Enzymes as silage additives. 1. Silage quality, digestion, digestibility and performance in growing cattle

Four grass silages were made from perennial ryegrass ensiled after a 1h wilt in 2-t silos without additive application, with application of formic acid or with one of two enzyme mixtures of hemicellulases and cellulases (enzyme 1 and enzyme 2). Effluent losses were monitored over the ensiling period (130 d).
Analyses of the silage showed that formic acid-treated silage had lower concentrations of lactic acid than the other silages. Both enzyme-treated silages had lower levels of cellulose, acid detergent fibre (ADF) and neutral-detergent fibre (NDF) than the untreated and formic acid treated silages. Effluent production was highest with enzyme-treated silages.
The silages were subsequently fed to growing steers equipped with rumen cannulae and T-piece duodenal cannulae. Apparent whole-tract digestibilities of organic matter constituents were significantly lower ( P < 0·05) with both enzyme-treated silages (untreated; 0·736, formic acid; 0·722, enzyme 1; 0·694, enzyme 2; 0·703). Both untreated and enzyme 2-treated silages sustained higher nitrogen digestibilities (g g⁻¹ intake) (untreated; 0·675, formic acid; 0·636, enzyme 1; 0·630, enzyme 2; 0·662) and N retentions (g d⁻¹) untreated; 16·0, formic acid; 14·0, enzyme 1; 11·6, enzyme 2; 16·6), but none of these differences was significant. When formic acid-treated silage was offered, there was a greater amount of organic matter apparently digested in the rumen (ADOMR). Non-ammonia nitrogen and microbial nitrogen flows at the duodenum were similar on all diets. The efficiency of microbial protein synthesis was highest with enzyme 2-treated silage and lowest with formic acid-treated silage (untreated, 35·4; formic acid, 25·2; enzyme 1, 30·4; enzyme 2, 39·4), but none of these differences were significant.     

The effect of dry feed additives on the nutritive value of silage

Silages were prepared in late September from a mixed crop of perennial ryegrass and white clover with low dry matter and high nitrogen content. Six different treatments were used during ensiling; addition of either molassed sugar beet pulp or rolled barley, at 50 kg and 25 kg (t fresh grass)^?1, formic acid at 51 t^?1 and no additive (control). All silages were well fermented with low levels of ammonia and pH. The addition of rolled barley or sugar beet pulp increased the dry matter content of the silages incrementally and appeared to assist the retention of nitrogen in the silage. Dry matter intakes of silages with 50 kg of barley or sugar beet pulp tonne^?1 were similar to the control silage when fed to wether sheep but at 25 kg t^?1, dry matter intake increased by 0·15 with barley and 0·04 with sugar beet pulp compared to the control. The digestibility of dry matter (DM) and organic matter (OM) were significantly higher than the control for silages treated with formic acid or high levels of barley and sugar beet pulp whereas neutral-detergent fibre (NDF) digestibility did not appear to be significantly affected. All treated silages had a significantly higher metabolizable energy (ME) content than the control, and additions of barley or sugar beet increased the ME content. The ME intakes of all treated silages were also significantly greater than those of the control, and the formic acid-treated and low barley silages were the highest. This appeared to be associated with significantly higher energy digestibility and DM intake. Addition of rolled barley during ensilage resulted in greater nitrogen intake, availability and retention compared to additions of sugar beet pulp. The higher retention with barley silages was associated with a significantly lower proportional loss of absorbed nitrogen in urine, which indicated a more efficient utilization of nitrogen. These differences require further study to determine the mechanisms involved in the interactions between the energy source and herbage protein, both during fermentation and in the rumen.     

The effects of different protein supplements on the utilization of untreated, formic acid-treated or enzyme-treated silages by growing steers

Three grass silages were made from perennial ryegrass ensiled without additive application (U) or with the application of formic acid (F) or an enzyme mixture of hemicellulases and cellulases (E).
Analysis of silages showed that both untreated and enzyme-treated silages had higher lactic acid concentrations than formic acid-treated silage. Enzyme-treated silage had lower levels of ADF and NDF but higher concentrations of residual WSC than other silages.
The silages were fed to growing steers supplemented with either rapeseed meal (RSM) (60 g kg⁻¹ silage DM) or fishmeal (FM) at a level isonitrogenous with RSM diets, so providing six diets (UR, UF, ER, EF, FR, FF). Organic matter intakes were similar, but ADF intakes were significantly ( P < 0·001) lower with enzyme-treated silage diets (UR, 1163; UF, 1160; ER, 1104; EF, 1035; FR, 1216; FF, 1213), as were intakes of NDF ( P < 0·01) (UR, 1946; UF, 1955; ER, 1877; 1772; FR, 2031; FF, 2041). Apparent whole tract digestibilities of organic matter were significantly ( P < 0·001) higher with enzyme-treated silages (UR, 0·644, UF, 0·644; ER, 0·668; EF, 0·678; FR, 0·633; FF, 0·633). Liveweight gains were generally higher with treated silage diets and RSM supported a greater response than FM (UR, 0·496; UF, 0·498; ER, 0·567; EF, 0·489; FR, 0·543; FF, 0·506) with both enzyme and formic acid-treated silages, although none of these differences were significant.     

Comparison of the fermentation quality and nutritive value of sulphuric and formic acid-treated silages fed to beef cattle

Five experiments were carried out in the years 1980-1983 and 1986 to study the effect of treating grass at ensiling with sulphuric acid (850 g kg^?1) and formic acid (850 g kg^?1) additives alone, and in mixtures with or without formalin on the preservation of grass, in vivo digestibility in sheep, in-silo loss, intake and performance of finishing cattle. Primary growth grass was ensiled in experiments 1 (3–4 June 1980), 2 (12-15 June 1981) and 3 (31 May-2 June 1982), primary regrowth grass in experiment 4 (1-2 August 1983) and secondary regrowth grass in experiment 5 (7-10 October 1986). During the ensiling period within each experiment, approximately 60 t of unwilted, double-chopped, additive-treated or untreated grass was packed into covered concrete-walled 60-t capacity silos. The dry matter (DM) contents of the ensiled grass in experiments 1, 2 and 5 ranged from 155-180 g kg^?1 and were lower than those recorded in experiments 3 and 4 (214 g kg^?1). With the exception of grass ensiled in experiment 2, where water-soluble carbohydrate (WSC) contents were low, at 104 g kg^?1 DM, grass in all other experiments contained relatively high WSC contents ranging from 140-154 g kg^?1 DM. In experiments 1, 3 and 4 all silages were well-preserved. However, in experiment 2 the 450 g kg^?1 sulphuric acid-treated and formic acid-treated silages displayed significantly lower pH, buffering capacity (Bc) and ammonia nitrogen contents than the untreated silage. In experiment 5, the sulphuric acid-treated and formic acid-treated silages displayed significantly lower pH, Bc, ammonia nitrogen, butyrate and volatile fatty acid (VFA) contents than the untreated silage. Each of the silages was offered daily with various levels of a supplementary concentrate for approximately 70-d periods to twelve animals of mixed breed in experiments 1, 3, 4 and 5 and to fifteen animals in experiment 2. All animals weighed between 380-470 kg at the start of the experiments. In experiments 1, 2 and 3 there were no significant differences between silages for any of the intake or animal performance parameters. In experiment 4, cattle fed the formic acid-treated silage displayed significantly higher silage DM intakes and daily liveweight gains than those fed the sulphuric acid-treated and untreated silages; in experiment 5, cattle fed the formic acid-treated silage displayed significantly higher silage DM intakes than those fed the untreated silage. It was concluded that formic acid was a more effective silage additive than sulphuric acid. Increasing the level of supplementation significantly decreased silage DM intakes in cattle in experiments 3 and 4, and significantly increased daily liveweight gains and daily carcass in cattle in experiments 1, 3 and 4.     

The effect of cell wall degrading enzymes or formic acid on fermentation quality and on digestion of grass silage by cattle

A first cut of timothy, treated with water (untreated), formic acid (FA), cellulase + lactic acid bacteria (CB), cellulase + hemicellulase (CH) or cellulase + hemicellulase + a lignin-modifying enzyme (CHL), was ensiled in pilot-scale silos. Silages, except CB, were fed to four male cattle, each equipped with a rumen and duodenal cannula, in a digestibility trial designed as a 4 × 4 Latin square. The animals were fed a diet of 400 g of concentrate and 600 g of silage at a level of 70 g DM kg^?1 live weight (LW^0·75). All enzyme-treated silages were well-preserved with a more extensive fermentation than in FA silage. The quality of untreated silage was poorer as indicated by higher pH and ammonia-N content. The amount of effluent from enzyme-treated silages ranged from 116 to 127 g kg^?1; for FA and untreated silages values were 101 g kg^?1 and 80 g kg^?1, respectively. Total DM losses from enzyme-treated silages were higher than from FA silage (P < 0·05). No significant differences were noticed between silages in the apparent digestibility of organic matter (OM), neutral-detergent fibre (NDF), acid-detergent fibre (ADF) or nitrogen (N). The apparent digestibility of cellulose was higher with enzyme-treated silages than with FA silage (P < 0·05). The values for microbial N flow at the duodenum were 80·0, 91·9, 80·7 and 70·5g N d^?1, and for the efficiency of rumen microbial N synthesis 38·6, 47·6, 36·9 and 32·5 g N kg^?1 OM apparently digested in the rumen for untreated, FA, CH and CHL silages, respectively. In the rumen the molar proportion of propionate was higher (P < 0·01) and that of butyrate lower (P < 0·01) with enzyme-treated silages when compared with FA silage. The proportion of butyrate was also lower with untreated than with other silages (P < 0·01). The rumen residence time of NDF and ADF was longer (P < 0·05) with enzyme-treated silages than with FA silage.     

Intake, liveweight gain and feed preference by steers fed combinations of lucerne and Westerwolds ryegrass silages

Nutritive value and voluntary intake of legumes are generally considered to be higher than those of grasses when ensiled at similar digestibility, although high levels of soluble protein can result in low N utilization by animals and high losses to the environment. The objectives of this experiment were to describe the optimum combination of Westerwolds ryegrass ( Lolium multiflorum Lam. cv. Aubade) and lucerne ( Medicago sativa L. cv. AC Caribou) silages to maximize liveweight gain of steers fed silage, determine chemical components that are important and ascertain whether steers selected the optimum mixture when given a choice. Both silages contained similar concentrations of dry matter (DM), acid-detergent fibre (ADF) and organic acids, but lucerne silage had higher concentrations of N, soluble-N and ammonia-N. Westerwolds ryegrass silage contained more neutral-detergent fibre (NDF). In a 12-week experiment, voluntary intake by Hereford steers was not influenced when the proportion of the two silages was changed from 1 to 0 in 0·25 increments. However, liveweight gain and feed efficiency increased linearly ( P  < 0·001) as the proportion of ryegrass silage fed was increased. When preconditioned to either of the two silages, steers showed a significant preference for ryegrass over lucerne ( P  < 0·05). When conditioned to a mixture of both silages, no preference was elicited. It is suggested that extensive solubilization and deamination of protein in the lucerne silage may have caused the preference for Westerwolds ryegrass silage and the higher liveweight gains on diets containing higher proportions of Westerwolds ryegrass silage.     

Effects of formic acid on silage fermentation, digestibility, intake and performance of young cattle

Data from twenty-two comparisons carried out at ADAS Experimental Husbandary Farms are used to compare untreated and formic acid-treated silages. Additive treatment led to an improved fermentation in some crops, particularly those of low DM concentration (<262 g kg^-1). Where this occurred there were associated benefits in silage digestibility (+0·234 units), intake (+16%) and the growth rate of young cattle (+0·28 kg d^-1). Where the fermentation of the untreated silage was good, both digestibility and animal performance associated with treated and untreated silages were similar. It is suggested that the justification for using formic acid in a commercial situation is thus restricted to occasions where the untreated crop would be liable to develop a clostridial fermentation. These may be when crops contain less than 35 g water-soluble carbohydrate kg^-1.     

Effect of stage of maturity and chop length on the chemical composition and utilization of formic acid-treated ryegrass and formic acid silage by sheep

Two areas of an early-heading perennial ryegrass cv. Cropper were harvested by either a precision-chop or a flail harvester at around 50% ear emergence (15 May 1978) and 14d later (29 May). Formic acid (85%) was applied at the rate of 2·2 litres t^-1. Mature crossbred wethers were used in a 2 × 2 factorial design to determine the effect of stage of maturity and method of harvesting (chop length) on the in vivo digestibilities of formic acid-treated grass in experiment 1 and formic acid silage in experiment 2. Apparent digestibility coefficients were determined at a fixed level of feeding for both grass and silage and at ad libitum access to feed for silage only. There were no significant differences in the concentrations of crude protein (CP), ether extract (EE), acid-detergent fibre (ADF) or acid-detergent lignin (ADL) in grass or silages of differing chop lengths but the later cut forages had significantly higher ADF and ADL concentrations and lower CP concentrations than the early-cut forages. The ADF and ADL concentrations were also higher in the silages than in the corresponding grasses. In general, the fermentation characteristics of precision-chopped silage were better than for the corresponding flail-cut silage but date of harvest was a more important determinant of quality and the late, flail-cut silage had the highest butyrate and ammonia N concentrations and the highest pH (411) of any treatment. There was a significantly higher intake of precision-chopped as compared with flail-cut silage with both the early-and the late-cut silage but there were no significant differences attributable to stage of maturity (i.e. date of harvest) or significant interaction between chop length and maturity. The slightly increased intake of early harvested, precision-chopped silage as compared with late precision-chopped silage was not significant. Dry matter digestibility (DMD) of the grass decreased at a rate of 0004 units d^-1 post 50% ear emergence. The results of experiment 2 indicated a decrease of 0·207 units d^-1 in silage fed at a similar level. The late-cut silage (DMD 0·292, mean of both harvesting treatments) thus had a significantly lower digestibility than the corresponding grass (mean DMD 0·247). Chop length had a variable influence on the DMD of both grass and silage fed at a fixed level but treatment differences were non-significant. However, a trend towards higher digestibility of flail-cut as compared with precision-chopped silage was apparent and this became statistically significant when the animals were allowed ad libitum access to feed. This may be a response to the generally lower intake of flail-cut silage.     

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 effect upon fermentation and nutritive value of silages produced after treatment by three different inoculants of lactic acid bacteria applied alone or in combination

Silages were made from the first cut of a predominantly perennial ryegrass sward. The silages were either untreated (W) or treated with formic acid (31 t⁻¹, F) or with 10⁶ lactic acid bacteria (LAB) g⁻¹ grass of each of three strains alone (A. Lactobacillus plantarum MTD1; B, Pediococcus species 6A2; C, L. plantarum 6A6) or in combination (AB. AC) to give seven treatments. The silage fermentation in 10-kg silos was followed chemically and microbiologically and the nutritive value of selected treatments evaluated using 2-t silos.
The control silage (W) fermented well. Addition of formic acid restricted fermentation and produced a silage with a high ethanol concentration. After day 4, all inoculated silages had lower pH values and higher lactic acid concentrations and a higher ratio of lactic acid to acetic acid than the control silage. Chemically there was little difference between the inoculated silages in terms of final composition. Microbiologically the LAB applied in treatments B and C dominated the LAB populations in those silages when applied alone; however, they were suppressed when applied in combination with inoculant A.
When fed to sheep, the intake of the formic acid-treated silage was significantly ( P < 0·01) lower than that of the other silages and the intake of silage treated with inoculant A significantly ( P < 0·001) higher than that of silages treated with inoculants B and C. The apparent organic matter ( P < 0·001) and nitrogen ( P < 0·01) digestibilities of the formic acid-treated silage were also significantly lower than those of the other silages.     

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).     

An evaluation through lactating cattle of a bacterial inoculant as an additive for grass silage

Three silages were prepared from herbage treated with either an inoculant (Ecosyl, Imperial Chemical Industries plc) at 3.21 t^?1, formic acid (850 g kg^?1, Add F BP Chemicals International Ltd) at 2·3 1 t^?1, or no additive (control). The herbage used was the first regrowth from perennial ryegrass swards. It was ensiled unwilted, and had mean dry matter and water soluble carbohydrate concentrations at ensiling of 154 and 24·1 g kg^?1 respectively. Time course studies showed only minor effects of additive treatment on fermentation patterns within the silo and all three silages had good fermentations. Over an 88 d feeding period, commencing on day 7 of lactation, forty-eight British Friesian cows were used to evaluate the silages in a three-treatment, randomized-block design experiment. The animals were stalled individually, offered the silages ad libitum, and in addition received 5 kg d^?1 of a supplement containing 196 g kg^?1 crude protein. On the basis of the data recorded during the final 28 d on treatment the animals receiving the inoculant-treated silage consumed 12 and 10% more silage dry matter and produced 2·1 and 2·3 kg d^?1 more milk than those given the control and formic acid-treated silages respectively. Over the total experimental period the milk yields were 1957, 1894 and 2094 (±41·3) kg for animals receiving the control, formic acid- and inoculant-treated silages respectively. Animals offered the formic acid treated silage produced milk of significantly higher fat concentration than those given the other two silages. Total ration digestibility studies, conducted with three cows per treatment, indicated no significant differences in digestibility coefficients, nitrogen utilization or metabolizable energy concentrations of the three treatment diets. It is concluded that the higher milk yield recorded with the inoculant-treated silage, and the higher milk fat concentration with the formic acid-treated silage, over that obtained with the control silage, were due to the increases in ME intake of 5 and 16 MJ d^?1 for the formic acid and inoculant-treated silages respectively.     

Protein supplementation of formic acid- and enzyme-treated silages. 2. Nitrogen and amino acid digestion

Two silages were made from primary growth perennial ryegrass and ensiled after the application of either formic acid or an enzyme mixture of cellulase and hemicellulase. Silage analysis showed both silages to be well preserved with low pH of 3·70 and 3·62 for the formic and enzyme treatments respectively. Formic acid-treated silage had a higher total amino acid concentration than enzyme-treated silage. The silages were offered to growing steers either as the sole diet or supplemented with rapeseed meal at 60 g or 120 g fresh weight kg⁻¹ silage DM offered, in a 6 × 6 Latin square arrangement.
Non-ammonia nitrogen and microbial nitrogen flows at the duodenum (g d⁻¹) were significantly ( P < 0·05) increased by supplementation of enzyme-treated silage compared with formic acid-treated silage (enzyme, 83·6, 58·7; enzyme + 60 g, 101·7, 75·3; enzyme + 120 g, 112·5, 80·7; formic, 91·9, 63·7; formic + 60g, 88·3, 67·9; formic + 120 g, 95·5, 67·1) respectively. Efficiencies of microbial protein synthesis were increased for supplemented enzyme-treated silage diets and values were reduced for supplemented formic acid-treated silage diets compared with the silage only diets (enzyme, 27·9; enzyme + 60 37·7; enzyme + 120 g, 38·6; formic, 33·7; formic + 60g, 31·2; formic + 120 g, 28·8). Total amino acid flow at the duodenum increased with supplementation of both silages; however, microbial amino acid flow increased significantly ( P < 0·05) with supplementation of enzyme-treated silage compared with formic acid-treated silage diets. Significantly greater amounts of cystine, methionine, alanine, valine and aspartic acid entered the small intestines of animals receiving supplemented enzyme silages compared with supplemented formic acid silages.     

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.     

Microscopic and chemical changes during the first 22 days in Italian ryegrass and cocksfoot silages made in laboratory silos

Although many aspects of grass silage have received intensive study, the changes that take place within the grass blades during ensilage have received little attention.
In two factorial experiments Italian ryegrass (cv. Lemtal) and cocksfoot (indigenous) were ensiled in laboratory silos (capacity 0·2 kg) with the grass under pressure (700 Pa) and subjected to two treatments (with or without 3·31 t^-1 85% formic acid) and two silos from each treatment opened on eight sampling dates(1,2,3,4,7,10,14 and 21 d).
For each sampling date transverse sections of grass laminae were examined and changes in the cross sections of the protoplasts and of cells, as defined by the cell walls, were recorded. These data were used to calculate the ratios of protoplast to cell volumes at each sampling date.
Each silage was analysed for dry matter, pH, lactic acid, VFA, ammonia and glucose. The distance settled by the silage (a measure of decrease in silage volume) and the silage conductivity were also recorded.
Both of the untreated grasses yielded silages with typical lactic acid levels and pH values. In all of the silages there was a marked shrinkage of the plast within the space defined by the cell wall. The ratio of protoplast to cell volume eventually stabilized at 0·4. The formic acid-treated grasses reached this level by day 1 but a longer period was required by untreated grasses.
It is suggested that the decrease in silage volume is related to the lactic acid content of the liquid phase due to their close relationship in silages produced from untreated grasses ( r = 0·97***).     

An evaluation of an inoculant/enzyme preparation as an additive for grass silage for dairy cattle

Herbage from the first regrowth of perennial ryegrass-based swards was directly ensiled after treatment with a bacterial inoculant/enzyme preparation (SIL-ALL, Alltech UK) at 3·0 1 t^?1, formic acid (850 g kg^?1) at 2·59 1 t^?1 or no additive (Control). The mean dry matter (DM) and water-soluble carbohydrate concentrations of the grass were 185 and 24·0 g kg^?1 (fresh basis) respectively. Lactic acid concentrations after ensiling increased at a lower rate in formic acid-treated herbage than with the other treatments. All silages were well preserved and formic acid-treated silage had a lower ultimate concentration of lactic acid and higher concentration of water-soluble carbohydrate. Effluent output was increased on a proportional basis by ?0·06 with formic treatment, whereas the inoculant reduced effluent output by 0·05 in comparison with the mean effluent production of the control silage. The in vivo digestibilities of the silages were determined using sheep. The digestibilities of DM, organic matter and energy were significantly higher with inoculant-treated silage than with formic acid treatment, whereas values for the control silage were intermediate. The three silages were offered ad libitum to forty dairy cows with individual recording of daily intakes for a 10-week period in a randomized block experiment with four treatments. Sixteen animals were offered the control silage with half of these offered 3 kg concentrates per day (C3) and the other half offered 7 kg concentrates per day (C7). Twelve animals were allocated to each of the additive-treated silages, with concentrates offered at 5 kg d^?1. Treatment effects on animal performance were measured in weeks 7–10. To compare animal performance for the treated silages with the control, an estimate of performance at 5 kg concentrates per day was obtained by regression using values obtained at 3 and 7 kg concentrates. In comparison with estimated silage intake for the control silage with 5 kg d^?1 concentrates, inoculant and formic acid treatment of the silages increased dry matter intake by 0·04 (P > 0·05) and 0·13 (P > 0·01) respectively. In comparison with estimated milk production and yield of fat plus protein for the control treatment with 5 kg d^?1 concentrates, neither inoculant treatment nor formic acid treatment produced any significant differences.     

Cell wall degrading enzymes for silage. 2. Aerobic stability of enzyme-treated laboratory silages

The effects of two commercial cellulase/hemicellulase enzymes derived from Trichoderma reesei on silage fermentation and aerobic stability were investigated in three laboratory-scale experiments. In Experiment 1, perennial ryegrass ( Lolium perenne ) was treated with enzyme A at the rates of 0. 0·125, 0·250, 0·500 and 0·750 cm³ kg^-1. In Experiment 2, Italian ryegrass ( Lolium multiflorum ) was treated with the same enzyme at the rates of 0, 0·250 and 0·500 cm³ kg^-1 and with 85% formic acid (3·5 cm³ kg^-1). In Experiment 3, perennial ryegrass was ensiled untreated, with enzyme A (0·250 and 0·500 cm³ kg^-1) and with 0·200 and 0·400 cm³ kg^-1 enzyme B which also contained glucose oxidase. All silages were well preserved. Aerobic deterioration was related to numbers of lactate assimilating yeasts. In Experiment 1, all silages were stable over a 4-day period. In Experiment 2, enzyme A treatment delayed the temperature rise compared with the untreated control ( P <0·05), whereas the formic acid-treated silage was stable. In Experiment 3, the temperature rise in the silage treated with the higher level of enzyme B occurred one day later than in the other silages ( P <0·05).     

Effects of inoculant treatment on silage fermentation, digestibility and intake by growing cattle

A changeover design experiment involving thirty-six 3-month-old Friesian male calves (mean initial live weight 127 kg) was carried out to evaluate a bacterial inoculant based on a single strain of Lactobacillus plantarum (Ecosyl, ICI) as a silage additive. On 25–31 August 1988, nine silages were harvested using double-chop forage harvesters from the second regrowth of three swards, namely permanent pasture which had received 100 kg N ha^?1 and perennial ryegrass which had received either 100 or 150 kg N ha^?1. Herbages (mean DM and WSC concentrations 144 and 11·2 g kg^?1 respectively) from each sward were treated with either no additive, formic acid (2·4 1 t^?1) or the inoculant (3·3·1 t^?1) and were ensiled in 126 silos of 0·8 t capacity. The only effects of the inoculant on chemical composition of the silages were a decrease in modified acid detergent fibre and an increase in endotoxin and crude and true protein concentrations. Silages were offered ad libitum and supplemented with 1·0 kg of concentrates per head daily for three periods each of 3 weeks in a partially balanced changeover design experiment. Digestibilities of the total diets were determined at the end of the experiment. For the untreated, formic acid-treated and inoculant-treated silages, silage dry matter intakes were respectively 3·58, 3·66 and 3·67 (s.e. 0·044) kg d^?1, estimated metabolizable energy (ME) intakes were 46·1, 46·7 and 47·1 (s.e. 0·44) MJ d^?1, energy digestibilities were 0·727, 0·727 and 0·738 (s.e. 0·0046) and organic matter digestibilities were 0·770, 0·771 and 0·788 (s.e. 0·0042). Rumen degradabilities of the silages were determined using two rumen-fistulated cows. Mean dry matter and nitrogen degradabilities for the control, formic acid-treated and inoculant-treated silages, assuming an outflow rate of 0·05 h^?1, were 10·508, 0·49, 0·491 and 0·702, 0·676 and 0·729. It is concluded that the inoculant significantly increased the digestibility of the silages but did not affect dry matter or ME intake.     

The effect of wilting and silage additives on the fermentation of autumn made grass silage ensiled in bunkers on commercial farms in South Wales 1983-85

Silage making practices in respect of 130 samples of autumn made grass silages ensiled in bunkers on commercial farms in South Wales during 1983-1985 were analysed to discern the effect of wilting and/or silage additives on fermentation. Silages were primarily made during late September and early October in fine weather from perennial ryegrass pasture which had not been grazed for 6 weeks. On average 13.9 ha of pasture was cut for silage. Analysis of 120 samples of grass showed it contained 176 g kg^?1 dry matter (DM) with (g kg^?1 DM) 215 protein, 240 modified acid detergent fibre (MADF), 78 water-soluble carbohydrate (WSC) and 95 ash. Most farmers attempted to pre-wilt grass for 1 day prior to ensilage and one quarter of them made unwilted silage. Silage making was usually completed within 6 days of starting to cut and was generally made with a precision-chop machine. Silage additives applied were (kg t^?1) formic acid (4·7), formic acid 4-formalin (5·5), sulphuric acid-+ formalin (5·0) sugars (14) and inoculants (0·65). Formic acid significantly reduced pH, and formic acid with or without formalin significantly reduced ammonia nitrogen (N) content of silages compared with other treatments. Protein contents of acid/formalin treated silages were significantly higher and MADF of acid with or without formalin treated silages were significantly lower than other treatments. Pre-wilting grass prior to ensilage did not significantly increase subsequent silage DM content and significantly increased the pH of non-additive treated silages. Unwilted silages treated with formic acid with or without formalin had a significantly lower ammonia-N content and higher residual WSC than other treatments. It is suggested that only formic acid application either alone or in conjunction with formalin to unwilted silage was successful in producing well preserved silages and that a grass WSC content of 17 g kg^?1 would be necessary to achieve this.     

Effects of additives on the fermentation and aerobic stability of grass silages and total mixed rations

Mown herbage of timothy–meadow fescue (dry matter 218 (LDM) or 539 (HDM) g kg^?1) was ensiled in laboratory silos to evaluate silage additives. For LDM silage, additives including formic acid (a blend of formic acid, sodium formate, propionic acid, benzoic acid, glycerol and another blend of formic acid and ammonium formate, both applied at 5 L t^?1) were able to restrict fermentation and thereby improve intake potential of the silage. Aerobic stability (AS) of total mixed ration (TMR) was also improved. LDM grass treated with homofermentative lactic acid bacteria (_hoLAB) resulted in silage containing lactic acid at 132 g kg^?1 DM, ammonium‐N <40 g kg^?1 total N, and pH < 3·8, and the AS was poor (<36 h). The treatment including heterofermentative strain (Lactobacillus brevis) produced more acetic acid and better AS than _hoLAB. Salt treatment (sodium benzoate, potassium sorbate, sodium nitrite) reduced pH compared to the Control treatment (3·89 vs. 4·24) and improved AS of TMR. The LDM Control silage had good AS, but the TMR based on it had poor AS. All additives were able to lower pH on HDM silages also, but other benefits of using additives were minimal. The treatment including L. brevis on HDM was able to improve AS of TMR.