Colorado State University, Department of Animal Sciences, Fort Collins, CO, 80523, USA.
North Carolina State University, Department of Animal Sciences, Raleigh, NC 27695, USA.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae319.
Two experiments were conducted to determine: 1) the impact of strained rumen fluid (SRF) alone or SRF with particle-associated microorganisms (PAO) included and dilution on in vitro dry matter digestibility (DMD) and 2) the impact of trace mineral (TM) source on in vitro fermentation characteristics and TM solubility under simulated abomasal and intestinal conditions. In experiment 1, 3 cannulated steers were adapted to a diet formulated to meet the nutrient requirements for lactating dairy cows. Strained RF was obtained by straining rumen content through 2 layers of cheesecloth. Half of the remaining digesta was washed with McDougall's buffer and filtered through 2 layers of cheesecloth to obtain PAO. Both SRF and PAO were filtered again through 8 layers of cheesecloth. Strained RF was mixed with either McDougall's buffer (SRF) or PAO (SRF+ + PAO) at a ratio of 1:2 or 1:4 and incubated at 39 °C for 12 h using the ground basal diet as the substrate. Digestibility of DM was greater in digestion tubes containing SRF and SRF + PAO at a 1:2 ratio. In experiment 2, 8 steers fitted with a ruminal cannula were blocked by body weight and assigned to 1 of the 2 treatment groups. Treatments consisted of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either: 1) sulfate (STM) or 2) hydroxychloride (HTM) sources. Steers were housed in individual pens and fed the same diet as described in experiment 1. Dietary TM treatments were mixed with dried distiller grains and mixed in the diet, by hand, immediately after basal diet delivery. Dietary treatments were fed for 14 d. On day 15, SRF + PAO was collected from each steer (STM-RF and HTM-RF) and used in a series of in vitro crossover experiments. In vitro substrates (S) used were the ground diets consumed by the animals on each treatment (STM-S and HTM-S). Incubations containing HTM-S had greater (P < 0.01) total volatile fatty acid (VFA) concentration and propionic acid molar proportions, but lesser (P < 0.01) acetic acid molar proportions than STM-S. Rumen fluid from steers supplemented with HTM had a greater (P < 0.03) total VFA than STM-RF at 24 h post incubation. After 12 h post incubation, the molar proportion of propionic acid in HTM-RF was lesser (P = 0.04) than in STM-RF. After simulated abomasal digestion, soluble Mn concentration in HTM-S was greater (P < 0.01) than in STM-S. These data indicate that the source of TM can influence in vitro rumen fermentation characteristics and Mn solubility under simulated abomasal conditions.
1）单独使用应变瘤胃液（SRF）或包含颗粒相关微生物（PAO）的 SRF 以及稀释对体外干物质消化率（DMD）的影响，2）痕量矿物质（TM）源对模拟真胃和肠道条件下体外发酵特性和 TM 溶解度的影响。在实验 1 中，3 头有瘘管的奶牛适应了一种按照满足泌乳奶牛营养需求配制的日粮。应变 RF 是通过将瘤胃液通过 2 层奶酪布过滤获得的。剩余消化物的一半用 McDougall 缓冲液冲洗并用 2 层奶酪布过滤以获得 PAO。SRF 和 PAO 都再次通过 8 层奶酪布过滤。应变 RF 与 McDougall 缓冲液（SRF）或 PAO（SRF+PAO）以 1:2 或 1:4 的比例混合，并在 39°C 下孵育 12 小时，使用基础日粮作为底物。含有 SRF 和 SRF+PAO 的消化管中的 DM 消化率更高，比例为 1:2。在实验 2 中，8 头安装有瘤胃瘘管的奶牛按体重分为 1 组，随机分为 2 个处理组之一。处理组由 10mg Cu、40mg Mn 和 60mg Zn/kg DM 组成，来自：1）硫酸盐（STM）或 2）羟氯化物（HTM）源。奶牛被安置在单独的围栏中，并按照实验 1 中描述的相同饮食进食。日粮 TM 处理与干燥的蒸馏酒糟混合，并在基础日粮交付后立即手工混合到日粮中。日粮处理饲喂 14 天。在第 15 天，从每头奶牛（STM-RF 和 HTM-RF）中收集 SRF+PAO，并在一系列体外交叉实验中使用。体外底物（S）是动物在每个处理中消耗的基础日粮（STM-S 和 HTM-S）。含有 HTM-S 的孵育物具有更高的（P<0.01）总挥发性脂肪酸（VFA）浓度和丙酸摩尔比例，但乙酸摩尔比例较低（P<0.01）。HTM 补充的瘤胃液在孵育后 24 小时的总 VFA 高于 STM-RF（P<0.03）。孵育 12 小时后，HTM-RF 中的丙酸摩尔比例低于 STM-RF（P=0.04）。经过模拟真胃消化后，HTM-S 中的可溶性 Mn 浓度高于 STM-S（P<0.01）。这些数据表明，TM 的来源可以影响模拟真胃条件下的体外瘤胃发酵特性和 Mn 溶解度。
