Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX.
Department of Plant and Soil Sciences, Texas Tech University, Lubbock, TX.
J Anim Sci. 2020 Mar 1;98(3). doi: 10.1093/jas/skaa048.
The use of portable X-ray fluorescence (PXRF) spectrometry to detect external markers on processed or unprocessed cattle and sheep fecal specimens to estimate apparent total tract digestibility (ATTD) was evaluated. Exp. 1: ruminally cannulated Angus-crossbred steers (n = 7; BW = 520 ± 30 kg) were individually fed ad libitum for 21 d in a completely randomized design (CRD). Markers (Cr2O3 and TiO2) were placed inside the rumen twice daily (7.5 g of each marker). Fecal samples were collected twice daily from day 14 to 21. Exp. 2: crossbred wethers (n = 8; BW = 68 ± 3 kg) were individually fed ad libitum for 21 d in a CRD. During this period, 2 g of Cr2O3 and TiO2 were top-dressed onto the feed twice daily. Sheep were housed in metabolism crates for 5 d for total fecal collection. Concentration of markers was determined on diets, refusals, and fecal specimens (fresh, dry-only, and dried/ground) using atomic absorption to detect Cr and spectrophotometry for Ti. Concentration of both markers was also determined via the PXRF spectrometer. Delta between ATTD estimated by wet chemistry and PXRF was not different from zero (P ≥ 0.14) when using cattle fresh fecal specimens for both markers, whereas ATTD estimated by PXRF with dry-only and dried/ground fecal specimens were 3.6 and 1.1 percent units lower (P ≤ 0.04), respectively, than ATTD estimated by wet chemistry for Cr and Ti, respectively. Regardless of the fecal sample preparation method on cattle specimens, Ti concentration was similar (P = 0.39) among methodologies, while Cr was underestimated (P < 0.01) by 13% when PXRF was used in dry-only or dried/ground samples. The ATTD of sheep was underestimated (P < 0.01) by 2.4 percent units compared with control when Cr was measured by PXRF in dry-only samples. The Cr concentration in dry-only fecal specimens of sheep tended (P = 0.09) to be lower compared with wet chemistry analysis. Fresh and dry/ground sheep fecal samples assessed for Cr, and dry-only assessed for Ti were not (P ≥ 0.49) affected by detection method. The Cr fecal recovery tended (P = 0.10) to be the lowest for dry-only, the greatest for wet chemistry, intermediate for fresh and dry/ground sheep-fecal specimens; while not affected (P = 0.40) for Ti. The PXRF is an accurate technology to detect Cr and Ti in fresh cattle fecal samples to estimate ATTD. For fresh and dry/ground, the technology was effective for determining the concentration of Cr, or dry-only fecal specimens when detecting Ti in sheep specimens.
利用便携式 X 射线荧光（PXRF）光谱仪检测加工或未加工的牛和羊粪便标本上的外部标记物，以估计表观全肠道消化率（ATTD），对此进行了评估。实验 1：用瘤胃内置管的安格斯杂交公牛（n = 7；BW = 520 ± 30 kg）在完全随机设计（CRD）中自由采食 21 天。每天两次（每种标记物 7.5 g）将标记物（Cr2O3 和 TiO2）置于瘤胃内。从第 14 天到第 21 天，每天两次收集粪便样本。实验 2：杂交公绵羊（n = 8；BW = 68 ± 3 kg）在 CRD 中自由采食 21 天。在此期间，每天两次将 2 g Cr2O3 和 TiO2 撒在饲料上。绵羊被安置在代谢笼中进行 5 天的总粪便收集。使用原子吸收法测定饲料、拒食物和粪便标本（新鲜、仅干燥和干燥/研磨）中标记物的浓度，以检测 Cr 和分光光度法检测 Ti。还使用 PXRF 光谱仪测定两种标记物的浓度。当使用牛新鲜粪便标本时，通过湿化学法和 PXRF 估计的 ATTD 与零没有差异（P ≥ 0.14），而仅使用干燥和干燥/研磨粪便标本通过 PXRF 估计的 ATTD 分别比通过湿化学法估计的 Cr 和 Ti 低 3.6 和 1.1 个百分点（P ≤ 0.04）。无论在牛标本上采用何种粪便样本制备方法，Ti 浓度在不同方法之间均相似（P = 0.39），而 Cr 仅在使用干燥/研磨样本时使用 PXRF 时会被低估（P < 0.01）13%。与对照相比，绵羊的 ATTD 被低估（P < 0.01）了 2.4 个百分点，当 Cr 通过干燥/研磨样本的 PXRF 进行测量时。绵羊干燥/研磨粪便标本中的 Cr 浓度趋于（P = 0.09）低于湿化学分析。新鲜和干燥/研磨绵羊粪便样本中 Cr 的检测（P ≥ 0.49）和 Ti 的干燥/仅检测不受检测方法的影响。Cr 的粪便回收率趋于（P = 0.10）最低，湿化学最高，新鲜和干燥/研磨绵羊粪便样本居中；而 Ti 不受影响（P = 0.40）。PXRF 是一种用于检测牛新鲜粪便样本中 Cr 和 Ti 以估计 ATTD 的准确技术。对于新鲜和干燥/研磨，该技术在检测绵羊样本中的 Cr 时，对于确定 Cr 或干燥/研磨粪便样本的浓度是有效的，而在检测 Ti 时，仅干燥样本有效。
