Effect of commercial inoculant and formic acid± formalin silage additives on silage fermentation and intake and on liveweight change of young cattle

Data from six experiments conducted at two Agricultural Development and Advisory Service Experimental Husbandry Farms during 1980–83 were used to compare low dry matter (DM, 160 g kg^-1), low water soluble carbohydrate (WSC, 15 g kg^-1), non-additive treated silage with silage treated with commercial inoculants or formic acid with or without added formalin (formic acid ± formalin). Formic acid ± formalin significantly decreased silage pH and ammonia-N and significantly increased silage residual WSC compared with inoculant or untreated silage. Formic acid ± formalin significantly increased oven DM and significantly reduced DM loss during ensiling compared with untreated silage. Formic acid ± formalin treatment significantly increased both silage DM and total DM intake compared with untreated silage. Daily liveweight gains of cattle offered formic acid ± formalin were significantly higher than those given inoculant or untreated silage.
It is suggested from the results that formic acid ± formalin additives can be used successfully to prevent a clostridial fermentation developing when crops contain 15 g WSC kg^-1.     

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.     

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.     

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.     

Effects of inoculant treatment on ryegrass silage fermentation, digestibility, rumen fementation, intake and performance of lactating dairy cattle

A randomized block experiment involving thirty-six lactating dairy cattle was carried out to evaluate a bacterial inoculant (Grazyme Grobac, Agritech), containing bacteria, enzymes and a rumen enhancer, as a silage additive. Herbage from the primary regrowth of predominantly perennial ryegrass swards was ensiled unwilted and precision-chopped after a 51-d growth interval on 4 and 5 August. Alternate loads of herbage were ensiled either untreated (C) or treated with formic acid at a rate of 2.65 1 (t herbage)^?1 (F) or the inoculant at a rate of 0.64 kg (t grass)^?1 (I). The treatments were harvested using the same harvester in the rotation of I, F and C treatments. Mean dry-matter (DM), water-soluble carbohydrate and nitrate nitrogen (N) concentrations and buffering capacity of the C herbages at ensiling were 198 g kg^?1, 18 2 g kg^?1, 290 mg (1 juice)^?1 and 379 mequiv. (kg DM)^?1 respectively. For silages C, F and I pH values were 3.7, 3.8 and 3.8 and ammonia N concentrations 61, 43 and 58 g (kg total N)^?1 respectively. Inoculant treatment did not alter aerobic stability of the silages, whereas formic acid treatment increased it. The silages were offered ad libitum and supplemented with 5 kg of concentrates per head daily. For treatments C, F and I silage DM intakes were 10.8, 11.2 and 10.8 (s.e. 0–33) kg d^?1, milk yields 21.3, 20.9 and 20.7 (s.e. 0.52) kg d^?1, fat concentrations 38.3, 40.3 and 37.2 (s.e. 0.83) g kg^?1 and protein concentrations 30.8, 32.6 and 32.6 (s.e. 0.49) g kg^?1 respectively. Inoculant treatment did not alter (P0.05) the digestibility coefficients of the total diets, whereas formic acid treatment decreased DM (P0.05), organic matter (P0.05), neutral detergent fibre (P0.01) and hemicellulose (P0.01) digestibilities. Formic acid treatment altered rumen fermentation patterns, whereas inoculant treatment had no effect. It is concluded that, relative to a well-preserved untreated silage, additive treatment did not alter DM intake, milk yield or fat plus protein yield. However, both additive treatments increased milk protein concentrations and formic acid treatment increased milk fat concentration relative to the well-preserved, untreated silage.     

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.     

The effects of wilting grass before ensiling on silage intake

Herbage, predominantly perennial ryegrass (Lolium perenne) grown in Northern Ireland, was harvested at four dates from June to October 1996 (H1, H2, H3 and H4). At each harvest approximately one-fifth of the grass harvested was artificially dried and pelleted (G). The remainder of the grass was either wilted for 28–52 h (W), depending on the weather conditions, or ensiled directly, i.e. unwilted (UW). Within the W and UW treatments an inoculant or formic acid additive was applied to the herbage before ensiling. After a minimum ensiling period of 10 weeks, sixty steers, mean initial live weight 432 (s.d. 37) kg, were offered the twenty forages in a four-period partially balanced changeover design experiment. Each period was of 2 weeks’ duration. Dry-matter (DM) intakes were recorded daily, with intakes in the second week of each period used in the statistical analysis of the data. The digestibility of each of the forages was also determined in vivo using four castrated male sheep per silage. Wilting increased the DM content of the silage and the pH, the largest increase in DM content occurring at the second harvest. On average, wilting proportionally increased silage DM intake by 0·21 compared with the unwilted silage (P < 0·001), but the intake of the wilted silage was not significantly different from that of the artificially dried and pelleted grass (P > 0·05). The intake of the wilted silage was higher than that of the unwilted silage at each harvest, the proportional increases being 0·22 (P < 0·001), 0·41 (P < 0·001), 0·19 (P < 0·001) and 0·05 (P > 0·05) at harvests H1, H2, H3 and H4 respectively. Treatment of the grass with formic acid before ensiling resulted in a proportional increase in silage intake of 0·08 compared with the inoculant-treated silage (P < 0·05). Compared with the inoculant-treated silage, formic acid increased silage intake by 0·08, 0·02, 0·14 and 0·10 at harvests H1 (P > 0·05), H2 (P > 0·05), H3 (P < 0·01) and H4 (P < 0·05). The results of this study indicate that the effect of wilting on silage intake varies across different harvests and additive treatments. The difference in response to wilting across different harvests is mainly a result of the prevailing weather conditions during wilting.     

Influence of maceration at cutting on lactic acid bacteria populations, silage fermentation and voluntary intake and digestibility of precision-chopped lucerne silage

Laboratory experiments with lucerne (Medicago sativa) have shown that maceration at cutting improves silage fermentation. Samples taken during wilting and after various ensiling periods were analysed for lactic acid bacteria (LAB) numbers and indices of silage fermentation. In Experiment 1, in which maceration was tested in unwilted and wilted lucerne, there was an additive effect of maceration and wilting on LAB numbers at ensiling, thus LAB numbers were approximately 108 colony-forming units (cfu) g^?1 fresh crop for wilted, macerated forage compared with 103 cfu g^?1 fresh crop for unwilted, unmacerated forage at ensiling. Initially, maceration reduced pH (P < 0·001) and increased lactic acid (unwilted comparison only; P < 0·001) and insoluble N (wilted comparison only; P < 0·001) concentrations. After 70 d ensiling, beneficial effects of maceration were associated only with the wilted silage. In Experiment 2, macerated lucerne was compared with unmacerated material, which was either ensiled after a wilting period of similar length or after wilting had proceeded to the same DM concentration as in the macerated forage. During wilting, LAB numbers were significantly higher in macerated than unmacerated forage (P < 0·05). This was also the case during the first 16 h of ensiling (P < 0·01). A decline in pH was observed earlier in macerated silage. Two days after ensiling, lactic acid concentration was higher in macerated silage (P < 0·05), but insoluble N concentration was not different. In a third experiment, unconditioned forage was compared with forages ensiled after regular conditioning or maceration. Although drying rate over 30 h was not influenced by degree of conditioning, LAB numbers during wilting increased with the degree of conditioning. In silages made from these treatments after 6 h wilting, there were no major effects on fermentation characteristics. In a fourth experiment, digestibility and voluntary intake of precision-chopped silage were measured in sheep and found not to be increased by maceration. It was concluded that maceration per se resulted in marginal improvements in fermentation; however, when maceration also increased DM concentration, fermentation was markedly improved. In these precision-chopped silages, maceration had no effect on intake or digestibility.     

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 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.     

Effect of concentrate, dried grass and dried white clover ratios on intake, digestibility and liveweight gain by early-weaned lambs

Early-weaned lambs were offered rations of conventional concentrate, dried grass and dried white clover pellets ad libitum for 52 days. In vivo OM digestibility coefficients of concentrate, grass and clover were 80.0, 53.4 and 66.6% respectively. Dry matter intake of dried grass was similar to that of concentrates but supported significantly lower (P < 0.001) daily gains (0.18 kg). Supplementation of dried grass with an equal proportion of dried clover significantly increased (P <0.05) DM and DOM intake and daily gains. Daily gains by lambs offered the 1:1 grass:clover diet (0.29 kg) were similar to gains by lambs offered either dried clover (0.30 kg) or concentrates (0.30 kg).     

The influence of grass and maize silage quality on apparent diet digestibility, metabolizable energy concentration and intake of finishing beef cattle

The effects of offering a range of grass silages and mixtures of grass and maize silages on the intake of beef cattle were studied. Four grass silages (GS1, GS2, GS3 and GS4) were used. Grass silage 1 was ensiled from a second regrowth in mid‐late September and treated with an inoculant additive. Grass silages 2, 3 and 4 were ensiled, without additive, from a primary regrowth harvested in early July, late May and mid‐June respectively. Wilting periods were 8, 30, 36 and 36 h for GS1, GS2, GS3 and GS4 respectively. Grass silages 1, 2 and 3 were precision chopped and ensiled in bunker silos, while GS4 was ensiled in round bales. The DM content (g kg^?1) and starch concentration (g kg^?1 DM) of the three maize silages (MS1, MS2 and MS3) used were 256 and 128, 256 and 184, and 402 and 328 for MS1, MS2 and MS3 respectively. Seventy‐two Charolais and Limousin cross‐bred steers were used in a changeover design with two 4‐week periods. The study consisted of sixteen treatments incorporating the four grass silages fed alone and with the three maize silages arranged as a 4 × 4 factorial design. The grass silage and maize silage mixtures were offered in a ratio of 0·60:0·40 (DM basis) once daily using individual Calan gates. All silages were offered ad libitum with 3 kg per head per day of a concentrate supplement. Dry matter and metabolizable energy (ME) intakes were highest with diets based on grass silage GS4 compared with diets containing the other grass silages. Metabolizable energy intakes of diets containing no maize silage, and those based on MS1 and MS2, were similar (P > 0·05) but lower than that of diets containing MS3. Only limited increases were found in DM and ME intakes with the inclusion of maize silage in grass silage‐based diets while offering high‐quality grass silage (assessed in terms of DM content, and fibre and N concentrations) promoted high voluntary intakes.     

Effects of applying a bacterial inoculant to silage immediately before feeding on silage intake, digestibility, degradability and rumen volatile fatty acid concentrations in growing beef cattle

In an experiment, involving twelve male cattle (initially 235 kg live weight), the effects of applying lactic acid bacteria [Lactobacillus plantarum; 10⁹ colony-forming units (g fresh silage)^?1] to grass silage, immediately prior to that silage being fed, on dry-matter (DM) intake of the silage, degradability of nitrogen (N) and fibre in the rumen, total tract digestibility and composition of rumen fluid in the animals were examined. A grass silage, which had been made from the primary growth of a predominantly perennial ryegrass sward, was offered as the sole diet. The inoculant was applied to the silage at the rate of 2 g of freeze-dried powder reconstituted in 12 ml of water (kg fresh silage)^?1 immediately prior to that silage being fed and an equivalent amount of water was applied to the silage in the control treatment. The two diets were compared in a change-over design. The silage was well preserved, having a pH and concentrations of ammonia N and butyrate of 3.72, 74 g (kg total N)^?1 and 0.11 g (kg DM)^?1 respectively. Application of the inoculant significantly increased true protein, acid-insoluble N and water-soluble carbohydrate concentrations (P < 0.001) in the diet. Silage DM intake was not significantly increased (P= 0.072) by this of inoculant treatment, which had no significant effect (P > 0.05) on rumen degradability or total tract digestibility of DM, N, neutral detergent fibre or modified acid detergent fibre. Rumen pH, ammonia concentration or the molar proportions of volatile fatty acids were not altered (P>0.05) by inoculant treatment. It is concluded that application of the inoculant to the silage prior to silage being fed did not significantly affect silage DM intake, total tract digestibility, or degradability or fermentation in the rumen of cattle offered grass silage as the sole diet. It is also concluded that the results of this experiment provide no evidence that the mode of action of L plantarum, applied as an additive to grass at ensiling in previous studies, is through ‘direct’ effects in the rumen.     

Effect of acetic acid,caproic acid and tryptamine on voluntary intake of grass silage by growing cattle

The objective of this study was to identify and quantify fermentation end‐products, detected with chromatographic techniques, that were negatively related to intake of grass silage by cattle. Further, the aim was to verify the intake‐depressing effect of these compounds in a feeding trial. A set of twenty‐four silages that had been used in a previous study to model variations in intake owing to fermentation quality was reanalysed with liquid and gas chromatography. Known and unknown chromatogram peaks were subjected to a regression analysis to determine which were negatively related to intake. Compounds were identified and quantified using a liquid chromatography–mass spectrometry system; acetic acid (AcA), caproic acid and tryptamine were chosen for verification. Growing steers were offered wilted silage with these three compounds added, separately or as a mixture, in proportions similar to the maximum values detected in the silages of the previous study. Dietary addition of AcA, either separately or mixed with the other two compounds, reduced silage dry matter (DM) intake. However, the reduction in silage DM intake equalled the amount provided by the added substances, so that no differences in total DM intake were observed for any of the dietary treatments.     

Effect of extent and rate of wilting on nitrogen components of grass silage

Wilting grass prior to ensiling generally increases the dry matter (DM) intake but the effect of wilting on animal performance is still poorly understood. There is a need to improve understanding of the effects of wilting on the nutritional components and chemical composition of grass silage. This study focused on the effects of the extent and rate of wilting on N components of grass silage. Meadow grass was wilted to four DM contents (200, 350, 500, 650 g kg^?1) at two different rates (fast, slow), creating a total of eight silages. Crude protein (CP) fractions were measured using the Cornell Net Carbohydrate and Protein System. Utilizable CP at the duodenum (uCP), a measure of feed protein value, was estimated using the modified Hohenheim gas test. Ruminally insoluble, undegraded feed CP (RUP) was measured using an in situ technique. Amino acid (AA) composition prior to and after rumen incubation was also investigated. Utilizable CP at the duodenum, RUP and true protein fractions B2 and B3 were increased by rapid wilting and high DM content (DM > 500 g kg^?1), although the increase with DM was only mild for uCP, probably due to lower ME content in the DM‐650 silages. Non‐protein‐N decreased with increasing DM and rapid wilting. The higher RUP content from both DM‐650 silages leads to a higher total AA content after rumen incubation. Treatment also influenced the AA composition of the ensiled material, but the AA composition after rumen incubation was similar across treatments. Rapid and extensive wilting (DM > 500 g kg^?1) improved protein value and reduced CP degradability. Increased uCP may result in higher milk protein yield, while reduced degradability may reduce N lost from urinary excretion. The primary effect of wilting on post‐ruminal AA supply from RUP appeared to be quantitative, rather than qualitative.     

Effects of the proportions of high or medium digestibility grass silage and concentrates in the diet of beef cattle on liveweight gain, carcass composition and fatty acid composition of muscle

Abstract An experiment was carried out over 2 years to evaluate the effects of increasing the proportion of cereal‐based concentrates in diets containing high‐digestibility and conventional medium‐digestibility grass silages on the dry‐matter (DM) intake, liveweight gain and carcass composition of beef cattle, and to examine the effects of grazed grass and the ratio of grass silage:concentrates in the diet on the fatty acid composition of selected muscle tissues. Late‐maturing steers (n = 231) were offered diets based on high‐digestibility (HD) (0·743 digestible organic matter (DOM) in DM) or medium‐digestibility (MD) (0·643 DOM in DM) grass silages supplemented with barley/soyabean meal‐based concentrates. The concentrates constituted 0·20, 0·40, 0·60 and 0·80 of total DM of the diets, which were offered ad libitum (AL). The two diets, which contained 0·80 concentrates, were also offered at 0·80 of AL intake. A further group of fourteen animals were given the medium‐digestibility silage only for 5 months and then grazed perennial ryegrass pastures for a further 5 months (silage/pasture treatment). For the diets containing HD silage and 0·20, 0·40, 0·60 and 0·80 concentrate, and 0·80 concentrate at 0·8 of AL intake, the DM intakes were 9·4, 10·2, 10·4, 10·2 and 8·1 (s.e. 0·16) kg d^?1, respectively, and daily carcass gains were 0·67, 0·78, 0·77, 0·79 and 0·62 (s.e. 0·029) kg d^?1, respectively; for those containing MD silage and 0·20, 0·40, 0·60 and 0·80 concentrate, and 0·80 concentrate at 0·8 of AL, the DM intakes were 8·2, 9·3, 10·1, 10·1 and 8·0 (s.e. 0·16) kg d^?1, respectively, and daily carcass gains were 0·38, 0·48, 0·64, 0·77 and 0·56 (s.e. 0·029) kg d^?1 respectively. Increasing the proportion of concentrates in silage‐based diets decreased the concentration of omega‐3 (ω‐3) polyunsaturated fatty acids (PUFA) (P < 0·001) and increased the concentration of ω‐6 PUFA (P < 0·001) in muscle. Cattle on the silage/pasture treatment had the highest concentration of ω‐3 PUFA in muscle (51 g kg^?1 lipid), this value being over three times that for animals given diets containing MD silage and 0·80 concentrate in the diet. These results demonstrate the potential of HD silage made from perennial ryegrass relative to high concentrate diets. The consumption of pasture‐finished beef could make a significant contribution towards increasing the intake of ω‐3 PUFA in the human diet.     

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.     

Effects of inoculants and wilting on silage fermentation and nutritive characteristics of red clover–grass mixtures

Various management practices (e.g. wilting, application of silage additives or adding a grass component) can be used to improve silage fermentation of pure red clover (Trifolium pratense L.). Therefore, the aim of this laboratory ensiling study was to investigate the effects of varying proportions of red clover and perennial ryegrass (100/0, 66/33, 33/66, 0/100) on silage quality during two consecutive years. In addition, two wilting levels [target dry matter (DM): 300 vs. 400 g kg^?1] in combination with lactic acid bacteria (LAB) additives were tested. Herbage was ensiled, either untreated or inoculated with homofermentative LAB (low wilted) or homo‐ and heterofermentative LAB (high wilted). In most cases, lactic and acetic acid decreased as the proportions of ryegrass were increased. Data concerning ammonia‐N concentrations showed considerable differences between cuts and years. Silages treated with homofermentative LAB generally had high lactic acid and low final pH, whereas acetic acid and 1,2‐propanediol tended to be higher when homo‐ and heterofermentative LAB were applied. Inoculants had a positive effect on DM losses and ammonia‐N in only a few silages. Wilting decreased DM losses and fermentation acids at most cuts, irrespective of the grass/clover ratio in the herbage mixture. There was a strong year effect on the organic matter digestibility (DOM) of the silages. In conclusion, the optimal strategy for successful silage fermentation of red clover is the ensiling in mixtures with ryegrass. Furthermore, herbage should be wilted to a DM content of about 300–350 g kg^?1. The application of LAB inoculants did not alter the DOM but did improve silage fermentation.     

Grass silage as a basic feed for store lambs. 1. Effect of wilting, chop length and stage of maturity of grass silage on intake and performance of store lambs

Two experiments were carried out with grass silages cut at a leafy (Experiment 1) and a more mature (Experiment 2) stage of growth to evaluate the effect of wilting and chop length on silage intake and performance of store lambs. In each experiment, the herbage was cut with a rotary mower and was either ensiled within 24 h as unwilled silage (U) or wilted for 1–3 d (W). Each silage type was harvested with either a double-chop harvester (D) or a precision-chop harvester (P). All silages were treated with formic acid at 3 1 t^?1 and were well preserved. The silages were fed ad libitum to Suffolk crossbred store lambs (twenty-four lambs per treatment) without any supplement over a period of 8 or 9 weeks. Wilting of the silages had little effect on silage intake (797 vs. 809g dry matter (DM) d^?1) or on lamb performance in Experiment 1. In Experiment 2, wilting of the D silage increased silage DM intake (589 vs. 534 g DM d^?1; +10%) and reduced the extent of liveweight losses. Wilting of the P silage reduced silage intake (770 vs. 791g DM d^?1; -3%) and reduced liveweight gains. In Experiment 1 intakes of the D silages were 650–667g DM d^?1 and just maintained lamb live weights. Intakes of the P silages were 39–49% higher than the D silages (927–968 g DM d^?1) and increased liveweight gains. In Experiment 2 intakes of the D silages were 534–589 g DM d^?1 and resulted in a loss in lamb live weight. Precision-chopping increased silage intakes by 31–48% (770–791 DM d^?1)in Experiment 2 and improved lamb liveweight gains. Lamb performance was higher on the UP silage than on the WP silage. The rumen retention lime (RRT), estimated from the rumen contents of the lambs at slaughter and their silage intake before slaughter, was much shorter for the lambs fed on the P silages (12.6–20.6 h) than those fed on the D silages (21.4–29.3 h) in each experiment. Silage intake and liveweight gain were positively related to silage in vivo DM digestibility (DMD), whereas RRT was negatively related to DMD. However, there were distinct differences between the P and D silages in the elevation and, to a lesser extent, in the slope of the regression lines, indicating that intake of D silage was limited by factors other than the digestibility of the silage The results of this study show that the chop length of grass silage had a far greater effect on intake and on lamb performance than silage digestibility, whereas wilting had little or no effect.