Insects as alternative feed for ruminants: comparison of protein evaluation methods

Abstract

Background 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. Results 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%). Conclusion 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.

Full-fat insect meals in ruminant nutrition: in vitro rumen fermentation characteristics and lipid biohydrogenation

“…Even though, the CP content of our samples were in line with those published in literature on the same species [ 42 , 46 ]. When comparing the CP values of insect meals with published literature, the N:P conversion factor used for CP calculation must be considered [ 9 ]. When using the conventional N:P conversion factor of 6.25, it is assumed that the matrix under analysis contains 160 g N/kg CP, and that all N is of protein origin.…”

“…The use of insects for monogastric feeding is increasing worldwide [ 5 ]. Even if their use for ruminant nutrition is limited in some countries due to the potential risk of Transmissible Spongiform Encephalopathies for humans [ 8 ], the interest in their use is growing up, as they are seen as promising alternative protein sources [ 9 ].…”

“…Research on the use of insects for ruminant feeds is still at an infant stage, with only few articles that have been published to date. Original research primarily focused on the assessment of in vitro fermentation parameters (e.g., [ 9 , 18 , 19 ]). Only two in vivo studies have been performed so far, evaluating the performance and physiological status of goat kids fed cricket meal [ 20 ] and the suitability of black soldier fly larvae as protein supplement to beef steers consuming low-quality forages [ 21 ].…”

Can insects be used in the nutrition of ruminants?

“…Low N degradation in the rumen may represent a positive aspect for ruminant nutrition purposes, if associated with a high intestinal digestibility. Toral et al (2022) found that the in vitro intestinal digestibility of the N non-degraded inside the rumen ranged from 64% in A. diaperinus to 78% in T. molitor, thus demonstrating the potential of the four tested insects as alternative feedstuffs for ruminants.…”

“…When evaluating insects as potential feed ingredients for ruminants, fundamental aspects to consider are related to protein, specifically the extent of ruminal protein degradation and the extent of intestinal digestibility of the protein not degraded inside the rumen. This was the goal of the work recently conducted by Toral et al (2022) who, using three different methodologies, investigated the potential of four insect species (T. molitor, Zophobas morio, Alphitobius diaperinus and A. domesticus) as alternative protein sources for ruminants. These authors showed that the ruminal degradation of insect nitrogen (N) ranged, on average, from 46% for T. molitor to 74% for Z. morio, such values being lower than that of SBM (>85%) used by the authors as reference feedstuff.…”