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AbstractThis study investigated the effects of developmental stage and store time on the chemical composition, microbial community, co-occurrence networks and fermentation characteristics of sweet sorghum silage. Sweet sorghum harvested at two developmental stages (heading stage, S1; hard dough stage, S2) was treated as follows: (I) natural fermentation of S1(NS1); (II) natural fermentation of S2(NS2) and ensiled for 1, 3, 7, 15, 30 and 60 days. After 60 days of ensiling, NS2silage had higher lactic acid concentration and the ratio of lactic to acetic acid, and lower pH value and acetic acid concentration than NS1silage. Meanwhile, NS2silage also had higher ammonia nitrogen (NH3-N) content than NS1silage, but the NH3-N content of both treatments was lower than 100 g/kg TN. Leuconostocand Lactococcuswere respectively dominant in both 7-day NS1and NS2silages, while Lactobacilluswas the most abundant genus in 30-day NS1and NS2silages. The developmental stage altered the bacterial co-occurrence networks of fresh and ensiled sweet sorghum. Spearman’s correlation heatmap showed that the higher lactic acid content and ratio of lactic to acetic acid in NS2silage could be associated with the higher water-soluble carbohydrate content in S2material, the higher abundance of Lactococcusin the initial phase of ensiling and the higher abundance of Lactobacillusin the late phase of ensiling. These results concluded that the sweet sorghum harvested at the hard dough stage is preferred for silage production over the sweet sorghum harvested at the heading stage.HIGHLIGHTSMicrobial succession pattern was studied on fresh and ensiled samples.Growth stage affected the chemical and microbial parameters of sweet sorghum.Epiphytic microbiota was correlated with the chemical composition of forage.Metagenomic sequencing showed Lactobacilluswas dominated in all silages.Growth stage accelerated the fermentation of sweet sorghum silage.

This study was conducted to evaluate the effect of lactic acid bacteria and propionic acid on the fermentation quality, aerobic stability and in vitrogas production kinetics and digestibility of whole-crop corn based total mixed ration (TMR) silage. Total mixed ration was ensiled with four treatments: (1) no additives (control); (2) an inoculant (Lactobacillus plantarum) (L); (3) propionic acid (P); (4) propionic acid+lactic acid bacteria (PL). All treatments were ensiled in laboratory-scale silos for 45 days, and then subjected to an aerobic stability test for 12 days. Further, four TMR silages were incubated in vitrowith buffered rumen fluid to study in vitrogas production kinetics and digestibility. The results indicated that all TMR silages had good fermentation characteristics with low pH (<3.80) and ammonia nitrogen (NH3-N) contents, and high lactic acid contents as well as Flieg points. Addition of L further improved TMR silage quality with more lactic acid production. Addition of P and PL decreased lactic acid and NH3-N contents of TMR silage compared to the control (P<0.05). After 12 days aerobic exposure, P and PL silages remained stable, but L and the control silages deteriorated as indicated by a reduction in lactic acid and an increase in pH, and numbers of yeast. Compared to the control, addition of L had no effects on TMR silage in terms of 72 h cumulative gas production, in vitrodry matter digestibility, metabolizable energy, net energy for lactation and short chain fatty acids, whereas addition of PL significantly (P<0.05) increased them. L silage had higher (P<0.05) in vitroneutral detergent fiber digestibility than the control silage. The results of our study suggested that TMR silage prepared with whole-crop corn can be well preserved with or without additives. Furthermore, the findings of this study suggested that propionic acid is compatible with lactic acid bacteria inoculants, and when used together, although they reduced lactic acid production of TMR silage, they improved aerobic stability and in vitronutrients digestibility of TMR silage.