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

Pablo G Toral; Gonzalo Hervás; Mariana Gabriela González-Rosales; Alejandro G Mendoza; Lizbeth E Robles-Jiménez; Pilar Frutos

doi:10.1186/s40104-021-00671-2

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

J Anim Sci Biotechnol. 2022 Feb 11;13(1):21. doi: 10.1186/s40104-021-00671-2.

Authors

Pablo G Toral¹, Gonzalo Hervás¹, Mariana Gabriela González-Rosales¹, Alejandro G Mendoza¹, Lizbeth E Robles-Jiménez^{1

2}, Pilar Frutos³

Affiliations

¹ Instituto de Ganadería de Montaña (CSIC-University of León), Finca Marzanas s/n, 24346 Grulleros, León, Spain.
² Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de México, No. 100 Instituto Literario 100, Col. Centro, 50000, Toluca, Estado de México, Mexico.
³ Instituto de Ganadería de Montaña (CSIC-University of León), Finca Marzanas s/n, 24346 Grulleros, León, Spain. p.frutos@csic.es.

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.

Keywords: In situ; In vitro; Livestock; Nitrogen degradation; Sheep.

Abstract

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