In this study, in which quality characteristics of corn silages with added LA bacteria were investigated, mean DM levels of silages were determined as about 31% at the beginning of the experiment, whereas DM levels declined in all groups on day 60 and came down to levels of 28% on average. No statistical difference was determined in these values between the groups by weeks. When intragroup evaluations were made, a statistically significant decrease in DM level was observed toward the end of fermentation in groups with added LP and LB (P<0.001). Tabacco et al.
11 prepared silages by adding LB and LP to corn and sorghum silages and reported that there was no statistically significant difference in DM level of silages at the end of a fermentation period of 90 days. Previous studies reported that addition of LAB to silages reduced DM losses in anaerobic phase
1.
pH value is one of the most important criteria in determining silage quality. In view of Table 1, a mean pH value of 5.4 was obtained for fresh forages, while on day 5 of the experiment, pH values of 4.58, 3.97, 3.98 and 3.99 were obtained for group C, LD, LP and LB, respectively. According to the findings of this research, addition of inoculant to corn silage can be said to cause a more rapid drop in the pH-value. In silages prepared by addition of LB and LP to whole crop corn, Tabacco et al.11 found a pH value of 3.57 for control group and values of 3.74 and 3.57 for other groups, respectively, on day 90, and demonstrated that pH value of the group with added LB was higher than pH values of the other two groups (P<0.05). Filya2 conducted a study by adding LB and LP to corn silage and found pH values of 3.72, 4.13, 3.75 and 3.88 for control, LB, LP and LB+LP groups, respectively on day 90 of the research, where the value obtained for LB was higher than the other groups and statistically significant (P<0.05). Other studies also reported a rapid decrease in silage pH after the addition of LAB to silages1.
Throughout the study, it was determined that CP and OM levels decreased as from day 10 of the fermentation in groups LP and LB with added inoculants and crude ash value increased in the same groups on day 60 (P<0.001) (Table 2 and 3). These values suggest that LP and LB broke down CP and OM. In some studies, different inoculants were added to corn silages and the inoculants were reported to have no significant effect on CP and CA5,12. Acosta Aragon et al.1 reported that addition of inoculants to silages increased CP level, while it had no effect on CF and CA levels.
Data related to the levels of NDF, ADF, ADL and hemicellulose, which are cell wall elements of forage, are presented in Table 4. On day 5 of the research, the highest NDF value was observed for group LP and the difference was found to be statistically significant (P<0.05), while such difference was insignificant in the following weeks. The highest ADF value was obtained for group LP on day 5 and 15 of the research, and the difference was found to be statistically significant (P<0.05). With regard to their silages prepared by adding different inoculants, Tabacco et al.11 concluded that inoculants had no effect on NDF, ADF and ADL values of the silages. Acosta Aragon et al.1 reported that addition of inoculants to silages had no effect on NDF (P>0.05), and decreased the ADF content (P<0.05), whereas Polat et al.12 suggested that addition of LAB + enzyme to corn silages did not change ADF content, however, significantly reduced NDF (P<0.01), ADL and cellulose content (P < 0.05).
Addition of different LAB to silages rapidly decreased pH level, whereas rapidly increased LA concentration. In view of data in Table 5, high LA concentrations were determined for the groups with added inoculant on day 5, and the highest concentration was obtained on day 30 (P < 0.001). However, LA concentration of group C with no added inoculant was low during the first several weeks, reached the highest level on day 30, however, it was less than the levels of other groups (P<0.001). AA values obtained in this study are given in Table 5. In view of Table 5, the highest AA value was observed for group LD on day 10 and the difference was found to be statistically significant (P<0.001). AA level in the groups with added LAB on day 10 and day 15 was determined to be higher than that in group C (P < 0.001). In their study conducted using corn and sorghum silages, Tabacco et al.11 used LP and LB as inoculants, and at the end of a conservation period of 90 days, they found similar levels of LA in control group with no added LAB and the groups with added LP, and a lower level of LA in LB group. In the same investigation, AA level was found to be higher in LB group. Previous studies determined that addition of LAB to silages increased LA and organic acid levels of silages2 accordingly metabolizable energy level of forage was improved1.
In view of BA levels in the study groups (Table 5), the highest BA value was obtained in the groups with added LAB on day 5 and 10, and these values steadily declined and dropped down to very low values on day 60.
Corn silages are rich in starch and sugar so when they are exposed to air, they become prone to aerobic decomposition due to the effect of oxygen. Decomposition is more common, especially in hot climates. Because yeast and mold growth would be faster between 20 and 30 °C13,14. In the aerobic stability test performed on day 60 of this research, the lowest pH value of 4.02 was observed in group LB, while the highest pH value of 4.84 in group LP (P>0.05). No statistically significant difference was found between the groups in terms of LA, total bacteria and yeast, and no mold growth was observed. These values suggested that the silages were of good quality. Addition of bacterial inoculants to silages was reported to have improved aerobic stability1,2,15. In a study by Hu et al.16 conducted by addition of LB 40788 to corn silage, the groups with added inoculants were found to have higher rates of acetic acid compared to the control group, and very low levels of yeast has been reported, and it was concluded that the inoculants improved aerobic stability. Addition of homofermentative LAB to silages was reported to improve aerobic stability17, however, there are also research findings which showed that domination of a medium by homolactic acid bacteria adversely affects aerobic stability18. In a study conducted by mixing homo- and heterofermentative LAB, Acosta Aragon et al.1 determined that internal temperature of silage began to increase in the control group with no added inoculant at 66 hrs after silages were exposed to air, that it increased by +2 ⁰C with respect to the temperature of the environment at 84 hrs, and such increase was more than +14 ⁰C at 186 hrs. In the same study, the authors stated that the temperature increase in silages at 156 hrs was +2 ⁰C in the groups with added inoculant, and this value increased to +6 ⁰C at 234 hrs, and they concluded that inoculants protected silages for 72 hrs longer, as compared to the control group.
In conclusion, in this study, which investigated the effects of addition as inoculants of LAB to silages on silage quality, addition of LAB to silages caused a rapid decrease in pH and a rapid increase in LA level. It was seen that in LD group, for which LD were selected from fresh whole crop corn and added to silages, pH value was lower, the group's DM, CP, OM and CA levels during fermentation period did not decrease, its LA level was higher, as compared to other groups. These results suggest that LD bacteria should be considered as inoculants. Inoculants were found to have no effect on aerobic stability. However, this result may change if the experiment is conducted in warmer environment, rather than at room temperature, or if the silages are allowed to stand longer than 5 days. This should be taken into account in further studies.
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