Fermentation profile, nutritional value, and microbial population of C4 grasses 1 silages with or without bacterial additive 2

- The objective of the present study was to evaluate the use of bacterial additive 7 ( Lactobacillus plantarum and Propionibacterium acidipropionici ) on chemical 8 composition, in vitro gas production, pH, losses, aerobic stability, and microbial 9 population of corn, pearl millet, and sorghum silages in plastic bags silos (without 10 vacuum ). The experiment was carried out in a randomized block design, in a 2 × 3 11 factorial scheme, with or without additive ([Control] without additive and Lactobacillus 12 plantarum [2.5 × 1010 cfu/g] and Propionibacterium acidipropionici [2.5 × 1010 cfu/g] 13 Biomax corn, Lallemand, Saint-Simon, France [LP]) and three crops of agricultural 14 interest; pearl millet, sorghum, and corn, with four replicates per treatment. We 15 performed chemical analyses and in vitro gas production to determine the nutritional 16 value of the silages. We also evaluated the aerobic stability, ammoniacal nitrogen (NH 3 ), 17 pH, and microbial population of the silages. The additive increased the crude protein 18 content ( P = 0.0062) in corn and sorghum and decreased the LIG content ( P = 0.0567). 19 The gas production was not affected ( P >0.05) by the additive and neither between crops. 20 In aerobic stability, we observed that the additive affected the temperature of the 21 sorghum silage ( P = 0.0123). The additive decreased NH 3 ( P = 0.0095) content. The 22 additive increased ( P = 0.0441) the lactic acid bacteria population in the pearl millet, 23 corn, and sorghum silages. Thus, the bacterial additive did not improve the fermentation 24 profile and nutritional value of corn, pearl millet, and sorghum silages in plastic bag 25 silos.


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In Brazil, milk and beef productions are based on pastures, as they are a less expensive 31 feed source for the farmers. However, the seasonality of forage production is a critical inoculants are used to increase aerobic stability (Queiroz et al., 2018). Lactobacillus 54 plantarum is one of the most used among homolactic bacteria due to its vigorous growth, 55 acid tolerance, and a high potential for lactic acid production (Muck, 2010). In the 56 heterofermentative bacteria group, the Propionibacterium acidipropionici uses lactic acid 57 3 and glucose as substrates to produce acetic and propionic acid, which effectively control 58 fungi under low pH (Zopollatto et al., 2009). 59 Therefore, we hypothesized that the bacterial additive would not affect the 60 fermentation of C4 grasses silages. Thus, the objective of the present study was to 61 evaluate the bacterial additive (Lactobacillus plantarum and Propionibacterium 62 acidipropionici) on chemical composition, in vitro gas production, pH, losses, aerobic 63 stability, and microbial population of corn, pearl millet, and sorghum silages in plastic 64 bag silos (without vacuum). an ambient temperature of 25±2.3 ºC for 90 days. The silos were packed with a density of 83 600 kg/m3 (fresh forage ensiled).

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The experiment was carried out in randomized blocks in a 2 × 3 factorial scheme, with or   The hemicellulose was calculated by the difference between the NDF and ADF contents, solution, respectively). The buffer solution was prepared as described by McDougall (1948).

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The flasks were immediately filled with CO2, closed, and placed in a water bath.

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The time profiles of gas production were obtained using a non-automated device, similar to throughout the measurement times. 126 We used the model described by Groot et al. (1996) to explain the cumulative gas 127 production profiles: Where, the parameter represents the amount of gas produced per unit of organic matter 131 incubated at time t after the incubation period; the parameter represents the asymptotic gas 132 6 production (mg/g OM); the parameter is the time (h) after incubation in which half of the 133 asymptotic gas was produced, it represents the gas production speed; the parameter is a 134 constant that determines the sharpness of the curve change characteristic. The RM represents 135 the maximum gas production rate when the microbial population does not limit the 136 fermentation and digestion is not reduced by chemical or structural barriers of the potentially 137 digestible matter. The gas production kinetics was not affected (P >0.05) by the additive and neither between 207 crops (Tables 1 and 3).  in the pearl millet, corn, and sorghum silages, respectively (Table 5). Corn silage presented a 232 more significant amount of fungi (P <0.0001) than pearl millet and sorghum silages, 233 regardless of the use of additive (Table 5). and noticed a difference between the crops, except for the CF, NDF, and NCF contents (Table   243 2). The lower DM content observed in pearl millet and sorghum silages can be explained by 244 the higher resistance to drought due to an adaptive process that prevents excessive 245 dehydration such as smaller stomata, early stomatal closure, low stomatal density, and 246 increased leaf serosity, retaining more water in the plant (Levitt, 1980). In addition to the 247 difference between crops, we also observed that the additive increased the CP contents (Table   248 2), but the additive could not reduce losses caused by proteolysis. Analyzing the ammoniacal 249 nitrogen (  increase of undesirable microorganisms such as mold ( substrates for microorganisms to produce acids during the ensiling; this fact was observed in 263 our study (Table 2). LIG and CEL contents were lower in corn silage (Table 2). These values contents were not different (P = 0.1429) between crops, but corn silage was 2.35% higher 267 than pearl millet silage and 11.36% higher than sorghum silage without additive ( Table 2).

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Corn silage presented the lowest ash content (Table 2). According to Ashbell (1995), the low  (Table 2), these concentrations were from 40 to 60 g/kg. However, we observed that 277 although there was no difference (P > 0.05), the time taken for half of the asymptotic gas to 278 be produced (Parameter B) in the corn silage with or without additive was shorter than the 279 other silages (Table 3). Gas production rates peaked in the first hours of incubation, being 280 longer in the corn silage without additive ( Figure 1C), but all silages had a final rate below 281 0.1 ml/h (Figure 1).

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The aerobic stability of the silage is expressed as the resistance of forage mass to 283 deterioration after opening the silo, i.e., the speed at which the mass deteriorates after its 284 contact with the air (Jobim et al., 2007). Thus, we observed that the silages' temperature at the 285 opening was not affected by the additive (P = 0.8911) and neither between crops (P = 286 0.3196). However, pH was affected by the additive (P = 0.0013) and crops (P <0.0001) 287 (Table 4). Lactobacillus plantarum, one of the inoculants in this study, aims to increase lactic 288 acid production, consequently reducing the pH of the ensiled mass and inhibiting the growth reduced its temperature more quickly ( Figure 2C). For Woolford (1990), the initial increase in  It is also essential to understand the microbial population, as the ensiling will preserve the 319 forage and inhibit undesired microorganisms (Clostridium sp, enterobacteria, yeasts, and 320 fungi), influencing the silage quality (Muck, 2010 The bacterial additive did not improve the fermentation profile and nutritional value of corn, 338 pearl millet, and sorghum silages in plastic bag silos.