The objective was to determine if the eating rate of individual feedlot heifers affects ruminal fermentation using an ex vivo model. Differences in eating rate could affect ruminal fermentation and predispose an animal to be susceptible to metabolic disorders. From a contemporary group of Simmental × Angus heifers (n = 90; BW = 323 kg), 14 heifers were selected for divergent individual eating rates. During the initial 30 d on the finishing diet, a GrowSafe feed intake system was used to identify the heifers with the 7 fastest (7.60 kg DM / h; 9.25 kg DMI in 1.2 h) and 7 slowest (1.38 kg DM / h; 9.24 kg DMI in 6.7 h) eating rates. Prior to feeding, rumen fluid was collected via esophageal tubing 1 d after intake evaluation period. Each rumen fluid sample was mixed with McDougall’s buffer and a common feed substrate (similar to finishing diet). Then the samples were incubated for 24 and 48 h. In vitro dry matter disappearance (IVDMD), pH, volatile fatty acids (VFA), and ammonia were measured following incubation. The MIXED procedure of SAS 9.4 was used for statistical analysis. No eating rate by incubation time interactions (P ≥ 0.11) were observed. Although heifer eating rate did not affect (P = 0.65) IVDMD, values were greater (P < 0.01) at 48 h compared with 24 h. While time affected pH as it decreased (P < 0.01) from 24 to 48 h, heifer eating rate did not affect (P = 0.84) pH. Eating rate had no effect (P ≥ 0.10) on ammonia, total VFA, and molar proportions of acetate, propionate, isobutyrate, butyrate, valerate, and isovalerate at 24 h. Overall, the results indicated individual eating rates of feedlot heifers did not affect ruminal fermentation using an ex vivo model.

中文翻译：

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PSI-8 使用离体模型评估饲养场小母牛个体采食率对瘤胃发酵的影响

目的是使用离体模型确定单个饲养场小母牛的采食率是否会影响瘤胃发酵。进食率的差异可能会影响瘤胃发酵并使动物易患代谢紊乱。从当代的一组西门塔尔 × 安格斯小母牛（n = 90；体重 = 323 公斤）中，选择了 14 头小母牛以实现不同的个体进食率。在育肥日粮的最初 30 天，使用 GrowSafe 采食系统来确定 7 个最快（7.60 kg DM/h；9.25 kg DMI 在 1.2 h）和 7 个最慢（1.38 kg DM/h；9.24 kg DMI in 6.7 h) 进食率。饲喂前，在采食评估期后 1 天通过食道管收集瘤胃液。每个瘤胃液样品与 McDougall's 缓冲液和共同的饲料底物（类似于育肥日粮）混合。然后将样品孵育 24 和 48 小时。孵育后测量体外干物质消失 (IVDMD)、pH、挥发性脂肪酸 (VFA) 和氨。SAS 9.4 的 MIXED 程序用于统计分析。未观察到孵化时间相互作用 (P ≥ 0.11) 的进食率。尽管小母牛采食率不影响（P = 0.65）IVDMD，但与 24 小时相比，48 小时的值更大（P < 0.01）。虽然时间会影响 pH 值，因为它从 24 到 48 小时降低（P < 0.01），但小母牛采食率不影响（P = 0.84）pH。进食速度对 24 小时的氨、总 VFA 和乙酸、丙酸、异丁酸、丁酸、戊酸和异戊酸的摩尔比没有影响 (P ≥ 0.10)。总体而言，结果表明饲养场小母牛的个体采食率不影响使用离体模型的瘤胃发酵。