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 caecum, 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 caecum cannulated horses were used in a 2×2 crossover design, with two 12-day periods consisting of 10 d of diet adaptation and two days of data collection. Hay was fed at 0600, 1400 and 2000 h, 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 DM hay and 474 g DM oats (0.4 g starch/kg BW), and data was collected until 8 h after feeding. Gastric emptying of oats was estimated using the 13C acetic acid breath test, where breath samples were analysed for 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 caecal fluid were collected at hourly intervals. Blood plasma was analysed for glucose and insulin and baseline concentrations, peak concentrations, time of peaks and area under the curves (AUC) were calculated. A pH probe was placed in the caecum measuring pH every min to find minimum pH and time to reach minimum pH. Hourly caecal samples were analysed for pH and short-chained fatty acids (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 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 to 170 min (P = 0.006) and 170 to 280 min (P = 0.006) for O-H than H-O. In general, 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 caecum pH than plasma glucose and insulin.

中文翻译：

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草料和燕麦的饲喂顺序对马胃排空相关的代谢和消化反应的影响


草料和精饲料的饲喂顺序可能会影响马的胃排空和随后的消化。本研究的目的是在改变燕麦 （O） 和干草 （H） 的摄食顺序时，分别测量血浆和盲肠中的胃排空以及代谢和消化反应（燕麦先吃，然后干草：O-H）。在 2×2 交叉设计中使用了 4 匹盲肠空心马，其中两个 12 天的周期包括 10 天的饮食适应和 2 天的数据收集。在 0600、1400 和 2000 小时饲喂干草，而燕麦在早上饲喂干草前 15 分钟或饲喂后 1 小时。在数据收集的天数，在饲喂 1.4 kg 干草和 474 g DM 燕麦（0.4 g 淀粉/kg 体重）之前收集基线样品，并在饲喂后 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，其中分析了 13C 乙酸与燕麦混合后呼吸样本的 12C：13C 比率。计算胃排空系数 （GEC）、排泄 13C 总累积恢复量的一半的时间 （t1/2） 和 13C 排泄最大量的时间 （Tmax）。每小时采集一次血液和盲肠液样本。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 （AUC）。在盲肠中放置一个 pH 探针，每分钟测量一次 pH 值，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 醋酸呼气试验的结果表明，喂养顺序会影响胃排空，因为 Tmax 更长 （P = 0.004） 时，饲喂 H-O （2.18 h） 比饲喂 O-H （1.09 h），但对 GEC 和 T1/2 没有影响。未发现喂养顺序对血浆葡萄糖和胰岛素测量的影响。饲喂顺序对最低 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 O-H 在 0 至 170 分钟 （P = 0.006） 和 170 至 280 分钟 （P = 0.006） 的区间内的平均 pH 值低于 H-O。一般来说，采样时间对 SCFA 浓度的影响大于饲喂顺序。总之，这项研究表明，喂养顺序会影响胃排空，消化和代谢反应在盲肠 pH 值中比血浆葡萄糖和胰岛素更明显地反映出来。