Metabarcoding analysis of the bacterial and fungal communities during the maturation of preparation 500, used in biodynamic agriculture, suggests a rational link between horn and manure [Squartini et al, 2023]

Abstract
Horn manure (Preparation 500) is a product used in the practice of biodynamic agricul-
ture. It is obtained by an underground fermentation of cow fecal material incubated in cow
horns for several months. The product is used as spray treatment meant to increase soil
fertility. In the present report, we analyzed the successional changes in bacterial and fun-
gal communities throughout the process of horn manure maturation by high throughput
sequencing of ribosomal 16S (bacterial) and ITS (fungal) gene markers. Marked shifts in
the microbial community were seen involving a general decrease from a Firmicutes-dom-
inated material to a product transiently enriched in Proteobacteria and later in Actinobac-
teria, mostly within the Nocardioidaceae family. In the fungal community evolution, the
most abundant taxon in the starting fecal material resulted a member of the Onygenales
order, known to specifically degrade keratin. Its abundance in the intestine is explained by
the fact that keratin, which is also the structural component of hairs and horns, is found in
all epithelial layers, including gut mucosae. This occurrence suggests a link of enzymatic/
catabolic nature between manure and horn.

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