灌服 6.35kg（干物质基础）粉碎后的大麦和小麦（1:1）。临产前饲喂 HS 日粮增加了产后第-10 天至-8 天的 pH 低于 5.8 的持续时间（369 比 49min/d）和面积（85.1 比 5.2pH×min/d）。此外，尽管所有奶牛产后均饲喂相同的日粮，但 HS 奶牛在产后第 7 天谷物挑战时 pH 低于 5.8 的持续时间（177 比 76min/6h）和面积（67.8 比 20.3 pH×min/6h）更大。HS 日粮组奶牛的胰岛素浓度有升高的趋势（1.40 比 1.09ng/mL），但在产后第 7 天谷物挑战时两组间游离脂肪酸浓度无差异。产后第 21 天，HS 和 LS 组奶牛的瘤胃 pH 和血液代谢物均无差异。这些结果表明，与饲喂 LS 日粮相比，临产前饲喂 HS 日粮不能减轻产后瘤胃 pH 降低，但可能会使其加重。
