Abstract
This study aimed to investigate the effect of epiphytic microbiota from alfalfa and red clover on the fermentative products, bacterial community compositions, and their predicted functional characteristics in Italian ryegrass silage. By microbiota transplantation and γ-ray irradiation sterilization, the irradiated Italian ryegrass was treated as follows: (1) sterile distilled water (STIR); (2) epiphytic microbiota on Italian ryegrass (IRIR); (3) epiphytic microbiota on alfalfa (IRAL); and (4) epiphytic microbiota on red clover (IRRC). The irradiated Italian ryegrass was ensiled for 1, 3, 7, 15, 30, and 60 days. STIR had similar chemical components with fresh Italian ryegrass. IRAL had higher lactic acid concentrations [64.0 g/kg dry matter (DM)] than IRIR (22.3 g/kg DM) and IRRC (49.4 g/kg DM) on day 3. IRRC had the lowest lactic acid concentrations (59.7 g/kg DM) and the highest pH (4.64), acetic acid (60.4 g/kg DM), ethanol (20.4 g/kg DM), and ammonia nitrogen (82.6 g/kg DM) concentrations and Enterobacteriaceae [9.51 log10 cfu/g fresh weight (FW)] populations among treatments on day 60. On days 3 and 60, Lactobacillus was dominant in both IRIR (42.2%; 72.7%) and IRAL (29.7%; 91.6%), while Hafnia-Obesumbacterium was predominant in IRRC (85.2%; 48.9%). IRIR and IRAL had lower abundances of “Membrane transport” than IRRC on day 3. IRIR and IRAL had lower abundances of phosphotransacetylase and putative ATP-binding cassette transporter and higher abundances of arginine deiminase on day 3. IRAL had the highest abundance of fructokinase on day 3. Overall, inoculating epiphytic microbiota from different legume forages changed the fermentative products, bacterial community compositions, and their predicted functional characteristics in Italian ryegrass silage. The microbial factors that result in the differences in fermentative profiles between legume forage and grass were revealed. Knowledge regarding the effect of epiphytic microbiota could provide more insights into the improvement of silage quality.
Highlights
Ensiling of forages is extensively conducted worldwide to provide continuous feeds for ruminants
The water-soluble carbohydrates (WSCs) content of fresh Italian ryegrass was 122 g/kg dry matter (DM), epiphytic lactic acid bacteria (LAB) count on fresh Italian ryegrass was 5.22 log10 cfu/g fresh weight (FW), and undesirable microbes containing Enterobacteriaceae, yeasts, and aerobic bacteria were higher than 6.40 log10 cfu/g FW
Higher populations (>6.40 log10 cfu/g FW) of undesirable microorganisms including aerobic bacteria, yeasts, and Enterobacteriaceae in three fresh materials may be adverse to the lactic acid fermentation after ensiling, because they would compete with LAB for the limited WSC contents
Summary
Ensiling of forages is extensively conducted worldwide to provide continuous feeds for ruminants. Legume forages, like alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.), have been widely cultivated due to their high crude protein (CP) contents Regarding grass, they have abundant fermentable substrates and high palatability when fed as silages. Numerous studies described that acetic acid is the primary fermentative product in legume forage silage, while lactic acid is produced in large quantities in most grass silages (Buxton et al, 2003). This difference is highly correlated with the chemical and microbial properties of raw materials. There is limited information investigating their effects on fermentative products of legume forage and grass
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