Effect of herbage water-soluble carbohydrate content and weather conditions at ensilage on the fermentation of grass silages made on commercial farms

A total of 1009 samples of silage made in bunker silos on commercial farms between 1972 and 1978 was analysed to investigate the effect of herbage water-soluble carbohydrate content (WSC) and weather conditions at ensilage on fermentation as measured by ammonia-N concentration and pH of first-cut grass silages.
Silage dry matter (DM) content had the major effect on fermentation. Factors influencing silage DM were rainfall and hours of sunshine during silage making, and DM content of the grass cut. WSC content of herbage ensiled also had a significant effect on subsequent fermentation. The major influences on herbage WSC were hours of sunshine and rainfall during the growing season.
The effect of chemical additives, albeit at poorly defined and often inadequate rates, was small in comparison to that of silage DM.
The minimum DM necessary to produce well-fermented silage without additive was approximately 260 g kg⁻¹. Use of formic acid significantly reduced this requirement to 240 g kg⁻¹ and to 252 g kg⁻¹ for sulphuric add + formalin. The results indicate that the minimum herbage WSC necessary to prevent a clostridial fermentation developing in silage with a DM content of 230 g kg⁻¹ is approximately 37 g kg⁻¹ without additive and 30 g kg⁻¹ with formic acid.
It is concluded that on commercial farms, weather conditions i.e. amount of rainfall and sunshine prior to and at ensilage, have a greater effect on subsequent silage fermentation than additive use.     

The effect of dry matter content on the preservation of big hale grass silages made during the autumn on commercial farms in South Wales 1983-87

A total of eighty-nine big-bale (BB) silages made on commercial farms in South Wales during the autumn in 1983-87 were analysed to discern the effect of dry matter (DM) content on fermentation. Silages were made predominantly in late September, during fine weather from permanent pasture or perennial ryegrass pastures, which had not been grazed for 9 weeks. On average 7·8 ha of pasture were cut; most farmers attempted to pre-wilt grass for an average of 36 h prior to ensilage in individual plastic bags. Silage making was usually completed within 4 d of starting to cut. Silage ammonia-N content was inversely correlated with DM content. The results indicated that a DM content of about 280 g kg⁻¹ was needed to produce well-preserved silage with an ammonia-N content of 100 g (kg total N)⁻¹. Silages were, therefore, generally poorly preserved because the DM increase from wilting was only 2·3 g kg⁻¹ h⁻¹.     

A study of the efficacy of a bacterial inoculant and formic acid as additives for grass silage in terms of milk production

In a two-year experiment, three silages were prepared from herbage treated either with an inoculant at 1·25 × 10⁵ organisms (g fresh material (FM))⁻¹. formic acid (850 g kg⁻¹) at 4 1 (t FM)⁻¹, or no additive (untreated). In Experiment 1, unwilted and in Experiment 2, wilted silages were investigated and had mean dry matter (DM) and water soluble carbohydrate (WSC) concentrations at ensiling of 171 g kg⁻¹ and 17·6 g (kg FM)⁻¹ and 263 g kg⁻¹ and 25·1 g (kg FM)⁻¹, respectively. In Experiment 1, 45 and in Experiment 2, 54 individually fed cows were used to evaluate the silages in three-treatment, randomized-block design experiments. During weeks 4-12 of lactation the cows were offered silages ad libitum and during weeks 15-26 a constant amount of silage was fed. There were few major differences in chemical composition of the resulting silages. Formic acid had no effect on silage digestibility. Inoculant treatment increased digestibility when the grass had been wilted. The use of formic acid resulted in increased silage DM intake of 9% during weeks 4-12 of lactation in Experiment 1 but not in Experiment 2. The inoculant gave no increase in silage DM intake over the control in Experiment 1 but increased silage DM intake by 7% in Experiment 2. There was no significant response in milk yield to formic acid. In Experiment 2 the response in milk yield to inoculant treatment was significant both in weeks 4-12 of lactation (4%) and in weeks 15-26 of lactation (5%). It is concluded that the response in milk yield to the use of a specific inoculant appears to be mediated through increased intake of metabolizable energy (ME).     

The effect of addition of sugar and inoculation with two commercial inoculants on the fermentation of lucerne silage in laboratory silos

Lucerne (DM 236 g kg^-1, WSC 49 g (kg DM)^-1) was ensiled in test-tube silos with or without either glucose or fructose and with or without one of two commercial inoculants. The WSC content of the forage as ensiled was too low to obtain a well preserved untreated silage. By day 4 the pH values of the silages with added sugar or inoculant were significantly lower (P< 0·001) than the control silage. A satisfactory fermentation was attained only in the silages to which sugar and an inoculant had been added. These silages had a lower pH, more protein-N (P< 0·001), less ammonia-N (P<0·001), a faster increase in counts of lactic acid bacteria, and decrease in counts of coliforms than the other silages. Homo-fermentative lactic acid bacteria dominated the fermentation in the inoculated silages while leuconostocs dominated the early stages of fermentation in the control silages. The results indicate that if there is insufficient sugar in the original crop, then the bacteria in an inoculant will not be able to produce enough lactic acid to lower the pH to an acceptable level. This has important implications for the ensilage of lucerne and other highly buffered low sugar crops.     

Enzymes as silage additives for grass–clover mixtures

Seven laboratory-scale experiments were carried out to study the effects of cellulases/hemicellulases on silage fermentation of herbage from mixed swards of timothy ( Phleum pratense ), meadow fescue ( Festuca pratensis ) and red clover ( Trifolium pretense ). Enzyme-treated silage (approximately 3500 HEC units kg⁻¹ grass) reached a low pH sooner, had lower end pH, contained less NH₃-N and more lactic acid than did the untreated silage ( P < 0·05). Applied with an inoculant, these effects were even stronger. With easily ensiled crops (experiments 1, 2, 5 and 6) preservation was first of all improved by inoculation of lactic acid bacteria; however, for the low-sugar crops (experiments 3, 4 and 7) enzyme treatment was more significant. The enzymes derived from Aspergillus spp. gave more acetic acid than the enzymes from Trichoderma reesei. The Trichoderma enzymes liberated 4·8 g WSC kg⁻¹ FM gamma-irradiated grass during 60 d at pH 4·3 ( P < 0·05). On average, for all silages enzyme treatment increased the sum of residual sugar and fermentation products by 3·7 g kg⁻¹ FM (21 g kg⁻¹ DM) compared with the silages not treated with enzymes ( P < 0·001). Enzyme treatment increased the instantly degradable part of the feed, but total in sacco and in vitro digestibilities were not affected.     

A comparison of formic acid and an acid-salt type additive on the performance of dairy cows in early lactation

Perennial ryegrass, harvested as second-cut material on 10 and 11 July 1990, was treated with either formic acid at 31 t^-1 or an acid-salt type additive at 61 t^-1 and ensiled in roofed 150 t bunker silos. Subsequently both silages underwent a predominantly lactic fermentation. Nevertheless the acid-salt-treated silage had a significantly higher quantity of formic acid (19 vs 12 g kg DM^-1) and significantly lower levels of lactic (98 vs 118 g kg DM^-1) and acetic acid (11 vs 17 g kg DM^-1) compared with formic acid-treated silage. In-silo losses and effluent production were similar.
Each silage was individually fed to 10 October-calving Friesian dairy cows (average weight 565 kg) from weeks 2 to 15 of lactation, together with 3 kg d^-1 of a compound feed containing 190 g kg DM^-1 crude protein and with an estimated metabolizable energy content of 12·6 MJ kg DM^-1. The acid-salt additive had no significant effect on silage DM intake, daily milk yield, milk protein or cow liveweight change, but significantly increased milk butterfat content compared with formic acid-treated silage.
It is concluded that the acid-salt type additive produced little difference in terms of either silage fermentation or animal performance compared with formic add treatment.     

The composition of first-cut grass for ensilage in England and Wales from 1988 to 1991

A total of 2225 samples of herbage, typical of that taken for first-cut silage on commercial farms in England and Wales, was taken between 1988 and 1991. Samples were analysed for dry matter (DM), water soluble carbohydrate (WSC), crude protein (CP) and metabolizable energy calculated from modified acid detergent fibre. The results were used to investigate the effect of weather conditions upon herbage quality for ensilage. In general, in areas of high rainfall, i.e. western areas, herbage DM and WSC were significantly lower than in eastern areas, whilst the reverse situation occurred with CP. Italian ryegrass (IRG) had a significantly higher WSC and lower CP than other grasses, whilst samples from permanent pasture (PP) had significantly lower DM and WSC, and significantly higher CP than other grasses. It was calculated that to produce a WSC concentration in the fresh grass of 37 g kg⁻¹, to produce well-fermented silage without additive use, IRG grown in the east would require a DM of 160 g kg⁻¹, In contrast PP grown in the west would require a DM content of 250 gkg⁻¹.     

Silage and milk production: studies with diets containing white clover silage

In three separate feeding experiments using a total of twenty-six individually-housed Ayrshire cows, three wilted silages made from Blanca white clover were offered ad libitum with either different supplements or different proportions of grass silage. The clover silages contained 680 g white clover kg⁻¹ on a DM basis, and had a mean DM concentration of 263 g kg⁻¹ with 231 g CP kg⁻¹ DM and 91 g ammonia-N kg⁻¹ N. The pH values averaged 4·16 and the DOMD concentrations 611 g kg⁻¹. In experiment 1 the daily intake of clover silage given alone was 15.2 kg DM per cow, i.e. 30·1 g kg⁻¹ live weight, and decreased by 0·76 kg DM kg⁻¹ barley DM and by 0·66 kg DM kg⁻¹barley plus soybean meal DM when these feeds were offered as supplements. Milk yield and fat concentration were higher on the supplement treatments than on the clover silage-only treatment. In experiments 2 and 3 the intakes of silage and total DM increased as the weight of clover in the diet increased from 0 to 700 g kg⁻¹ with parallel increases in milk yield. The effects on milk composition were small and generally non-significant. Although white clover silages with excellent fermentations were made, it is concluded that the main role of white clover in a silage system will be in mixed swards with grass to reduce the input of fertilizer N and to increase the voluntary intake of silage.     

A note on ensiling safflower forage

Abstract The ensiling characteristics of safflower ( Carthamus tinctorius ) wilted to 290 and 411 g dry matter (DM) kg⁻¹ fresh material were studied in 1·5 l glass jars. The experiment included a control and the application of Lactobacillus plantarum at 3·3 × 10⁵ colony-forming units (cfu) per g of crop. After 60 days of ensiling, the pH of safflower silages was 4·6 and 4·0 in the control and inoculated silages respectively, with corresponding values for lactic acid, the major fermentation product, of 20 and 45 g kg⁻¹ DM. The silages from the anaerobic jars were stable upon aerobic exposure. It is concluded the safflower silage has potential as an alternative fodder in semiarid regions.     

RESEARCH NOTE

Data from twenty-two experiments conducted at tour ADAS Research Centres during 1980–92 were used to compare untreated silages with silages treated with formic acid, with or without added formalin, commercial inoculants or molasses. The sillages were made from herbage whose dry-matter (DM) and water-soluble carbohydrate (WSC) contents were 277 (s.e. 0.46) g DM kg⁻¹ and 36 (s.e. 8.1) g kg⁻¹ respectively. Inoculant use significantly decreased silage pH and ammonia-N, significantly increased lactic acid and total acid content, and decreased butyric acid and total short-chain fatty acids. Formic acid use significantly increased silage lactic acid and total acid content, and decreased butyric acid content, whereas formic acid+formalin significantly decreased silage ammonia-N level. Molasses had little effect upon silage fermentation. Improvements in silage fermentation, however, produced little benefit in terms of either silage DM intake or liveweight gain when the silages were offered to growing lambs.
It is suggested from the results that inoculant- and formic acid-based additives can be used to improve the fermentation of big-bale silages.     

An evaluation of three bacterial inoculants and formic acid as additives for first harvest grass

An experiment was carried out during 1984 to study the effect of treating grass at ensiling with three commercially available inoculant-type additives (H/M Inoculant, Grass Sile and Siron), formic acid (850 g kg⁻¹; Add-F) or no additive on grass preservation, in-silo loss, intake and animal performance. Primary growth grass ensiled from 28–29 May into concrete-walled covered silos was of high dry matter (DM, 234 g kg⁻¹), water-soluble carbohydrate content (WSC. 212 g kg DM⁻¹) and digestibility (MADF, 250 g kg DM⁻¹).
The untreated silage displayed good preservation and with the exception of the Sirontreated silage which showed significantly lower buffering capacity (Be) and volatile fatty acid (VFA) contents than the untreated silage, the application of inoculant-type additives did not improve silage preservation or decrease in-silo DM losses. The formic acid-treated silage displayed significantly lower Be, water-soluble carbohydrate, ash, ammonia nitrogen (g kg total N⁻¹) and lactate contents than the untreated silage.
After a 133 d storage period, silages were offered to finishing beef cattle for an 84-d period. Cattle offered the silages displayed similar and non-significant daily DM intakes, daily liveweight gains, dressing proportions and daily carcass gains. From this experiment it appears unlikely that any of the additives evaluated will improve animal performance relative to a well-preserved untreated silage.     

The digestion by cattle of grass silages made with no additive or with the application of formic acid or formic acid and formaldehyde

The aim of the experiment was to assess the effect of applying, at commercially recommended rates, formic acid or formic acid/formaldehyde at ensilage upon the subsequent digestion of the silages by cattle. Three wilted grass silages were made from perennial ryegrass ensiled at a DM concentration of 206 g kg⁻¹ after a poor wilting period of 49 h without additive application and with application of 2.5 litres t⁻¹ of formic acid or of 4.5 litres t⁻¹ of a mixture of (gkg⁻¹) 500 formic acid, 200 sulphuric acid and 200 formatin giving an application rate of 15 g formaldehyde kg⁻¹ herbage crude protein (N × 6.25).
The silages were fed to cattle equipped with rumen cannulae and duodenal re-entrant cannulae. Results from analyses of silage composition and from the digestion of organic matter and N showed no major differences between silages. The efficiency of rumen microbial N synthesis, the rumen degradability of silage N (determined in vivo or in sacco ) and in vivo digestion of individual amino acids were also unaffected by additive treatment. These results indicate that poor wilting conditions before ensilage restricted the effectiveness of additive treatment; the ineffectiveness of formaldehyde in reducing the rumen degradability of silage N may also have been related to the low rate of formaldehyde application.     

Growth performance, appetite and plasma ammonia concentrations in heifers fed inoculated lucerne prior to ensilage, then supplemented with sodium bicarbonate

A study was conducted to explore the possibility of a synergistic effect of an inoculum of lactic acid bacteria and sodium bicarbonate in improving the nutritive value of lucerne silage. Twenty Holstein heifers (live weight 183 ± 9·4 kg) were assigned to four dietary treatments consisting of: lucerne uninoculated or inoculated prior to ensilage and then either unsupplemented or supplemented with NaHCO₃ (40 g kg⁻¹ dry matter (DM)). The lucerne silage contained 320 g kg⁻¹ DM and constituted 600 kg⁻¹ diet DM. The animals were fed once daily for 90 d and samples of jugular blood were analysed for plasma ammonia and indices of blood acid-base status. Inoculation of Lucerne reduced ( P <0·01) silage pH but had no other effect on silage composition. In the absence of NaHCO₃, liveweight gain and organic matter intake were improved by inoculating lucerne prior to ensilage; however, in the presence of NaHCO₃, inoculation reduced growth rate but had no major effect on intake. Dietary treatment did not (P>0·05) affect the concentration of plasma ammonia or measures bf blood acid-base status. The results suggest that NaHCO₃ may have nullifled any potential benefit of inoculating lucerne silage to improve its nutritive value for heifers.     

Determination of microbial protein in perennial ryegrass silage

The microbial matter fraction was determined in perennial ryegrass silages of different dry-matter (DM) contents, ensiled with or without Lactobacillus plantarum . ¹⁵N-Leucine and the bacterial cell wall constituent diaminopimelic acid (DAPA) were used as markers for microbial-N. Perennial ryegrass crops with DM contents of 202, 280 or 366 g kg⁻¹ fresh weight were ensiled in laboratory-scale silos and stored for 3 to 4 months. At different times after ensiling, silages were analysed and microbial fractions were isolated. Microbial-N concentration determined with ¹⁵N-leucine reached a maximum during the first week of ensilage. It remained unchanged thereafter, except in silage with a DM content of 280 g kg⁻¹ in which it decreased ( P  < 0·01) by 32% during storage. After 3 to 4 months ensilage, microbial-N concentration varied from ≈0·3 to ≈1·7 g kg⁻¹ DM. A negative relationship was observed between microbial-N concentration and silage DM content. Inoculation resulted in an approximately twofold increase ( P  < 0·001) in microbial-N concentration. Microbial-N concentrations determined with DAPA were 1·14–2·07 times higher than those determined with ¹⁵N-leucine. However, 19–35% of the DAPA in silage occurred in a soluble form, indicating that this fraction of DAPA was not associated with intact bacteria.     

A comparison of unwilted and wilted grass silages offered to beef cattle without and with monensin sodium

A randomized block experiment was conducted to compare unwilted and wilted grass silages and the effects of the feed additive monensin sodium on the silage intake and performance of finishing beef cattle. Two regrowths from a predominantly perennial ryegrass (cv. S24) sward were ensiled either without wilting or after field wilting for 3 d (dry matter (DM) concentrations 161 and 266 g kg⁻¹ respectively). Both silages were treated with formic acid (2·6 and 30 litre t⁻¹ respectively) and were well preserved. The silages were offered ad libitum to forty-eight Charolais-cross cattle (thirty-two steers and sixteen heifers, mean initial live weight 351 kg) for 145 d. All animals received 2·2 kg concentrates per head daily and half of those on each silage treatment received in addition 200 mg monensin sodium per head daily. Silage DM intake was 5.04, 504. 5·48, 5·63 ± 0.134 kg d^−l; fasted liveweight gain was 0·69, 0·77. 0·64 and 0·73 ± 0.033 kg d^−l and carcass gain was 0·47, 0·50, 0·40 and 0·45 ± 0·020 kg d⁻¹ for the unwilted silage without and with monensin and the wilted silage without and with monensin respectively. It is concluded that wilting grass of low DM concentration for 3 d prior to ensiling reduced the performance of finishing beef cattle below that obtained from well-preserved unwilted silage in spite of a higher DM intake being achieved with the wilted silage. The inclusion of monensin sodium in a silage-based diet increased performance without significantly affecting feed intake.     

The chemical composition and nutritive value of grass silages prepared with no additive or with the application of additives containing either Lactobacillus plantarum or formic acid

A mixture of perennial and hybrid ryegrasses(234 g DM kg^-1) was forage harvested and ensiled after a 24-h wilt in good ensiling conditions in 2-t capacity silos with no additive application (control) or with the application of either Lactobacillus plantarum , 4 × 10⁶ (g fresh weight of grass)^-1, or of 31 formic acid t^-1. Sufficient 2-kg capacity laboratory silos were also filled with grass to monitor the changes in chemical composition of the ensiled grass with time. In laboratory silos, inoculation with L. plantarum resulted in a more rapid fall in silage pH ( p < 0.001) and a more rapid production of lactic acid ( P < 0.001) than in the control silage. At the end of the storage period (laboratory silos, 80 d; 2-t silos, 200-300 d), the inoculated silos had lower pH ( p ammonia-N (g kg N¹) and acetic acid contents ( p < 0.01) and higher water soluble carbohydrate (WSC), lactic acid (P<00.1) and ethanol ( p < 0.05) contents than the control silage. The formic acid-treated silage had significantly lower contents of ammonia-N (g kg N^-1, p < 0.05), acetic and tactic acids (p<0.01) and higher contents of WSC and ethanol ( p < 0.01) than the control silage. When fed to wether sheep, the digestibilities of DM, organic matter and gross energy were not altered by additive treatment. The digestibility of modified acid-detergent fibre was lower for both the inoculated ( P < 0.01) and formic acid-treated silages ( p < 0.05). However, N retention was improved ( p < 0.05) by both additive treatments. Silage intake was improved ( p < 0.01) by additive treatment from 53.4 (control) to 58.0 (inoculated) and 60.4 (formic acid) g DM (kg live weight^0.75)^-1d^-1.     

Influences of enterobacteria on the fermentation and aerobic stability of grass silages

Grass (220 g DM kg⁻¹ was ensiled after adding 10⁶ and 10⁸ enterobacteria (90% Rahnella aquatilis , 9·9% Hafnia alvei and 0·1% Escherichia coli g⁻¹ fresh mutter. The silages were exposed to aerobic conditions alter 125 d of storage. In all treatments H. alvei rapidly superseded the initial high number of Enterobacter agglomerans (naturally present) and R. aquatilis. The maximum number of enterobacteria was detected about I d after initiation of fermentation. After 4 d of fermentation, when concentrations of undissociated lactic and acetic acids ranged from 52 to 36 mM and 41 to 51 mM respectively, no enterobacteria were detectable. Inoculating the crop with enterobacteria restilted in a temporarily retarded rate of production of lactic and acetic acids and a 50% increase in the concentration of ammonia-N. The concentration of endotoxin in the silages was 6–7 μg g⁻¹ fresh matter. There was no change in the level of endotoxin during ensiling. High numbers of enterobacteria at the beginning of the fermentation improved the aerobic stability of the silages. There was a lag in the decrease in concentrations of acids and delays in the increase in pH, respiration rate and numbers of yeast and Bacillus spores, in uninoculated silages the pH increased from 4·1 to 5·0 after 8 d of aerobic storage, whereas in inoculated silages a pH of 5·0 was not reached until after 16 d of storage.     

Silage and milk production: studies with molasses and formic acid as additives for grass silage

In two separate feeding experiments using a total of twenty-four individually housed Ayrshire cows six silages made from perennial ryegrass were offered ad libitum with supplements of concentrates. In Experiment I herbage with a dry matter (DM) concentration of 225 g kg⁻¹ received either formic acid ('Add-F') at the rate of 2·0 litres t⁻¹ or undiluted cane molasses at rates of 10, 20 and 30 litres t^−l; the mean daily silage intakes were 9·54, 908, 9·27 and 9·49 kg DM per cow and the daily milk yields, corrected to 40 g fat kg⁻¹, were 23·2, 22·3, 22·8 and 22·9 kg per cow respectively but none of the differences between the four treatments was significant. In Experiment 2 herbage with a DM concentration of 269 g kg⁻¹ received formic acid at a uniform rate of 2·6 litres t⁻¹ either with or without an additional application of molasses at 20 litres t⁻¹; the mean daily silage DM intakes were 8·70 and 9·28 kg per cow and the daily fat-corrected milk yields were 22·2 and 21·9 kg per cow respectively and were not significantly different. In both experiments the effects of the treatments on milk composition were small and not significant. It is concluded that there were no advantages in applying molasses to herbage treated with formic acid, and that the rate of application of molasses to untreated herbage which equated with the formic acid application was 20·30 litres t^−l when assessed on the basis of silage composition, intake and milk production.     

Comparison of a straw/concentrate mixture with silage as a buffer feed for grazing dairy cows

Over a 24-week period during the 1986 summer, three groups of January- to March-calving dairy cows were either grazed conventionally (G) or grazed between morning and afternoon milkings and housed overnight and offered grass silage (Si) or a straw/concentrate mixture (St) ad libitum. The straw/concentrate mixture contained proportionately, 0-33 long barley straw, 0·28 ground barley, 0·12 soya bean meal, 0·25 molaferm and 0·22 minerals. The metabolizable energy (ME) and crude protein (CP) contents of the silage fed in weeks 1-8 and weeks 9-24 were 9-5 and 10⁻⁶ MJ kg MD⁻¹ and 160 and 191 g kg DM⁻¹ respectively. The straw mix had an ME content of 10⁻¹ MJ kg DM⁻¹ and CP content of 134 g kg DM⁻¹. Partial storage feeding with silage or a straw/concentrate mixture led to a decrease in estimated herbage DM intake. The feeding of the straw/concentrate mixture increased total DM intake, but the estimated total ME intake was similar for treatments G and St. The intakes (kg DM d⁻¹) for treatments G, Si and St were respectively, herbage 11·7,6·8,4·1; total l3·5,13·6,15·0; total ME intake (MJd⁻¹) 163, 155, 163.
Animal performance was, for treatments G, Si and St respectively: milk yield (kg d⁻¹) 19·2, 17·5, 19·1 (s.e.d. 0-87); milk fat content (g kg⁻¹) 36·9, 37·6, 37.1 (s.e.d. 1.22); milk protein content (g kg⁻¹) 35·3, 32·9, 33·4 (s.e.d. 0·76).     

Enzymes as silage additives 2. The effect of grass dry matter content on silage quality and performance in sheep

Eight grass silages were made from two contrasting varieties of perennial ryegrass, four silages each from a late-cut early-maturing (high dry matter, HDM) variety and from an early-cut, late-maturing (low dry matter, LDM) variety. The grass was ensiled without additive (untreated), or with formic acid, or with one of two enzyme mixtures of hemicellulases and cellulases (enzyme 1 and enzyme 2) for a period of 130 d.
Formic acid-treated silage had lower levels of lactic acid at both levels of dry matter than the other silages. Enzyme treatment of grass prior to ensilage resulted in reduced levels of cellulose, acid-detergent fibre and neutral-detergent fibre in LDM silages and lower acid-detergent fibre and neutral-detergent fibre in the HDM silages compared with the corresponding untreated and formic acid-treated silages. Voluntary intakes (g DM d⁻¹) of untreated and enzyme-treated silages were significantly ( P <0·01) lower at both digestibilities compared with formic acid-treated silages (LDM: untreated, 982; formic, 1069; enzyme 1, 868; enzyme 2, 937; HDM: untreated, 931; formic, 1027; enzyme 1, 943; enzyme 2, 914). The organic matter, carbohydrate and nitrogen digestibility coefficients of LDM silages were significantly ( P <0·001) higher than those of HDM silages. There were no significant differences in any component digestibility related to silage additive.
Comparison of digestibility coefficients for constituents of the LDM silages fed to sheep or steers showed no differences between species.