Metagenomic Characterization and Volatile Compounds Determination in Rumen from Saanen Goat Kids Fed Olive Leaves

Abstract

The accumulation and disposal of by-products deriving from the agro-food industry represents a problem both from an economic and environmental point of view. The use of these matrices in zootechnical nutrition could represent a feasible solution. The aim of the study was to examine the effect of a diet containing olive leaves (OL), a by-product of the olive industry, on the ruminal microbial community of Saanen goat kids and on volatile organic compounds (VOCs) produced during the digestion. Twenty goat kids were randomly divided into two groups of ten goat kids each. The control group (CTR) was fed with a standard diet, while the experimental group (OL+) received a custom-formulated diet containing 10 % OL on a dry matter (DM) basis. After 30 days of trial, genomic DNA was extracted from the rumen liquor and prepared for 16S rRNA-gene sequencing to characterize the rumen microbiota; furthermore, rumen VOCs were also characterized by solid-phase microextraction coupled with gas chromatography-mass spectrometry. The Shannon’s alpha index was not significantly different between the two groups, on the contrary, Bray-Curtis (p < 0.01) and Jaccard (p < 0.01) distances evidenced that feed affected microbial community. Eleven genera were influenced by OL supplementation, with a significant increase (p < 0.05) in Paludibacter, Fibrobacter, Sphaerochaeta Christensenella, Rikenella, Oligosphaera, Candidatus Endomicrobium, Anaerovorax, and Atopobium was observed, while the percentages of Bacteroides and Selenomonas were reduced (p < 0.05). Differences were also observed between the two groups at the family level (p < 0.004). Fibrobacteriaceae, Christensenellaceae, Coriobacteriaceae, Oligosphaeraceae, Candidatus Endomicrobium, and Planctomycetaceae were significantly higher (p < 0.05) in goat kids fed OL diet compared to CTR, while the levels of other identified families, Succinivibrionaceae and Bifidobacteriaceae, were opposite (p < 0.05). Finally, results showed that the main phyla in both groups were Bacteroidetes and Firmicutes; however, no significant differences in the relative abundance of any phyla were observed between the two groups. In addition to what has been reported, the analysis of VOCs at the rumen level showed the ability of the OL integration to induce an increase in hexanoic acid and a parallel decrease in decanal. Furthermore, only in OL+ samples there was the accumulation of α-terpineol to which a wide range of interesting biological properties is attributed. The presence of VOCs associated with health status suggests a favorable role of OL in preserving and improving animal welfare.

Using short-read 16S rRNA sequencing of multiple variable regions to generate high-quality results to a species level.

“…Being relatively new, there are only a few publications in which the SNAPP-py3 pipeline has been used to analyse data sequenced with the xGen kits (Nuccio et al, 2023, Bennato et al, 2022). However, neither of these studies took advantage of the species-level classification that can be achieved with the xGen kits and SNAPP-py3 pipeline.…”

“…However, neither of these studies took advantage of the species-level classification that can be achieved with the xGen kits and SNAPP-py3 pipeline. Although Bennato et al (2022) included a control containing DNA for 20 known bacterial species, they only reported the ability to pick up these bacteria at a genus level. To our knowledge, the combined ability of these kits and pipeline to obtain accurate species-level classification has not been assessed.…”

Changes in the Concentration of Amino Acids and Bacterial Community in the Rumen When Feeding Artemisia absinthium and Cobalt Chloride

“…An increase in the number of cattle will consistently lead to an increase in the requirements for the use of diets in order to reduce greenhouse gas emissions such as methane [1] and ammonia [2], as well as the loss of nutrients by the body [3]. This process cannot do without the use of special feed additives [4][5][6], affecting the microbiome in order to increase the functional activity of the digestive system and the rejection of antibiotics [7,8].…”