The effect of dry matter content and silage additives on the fermentation of grass silage on commercial farms

A total of 1713 samples of silage from commercial farm silos were analysed to investigate the effect of dry matter (DM) content and chemical additives on fermentation as measured by ammonia-N concentration and pH, Increasing DM content without additive use had a major beneficial influence upon fermentation. When silage DM contents were greater than 260 g kg^-1 83% of silages were well fermented, with average ammonia-N concentrations of 94 g (kg total N)^-1 and pH 4.36. With diminishing DM concentration the proportion of well fermented silages declined. In the DM range 220-260 g kg^-1 67% of silages were well fermented with ammonia-N concentrations of 125 g (kg total N)^-1 and pH 4.30, in the DM range 180-220 g kg^-1 48% were well fermented with ammonia-N at 151 g (kg total N)^-1 and pH 4.38 and with DM below 180 g kg^-1 no silages were well fermented with ammonia-N concentration of 252 g (kg total N)^-1 and pH 4.84. The benefit of chemical additives, albeit at poorly defined and often inadequate rates, was small in comparison to that of increased DM concentration. Below DM concentrations of 180 and 220 g kg^-1, the only benefit was that formic acid decreased ammonia-N to 151 g (kg total N)^-1 and pH to 4.32 compared with 163 g (kg total N)^-1 and pH 4.43 for untreated silages. Within the DM range 220-260 g kg^-1 formic acid decreased ammonia-N level to 104 g (kg total N)^-1 and pH to 4.07, and there was a slight benefit from using sulphuric acid/formalin which decreased ammonia-N to 117 g (kg total N)^-1 and pH to 4.23 compared with 125 g (kg total N)^-1 and pH 4.27 for untreated silages. Above 260 g DM kg^-1 both formic acid and sulphuric acid/formalin provided a small but consistent decrease in ammonia-N and pH compared with untreated silages. Chemical additive use conferred no other benefit when compared with untreated silage. Calcium formate/sodium nitrite mixtures and acid mixture use provided no benefit in fermentation compared with untreated herbage.     

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.     

Susceptibility to losses during mechanical silage and haymaking operations in relation to grass dry matter content

A series of laboratory experiments is described to investigate the susceptibility of grass forage to losses during mechanical field conservation operations in relation to dry matter content. Losses were measured during a simulated manual 'tedding' treatment carried out on grass samples being dried on a laboratory thin-layer drying rig. Values of loss per successive treatment remained at a near constant low level at low dry matter (DM) contents, except for a somewhat higher loss level from the first treatment. As DM content rose above about 60%, the level of loss per treatment rose rapidly with increase in DM content. A relationship between loss per treatment and DM content was derived from the data by a bilinear regression analysis, and this will be incorporated into an Operational Research model of forage conservation systems.     

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 influence of the carbohydrate fraction and additives on silage quality

Respiration losses, effect of sugar content, formic acid addition and inoculation were evaluated in relation to initial fermentation and silage quality in three experiments. Changes in the content of fermentable substrate during post–harvest respiration and initial fermentation were studied in the laboratory. Soluble carbohydrates were estimated as glucose, fructose, sucrose, fructans and starch by an enzymatic method.
About 70% of the sugars remained after 30 h of conventional wilting, as opposed to less than 50% in a chopped sample kept in the dark. During the first days of fermentation the metabolic activity was very intensive. Sugars, which accounted for 10% of the dry matter, were fermented within 4 d. There were indications, mainly in clover silages, that substances other than water-soluble carbohydrates were used as energy sources.
Low-sugar crops were obtained by shading the fields. After 3 d the sugar in the grass had decreased to half of the original content. This effect was less pronounced in clover. The amount of available substrate and dry matter (DM) content had a major influence on silage quality. In an unwilted crop at least 25 g of water-soluble carbohydrate was needed per kg of fresh material to obtain an acceptable silage quality in the controls, while 20 g was sufficient in inoculated silage. Formic acid addition makes the fermentation less sensitive to water–soluble carbohydrate content. Inoculation of willed silage increased lactic acid production and decreased the pH. There was also less variation in silage quality.     

Grass silage as a basic feed for store lambs. 2. Effect of harvesting system and chop length of grass silage on silage intake and performance of store lambs

A perennial ryegrass sward was cut at a leafy stage of growth and harvested with different harvesters to produce silages differing in chop length to evaluate the effect of silage chop length on silage intake and on the performance of store Iambs when silage was fed as the sole diet. The silage was harvested in late May either as long silage (L), single-chopped (S). double-chopped (D). long precision-chopped (LP) or medium precision-chopped (MP) silage with (he appropriate machinery. The silages were treated with formic acid at 2.5 1 t^?1. were well preserved (pH 3.7–3.8) and were of high dry-matter digestibility [749–810 g DMD kg^?1 dry-matter (DM)]. The silages were fed ad libitum as the sole diet to Suffolk crossbred store lambs over a period of 11 weeks. Silage intake and lamb performance progressively increased as silage chop length declined from 32.4 cm (L) to 6.8 cm (MP). Silage intakes were 572, 661, 750, 893 and 1129 (± 21) g DM d^?1 for silages L, S, D, LP and MP respectively. The corresponding daily liveweight gains were -3, 40, 53, 85 and 151 (± 7.6) g d^?l. Similar increases in empty body weight gain and carcass weight gain were obtained as silage chop length declined. Rumen retention time (RRT), estimated from the rumen contents of the lambs at slaughter and their silage intake in the week before slaughter, was much shorter for silages LP and MP compared with silages L or S. Silage intake was negatively related to RRT(b= -24.5 ± 6.1 gDM h^?l RRT). The results of this study showed that high intakes of grass silage and liveweight gains were achieved when grass was cut at a leafy stage of growth and harvested with a precision-chop harvester set to produce a moderate chop length (7 cm). The feeding of long or flail-chopped silages resulted in lower intakes and lower liveweight gains.     

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.     

The effect of oxygen concentration on changes in the microbial population, temperature and dry-matter content in grass silage

The effects of transfusing cores of grass silage with mixtures of oxygen and nitrogen containing 0%, 0·2%, 2%, 5% and 20% oxygen were investigated. Changes in populations of yeasts, lactobacilli and streptococci were measured and the relationship between populations after 7 days' transfusion and oxygen concentration were tested against the predictions of two models, based on Monod and logistic growth functions. Yeasts were related to oxygen by the Monod model, while lactobacilli and streptococci were related by the logistic model. The differences were ascribed to yeasts initiating deterioration by growing aerobically, while lactobacilli and streptococci grew fermentatively once the environment had changed following yeast growth. Dry-matter losses were related to oxygen by the Monod model. Changes in temperature were related to dry matter loss (through measurements of CO₂ evolution) using a simple heat balance model.     

The effect of fertilizer sulphur on grass production for silage

The effects of rate and pattern of fertilizer S application on herbage production from Perennial ryegrass-dominant swards at six potentially S-deficient sites in south-west Scotland were measured under a silage cutting regime (3 cuts year-1) with high fertilizer N application (300 kg ha⁻¹ year-1). Fertilizer S (as gypsum) was applied at annual rates from 0 to 48 kg ha⁻¹ as single spring applications before the first cut or split before each of the three cuts. The residual effect of S in the year following its application was assessed at one site.
Applied S increased total DM production at four of the six sites. These increases were restricted to the second and/or third cuts and were generally in the range 10-30% greater than where no S was applied. Timing of S application was not important in influencing annual DM yield. The residual effect of gypsum in the year following application was small.
The supply of available soil S is limiting herbage production in certain areas and soil types of south-west Scotland. Areas of S deficiency are likely to increase in the future and need to be identified more precisely than they are at present.     

The effect of frequency of harvesting grass for silage on the intake and performance of beef cattle

Two randomized-block experiments were conducted to examine the effects of frequency of harvesting grass for silage on the intake and performance of beef cattle. In both experiments swards of S24 perennial ryegrass were harvested at 63-, 49- and 38-d intervals throughout the growing season. Grass harvested before and after 10 July was ensiled separately and termed spring and autumn silage respectively. In Experiment 1 the silages were offered ad libitum either unsupplemented or supplemented with 2 kg barley per head daily to eighty-four Hereford-cross weaned, single-suckled steer calves of mean initial live weight 284 kg, in a 3 × 2 × 2 factorial design. Silage dry matter (DM) intakes and liveweight gains for the silages harvested at 63-, 49- and 38-d intervals were 4.80, 0.72; 4.49,0.76; and 4.62,0.78 kg d⁻¹ for the spring silages and 4.69, 0.67; 4.59, 0.85; and 4.55,0.86 kg d⁻¹ for the autumn silages respectively. There was no significant interaction between frequency of harvesting and concentrate supplementation. In Experiment 2 the silages were offered ad libitum and unsupplemented to forty-two Hereford-cross weaned, single-suckled steer calves of mean initial live weight 240 kg, and forty-two Hereford-cross store cattle of mean initial live weight 356 kg, in a 3 × 2 × 2 factorial design. Silage DM intakes and liveweight gains for the silages harvested at 63-, 49- and 38-d intervals were 4.94,0.49; 5.69,0.80; and 619,0.93 kg d⁻¹ for the spring silages and 5.50, 0.61; 5.57, 0.72; and 505, 0.65 kg d⁻¹ for the autumn silages respectively. There were no significant interactions between frequency of harvesting and type of animal. It is concluded that a cutting interval of 49 d commencing on 21 May is likely to be optimum for this type of sward except under exceptional weather conditions.     

Effects of polyethylene colour and thickness on grass silage quality

The aim of the investigation was to determine the influence of variations in thickness and colour of agricultural plastic film on silage preservation conditions and grass silage quality. For this purpose, 30 cylindrical plastic containers (mini‐silos; 0·3 m³) were filled with chopped grass and covered with five films of different thickness and colour: 90 μm, white; 125 μm, green; 150 μm, black; 200 μm, green and 200 μm, white. Four replications of each film type were placed in the open air. Two replications were housed indoors and exposed to an ‘artificial sky’ in a test apparatus. The surface temperature of the films was found to be strongly dependent on film thickness and colour. Results of the chemical analysis of silages did not reveal any significant influence of the films. This was also the case when restricting the analysis to the uppermost silage layer. The results showed that under the conditions of this experiment, well preserved forage can be produced with films of differing colour, as well as of lesser thickness.     

The effect of sugar beet pulp-based silage additives on effluent production, fermentation, in-silo losses, silage intake and animal performance

First-harvest direct-cut, double-chopped grass (190 and 164g DMkg^?1 in Experiments 1 and 2 resptectively) was ensiled without an additive or, in Experiment 1, with 30 kg t^?1 grass of an absorbent additive based on sugar beet pulp (Sweet ‘n’ Dry) or with 3·441 t^?1 grass of formic acid and, in Experiment 2, with 30, 50 and 70 kg t^?1 grass of Sweet ‘n’ Dry or with 50kg t^?1 grass of unmolassed sugar beet pulp. The preservation and nutritive value of the silage, in-silo losses (including silage effluent production), silage intake and animal performance of adult and growing cattle were examined. In Experiment 1 all three silages were well preserved, although the formic acid-treated silage displayed significantly lower pH, ammonia nitrogen (NH₃N) [g kg^?1 total nitrogen (TN)] and volatile fatty acids (VFAs) than the other two silages. In Experiment 2 absorbent-treated silages displayed significantly lower pH, buffer capacity (Bc), NH₃N (gkg^?1 TN), CP, modified acid detergent fibre (MADF) and VFAs than untreated silage. Treatment of grass with the absorbent additives at ensiling resulted in reduced effluent production. In Experiment 1 each kilogram of Sweet ‘n’ Dry retained approximately 11 effluent, and in Experiment 2 silages made with Sweet ‘n’ Dry applied at 70kgt^?1 and sugar beet pulp applied at 50 kg t^?1 produced similar volumes of effluent and each kilogram of absorbent retained 1·0 and 1·31 of effluent respectively. In Experiment 1 sixty beef cattle [mean initial live weight (LW) 460 kg] were grouped according to LW and allocated to treatment at random. For untreated silage (unsupplemented or with 1 or 2 kg supplement head^?1 day^?1), absorbent-treated silage (unsupplemented or with 1 or 2 kg supplement head^?1 day^?1) and formic acid-treated silage (1 kg supplement head^?1 day^?1) the daily silage DM intakes were 6·12, 6·21, 6·40, 7·65, 7·45, 7·11 and 7·85 (s.e. 0·280) kg respectively, the daily liveweight gains were 0·22, 0·56, 0·81, 0·59, 0·74, 0·81 and 0·75 (s.e. 0·071) kg respectively and daily carcass gains were 0·31, 0·47, 0·67, 0·47, 0·61, 0·70 and 0·57 (s.e. 0·043) kg respectively throughout a 75-day feeding period. In Experiment 2, fifty-six growing cattle (mean initial weight 312 kg) were grouped according to LW and allocated to treatment at random. For untreated silage (unsupplemented or with 1·5 kg Sweet ‘n’ Dry or 1·5 kg commercial concentrates head^?1 day^?1), silage treated with Sweet ‘n’ Dry at 30, 50 and 70 kg t^?1 grass and silage treated with 50kg sugar beet pulp t^?1 grass the daily silage DM intakes were 5·46, 5·28, 5·33, 6·21, 6·27, 6·60 and 6·62 (s.e. 0·154) kg respectively and daily liveweight gains were 0·39, 0·75, 0·81, 0·63, 0·76, 0·94 and 1·75 (s.e. 0·052) kg respectively throughout a 122-day feeding period. In this experiment 360g kg^?1 more absorbent was required when it was included at ensiling rather than offered as a supplement to untreated silage to achieve the same individual animal performance.     

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.     

The effect of glucose oxidase on the preservation of grass silage

Five experiments were carried out to investigate the effects of glucose oxidase (GO) on the preservation of grass silage in the absence of micro-organisms. In the first experiment, GO was tested in a 3% glucose solution. At the level of 1190 U GO l^-1 the pH value decreased to 3·94 in 1 h and to 3·02 in 24 h. At the level of 11·9 U l^-1 the pH decreased to 3·45 in 24 h.
The second experiment was performed by packing chopped grass into glass jars, sterilizing in an autoclave and adding GO. One day later the pH value had decreased to 4·65; 1·60% gluconic acid was found in the dry matter.
In the other three experiments grass was sealed in polythene bags and sterilized by gamma-irradiation. GO was found to cause a faster decrease in pH. Removing air from the silage by compaction decreased the GO activity. The addition of cellulase delayed the GO functioning for one day. Lactobacillus inoculant had no effect. Evidence was obtained that GO may affect the profile or activity of the original microflora of grass silage.     

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.     

Effect of forage matting on rate of grass drying, rate of silage fermentation, silage intake and digestibility of silage by sheep

The effects of forage matting on rate of grass drying and silage fermentation, digestibility, and intake were examined using perennial ryegrass swards. Treatments compared were: forage mats, where grass was processed through a laboratory scale macerator prior to matting and wilting to 228 g dry matter (DM) kg^?1 (FM treatment); unconditioned grass which was direct ensiled at 163 g DM kg^?1 (DE treatment); unconditioned grass which was wilted for the same period as FM to 213 g DM kg^?1 (UC treatment); unconditioned grass which was wilted to 234 g DM kg^?1 (UC₂₅, treatment). All forages were dried on black plastic sheeting. For each treatment a total of approximately 80 kg grass DM was ensiled in seven 290 I plastic bins for 136 d prior to feeding to wether sheep. A further total of 14 kg grass DM from each treatment was ensiled in twenty-one plastic pipes (152 mm diameter, 762 mm long) to give a total of 84 pipes. Rate of silage fermentation was determined by destructively sampling pipes following 1, 2, 4, 6, 13, 20 and 50 d of ensilage. Over the mean wilting period of 6·9 h, grass from the FM treatment dried significantly faster (P < 0·001) and required less solar energy per unit of moisture loss than unconditioned grass. The rate of grass drying was highly correlated with solar radiation. The FM treatment did not influence the rate or extent of silage fermentation. The intakes and digestibilities of FM, UC and UC₂₅ were not significantly (P < 0·05) different from each other but were higher than for the DE treatment (P < 0·05 for digestibility and NS for intake). In Northern Ireland it is unlikely that there will be sufficient solar radiation to allow forage mats to be made, wilted to a level to prevent effluent production and harvested within one working day. Further work is required to optimize mat-making technology for more rapid drying and to determine the effect of adverse weather on nutrient losses from mats.     

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.     

The effect of partial replacement of grass silage with fresh grass on rumen fermentation characteristics and rumen outflow rates in cattle

An experiment was designed to examine the effects of partially replacing extensively fermented grass silage with varying proportions of fresh grass (0, 0–33, 0–67 and 100) on rumen fermentation, degradation of dry matter (DM) and rate of outflow of liquid and particulate phases from the rumen with four mature Limousin steers. The fresh grass had a higher pH and water-soluble carbohydrate and lower ammonia-N and lactic acid concentrations than the silage. Partial replacement of silage with fresh grass resulted in a reduction in rumen ammonia concentration, and in the proportion of rumen propionate, i-butyrate and n -valerate and an increase in the proportion of rumen acetate and in both die particulate and liquid outflow rates from the rumen. These changes in rumen fermentation parameters could account for increases in animal performance in situations in which grass silage is partially replaced with fresh grass.     

Specific gravity and dry matter content of potato

Summary Data obtained from 516 pairs of specific gravity and dry matter determinations were used to derive a relationship for estimation of dry matter content of potatoes grown in India.     

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).