386 XVI International Silage Conference
Effi cacy of three different silage inoculants on the fermentation quality and aerobic stability of ryegrass ensiled with three different prewilting degrees
Ueli Wyss1 and Ulrich Rubenschuh2
1 Agroscope Liebefeld-Posieux Research Station ALP-Haras, 1725 Posieux, Switzerland, ueli.wyss@alp.admin.ch
2 DLG Test Center Technology and Farm Inputs, 64823 Gross-Umstadt, Germany, U.Rubenschuh@dlg.org
Keywords: inoculants, silage quality, aerobic stability, pre-wilting degree
Introduction Inoculants containing lactic acid bacteria (LAB) are the most common additives used in silage making. The homofermentative strains promote an intensive lactic acid production and a rapid decrease in pH. The inoculants with heterofermentative LAB especially improve the aerobic stability of silages. In heavily wilted forage, the water availability becomes a limiting factor for the development of LAB (Pahlow and Weissbach1996). Under these conditions osmotolerant LAB are more active.
The objective of the study was to investigate the effi cacy of three different silage inoculants on fermentation quality and on aerobic stability of ryegrass silage with three different prewilting degrees.
Material and methods Italien ryegrass of the fi rst cut was wilted to three different dry matter levels, chopped and ensiled in 1.5 l laboratory silos. The DM contents amounted 34, 46 and 61%. Fermentation coeffi cients (FC) were calculated with DM, water soluble carbohydrates (WSC) and buffering capacity in the fresh forage. Besides a control treatment without additive, three treatments were inoculated with LAB (Table 1). One inoculant contained homo and heterofermentative LAB. The two others contained only homofermentative LAB. After a storage period of 3, 49 and 91 days three silos per treatment were opened. The silos that were opened at day 49 were exposed two times to an air stress and aerobic stability was measured. DM losses, nutrient contents, fermentation parameters and aerobic stability were analyzed after a storage period of 91 days. DLG points were calculated on the basis of the results for butyric and acetic acids as well as for pH values (DLG 2006). Concerning the aerobic stability test, silages were instable, when the temperature was 3 degrees above ambient. The trial was carried out according to the methods of DLG (Staudacher et al. 1999). The data were analysed with SYSTAT 12 using two-way ANOVA.
Table 1. Treatments.
Treatment LAB-strains CFU/g fresh forage
Control - -
Inoculant 1 L. plantarum, L. rhamnosus, P. pentosaceus, L. buchneri and L. brevis 100‘000 Inoculant 2 L. plantarum, E. faecium, P. acidilactici and L. lactis 495’000 Inoculant 3 E. faecium, L. plantarum, P. Acidilactici and L. salivarius 1’000’000 CFU: colony forming unit
Results and discussion The DM and nutrient contents at ensiling time are presented in Table 2. The forage was characterized by high contents of water soluble carbohydrates and high values of fermen- tation coeffi cients. These parameters indicate, that the forage was easy to ensile. The DM losses de- creased in the treatments without additives with increasing DM content (Table 3). The three inoculants reduced the DM losses in the treatments with 34 and 46% DM. In the treatment with 61% DM only the inoculant 1 with homo and heterofermentative LAB reduced strongly the DM losses.
Table 2. Dry matter (DM), nutrient contents (g/kg DM) and fermentation coeffi cient (FC) of ryegrass ensiled at three different DM levels.
DM DM Ash Crude Crude ADF NDF WSC FC
level g/kg protein fi ber
1 344 71 60 260 289 478 345 97
2 460 71 62 259 282 471 344 110
3 611 70 59 258 280 469 370 134
Concerning the fermentation quality, most silages showed high DLG points and therefore a very good quality except for the treatment without additive and 34% DM. Here, butyric acid was produced. When the inoculants were applied, the pH decreased already after 3 days in the forages with 34 and 46% DM, but not in the forage with 61% DM. The addition of the inoculants increased the lactic acid production in all three wilting degrees. Acetic acid was mainly produced in the treatment with the inoculant 1, which contained homo and heterofermentative LAB. This additive limited also the ethanol production in all si-
2 - 4 July 2012, Hämeenlinna, Finland 387 lages. For the other treatments, the highest ethanol production was found in the silages with the highest DM content.
After 91 days and without air stress the silages were more stable in comparison to the one after 49 days and with air stress (Figure 1 and 2). The bad wet silage without additive showed a very good aerobic stability. But here the butyric acid was responsible for the good stability. The silages treated with the inoculant 1 showed a very good aerobic stability. This can be explained by the higher acetic acid contents. The aerobic stability of the silages treated with the two homofermentative inoculants increased with increasing prewilting degree in the silages after 49 days with air stress and also 91 days without air stress.
Table 3. Fermentation quality of the different silages and a storage period of 91 days.
Treatment DM DM pH pH Lactic Acetic Butyric Ethanol NH3-N DLG DM
level Day 3 Day 91 acid acid acid N total points losses
g/kg g/kg DM % %
Control 1 307 6.0 4.9 35 2 17 24 14 38 11.7
Inoculant 1 1 333 4.3 3.9 118 15 0 3 7 100 4.5
Inoculant 2 1 330 4.3 4.0 114 5 0 9 5 100 4.4
Inoculant 3 1 331 4.4 4.0 111 6 0 6 6 100 4.4
Control 2 431 6.1 5.8 21 3 1 55 9 90 10.5
Inoculant 1 2 452 4.9 4.1 100 16 0 2 6 100 4.6
Inoculant 2 2 442 5.0 4.2 92 4 0 3 5 100 3.8
Inoculant 3 2 452 5.3 4.2 92 4 0 2 5 100 3.9
Control 3 593 6.1 6.0 4 1 0 46 3 90 8.1
Inoculant 1 3 594 6.1 4.4 47 24 0 3 4 100 5.0
Inoculant 2 3 596 6.1 5.3 36 2 0 38 6 90 7.6
Inoculant 3 3 586 6.1 4.9 46 2 0 30 5 90 6.7
SD 3 0.4 0.6 2 1 1 3 1 1 1
Treatment (T) *** *** *** *** *** *** *** *** *** ***
DM level (D) *** *** *** *** * *** *** *** *** ***
Interaction TxD *** *** *** *** *** *** *** *** *** ***
SD: standard deviation; * P < 0.05; ** P < 0.01; *** P < 0.001
Figure 1. Aerobic stability of the silages with a
storage period of 49 day and air stress. Figure 2. Aerobic stability of the silages with a storage period of 91 days without air stress.
Conclusions The addition of the three different inoculants reduced the pH of the silages and improved the silage quality mainly in the forage with 34 and 46% DM. In addition, the inoculant with homo and het- erofermentative LAB improved the aerobic stability of all silages. On the other hand, the variants treated only with homofermentative LAB and with 34% DM heated up earlier in comparison to the control.
References
DLG 2006. Grobfutterbewertung. Teil B – DLG-Schlüssel zur Beurteilung der Gärqualität von Grünfuttersilagen auf Basis der chemischen Untersuchung DLG-Information 2/2006.
Pahlow G. & Weissbach F. 1996. Effect of numbers of epiphytic lactic acid bacteria (LAB) and of inoculation on the rate of pH-decline in direct cut and wilted grass silages. 11th International Silage Conference, Aberyt- wyth, September 1996, pp. 104-105.
Staudacher W., Pahlow G & Honig H. 1999. Certifi cation of silage additives in Germany by DLG. Proceedings 12th International Silage Conference, Uppsala, July 1999, pp. 239-240.
