Twelve Angus steers (BW 452.8 ± 6.1 kg) fitted with ruminal cannulae were used to determine the impact of trace mineral (TM) source on digestibility, ruminal volatile fatty acid (VFA) composition, ruminal soluble concentrations of Cu, Zn, and Mn, and relative binding strength of trace minerals located in the rumen insoluble digesta fraction. Steers were fed a medium-quality grass hay diet (DM basis: 10.8% CP, 63.1% neutral detergent fiber [NDF], 6.9 mg Cu/kg, 65.5 mg Mn/kg, and 39.4 mg Zn/kg) supplemented with protein for 21 d. Treatments consisted of either sulfate (STM) or hydroxy (HTM) sources (n = 6 steers/treatment) to provide 20, 40, and 60 mg supplemental Cu, Mn, and Zn/kg DM, respectively. Following a 21-d adaptation period, total fecal output was collected for 5 d. Dry matter (P < 0.07) and CP (P < 0.06) digestibility tended to be reduced, and NDF (P < 0.04) and acid detergent fiber (ADF) (P < 0.05) digestibility were reduced in STM- vs. HTM-supplemented steers. On day 6, ruminal fluid was collected at 0, 2, and 4 h post-feeding and analyzed for VFA. There were no treatment x time interactions for VFA. Steers receiving HTM had less (P < 0.02) molar proportions of butyric acid and greater (P < 0.05) total VFA concentrations than STM-supplemented steers. Steers were then fed the same diet without supplemental Cu, Zn, or Mn for 14 d. On day 15 steers received a pulse dose of 20 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either STM or HTM (n = 6 steers/treatment). Ruminal samples were obtained at 2-h intervals starting at −4 and ending at 24 h relative to dosing. There was a treatment x time interaction (P < 0.03) for ruminal soluble Cu, Mn, and Zn concentrations. Ruminal soluble mineral concentrations were greater (P < 0.05) for Cu at 4, 6, 8, 10, 12, and 14 h; for Mn at 4 and 6 h; and for Zn at 4, 6, and 8 h post-dosing in STM compared with HTM-supplemented steers. Copper concentrations were greater (P < 0.05) at 12 and 24 h and Zn concentrations in ruminal solid digesta were greater at 24 h in HTM-supplemented steers. Upon dialysis against Tris-EDTA, the percent Zn released from digesta was greater (P < 0.05) at 12 h (P < 0.03) and 24 h (P < 0.05), and the percent Cu released was greater (P < 0.02) at 24 h post-dosing in HTM steers when compared with STM-supplemented steers. Results indicate that Cu and Zn from HTM have low solubility in the rumen and appear to be less tightly bound to ruminal solid digesta than Cu and Zn from STM. The lower ruminal soluble concentrations of Cu and Zn in steers given HTM were associated with greater fiber digestibility.

中文翻译：

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微量矿物质来源影响饲喂中等品质干草饲料的肉牛的瘤胃微量矿物质代谢和纤维消化

12 头装有瘤胃插管的安格斯公牛 (BW 452.8 ± 6.1 kg) 用于确定微量矿物质 (TM) 来源对消化率、瘤胃挥发性脂肪酸 (VFA) 组成、瘤胃可溶性铜、锌和锰浓度的影响，和位于瘤胃不溶性食糜部分的微量矿物质的相对结合强度。给阉牛喂食中等品质的干草饲料（干物质基础：10.8% CP、63.1% 中性洗涤纤维 [NDF]、6.9 mg Cu/kg、65.5 mg Mn/kg 和 39.4 mg Zn/kg），并补充蛋白质21 天。处理由硫酸盐 (STM) 或羟基 (HTM) 来源（n = 6 头牛/处理）组成，分别提供 20、40 和 60 mg 补充铜、锰和锌/kg DM。在 21 天的适应期后，收集 5 天的粪便总量。干物质 (P < 0.07) 和 CP (P < 0. 06) 消化率趋于降低，并且 NDF (P < 0.04) 和酸性洗涤纤维 (ADF) (P < 0.05) 的消化率在 STM 与 HTM 补充的阉牛中降低。第 6 天，在饲喂后 0、2 和 4 小时收集瘤胃液并分析 VFA。VFA 没有治疗 x 时间的相互作用。与补充 STM 的阉牛相比，接受 HTM 的阉牛具有较少 (P < 0.02) 摩尔比例的丁酸和较高 (P < 0.05) 的总 VFA 浓度。然后给阉牛饲喂相同的饮食，不添加铜、锌或锰，持续 14 天。在第 15 天，公牛从 STM 或 HTM（n = 6 头公牛/处理）接受 20 mg Cu、40 mg Mn 和 60 mg Zn/kg DM 的脉冲剂量。相对于给药，以 2 小时间隔获得瘤胃样品，从 -4 开始到 24 小时结束。存在治疗 x 时间交互作用（P < 0。03) 瘤胃可溶性铜、锰和锌浓度。在 4、6、8、10、12 和 14 小时，Cu 的瘤胃可溶性矿物质浓度更高（P < 0.05）；对于 4 小时和 6 小时的 Mn；与补充 HTM 的阉牛相比，STM 给药后 4、6 和 8 小时的锌。添加 HTM 的阉牛在 12 小时和 24 小时时铜浓度较高（P < 0.05），而瘤胃固体食糜中的锌浓度在 24 小时时较高。在对 Tris-EDTA 进行透析时，12 h (P < 0.03) 和 24 h (P < 0.05) 从食糜中释放的 Zn 百分比更大 (P < 0.05)，释放的 Cu 百分比更大 (P < 0.05) ; 0.02) 与添加 STM 的公牛相比，HTM 公牛在给药后 24 小时。结果表明，HTM 中的铜和锌在瘤胃中的溶解度较低，与瘤胃固体食糜的结合似乎不如 STM 中的铜和锌。给予 HTM 的肉牛瘤胃可溶性铜和锌浓度较低，与较高的纤维消化率有关。