peer-reviewedThe effects of contrasting conventional silage additives on chemical composition,
aerobic stability and deterioration, and mould development in baled silage were investigated.
Herbage from a grassland sward was wilted for 24 h and treated with acid (formic
or sulphuric), sugar (molasses), bacterial (Lactobacillus plantarum, L. plantarum + Serratia
rubidaea + Bacillus subtilis, or L. buchneri) or sugar + bacterial (molasses + L. plantarum)
additives prior to baling and wrapping. Silage made without an additive preserved
well and had a low incidence of mould growth, and the effects of additives were minor or
absent. It is concluded that little practical benefit was realised when conventional additives
were applied to wilted, leafy, easy-to-ensile grass prior to baling and ensilage

Forristal, P.D.

Keles, G.

O'Kiely, Padraig

Irish Journal of Agricultural and Food Research

English

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81A note on the conservation characteristics of baled grass silages ensiled with different additivesG. Keles1*, P. O’Kiely1† and P.D. Forristal21Teagasc, Grassland Science Research Department, Animal & Grassland Research and Innovation Centre, Grange, Dunsany, Co. Meath, Ireland2Teagasc, Crops Research Centre, Oak Park, Co. Carlow, IrelandThe effects of contrasting conventional silage additives on chemical composition, aerobic stability and deterioration, and mould development in baled silage were investi-gated. Herbage from a grassland sward was wilted for 24 h and treated with acid (formic or sulphuric), sugar (molasses), bacterial (Lactobacillus plantarum, L. plantarum + Serratia rubidaea + Bacillus subtilis, or L. buchneri) or sugar + bacterial (molasses + L. planta-rum) additives prior to baling and wrapping. Silage made without an additive preserved well and had a low incidence of mould growth, and the effects of additives were minor or absent. It is concluded that little practical benefit was realised when conventional addi-tives were applied to wilted, leafy, easy-to-ensile grass prior to baling and ensilage.Keywords: baled silage; conservation characteristics; silage additivesIrish Journal of Agricultural and Food Research 49: 81–86, 2010†Corresponding author: padraig.okiely@teagasc.ie*Current address: Bahri Dagdas International Agricultural Research Institute, Konya, TurkeyIntroductionThe rapid achievement of anaerobic conditions and inhibition of undesirable anaerobic microorganisms are essential components of silage production. In baled silage systems, anaerobic conditions are achieved by wrapping the bale in adequate plastic stretch film, and this should inhibit mould growth. However, on-farm studies indicate that extensive fungal growth on baled silage is common (O’Brien et al., 2008). In a previous study, McEniry et al. (2007) showed that silage additives based on formic acid, sucrose + Lactobacillus plantarum or a combination of anti-micro-bial salts could create conditions inhibitory 82     IRISH JOURNAL OF AGRICULTURAL AND FOOD RESEARCH, VOL. 49, NO. 1, 2010to fungal growth. Consequently, applying silage additives could help reduce fungal activity in baled silage.The objective in this experiment was to assess the effects of acid (for-mic or sulphuric), sugar (molasses), bacterial (L. plantarum, L. plantarum + Serratia rubidaea + Bacillus subtilis, or L. buchneri) or sugar + bacterial (molasses + L. plantarum) additives on the chem-ical composition, aerobic stability and deterioration, and mould development in baled silage, relative to the effects of baled silage made without the use of an additive. Materials and methodsBaling procedureThe primary growth of an Agrostis and Poa dominant permanent grassland sward was mown on 28 May, to a stubble height of approximately 6 cm, with a disk mower-conditioner set to place wide windrows on the stubble (windrows covered approxi-mately 70% of the ground area). Forage was wilted for 24 h without tedding. The following additive treatments were applied to forage in the windrows: (1) Control – no additive (C), (2) formic acid based additive (FA; Add SafeR, 70 g ammonia and 640 g formic acid per kg, Trouw Nutrition Ltd., UK) applied at 2.5 L/t herbage, (3) sulph-uric acid (SA; Cosil, 450 g sulphuric acid per kg, Nutribio Ltd., Cork) applied at 2.5 L/t herbage, (4) molasses (M) applied at 9 L/t herbage, (5) homofermentative lactic acid bacterial inoculant (LP; Ecosyl, L. plantarum, strain MTD/1 (NCIMB 40025), Novokem Ltd., Dublin) applied at 3 L/t herbage to achieve a target of at least 1.0 × 106 colony forming units (cfu) per 1 g herbage, (6) molasses + Ecosyl (M + LP) at the same rates as treatments 4 and 5, respectively, (7) homofermenta-tive lactic acid bacterial inoculant (EB; Ecobale, L. plantarum, strain MTD/1 (NCIMB 40027), S. rubidaea (NCIMB 40285) and Bacillus subtilis (NCIMB 40286), Novokem Ltd., Dublin) applied at 3 L/t herbage to achieve a target of at least 2 × 106 cfu/g herbage, and (8) heterofer-mentative lactic acid bacterial inoculant (LB; AxCool, L. buchneri, strain NCIMB 40788, Biotal Ltd., Wales) applied at 4 L/t herbage to achieve a target of at least 1 × 105 cfu/g herbage. Each additive treat-ment was applied to a randomly selected individual windrow within a group of eight adjacent windrows and a single bale was made from within each windrow. This procedure was repeated in seven further blocks across the field. Additives were applied across the full width of the top of grass windrows through a perforated dribble bar, and baling (ClassTM Rollant 46 Roto Cut Baler, with the 14 stationary cutting blades engaged; baler capacity was for a bale 1.2 m wide and 1.2 m diameter) was within 15 min of additive application. The 64 bales were immediately transport-ed to the storage area where they were core sampled, weighed and individually wrapped (McHaleTM 991 BE wrapper) with four layers of black plastic stretch film (25 µm film thickness; stretched by 70% during wrapping). Wrapping was complet-ed within 60 min of baling. Wrapped bales were stored on their curved side, outdoors on a grass base for 273 days. After storage the bales of silage were scored for visible surface mould growth and core sampled. Analytical proceduresChemical analysis of pre-ensilage (dry matter (DM), crude protein (CP), ash, in vitro DM digestibility (DMD) and buffer-ing capacity (BC)) and post-ensilage (DM, CP, DMD, pH, lactic acid, acetic acid, propionic acid, butyric acid, water-soluble carbohydrates (WSC) and ammonia-N) core samples was undertaken as described  KELES ET AL.: CONSERVATION OF BALED GRASS SILAGES 83by Keles et al. (2009) and Playne and McDonald (1966). Fermentation products are the sum of lactic, acetic, propionic and butyric acids.Each bale was scored for visible mould growth on its ends and barrel (total = ends + barrel). Bales were representa-tively sampled and aerobic stability (days to temperature rise > 2 °C above ambi-ent) and aerobic deterioration (accumu-lated temperature rise to day 5 (°C)) were assessed (n = 4 bales/treatment) at 20 °C for 8 days as described by McEniry et al. (2007).Data were statistically analysed as a randomised complete block design, using the general linear model procedure of the Statistical Analysis System (SAS, 2000). Paired comparisons of each additive treat-ment with the control (C) treatment were undertaken using Dunnett’s two-tailed test procedure. ResultsBale weight and grass compositionThe mean (s.d.) fresh and DM weights of bales at ensiling were 629 (54.9) and 193 (30.7) kg, respectively, and the cor-responding densities were 464 (40.5) and 142 (22.6) kg/m3. The mean (s.d.) com-position of the herbage pre-ensiling was DMD 768 (9.8) g/kg, ash 119 (3.5) g/kg DM, CP 154 (7.9) g/kg DM and BC 364 (12.1) mEq/kg DM. Silage compositionWhereas neither silage DM nor CP con-centration was affected (P > 0.05) by treatment, DMD was increased (P < 0.05) by LB (Table 1) compared to the control silage (C). Relative to C, both FA and SA reduced (P < 0.05) the concentration of lactic acid, but only FA reduced (P < 0.05) the concentration of fermentation products. None of the fermentation characteristics was altered by treatment M. Both EB and LB reduced (P < 0.05) WSC concentra-tion. There were no (P > 0.05) treatment effects on pH, on the concentration of propionic acid, butyric acid or ammonia-N, or on lactic acid as a proportion of fermentation products. Visible mould growth occurred mainly on the bale surfaces and rarely penetrated more than 2.5 cm below the surface. The extent of surface mould growth was small (mean of 0.015 of the bale surface area) for all treatments (data not presented). Treatment had no effect (P > 0.05) on aerobic stability, while the extent of aero-bic deterioration was larger (P < 0.05) for the M + LP treatment than for the C treatment.Discussion Pre-ensilageThe herbage used was of high digestibility and underwent relatively rapid drying. The slightly elevated ash concentration sug-gests some soil contamination occurred during mowing or baling. Silage compositionSilage preservation was satisfactory as indi-cated by the relatively low pH, the domi-nance of fermentation products by lactic acid, the low concentration of butyric acid and the moderately low ammonia-N con-centration. Additionally, the incidence of visible mould growth was low.Under conditions where the control silage had a relatively extensive fermen-tation (fermentation products = 94 g/kg DM at a DM concentration of 308 g/kg) that was dominated by lactic acid (729 g/kg fermentation products) it is not sur-prising that FA restricted the extent of fermentation (fermentation products of 75 g/kg DM). This, together with the 84     IRISH JOURNAL OF AGRICULTURAL AND FOOD RESEARCH, VOL. 49, NO. 1, 2010Table 1. Chemical composition (g/kg DM, unless otherwise stated in footnotes; no units for pH), aerobic stability and aerobic deterioration of baled silageVariable2Treatment1CFASAMLPM + LPEBLBs.e.SignificanceChemical compositionDM30828629127728528928525911.5CP1481531591531591571671584.0DMD7257467317437457407377535.7*pH4.334.294.184.264.264.214.364.280.041LA68555672767672763.0***AA23.016.319.725.820.119.026.827.12.41*PA0.70.40.50.70.61.00.71.00.20BA2.42.53.44.54.24.85.43.81.00WSC35443030242721212.8***NH3-N110112951081151051141277.5LA/AA3.13.73.13.14.24.53.12.90.37*FP9475801031011011041084.4***LA/FP72974471270475575869770324.3Aerobic stabilityDays to temperature rise > 2 oC3.83.03.33.53.32.32.52.50.46Aerobic deteriorationAccumulated temperature rise to day 5 (o C)11121613112316192.03**1 C = control; FA = Formic Acid; SA = Sulphuric Acid; M = Molasses; LP = L. plantarum; M + LP = Molasses + L. plantarum; EB = Ecobale; LB = L. buchneri.2 DM = dry matter (g/kg); CP = crude protein; DMD = in vitro DM digestibility (g/kg); LA = lactic acid; AA = acetic acid; PA = propionic acid; BA = butyric acid; NH3-N = ammonia-N (g/kg N); LA/AA (g/g); FP = fermentation products (LA + AA + PA + BA) (g/kg); LA/FP (g/g). KELES ET AL.: CONSERVATION OF BALED GRASS SILAGES 85higher concentration of unfermented sub-strate in the silage made using FA com-pared to that made with SA, is in accord with O’Kiely (1998), and reflects the lower anti-microbial effect of SA compared with FA. The apparent absence of an effect of added sucrose (as molasses) on fermenta-tion agrees with McEniry et al. (2007) who suggested that such an outcome indicates that the supply of fermentable substrate from the herbage to the indigenous epi-phytic microbial population did not limit the ability of the microbes to produce adequate lactic acid. It is possible that much of the added sucrose, which was surplus to requirements for fermentation, was converted to ethanol (not measured) as reported by Chamberlain (1988).The extent of the dominance of lactic acid among fermentation products in the control silage suggests that homofermen-tative lactic acid bacteria were present in adequate numbers on the herbage at baling. These bacteria would have posed a challenge to the added homofermentative lactic acid bacteria in LP, LP + M and EB. Hence, any numerical responses recorded were not statistically significant. However, both EB and LB tended to increase ace-tic acid concentration. This reflected the less exclusively homofermentative lactic-acid-bacterial composition of EB and the heterofermentative L. buchneri in LB. Intimate mixing of additive with herb-age may be more difficult to achieve when wilted (less translocation via juice from lysed cells) herbage is harvested by a round baler (less mixing than with preci-sion-chop system). The method of additive application used in the present experiment was considered a practical approach that could be undertaken on farms. However, it may have limited the extent of uniform mixing, and thus the opportunity for these additives to fulfil their potential may have been restricted. This may, at least par-tially, explain the smaller then expected effects of most of the additives.  Other conservation characteristicsThere was no treatment effect on aerobic stability and, although some treatment effects occurred for aerobic deterioration, the overall scale of aerobic deterioration was small across all treatments and the treatment effects were therefore of minor importance. It is concluded that baled silage made from well-wilted grass underwent a satis-factory preservation when ensiled with-out an additive, and that even though some additives modified fermentation characteristics their effects were gener-ally quite modest. These findings, together with the small amount of visible mould growth, suggest that little practical benefit occurred when additives were applied to wilted, leafy easy-to-ensile grass that was then baled and securely wrapped in plastic stretch film. AcknowledgementsThe input of Mr. J. Hamill, Grange Farm staff, and the staff of Grange Laboratories is acknowledged. ReferencesChamberlain, D.G. 1988. Effect of added glucose and xylose on the fermentation of perennial rye-grass silage inoculated with Lactobacillus planta-rum. Journal of the Science of Food and Agriculture 46: 129–138.Keles, G., O’Kiely, P., Lenehan, J.J. and Forristal, P.D. 2009. Conservation characteristics of baled grass silages differing in duration of wilting, bale density and number of layers of plastic stretch-film. Irish Journal of Agricultural and Food Research 48: 21–34.McEniry, J., O’Kiely, P., Clipson, N.J.W., Forristal, P.D. and Doyle, E.M. 2007. Manipulating the ensilage of wilted, unchopped grass through the use of additive treatments. Irish Journal of Agricultural and Food Research 46: 77–91.O’Brien, M., O’Kiely, P., Forristal, P.D. and Fuller, H.T. 2008. Fungal contamination of big-bale grass silage on Irish farms: predominant mould and 86     IRISH JOURNAL OF AGRICULTURAL AND FOOD RESEARCH, VOL. 49, NO. 1, 2010yeast species and features of bale and silages. Grass and Forage Science 63: 121–137.O’Kiely, P. 1998. A note on the conservation char-acteristics of physiologically immature forage maize ensiled with different additives. Irish Journal of Agricultural and Food Research 37: 237–242.Playne, M.J. and McDonald, P. 1966. The buffering constituents of herbage and of silage. Journal of the Science of Food and Agriculture 17: 264–268.SAS. 2000. Version 8.02, SAS Institute Inc., Cary, NC, USA.Received 22 October 2009

A note on the conservation characteristics of baled grass silages ensiled with different additives.

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