Jensen Rasmus Bovbjerg, Walslag Ingrid Hornnes, Marcussen Caroline, Thorringer Nana Wentzel, Junghans Peter, Nyquist Nicole Frost
Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, Ås, Norway.
Department of Paraclinical Sciences, Norwegian University of Life Sciences, Ås, Norway.
J Anim Sci. 2025 Jan 4;103. doi: 10.1093/jas/skae368.
Feeding order of forage and concentrate might affect gastric emptying and subsequently digestion in horses. The objective of this study was to measure gastric emptying in combination with metabolic and digestive responses in the plasma and cecum, respectively, when changing the feeding order of oats (O) and hay (H) (oats first, then hay: O-H vs. hay first, then oats: H-O). Four cecum cannulated horses were used in a 2 × 2 crossover design, with two 12-d periods consisting of 10 d of diet adaptation and 2 d of data collection. Hay was fed at 0600, 1400, and 2000 hours, while oats were fed in the morning either 15 min before or 1 h after feeding hay. On days of data collection, baseline samples were collected before feeding 1.4 kg dry matter (DM) hay and 474 g DM oats (0.4 g starch/kg body weight), and data were collected until 8 h after feeding. Gastric emptying of oats was estimated using the 13C acetic acid breath test, where breath samples were analyzed for a 12C:13C ratio after administration of 13C acetic acid mixed with oats. Gastric emptying coefficient (GEC), time where half of the total cumulative recovery of 13C was excreted (t1/2), and time where the maximal amount of 13C was excreted (Tmax) were calculated. Samples of blood and cecal fluid were collected at hourly intervals. Blood plasma was analyzed for glucose and insulin, and baseline concentrations, peak concentrations, time of peaks, and area under the curves were calculated. A pH probe was placed in the cecum measuring pH every minute to find minimum pH and time to reach minimum pH. Hourly cecal samples were analyzed for pH and short-chained fatty acid (SCFA) concentrations. Results from the 13C acetic acid breath test indicated that feeding order affected gastric emptying, as Tmax was longer (P = 0.004) when feeding H-O (2.18 h) than O-H (1.09 h), but there was no effect on the GEC and T1/2. No effect of feeding order was found for plasma glucose and insulin measures. Feeding order had no effect on minimum pH, but the time to reach minimum pH increased (P = 0.014) from 170 min for O-H to 280 min for H-O, and average pH was lower in the intervals 0-170 min (P = 0.006) and 170-280 min (P = 0.006) for O-H than H-O. In general, the time of sampling had a larger effect on SCFA concentrations than feeding order. In conclusion, this study indicates that feeding order affected gastric emptying, and the digestive and metabolic responses were more clearly reflected in cecum pH than in plasma glucose and insulin.
草料和精饲料的投喂顺序可能会影响马匹的胃排空，进而影响消化。本研究的目的是在改变燕麦（O）和干草（H）的投喂顺序（先喂燕麦，再喂干草：O-H 与先喂干草，再喂燕麦：H-O）时，分别结合血浆和盲肠中的代谢及消化反应来测量胃排空情况。四匹装有盲肠瘘管的马采用 2×2 交叉设计，两个 12 天的周期包括 10 天的饮食适应期和 2 天的数据收集期。干草在 06:00、14:00 和 20:00 投喂，而燕麦在早上投喂干草前 15 分钟或投喂干草后 1 小时投喂。在数据收集日，在投喂 1.4 千克干物质（DM）干草和 474 克 DM 燕麦（0.4 克淀粉/千克体重）前采集基线样本，并在投喂后 8 小时内收集数据。使用 13C 乙酸呼气试验估计燕麦的胃排空情况，在将 13C 乙酸与燕麦混合给药后，分析呼气样本中的 12C:13C 比值。计算胃排空系数（GEC）、13C 总累积回收率排出一半的时间（t1/2）以及 13C 排出量最大的时间（Tmax）。每隔一小时采集血液和盲肠液样本。分析血浆中的葡萄糖和胰岛素，并计算基线浓度、峰值浓度、峰值时间和曲线下面积。将 pH 探头置于盲肠中，每分钟测量一次 pH，以找到最低 pH 值和达到最低 pH 值的时间。每小时分析盲肠样本的 pH 值和短链脂肪酸（SCFA）浓度。13C 乙酸呼气试验的结果表明，投喂顺序会影响胃排空，因为投喂 H-O（2.18 小时）时的 Tmax 比投喂 O-H（1.09 小时）时更长（P = 0.004），但对 GEC 和 T1/2 没有影响。在血浆葡萄糖和胰岛素测量方面未发现投喂顺序的影响。投喂顺序对最低 pH 值没有影响，但达到最低 pH 值的时间从 O-H 的 170 分钟增加到 H-O 的 280 分钟（P = 0.014），并且在 0-170 分钟（P = 0.006）和 170-280 分钟（P = 0.006）期间，O-H 的平均 pH 值低于 H-O。总体而言，采样时间对 SCFA 浓度的影响大于投喂顺序。总之，本研究表明投喂顺序会影响胃排空，并且消化和代谢反应在盲肠 pH 值中比在血浆葡萄糖和胰岛素中更明显地体现出来。
