Metagenomic Comparison of the Microbial Load Colonizing Lucerne Hay and Gum Astralagus (Astragalus Glycyphyllos) in Ruminants

Abstract

Context. Rumen microbiota plays an important role in the evaluation of roughages. Gum astragalus hay is a non-traditional roughage in ruminant feeding, and it is curious how it affects rumen microbiota in comparison with lucerne hay (LH). Aim. This study compares the in vitro true digestibility and rumen fermentation parameters of lucerne hay (LH) and gum astralagus hay (Astragalus glycyphyllos, AG), as well as the metagenomic profile of the bacterial community in sheepruminal fluid following 48 h in vitro incubation with either forage type. Methods. The study was carried out in vitro in a Daisy incubator. A total of 100 samples, including 48 samples from each of the experimental roughages and two blind samples, were weighed into F57 bags for in vitro incubation with ruminal fluid, obtained from the rumen of two sheep fed on roughage and brought to the slaughterhouse from a private enterprise. Key results. Crude protein (CP) content of AG was higher (P < 0.0014) and ADF content (P < 0.001) was lower than LH. After 48 h incubation of roughage samples, AG was superior to LH in terms of in vitro true digestibility parameters (true digestion of roughages, true dry matter digestion, and true organic matter digestion; P < 0.001). Taxonomy results of bacteria colonizing both roughages were obtained at genus and species level, according to the Shannon and Simpsons index. The bacterial community of the genus Provetalla was dominant in both forages, whereas Pseudomonas genus bacteria were observed in AG, but not in LH. According to the total Operational Taxonomc Units (OTU) in the samples, it was observed that LH and AG had similarity, as well as diversity in terms of species. Due to the current shortage of roughage, it is very important to consider AG as an alternative source of roughage in animal nutrition. Conclusions. The differences in nutrient composition between the two roughage types also indicate differences in the composition and density of bacterial microbiota. These results were very important for improving the nutrient utilization efficiency of roughages in the desired direction. Implication. The nutrient composition and in vitro digestion parameter results of AG were comparable to LH, and there were similarities, as well as differences, in the colonized bacterial community in both roughages.