The high dependence of intensive ruminant production on soybean meal and the environmental impact of this crop encourage the search for alternative protein-rich feeds. The use of insects seems promising, but the extent of their ruminal protein degradation is largely unknown. This parameter has major influence not only on N utilization efficiency but also on the environmental burden of ruminant farming. In addition, although assessing ruminal N degradation represents a key first step to examine the potential of new feeds, it is a challenging task due to the lack of a reference method. This study was conducted to investigate the potential of 4 insects (Tenebrio molitor, Zophobas morio, Alphitobius diaperinus and Acheta domesticus) as alternative protein sources for ruminants, using 3 methodologies: 1) a regression technique based on the in vitro relationship between gas production and ammonia-N concentration; 2) a conventional in vitro technique of batch cultures of ruminal microorganisms, based on filtering the incubation residue through sintered glass crucibles; and 3) the in situ nylon bag technique. The in vitro intestinal digestibility of the non-degraded protein in the rumen was also determined. Soybean meal was used as a reference feedstuff. Comparison of evaluation methods (regression, in vitro and in situ) did not allow to reliably select a single value of ruminal N degradation for the studied substrates, but all techniques seem to establish a similar ranking, with good correlations between methods, particularly between regression and in situ results. Regardless of the methodology, nitrogen from the 4 insects (with contents ranging from 81 to 112 g/kg of dry matter) did not show high ruminal degradation (41–76%), this value being always lower than that of soybean meal. Furthermore, the in vitro intestinal digestibility of non-degraded N was relatively high in all feeds (≥ 64%). Overall, these results support the potential of the 4 studied insects as alternative feedstuffs for ruminants. Among them, T. molitor showed the lowest and greatest values of ruminal N degradation and intestinal digestibility, respectively, which would place it as probably the best option to replace dietary soybean meal and increase the sustainability of ruminant feeding.

中文翻译：

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昆虫作为反刍动物的替代饲料：蛋白质评估方法的比较

反刍动物集约化生产对豆粕的高度依赖以及这种作物对环境的影响促使人们寻找富含蛋白质的替代饲料。昆虫的使用似乎很有希望，但它们瘤胃蛋白质降解的程度在很大程度上是未知的。该参数不仅对氮的利用效率有重大影响，而且对反刍动物养殖的环境负担也有重大影响。此外，虽然评估瘤胃氮降解是检查新饲料潜力的关键第一步，但由于缺乏参考方法，这是一项具有挑战性的任务。本研究旨在使用 3 种方法研究 4 种昆虫（黄粉虫、Zophobas morio、Alphitobius diaperinus 和 Acheta domesticus）作为反刍动物替代蛋白质来源的潜力：1) 基于产气量与氨氮浓度的体外关系的回归技术；2) 瘤胃微生物分批培养的常规体外技术，基于通过烧结玻璃坩埚过滤培养残渣；3)原位尼龙袋技术。还测定了瘤胃中未降解蛋白质的体外肠道消化率。豆粕用作参考饲料。评估方法（回归、体外和原位）的比较不能可靠地为研究的底物选择瘤胃 N 降解的单一值，但所有技术似乎都建立了相似的排名，方法之间具有良好的相关性，特别是回归之间和现场结果。无论采用何种方法，来自 4 种昆虫的氮（含量从 81 到 112 g/kg 干物质）没有表现出高瘤胃降解（41-76%），这个值总是低于豆粕。此外，所有饲料中未降解氮的体外肠道消化率都相对较高（≥ 64%）。总体而言，这些结果支持了 4 种研究昆虫作为反刍动物替代饲料的潜力。其中，T. molitor 分别表现出瘤胃氮降解和肠道消化率的最低和最高值，这可能使其成为替代日粮豆粕和增加反刍动物饲养可持续性的最佳选择。所有饲料中未降解氮的体外肠道消化率均较高（≥64%）。总体而言，这些结果支持了 4 种研究昆虫作为反刍动物替代饲料的潜力。其中，T. molitor 分别表现出瘤胃氮降解和肠道消化率的最低和最高值，这可能使其成为替代日粮豆粕和增加反刍动物饲养可持续性的最佳选择。所有饲料中未降解氮的体外肠道消化率均较高（≥64%）。总体而言，这些结果支持了 4 种研究昆虫作为反刍动物替代饲料的潜力。其中，T. molitor 分别表现出瘤胃氮降解和肠道消化率的最低和最高值，这可能使其成为替代日粮豆粕和增加反刍动物饲养可持续性的最佳选择。