Department of Animal and Veterinary Sciences, University of Idaho, Moscow, ID.
Nancy M. Cummings Research, Extension and Education Center, University of Idaho, Carmen, ID.
J Anim Sci. 2018 Jul 28;96(8):3420-3432. doi: 10.1093/jas/sky202.
Teff (Eragrostis tef cv. Moxie), a warm-season annual grass, could be an excellent forage for beef cattle. However, there is limited information on its nutritive value to cattle when harvested at different stages of maturity. Thus, the objective of this research was to determine the effect of feeding teff hay harvested at the boot (BT), early-heading (EH), or late-heading (LH) stages of maturity on nutrient intake, ruminal fermentation characteristics, omasal nutrient flow, and N utilization in beef cattle. Six ruminally cannulated beef heifers (mean initial BW ± SD, 476 ± 32.6) were used in a replicated 3 × 3 Latin square design with 28-d periods (18 d for adaptation and 10 d for measurements). Dry matter intake was measured daily. Indwelling pH loggers were used to measure ruminal pH from days 21 to 28. Ruminal fluid and omasal digesta were collected from days 26 to 28 to determine fermentation characteristics and omasal nutrient flow. Fecal and urine samples to quantify N excretion were also collected (days 26 to 28). Blood samples for plasma urea-N (PUN) determination were collected 3 h post-feeding on day 28. There were no changes (P > 0.28) in the ADF or NDF content of teff with advancing maturity, but indigestible NDF increased (P < 0.01) with increasing maturity. Maturity had no effect (P ≥ 0.14) on DMI, and ruminal total short-chain fatty acid (SCFA) concentration, pH, digestibility, and outflow of DM, OM, NDF, ADF, and CP. However, the CP content of BT hay was greater (P < 0.01) than for EH and LH hay (18.1, 14.1, and 11.5%, respectively, DM basis), and this resulted in the higher CP intake (P < 0.01) for heifers fed the BT than the EH and LH hay. Consequently, ruminal ammonia-N (NH3-N) concentration was greater (P < 0.01) for heifers fed BT than EH and LH hay, thereby possibly explaining the tendency for a decrease (P = 0.08) in PUN concentration, and a decrease (P < 0.01) in the excretion of total N, urine N, and urea-N (UUN) with advancing maturity. However, fecal N excretion (g/d) did not differ (P = 0.76). In conclusion, despite a decrease in CP intake and ruminal NH3-N concentration, feeding beef heifers EH and LH compared to BT teff hay did not compromise ruminal digestion and outflow of DM, OM, NDF, ADF, and CP, and microbial protein synthesis. Advancing maturity in teff hay also resulted in a decrease in the excretion of total N and urine N and UUN when fed to cattle.
埃塞俄比亚画眉草（Eragrostis tef cv. Moxie）是一种温暖季节的一年生草本植物，可为肉牛提供优质饲料。然而，关于在不同成熟阶段收获的画眉草干草对牛的营养价值的信息有限。因此，本研究旨在确定以不同成熟阶段（萌芽初期 BT、早期头状花序 EH 和晚期头状花序 LH）收获的画眉草干草对肉牛的养分摄入、瘤胃发酵特性、瘤胃后养分流量和氮利用的影响。6 头瘤胃内置有测压管的肉牛阉牛（平均初始体重 ± 标准差，476 ± 32.6）采用 3×3 拉丁方设计进行重复试验，每个试验期为 28d（适应期 18d，测量期 10d）。每天记录干物质摄入量。使用内置 pH 记录仪从第 21 天到第 28 天测量瘤胃 pH。从第 26 天到第 28 天收集瘤胃液和瘤胃后食糜以确定发酵特性和瘤胃后养分流量。还收集粪便和尿液样本以定量氮排泄量（第 26 天到第 28 天）。第 28 天，在第 3 小时饲喂后采集血液样本以测定血浆尿素氮（PUN）。随着成熟度的提高，画眉草的 ADF 和 NDF 含量没有变化（P＞0.28），但不可消化 NDF 增加（P＜0.01）。成熟度对 DMI 以及瘤胃总短链脂肪酸（SCFA）浓度、pH 值、消化率以及 DM、OM、NDF、ADF 和 CP 的流出量没有影响（P≥0.14）。然而，BT 干草的 CP 含量大于 EH 和 LH 干草（分别为 DM 基础上的 18.1%、14.1%和 11.5%），导致饲喂 BT 干草的阉牛 CP 摄入量更高（P＜0.01）。因此，与 EH 和 LH 干草相比，饲喂 BT 干草的阉牛瘤胃氨氮（NH3-N）浓度更高（P＜0.01），这可能解释了 PUN 浓度有下降趋势（P=0.08）以及总氮、尿氮和尿素氮（UUN）排泄量随成熟度提高而降低（P＜0.01）的原因。然而，粪便氮排泄量（g/d）没有差异（P=0.76）。总之，尽管 CP 摄入量和瘤胃 NH3-N 浓度降低，但与 BT 画眉草干草相比，饲喂肉牛 EH 和 LH 画眉草干草并未影响瘤胃消化和 DM、OM、NDF、ADF 和 CP 的流出以及微生物蛋白合成。画眉草干草成熟度的提高也会导致牛采食后总氮和尿氮及 UUN 的排泄量减少。
