The effect of delayed sealing on fermentation and losses during ensilage

In two separate experiments plastic silos were left opened to air for 3 days and then sealed. The composition of the resultant silages was compared with silages made in silos sealed immediately after filling. In the first experiment Lolium multiflorum of high water soluble carbohydrate (w.s.c.) content (27.3%) and low crude protein (c.p.) content (10.7%) was used and although variations in composition between the inside and outside layers of the “unsealed” silage occurred, both treatments produced well-preserved silage. In a second experiment using a later cut of similar grass but of low w.s.c. content (10.8%) and high c.p. content (23%), delayed sealing resulted in silages of high pH value with relatively high butyric acid and volatile N contents and low lactic acid levels. Dry matter losses during ensiling were also high in these aerated silages.     

Nutritive value of maize silage in relation to dairy cow performance and milk quality

Maize silage has become the major forage component in the ration of dairy cows over the last few decades. This review provides information on the mean content and variability in chemical composition, fatty acid (FA) profile and ensiling quality of maize silages, and discusses the major factors which cause these variations. In addition, the effect of the broad range in chemical composition of maize silages on the total tract digestibility of dietary nutrients, milk production and milk composition of dairy cows is quantified and discussed. Finally, the optimum inclusion level of maize silage in the ration of dairy cows for milk production and composition is reviewed. The data showed that the nutritive value of maize silages is highly variable and that most of this variation is caused by large differences in maturity at harvest. Maize silages ensiled at a very early stage (dry matter (DM) < 250 g kg^?1) were particularly low in starch content and starch/neutral detergent fibre (NDF) ratio, and resulted in a lower DM intake (DMI), milk yield and milk protein content. The DMI, milk yield and milk protein content increased with advancing maturity, reaching an optimum level for maize silages ensiled at DM contents of 300–350 g kg^?1, and then declined slightly at further maturity beyond 350 g kg^?1. The increases in milk (R² = 0.599) and protein (R² = 0.605) yields with maturity of maize silages were positively related to the increase in starch/NDF ratio of the maize silages. On average, the inclusion of maize silage in grass silage‐based diets improved the forage DMI by 2 kg d^?1, milk yield by 1.9 kg d^?1 and milk protein content by 1.2 g kg^?1. Further comparisons showed that, in terms of milk and milk constituent yields, the optimum grass/maize silage ratio depends on the quality of both the grass and maize silages. Replacement of grass silage with maize silage in the ration, as well as an increasing maturity of the maize silages, altered the milk FA profile of the dairy cows, notably, the concentration of the cis‐unsaturated FAs, C18:3n‐3 and n‐3/n‐6 ratio decreased in milk fat. Despite variation in nutritive value, maize silage is rich in metabolizable energy and supports higher DMI and milk yield. Harvesting maize silages at a DM content between 300 and 350 g kg^?1 and feeding in combination with grass silage results in a higher milk yield of dairy cows. © 2014 Society of Chemical Industry     

Effects of extraction and reconstitution of ryegrass juice on fermentation,digestion and in situ degradation of pressed cake silage

Primary growth of Italian ryegrass was fractionated into green juice and pressed cake (PC). PC was ensiled either directly or after reconstitution with the juice which was spray dried and then added to water before ensiling (RPC). This process was aimed at distinguishing between chemical (removal of nutrients) and physical (mechanical disintegration) effects of fractionation. Two additional wilted silages were prepared from long cut or chopped Italian ryegrass (WL and WC, respectively). The fermentative quality, digestion and in situ degradation of dry matter for the four silages were compared. WC, RPC and PC silages indicated lactate-rich fermentation while WL silage had a comparatively low lactate content. PC silage had a lower (P<0·05) pH value with lower (P<0·05) amounts of organic acids compared with WC and RPC silage, suggesting that removal of buffering components with the juice had greater effects than shredding on fermentation of PC silage. The digestibility of protein was lower (P<0·05) in PC than WL silage but the reduction was compensated for in RPC silage. Ruminal concentrations of total volatile fatty acids were the highest (P<0·05) when goats fed WL silage while those on the other silages had similar concentrations. Ruminal pH was lower (P<0·05) in goats fed PC than WC silage and the difference was not fully reversed by reconstituting the juice to PC. Juice extraction decreased (P<0·05) the soluble fraction and the rate of disappearance of dry matter in the rumen but the potential degradability was not different among treatments. These results suggest that both chemical and physical changes due to the fractionation affect the characteristics of digestion of PC silage while the removal of nutrients has a major role in the modified silage fermentation. © 1997 SCI.     

Ensiling characteristics and ruminal degradation of Italian ryegrass and lucerne silages treated with cell wall-degrading enzymes

Two experiments were carried out to investigate the effect of added cell wall-degrading enzymes at ensiling on the fermentation and in situ degradation of grass and legume silages. Primary growths of Italian ryegrass (Lolium multiflorum Lam) and lucerne (Medicago sativa L) were wilted and ensiled in laboratory-scale silos with or without enzymes. Silages were opened at 2, 5, 15 and 45 days after storage; the fermentation quality and the contents of cell wall components (NDF, ADF, ADL) were determined. The 45 day silages were subjected to in situ incubation experiments, and the kinetics of DM and NDF degradation was estimated. The enzyme treatment enhanced the lactic acid production (P < 0.01) and reduced the pH value (P < 0.01) of both Italian ryegrass and lucerne silages. The contents of cell wall components, however, were not affected by enzymes, except for NDF of Italian ryegrass silage. The in situ incubation experiments revealed that added enzymes increased the rapidly degradable DM (P < 0.01) and appeared to decrease the rate of degradation of DM and NDF of Italian ryegrass silage. The rapidly degradable DM was not altered when lucerne was treated, but the rate of degradation of NDF was significantly reduced (P < 0.05). These results suggest that although added cell wall-degrading enzymes could improve the preservation of grass and legume silages, the effects on ruminal degradation may be different according to the herbage treated. Enzymatic hydrolysis during ensilage may be restricted to easily digestible cell walls, leaving relatively less digestible components that would be retained in treated silages. © 1999 Society of Chemical Industry     

Aerobic deterioration of lucerne (Medicago sativa) and maize (Zea mais) silages—effects of fermentation products

Eleven laboratory lucerne silages, ten farm-scale lucerne silages and one maize silage were analysed for fermentation products to determine if chemical composition could explain differences in aerobic stability. Three of the farm-scale lucerne silages and the maize silage heated within 4 days of exposure to air whereas the other lucerne silages were stable for longer than 7 days even after inoculation with a destabilising yeast inoculum. The silages were analysed for lactic acid, volatile fatty acids (C₁ to C₆), succinic acid, ethanol, and 2,3-butanediol. The concentrations of these compounds in the unstable silages were not different from levels found in stable silages on either a dry matter basis or an undissociated water basis. However, unstable silages tended to be lower in 2,3-butanediol than other silages. The time until heating in these silages was simulated using a model of aerobic fungal growth in silage. This model considered the effects of yeast and mould numbers, pH, moisture content, and lactic and acetic acid concentrations on stability. Aerobic stability in three of the four unstable silages, with and without inoculation of destabilising yeasts, was reasonably predicted by the model. Stability in the other silages was consistently underpredicted by the model. These results indicate that the stability factor found in many lucerne silages is unlikely to be one of the principal products of silage fermentation.     

Effect of long-term application of animal slurries to grassland on silage quality assessed in laboratory silos

The effect on silage quality of slurry type (pig or cow), rate of application of slurry (50, 100 or 200 m³ ha^?1 year^?1) and use of a bacterial silage inoculant, was assessed on grass from a long-term slurry experiment ensiled in laboratory silos. There was no significant effect of slurry type or the quality of silage made from grass re growths. However, on the basis of ammonia-N, lactate and volatile fatty acid contents, spring (first cut) grass treated with cow slurry in both years of the study produced significantly poorer fermentation (P < 0.001) than silage from grass treated with pig slurry. The quality of silage made from slurry-treated swards compared favourably with that from swards treated with granular fertiliser. Although increasing the rate of slurry application was shown to reduce fermentation quality in most treatments, this was seen as an effect of increasing the total-N content of the herbage rather than of slurry application per se. From a study, in selected treatments, of the bacterial flora at harvest, it was also observed that slurry application had little impact on either the composition or diversity of herbage enter bacteria at harvest, and therefore probably upon subsequent fermentation. No evidence was found for the occurrence of clostridia on herbage from slurry-treated swards. Use of a bacterial inoculant (Ecosyl; ICI plc) improved fermentation quality significantly (P < 0.001) even where high rates of slurry (200 m³ ha^?1 year^?1) had been applied to swards. The high acetate and butyrate contents typical of laboratory silages untreated with additive were not seen in the inoculated silages.     

Relationship between oven and toluene dry matter in grass silage

Dry matter (DM) contents of 205 silages were determined by toluene distillation and oven drying at 100°C. The toluene distillation method gave values up to 11% higher than the oven drying method, the largest differences occurring with silages of high volatile fatty acid concentration, low lactic acid concentration and high ammonia nitrogen content expressed as a percentage of total nitrogen. Highly significant (P < 0.01) correlations were shown between toluene dry matter and oven dry matter for various ranges of ammonia nitrogen, and equations are presented which allow toluene dry matter to be readily estimated on a routine basis for grass silage.     

Conservation of fresh and wilted grass in air-tight metal containers

Fresh and wilted timothy-meadow fescue herbage of 19 and 46.6° dry matter content, respectively, was ensiled in rubber-sealed steel cylinders 5 ft deep and 3 ft in diameter. Mean dry matter losses from all silos were about 6%. All silages were well preserved, the wilted material containing less lactic acid and volatile acids and having a higher pH. The dry matter digestibility coefficients from fresh and wilted grass silages were 71.5 and 70.2%, respectively, and were slightly higher than for the grass before ensilage. Ensilage resulted in a fall in metabolisable energy of the wilted grass. Intake of wilted silage by sheep was higher than that of silage from fresh grass.     

Comparison of grass and legume silages for milk production. 2. In vivo and in sacco evaluations of rumen function

Two experiments were conducted to investigate the basis for higher voluntary intakes and increased alpha-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of isobutyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of alpha-linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of alpha-linolenic acid passing through the rumen. This explains the increased recovery of alpha-linolenic acid from feed into milk with diets based on red clover silage.     

The occurrence and prevention of ethanol fermentation in high‐dry‐matter grass silage

Ethanol is a common, usually minor fermentation product in ensiled forages, the major product being lactic acid. Occasionally, high levels of ethanol are found in silages. The aim of this study was to determine the incidence of high‐dry‐matter (DM) grass silages containing ethanol as the main fermentation product (ethanol silages), to describe the fermentation process in such silages and to determine the effect of grass maceration prior to wilting and addition of a bacterial inoculant containing Lactobacillus plantarum and Enterococcus faecium strains on fermentation. Twenty‐one laboratory silages produced between 1993 and 1995, 21 farm silages produced between 1980 and 1989 and 36 farm silages produced in 1995 (all produced without additive) were examined for pH and chemical composition. Dry matter (DM) loss during ensilage was determined for the laboratory silages only. Four laboratory silages were identified as ethanol silages. Mean concentrations of ethanol, lactic acid and acetic acid were 48.1, 15.5 and 6.0 g kg⁻¹ DM respectively. In the silages that contained lactic acid as the main fermentation product (lactic acid silages) these values were 7.7, 45.5 and 15.1 g kg⁻¹ DM. Mean DM loss and pH were 62.8 g kg⁻¹ DM and 5.32 respectively for ethanol silages and 24.4 g kg⁻¹ DM and 4.69 for lactic acid silages. There was no difference between ethanol silages and lactic acid silages in the mean concentration of ammonia‐N (94 g kg⁻¹ total N), and butyric acid was not detected (<0.2 g kg⁻¹ DM), indicating that both types of silages were well preserved. Analysis of the composition of the grass at ensiling showed a positive correlation between the concentration of soluble carbohydrates and the development into ethanol silage. Analysis of the farm silages indicated that 29% of the silages produced between 1980 and 1989 and 14% of those produced in 1995 were ethanol silages. Maceration prior to wilting and addition of silage inoculant improved lactic acid fermentation and prevented high ethanol levels. The micro‐organisms responsible for ethanol fermentation as well as the implications of feeding ethanol silages to livestock remain to be resolved. © 2000 Society of Chemical Industry     

Sodium benzoate,potassium sorbate and sodium nitrite as silage additives

BACKGROUND: The hygienic quality of silage is important for animal health, animal production and food quality. The aim of this study was to evaluate the effect of five silage additive mixtures on yeast, mould, and clostridia growth and other silage quality criteria. The additives, composed of sodium nitrite, sodium benzoate and/or potassium sorbate, were used to treat a grass forage crop before ensiling. The silages were compared with untreated silage and silages treated with two commercial additives: Promyr NF (PNF), which is based on formic and propionic acid, and Kofasil Ultra (KU), a mixture of sodium nitrite, sodium benzoate, sodium propionate and hexamine. RESULTS: All tested additives significantly (P < 0.001) reduced butyric acid and ammonia‐N formation in low‐dry‐matter (DM) silages compared to the control. Only KU and the mixtures of 600 g sodium nitrite, 250 g sodium propionate, 750 g sodium benzoate (A1) and 250 g sodium nitrite with 1000 g sodium benzoate and 500 g potassium sorbate (A5) ton^?1 of fresh forage were found to reduce (P < 0.001) the presence of clostridia spores in low‐DM silages. In high‐DM silages, treatments A1, A5 and A2 (250 g sodium nitrite and 1000 g sodium benzoate) contained less (P < 0.02) yeast than the control and PNF, but not KU. All treated silages were aerobically stable. The concentrations of nitrate‐N in all silages and nitrite‐N in low‐DM were below the threshold level for feed at the end of storage. CONCLUSIONS: The additive mixtures A1 and particularly A5 improved silage quality at least to the same extent as commercial products, even though they contained no hexamine and less nitrite. Copyright © 2009 Society of Chemical Industry     

A meta-analysis of the effects of Lactobacillus buchneri on the fermentation and aerobic stability of corn and grass and small-grain silages

The results of adding Lactobacillus buchneri to silages from 43 experiments in 23 sources reporting standard errors were summarized using meta-analysis. The effects of inoculation were summarized by type of crop (corn or grass and small grains) and the treatments were classified into the following categories: 1) untreated silage with nothing applied (LB0), 2) silage treated with L. buchneri at ≤100,000 cfu/g of fresh forage (LB1), and 3) silage treated with L. buchneri at > 100,000 cfu/g (LB2). In both types of crops, inoculation with L. buchneri decreased concentrations of lactic acid, and this response was dose-dependent in corn but not in grass and small-grain silages. Treatment with L. buchneri markedly increased the concentrations of acetic acid in both crops in a dose-dependent manner. The numbers of yeasts were lower in silages treated with LB1 and further decreased in silages treated with LB2 compared with untreated silages. Untreated corn silage spoiled after 25 h of exposure to air but corn silage treated with LB1 did not spoil until 35 h, and this stability was further enhanced to 503 h with LB2. In grass and small-grain silages, yeasts were nearly undetectable; however, inoculation improved aerobic stability in a dose-dependent manner (206, 226, and 245 h for LB0, LB1, and LB2, respectively). The recovery of DM after ensiling was lower for LB2 (94.5%) when compared with LB0 (95.5%) in corn silage and was lower for both LB1 (94.8%) and LB2 (95.3%) when compared with LB0 (96.6%) in grass and small-grain silages.     

Effects of feeding grass or red clover silage cut at two maturity stages in dairy cows. 2. Dry matter intake and cell wall digestion kinetics

This study examined the effects of red clover or grass silages cut at 2 stages of growth on feed intake, cell wall digestion, and ruminal passage kinetics in lactating dairy cows. Five dairy cows equipped with rumen cannulas were used in a study designed as a 5 × 5 Latin square with 21-d periods. Diets consisted of early-cut and late-cut grass and red clover silages and a mixture of late-cut grass and early-cut red clover silages offered ad libitum. All diets were supplemented with 9 kg/d of concentrate. Ruminal digestion and passage kinetics were assessed by the rumen evacuation technique. Apparent total-tract digestibility was determined by total fecal collection. The silage dry matter intake was highest when the mixed forage diet was fed and lowest with the early-cut red clover diet. Delaying the harvest tended to decrease DMI of grass and increase that of red clover. The intake of neutral detergent fiber (NDF) and potentially digestible NDF (pdNDF) was lower but the intake of indigestible NDF (iNDF) was higher for red clover diets than for grass diets. The rumen pool size of iNDF and the ratio of iNDF to pdNDF in the rumen contents were larger, and pool sizes of NDF and pdNDF were smaller for red clover than for grass silage diets. Outflow of iNDF and the ratio of iNDF to pdNDF in digesta entering the omasal canal were larger, and the outflow of pdNDF was smaller for red clover than for grass silage diets. The digestion rate (k_d) of pdNDF was faster for red clover diets than for grass silage diets. Delaying the harvest decreased k_d for grass but increased it for red clover silage diets. Observed differences in fiber characteristics of red clover and grass silages were reflected in ruminal digestion and passage kinetics of these forages. The low intake of early-cut red clover silage could not be explained by silage digestibility, fermentation quality, or rumen fill, but was most likely related to nutritionally suboptimal composition because inclusion of moderate quality grass silage improved silage intake. Increasing the maturity of ensiled red clover does not seem to affect silage dry matter intake as consistently as that of grasses.     

The effects of some additives on the microflora of silage

The microflora of experimental batches of grass silage treated with formaldehyde, with formaldehyde plus formic acid, or with sodium benzoate and held at a constant temperature of 20°C was examined during fermentation and after exposure to air. The formaldehyde treatments inhibited the development of lactobacilli during fermentation but their biocidal effect did not persist and on exposure to air microbial numbers increased and the pH of the silages rose at a similar rate to that in untreated silage. Treatment with sodium benzoate had little effect on fermentation but its biostatic, particularly fungistatic, activity persisted through 17 days of exposure to air during which the pH did not rise and fungal numbers remained low. The yeast flora of all treatments was predominantly of fermenting species similar to that found in stack silages but the mould flora, of Geotrichum candidum, Mucor spp. and Penicillium spp., was dissimilar and could be related to the lack of heating in the experimental silages.     

Effect of inoculation of vegetable processing wastes with lactobacillus plantarum on silage fermentation

Small amounts (450 g) of experimental silages were prepared from green beans and potato processing wastes. Green bean wastes were dried or mixed with peanut (groundnut) hulls to reduce the percentage of moisture in the silage. Potatoes were not treated to remove moisture. The effects of inoculating these food processing wastes with Lactobacillus plantarum (5 × 10⁶ g^?1 wet weight) on pH decline, microbial populations and volatile and non-volatile fatty acids were determined. The inoculum decreased pH, increased lactic acid and decreased acetic and other volatile acids in some silages. All silages had high numbers of streptococci initially and this population was succeeded by lactobacilli with higher numbers of the latter microflora observed in inoculated silages. Yeasts, moulds and clostridia were recovered in high numbers only in un-inoculated silages prepared with peanut hulls. Although control silages had pH declines probably adequate for preservation, the bacterial additive had an overall beneficial effect on these fermentations.     

Concentrations of butyric acid bacteria spores in silage and relationships with aerobic deterioration

Germination and growth of spores of butyric acid bacteria (BAB) may cause severe defects in semihard cheeses. Silage is the main source of BAB spores in cheese milk. The objectives of the study were to determine the significance of grass silages and corn silages as sources of BAB spores and to investigate the relationships between high concentrations of BAB spores in corn silage and aerobic deterioration. In the first survey, samples were taken from various locations in silos containing grass and corn silages and from mixed silages in the ration offered to the cows on 21 farms. We demonstrated that the quantity of BAB spores consumed by cows was determined by a small fraction of silage with a high concentration of spores (above 5 log₁₀ BAB/g). High concentrations were most often found in corn silage within areas with visible molds (69% of the samples). Areas with visible molds in grass silage and surface layers of corn silage contained, respectively, 21 and 19% of the cases of concentrations above 5 log₁₀ BAB spores/g. Based on these results, we concluded that currently in the Netherlands, corn silage is a more important source of BAB than is grass silage. In a second survey, 8 corn silages were divided into 16 sections and each section was studied in detail. High concentrations of BAB spores were found in only the top 50 cm of these 8 silages. Elevated concentrations of BAB spores were associated with different signs of aerobic deterioration. In 13% of the sections in corn silage with more than 5 log₁₀ yeasts and molds/g, more than 5 log₁₀ BAB spores/g were found. Sections with a temperature of more than 5°C above ambient temperature contained, in 21% of the cases, more than 5 log₁₀ BAB spores/g. Concentrations above 5 log₁₀ BAB spores/g were measured in 50% of the sections with a pH above 4.4. All sections with a pH above 4.4 also showed a temperature that was more than 5°C above ambient temperature and a concentration of yeasts and molds above 5 log₁₀ cfu/g. Based on these results, we postulated that high concentrations of BAB spores in corn silage are the result of oxygen penetration into the silage, resulting in aerobic deterioration and the formation of anaerobic niches with an increased pH just below the surface. Growth of BAB in these anaerobic niches with an increased pH caused the locally high concentrations of BAB in corn silage.     

Ensiling characteristics and aerobic stability of direct‐cut and wilted grass silages inoculated with Lactobacillus casei or Lactobacillus buchneri

Two experiments were conducted to study the effects of wilting and inoculating Lactobacillus casei or Lactobacillus buchneri on the fermentation and aerobic stability of grass silages. Chopped Italian ryegrass (IR) and Festulolium (FE) were ensiled with or without wilting and added L casei (>10⁶ cfu g^?1 fresh matter (FM)) or L buchneri (>10⁶ cfu g^?1 FM). Silos were opened after 120 days and microbial counts, fermentation products and aerobic stability were determined. Addition of L casei increased lactic acid and decreased acetic acid and dry matter loss regardless of wilting and forage species. Inoculation of L buchneri decreased lactic acid and increased acetic acid and 1,2‐propanediol, while the effects appeared greater in direct‐cut than in wilted grass silages. Although 1,2‐propanediol accumulated in FE silage, the diol was degraded further to propionic acid and 1‐propanol in IR silage. The activity of 1,2‐propanediol degradation was lowered when IR was wilted prior to ensiling; 1,2‐propanediol remained and the production of propionic acid and 1‐propanol was less than one‐third of that in direct‐cut silage. Regardless of forage species, addition of L buchneri increased dry matter loss compared with the untreated control, whereas the loss was not significant in wilted silages. Ammonia production was increased by L buchneri in direct‐cut but not in wilted silages. No heating was observed with or without inoculation in direct‐cut IR silage after exposure to air. Other silages were deteriorated when L buchneri was not inoculated, while the spoilage was accelerated when L casei was added to FE. Copyright © 2005 Society of Chemical Industry     

Changes during ensilage in the nitrogenous components of fresh and additive treated ryegrass and lucerne

The changes in the major nitrogenous components of herbage during the ensilage of lucerne and Italian ryegrass, with and without the addition of 85% formic acid and 40% formaldehyde at the rates of 3.2 and 7.4 g kg^?1 fresh herbage respectively, were studied. Both herbages were of similar amino-N composition except for asparagine which was about 10% of total nitrogen (TN) in lucerne and only 0.2% of TN in Italian ryegrass. After 90 days ensiling about 90% of the sum of protein-, peptide-, amino- and amide-N was preserved in the additive-treated silages while only 58% was recovered in the untreated lucerne (butyrate) silage. Recoveries of these compounds in the untreated ryegrass (lactate) silage was 83%. In the butyrate silage, the branched chain amino acids, valine, leucine and isoleucine were well preserved. In addition to these, proline, phenylalanine, glycine, methionine and threonine were well preserved in the lactate silages. Both the untreated silages contained more alanine than in their original respective herbages. Most of the losses from the amine-forming amino acids were recovered as their corresponding amines. Alpha-amino butyric acid and δ-amino valeric acid were found in both the untreated silages and the quantity present was dependent on the silage quality. In both the additive-treated silages, recoveries of amino acids, other than sulphur amino acids, lysine, histidine, tyrosine and tryptophan, were ca 90% or greater. The losses of these amino acids, excluding the sulphur amino acids, can be attributed mainly to the direct effects of formaldehyde in preventing their estimation following freeze drying or acid hydrolysis.     

Chemical changes and losses during the ensilage of wilted grass treated with formic acid

Formic acid (85%) was added to wilted perennial ryegrass (36% dry matter) at the rate of 0.39%. Changes during ensilage of this material were compared with changes occurring during ensilage of untreated wilted ryegrass and freshly harvested herbage. All silages were well preserved, of low volatile N content and contained only traces of butyric acid. Formic acid restricted fermentation in the wilted grass resulting in silage of high water-soluble carbohydrate content (15.3%) compared with untreated wilted (4.7%) and fresh (1.2%) silages. Results of microbiological studies indicated that yeasts were more active in the formic acid-treated herbages. Surface waste production and fermentation plus oxidation losses were higher in the acid-treated wilted silages (21%) than in the untreated wilted materials (14%).     

不同冷藏期鲳鱼及草鱼气味变化分析

以鲳鱼和草鱼分别作为海水鱼和淡水鱼代表,利用电子鼻评价冷藏条件下不同贮藏期的鱼肉气味,并通过气相色谱-质谱检测挥发性风味成分的变化。结果表明,电子鼻可以较好区分不同贮藏期的鱼肉气味,且草鱼的气味变化较鲳鱼更为显著。贮藏期间鲳鱼和草鱼分别鉴定出22 种和19 种挥发性物质,主要包括醛类、醇类、酯类及腐败性化合物等。新鲜鲳鱼挥发性风味主要以1-戊烯-3醇、己醛、1-辛烯-3醇、庚醛、2-辛烯醛为主,草鱼以己酸甲酯为主。贮藏期间,鲳鱼和草鱼气味成分变化也具有差异性,鲳鱼中和腐败相关的化合物主要为三甲胺和3-甲基丁醇等,且贮藏过程中醛类、醇类均呈下降趋势;草鱼贮藏过程中的第2天及第4天较为相关的化合物为癸醛、1-辛烯-3醇、己醛和壬醛等脂肪氧化的产物,而贮藏后期与腐败相关的化合物较少。上述结果初步说明生长环境、脂肪氧化及微生物腐败影响了海鱼和淡水鱼冷藏期气味形成。