Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, NO-1433 Ås, Norway.
Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, NO-1433 Ås, Norway.
Animal. 2021 Jan;15(1):100050. doi: 10.1016/j.animal.2020.100050. Epub 2020 Dec 10.
Total collection of faeces is considered the golden standard for estimating apparent total tract digestibility (ATTD) in horses. However, the evaluation of individual feedstuffs is limited and determination of nutrient digestibility in different segments of the gastrointestinal tract (GIT) is excluded. The rationale for performing this study was that the mobile bag technique (MBT) can provide information on individual feedstuffs' degradation, and the use of fistulated animals does provide additionally information regarding degradation in individual segments of the GIT. Recommendations for using the MBT in ruminants are well established, but limited methodical studies have been published with horses. The objective of this study was to evaluate the MBT by comparing the ATTD with the nutrient disappearance and degradation kinetics of hay in horses. It was hypothesised that DM degradation as estimated by the MBT is equal to the ATTD of the DM. Furthermore, we hypothesised that bag size has no effect on nutrient disappearance but increasing the feed to surface area (FSA) decreases the DM disappearance. Five caecum cannulated horses were fed a hay-only diet (6.7 kg DM/day) with 14 days of adaptation followed by four consecutive days of total faeces collection. Three bag sizes (height × length × side, cm; 1.2 × 10 × 2, 3 × 4 × 2, 1 × 6 × 2) and three FSAs (10.4, 20.8 and 41.7 mg/cm) were administrated at each meal (3 meals/day) on days 1 and 2 of the collection. Faeces were checked for bags every 6th h, the collection time was noted and the DM disappearance together with the transit time (TT) for each bag type was estimated. Dry matter disappearance from the individual bags was fitted to degradation profiles, and the effective degradability (ED) and degradation (D) were determined. The results of the study showed that the ATTD of DM, organic matter (OM), NDF and ADF can be predicted based on their disappearance from the mobile bags, but that ash and CP are overestimated in comparison to the ATTD. The TT for the bags was 29.2 h, and when using a mean retention time of 30 h to predict ED and D, it was clear that ED was underestimated, whereas D reflected the ATTD of DM. In conclusion, the MBT can be used to estimate the degradability of DM, OM and fibre as these nutrients resemble the ATTD. The bag size did not affect the DM disappearance, but the FSA should be kept below 20 mg/cm as higher levels might limit the degradation kinetics.
粪便的全面收集被认为是估计马表观总肠道消化率（ATTD）的金标准。然而，这种方法的评估仅限于个别饲料，并且排除了胃肠道（GIT）不同部位的营养消化率的测定。进行这项研究的基本原理是，移动袋技术（MBT）可以提供有关个别饲料降解的信息，而使用有瘘管的动物确实可以提供关于 GIT 个别部位降解的额外信息。关于在反刍动物中使用 MBT 的建议已经很完善，但在马身上发表的方法学研究有限。本研究的目的是通过比较干草的 ATTD 与养分消失和降解动力学来评估 MBT。我们假设 MBT 估计的 DM 降解与 DM 的 ATTD 相等。此外，我们假设袋的大小不会影响养分消失，但增加饲料与表面积（FSA）会降低 DM 的消失。5 头盲肠有瘘管的马被喂食仅干草的饮食（6.7kg DM/天），适应期为 14 天，然后连续 4 天收集总粪便。在收集的第 1 天和第 2 天，每餐（每天 3 餐）施用三种袋尺寸（高×长×宽，cm；1.2×10×2、3×4×2、1×6×2）和三种 FSA（10.4、20.8 和 41.7mg/cm）。每 6 小时检查一次粪便中的袋子，记录收集时间，并估计每个袋子类型的 DM 消失量和转移时间（TT）。从个体袋中消失的干物质被拟合到降解曲线，确定有效降解率（ED）和降解率（D）。研究结果表明，可以根据 DM、有机物（OM）、NDF 和 ADF 从移动袋中消失的情况预测其 ATTD，但与 ATTD 相比，灰分和 CP 被高估。袋子的 TT 为 29.2h，当使用 30h 的平均保留时间来预测 ED 和 D 时，很明显 ED 被低估，而 D 反映了 DM 的 ATTD。总之，MBT 可用于估计 DM、OM 和纤维的降解率，因为这些营养素与 ATTD 相似。袋的大小不会影响 DM 的消失，但 FSA 应保持在 20mg/cm 以下，因为较高的水平可能会限制降解动力学。
