Total Fermentation Acids Research Articles

Nutritive value, silage fermentation characteristics, and aerobic stability of grass-legume round-baled silages at differing moisture concentrations with and without manure fertilization and microbial inoculation.

For baled silages, production of clostridial fermentation products can be exacerbated by exceeding normal moisture targets (45% to 55%), and/or by the application of dairy slurry before harvest. Our objectives were to test a microbial inoculant as a mitigant of clostridial products in high-moisture, grass-legume (52% ± 13.8% cool-season grasses, 44.0% ± 14.0% legumes [predominately alfalfa]) baled silages in swards that were fertilized with dairy slurry. A secondary objective was to examine the effects of bale moisture and inoculation on the aerobic stability of these fermented silages following exposure to air. After the first-cutting was removed, three manure treatments were applied as a whole-plot factor: 1) control (no manure); 2) slurry applied immediately to stubble (63,250 L/ha); or 3) slurry applied after a 1-wk delay (57,484 L/ha). An interactive arrangement of bale moisture (64.1% or 48.4%) and inoculation (yes or no) served as a subplot term in the experiment. The inoculant contained both homolactic (Lactococcus lactis 0224) and heterolactic (Lactobacillus buchneri LB1819) bacteria. The experimental design was analyzed as a randomized complete block with four replications, and the study included 48 experimental units (1.2 × 1.2-m round bales). Total fermentation acids were affected (P ≤ 0.021) by slurry application strategies, but this was likely related to inconsistent bale moisture across slurry-application treatments. Concentrations of butyric acid were low, and there were no detectable contrasts comparing manure treatments (mean = 0.05%; P ≥ 0.645). Bale moisture affected all measures of fermentation, with bales made at 64.1% moisture exhibiting a more acidic final pH (4.39 vs. 4.63; P < 0.001), less residual water-soluble carbohydrates (2.1% vs. 5.1%; P < 0.001), as well as greater lactic acid (4.64% vs. 2.46%; P < 0.001), acetic acid (2.26% vs. 1.32%; P < 0.001), and total fermentation acids (7.37% vs. 3.97%; P < 0.001). Inoculation also reduced pH (4.47 vs. 4.56; P = 0.029), and increased acetic acid (1.97% vs. 1.61%; P < 0.001) and 1,2-propanediol (1.09% vs. 0.72%; P < 0.001) compared to controls. During a 34-d aerobic exposure period, maximum surface bale temperatures were not affected (P ≥ 0.186) by any aspect of treatment, likely due to the prevailing cool ambient temperatures; however, yeast counts were numerically lower in response to greater (P < 0.001) production of acetic acid that was stimulated by both high bale moisture and inoculation.

Nutritive value and fermentation characteristics of alfalfa-mixed grass forage wrapped with minimal stretch film layers and stored for different lengths of time

A key aspect of managing baled silages is to quickly achieve and then rigorously maintain anaerobic conditions within the silage mass. The concept of inserting an O2-limiting barrier (OB) into plastic commercial silage wraps has been evaluated previously, yielding mixed or inconclusive results. Our objective for this study was to maximize the challenge to a commercial polyethylene bale wrap, or the identical wrap containing an OB, by using minimal plastic (4 layers), and then extending storage periods as long as 357 d. Forty-eight 1.2 × 1.2-m large-round bales of alfalfa (Medicago sativa L.) and mixed grass forage (66.3 ± 8.66% alfalfa; DM basis) were made at 2 moisture concentrations [47.5 (ideal) or 36.1% (dry)], wrapped with 4 layers of plastic containing an OB or no OB, and then stored for 99, 243, or 357 d. After storage, yeast counts within the 0.15-m deep surface layer were not affected by treatment (mean = 5.85 log10 cfu/g); mold counts could not be analyzed statistically because 26 bales were nondetectable at a 3.00 log10 cfu/g detection limit, but means among detectable counts were numerically similar for OB (4.74 log10 cfu/g) and no OB (4.77 log10 cfu/g). Fermentation characteristics were most affected by initial bale moisture, resulting in a more acidic final pH for ideal compared with dry bales (5.52 vs. 6.00). This was facilitated by greater concentrations of total fermentation acids (3.80 vs. 1.45% of dry matter), lactic acid (2.24 vs. 0.71% of dry matter), and acetic acid (1.07 vs. 0.64% of dry matter) within ideal compared with dry silages. Plastic wrap type had no effect on final concentrations of any fermentation product. During fermentation and storage, we noted greater change in concentrations of fiber components and whole-plant ash within the 0.15-m deep surface layer than in the bale core, and these changes always differed statistically from 0 (no change) based on pre-ensiled baseline concentrations. Overall, concentrations of water-soluble carbohydrates were reduced (mean = 2.3 percentage units) during fermentation and storage, which resulted (indirectly) in increased concentrations of fiber components and crude protein, as well as an overall energy cost of 2.2 percentage units of total digestible nutrient. It remains unclear under what conditions an OB plastic wrap will consistently benefit the fermentation and preservation of baled silages.

Storage characteristics, nutritive value, and fermentation characteristics of large, round bales of alfalfa–mixed grass forage wrapped with different layers of stretch film

ABSTRACT Baled silage has become a popular form of forage conservation; however, many practical management questions have not been investigated thoroughly. Our objectives were to evaluate the number of polyethylene wrapping layers and the presence (OB) or absence (SUN) of an O 2 -limiting barrier within the wrap on the storage characteristics, nutritive value, and silage fermentation characteristics of alfalfa–mixed grass round-bale silages. Thirty-six 1.2 × 1.2-m large, round bales of a mixed sward composed predominantly of alfalfa ( Medicago sativa L.; 82 ± 3.8% alfalfa, DM basis) were packaged at 59.8 ± 3.2% DM and wrapped the same day with 4, 5, or 6 layers of the 2 polyethylene films (OB or SUN). Bales were sampled after 127 d at 0 to 0.15-m (SURFACE) and 0.15 to 0.61-m (CORE) depths. Generally, plastic type and number of wrapping layers had minimal effect on nutritive value and silage fermentation characteristics. However, greater concentrations of total fermentation acids, lactic acid, and NH 3 -N were found within the SURFACE compared with CORE layer ( P ≤ 0.03), but the titratable acidity (mean = 15.4 mEq/kg of DM; P = 0.27) and final pH (mean = 5.70; P = 0.23) did not differ. Although yeast and mold counts at the SURFACE layer often were nondetectable ( 10 cfu/g), elevated counts were most frequently associated with SUN. An O 2 -limiting barrier may improve anaerobic integrity at the surface layer of baled silages, but the potential to reduce polyethylene usage may be limited by the risk of internal physical puncture by coarse alfalfa stems.

Storage characteristics, nutritive value, and fermentation characteristics of alfalfa packaged in large-round bales and wrapped in stretch film after extended time delays

The production of baled silage is attractive to producers because it offers advantages over dry hay, particularly by limiting risks associated with wet or unstable weather conditions. Our objectives were to test the effects of delayed wrapping on silage fermentation, storage characteristics, and the nutritive value of baled alfalfa silages. To accomplish this, large-round bales of alfalfa were wrapped in plastic film within 4h of baling (d 0), or after delays of 1, 2, or 3 d. A secondary objective was to evaluate a prototype bale wrap containing an O2-limiting barrier (OB) against an identical polyethylene wrap without the O2 barrier (SUN). Sixty-four 1.19×1.25-m bales of alfalfa were made from 4 field blocks at a mean moisture concentration of 59.1±4.3% with a mean initial wet bale weight of 473±26.4kg. Two bales per field block were assigned to each combination of bale wrap (SUN or OB) and wrapping time (0, 1, 2, or 3 d postbaling), and one bale of each pair was fitted with a thermocouple placed in the geometric center of each bale. All bales were sampled after a 97-d storage period. Internal bale temperatures, recorded at the time bales were wrapped, were greater for all bales with wrapping delays compared with bales wrapped on d 0 (54.9 vs. 34.9°C), and increased to a maximum of 63.9°C after a 3-d delay exhibiting a linear effect of time delay. Total silage fermentation acids (lactic, acetic, propionic, butyric, and isobutyric) were greatest when bales were wrapped on d 0 compared with all bales wrapped with time delays (4.64 vs. 2.26% of DM), and declined with linear and quadratic effects of wrapping delay. Total fermentation acids also were related quadratically to internal bale temperature by regression [y (% of DM)=0.0042x2 – 0.50x + 17.1; R2=0.725]. Similar responses were observed for lactic acid, except that trends were linear, both for orthogonal contrasts evaluating length of wrapping delay, and in regressions on internal bale temperature [y (% of DM)=−0.046x + 3.5; R2=0.663]. Butyric acid also was detected, regardless of treatment, but was greatest within bales wrapped on d 0 compared with those with wrapping delays (0.99 vs. 0.38% of DM), and a similar response (0.68 vs. 0.52% of DM) was observed for NH3-N, suggesting that clostridial activity occurred during silage fermentation. Based on these results, silage fermentation characteristics and the nutritive value declined with time delays before wrapping, but responses were exacerbated when delays exceeded 1 d.

Isolating and evaluating lactic acid bacteria strains with or without sucrose for effectiveness of silage fermentation

AbstractThe aim of this study was to screen and evaluate lactic acid bacteria strains for their ability to ferment alfalfa, Leymus chinensis and native grass into silage. We isolated 186 lactic acid bacteria strains from alfalfa, native grass and selected eight strains by acid production test and growth rate test. The eight stains were identified using morphological observations, Gram staining, physiological and biochemical tests, an acid tolerance test and 16S rDNA sequencing. All eight strains (LP1, LP2, LC1, LC2, PP1, PP2, EF1 and EF2) grew at pH 4.0 and 6.5%NaCl. Strains LP1 and LP2 were identified as Lactobacillus plantarum, LC1 and LC2 as Lactobacillus casei, PP1 and PP2 as Pediococcus pentosaceus, EF1 as Enterococcus faecalis, and EF2 as Enterococcus faecium based on their 16S rDNA sequences. The eight strains and two commercial inoculants (PS and CL) were added with or without sucrose to native grass, L. chinensis, and alfalfa to produce silage. All eight screened strains decreased the pH and ammonia nitrogen (N) content and increased the lactic acid content of alfalfa silages. No butyric acid was detected in the L. chinensis and alfalfa silages. Addition of sucrose with the screened strains resulted in lower pH and ammonia N content, and higher lactic acid content and total fermentation acids content in all three silages. The eight strains improved the fermentation quality of alfalfa silage. All strains were more effective when supplemented with sucrose. No efficient lactic acid bacteria strain was found for ensiling the native grass, but the high fermentation quality native grass silage could be obtained using the combination of lactic acid bacteria strains and 2% sucrose.

Effect of stage of growth on the chemical composition, nutritive value and ensilability of whole-crop barley

Chemical composition, nutritive value and ensilability of whole-crop barley as a supplementary feed for dairy cows was investigated using a range of maturities of barley (seed coat ripe—GS 69, early dough stage—GS 82, soft dough—GS 87 and grain ripe—GS 90) in small scale silos. The ensiling experiment was based on a complete randomised design with three replicate silos per harvest date. Twelve 0.225 m 3 plastic silo (were used in the experiment and silo were sampled on opening for chemical composition and nutritive value. The fermentation process reduced the concentrations of water-soluble carbohydrate in the ensiled forage compared to the fresh forage. The proportion of residual WSC in silage did however increase with increasing crop maturity (0.051, 0.077, 0.167 and 0.560 of WSC retained in the silage after the process of fermentation from forages cut at GS 69, 82, 87 and 90 respectively). Silages that were made from forage cut at the most mature stage of growth had a substantially lower production (P<0.001) of total fermentation acids (38.9 g/kg DM for GS 90) compared to those made from the least mature forage (203.4 g/kg DM for GS 69). The pH and concentrations of the various fermentation acids for silages made with the least mature forage (GS 69) were typical of acetic acid dominated fermentation. These silages contained little or no butyric acid and had a pH of 4.5 and contained high concentrations of ammonia-N (186 g/kg total N). Silages produced from forages cut at growth stage 82 were similar to those conserved from immature forages, having acetic acid dominated fermentation (lactic acid to acetic acid ratio of 1:1.22), relatively high pH (4.85) and high concentrations of ammonia-N (141 g/kg total N). These silages differed from those made from the most immature forage insofar that they contained high concentrations of butyric acid (50.5 g/kg DM). The processes of fermentation were affected by the stage of growth of the forage at ensiling and hence the economics of silage production. If the forage was too immature at ensiling, the yield of crop would be compromised but the silage produced may have moderate to high nutritive value and reasonable aerobic stability during the feed out phase. If the whole-crop forage was grown as a crop to secure high levels of supplementary feed from an alternative forage source (other than grass), the trade-off between yield, nutritive value and losses of feed immediately after silo opening would suggest the crop should be harvested between 350 and 450 g DM/kg dry matter.

Effects of an esterase-producing inoculant on fermentation, aerobic stability, and neutral detergent fiber digestibility of corn silage

This experiment evaluated effects of an inoculant containing esterase-producing bacteria on fermentation, aerobic stability, in situ dry matter digestibility (DMD), and neutral detergent fiber (NDF) digestibility (NDFD) of corn silage. Two corn hybrids grown on adjacent fields [Croplan Genetics 851RR2 (CS1) and Vigoro 61R36 (CS2)] were harvested at approximately 39% dry matter. Each forage was conserved in quadruplicate in 20-L mini silos with or without application of an inoculant at a level to achieve 1.0×104cfu/g of Lactobacillus casei and 1.0×105cfu/g of Lactobacillus buchneri. After 110 d of ensiling, silos were opened and silages were analyzed for chemical composition, fermentation indices, microbial counts, and aerobic stability. In situ DMD, 24-h and 48-h DMD, and NDFD were measured by incubating ground (6-mm) samples in triplicate in each of 2 lactating, fistulated dairy cows fed a corn silage-based diet. Inoculation decreased concentrations of total fermentation acids and lactate, as well as lactate to acetate ratio, and increased propionate concentration compared with the uninoculated control in CS1 but not CS2. Inoculation tended to decrease yeast counts of CS1 but increased yeast counts and tended to increase the mold counts of CS2. Consequently, inoculation improved the aerobic stability of CS1 by 57.3h (98%) but decreased that of CS2 by 20.5h (20%). Inoculation also increased the potentially degradable fraction of CS1 and the total degradable fraction, 24-h and 48-h DMD, and 48-h NDFD of CS2. Inoculation of CS1 modified the fermentation, improved the aerobic stability, and increased the potentially degradable DM fraction. Inoculation of CS2 did not affect fermentation, but decreased the aerobic stability and increased the total degradable DM fraction, 24-h and 48-h DMD, and 48-h NDFD.

Prediction of the relative intake potential of grass silage by dairy cows

Data based on the mean treatment values from production studies in lactating dairy cows were used to estimate relationships between silage composition and silage dry matter intake (SDMI). Data from 21 studies were used to estimate relationships between D-value (g digestible organic matter in kg dry matter (DM)) and crude protein (CP) content, and SDMI. The silages were harvested at different maturities but using the same ensiling techniques within the study. Relationships between silage fermentation characteristics and SDMI were estimated using data from 47 studies. The silages were harvested at the same time from the same sward but using various additives. When factorial designs were used, silage data within each treatment (subexperiment) were recorded separately. The data sets included 125 D-value and 234 fermentation observations. Relationships between SDMI and silage parameters were analyzed using mixed model regression analyses with experiment as a fixed factor and subexperiment within experiment as a random factor. The ranges for silage CP concentration and D-value were 111 to 238 (S.D. 25.2) and 589 to 756 (S.D. 48.5) g/kg DM, respectively. D-value was a much better predictor of SDMI than CP ( R 2 within experiment 0.71 vs. 0.26). The effect of D-value on SDMI diminished with increasing level of concentrate supplementation (interaction P<0.001). D-value had a greater effect on SDMI when the total DM intake was high. SDMI was negatively correlated with concentrations of ammonia N, lactic acid, individual and total volatile fatty acids and total fermentation acids and positively correlated to the concentration of residual water soluble carbohydrates. Total acid concentration was the best SDMI predictor of individual fermentation parameters ( R 2 within experiment 0.41) followed by lactic acid and ammonia N. Use of quadratic regressions generally increased the variation accounted for by the model. The best multiple regression accounted for 0.51 of the variation in SDMI within experiment. To facilitate interpretation of data, a theoretical model is presented. An interplay between physical load and capacity to use energy determines SDMI of well-fermented silages over the whole range of D-values. With increasing extent of fermentation SDMI is constrained by nutrient imbalance, most probably amino acid to energy ratio at the tissue level, resulting from reduced microbial protein synthesis in the rumen. Low palatability can further constrain silage DM intake. For advisory silage evaluation the following model predicting relative SDMI is proposed: SDMI index=100+0.151×( D-value−690)−0.000531×(TA 2−6400)−4.7650 [Ln(Ammonia N) −Ln(50)], where D-value and total acids (TA) are expressed as g/kg DM and ammonia N as g/kg total N, respectively. Regression coefficients are scaled to a mean SDMI of 10 kg DM/day. The values of 690, 80 and 50 are used as standard D-value (g/kg DM), total acid (g/kg DM) and ammonia N (g/kg N) for high quality restrictively fermented silages. The model parameters were limited to those which are currently available for Finnish farm silage analyses, i.e., by near infra-red reflectance spectra ( D-value) and electrometric titration (fermentation parameters).

Effect of stage of growth at harvest and level of urea application on chemical changes during storage of whole-crop wheat

Winter wheat ( Triticum aestivum L.) harvested at a range of stages of growth has become a popular conserved forage for winter feeding of dairy cattle. The detailed processes of the preservation of whole-crop wheat were studied in three experiments in 1989 (Experiment 1) and in 1990 (Experiments 2 and 3). A range of maturities of wheat (growth stages 49, 71 and 87 in Experiment 1 and growth stages 53, 70, 80, 83 and 85 in Experiment 2) were selected and ensiled with three (0, 20 and 40 kg (t DM) −1; Experiment 1) or four rates (0, 20, 40 and 60 kg (t DM) −1; Experiment 2) of application of urea in small-scale silos. The experiments were based on factorial designs with crop maturity (oven dry matter (DM) content) and level of application of urea as the principal factors. Experiment 3 considered the changes in chemical composition over time (silos opened after 0, 10, 20, 30, 60 and 90 days ensiling) at two level of urea treatment (0 and 40 kg (t DM) −1) and two stages of growth (GS 70 and 83). The rate of hydrolysis of urea was dependent on the moisture content of the ensiled forage and the level of urea applied (Experiment 3). Microbial activity, measured by the production of total fermentation acids (lactic acid+VFA), was progressively reduced in both experiments by the level of urea applied ( p<0.001; Experiments 1 and 2) and increasing maturity of forage at harvest ( p<0.001; Experiments 1 and 2). An interaction ( p<0.001; Experiments 1 and 2) was observed for production of total fermentation acids between level of urea applied and maturity of forage, reflecting the relative availability of nutrients, in particular sugars (WSC)) for microbial utilization. Losses of DM during ensiling were progressively reduced ( p<0.001; Experiments 1, 2 and 3) by the addition of urea at ensiling and by increasing maturity of the forage ( p<0.001; Experiments 1 and 2) and duration of storage (Experiment 3). Ensiling the forage without urea reduced its NDF content ( p<0.01; Experiment 1 and p<0.001, Experiment 2), but with increasing crop maturity the extent of the reduction in NDF was decreased. Application of urea at a rate >40 kg (t DM) −1 increased ( p<0.01; Experiments 1 and 2) the reduction in NDF content compared to forage ensiled without urea. Treatment of harvested forage at ensiling with urea reduced ( p<0.001; Experiments 1 and 2) the conversion of WSC to fermentation acids during conservation but slightly enhanced the loss of starch ( p<0.05; Experiment 2). There was a marked reduction (ranging from 6 to 17 g kg −1 ( p<0.01); Experiments 1 and 2 to 23 g kg −1 ( p<0.01); Experiment 2) in the digestibility of the ensiled forage compared to fresh forage, dependent on maturity of the forage, but no differences in digestibility were observed between urea treated forage and fresh forage. Treatment of whole-crop wheat forage with urea at harvest can be considered an effective method of preserving forage nutritive value.

Factors affecting water intakes of lactating dairy cows offered grass silages differing in fermentation and intake characteristics

AbstractThe objective of this study was to investigate the effects of silage characteristics on water intake of lactating dairy cows and to examine the prediction of water intake. Sixteen grass silages, differing in fermentation and intake characteristics, were offered ad libitum to dairy cows in early lactation supplemented with 7 kg/day of concentrate (13·3 MJ metabolizable energy per kg dry matter (DM) and 216 g crude protein per kg DM). Four silages were offered in each of four incomplete change-over design experiments, consisting of three 3-week periods. Water intakes were recorded through individual Kent water meters and press water bowls over the final week of each period. Tree (drinking) water intake ranged from 20·1 to 89·9 (mean = 45·2; s.d. = 12·96) I/day whilst total water intake (also including food water) ranged from 48·4 to 123·8 (mean = 87·3; s.d. = 14·12) I/day. Water intake increased with increasing silage DM concentration, however free water replaced silage water at a rate less than 1. Milk yield and silage D value (digestible organic matter, g/kg DM) were strongly positively correlated with free water intake (r = 0·751 and 0·595 respectively), though fermentation indices were not good single predictors of water intake. Further analysis revealed problems owing to collinearity within the predictors of water intake: DM intake, silage D value and milk yields being significantly correlated, as were pH and volatile fatty acids as a proportion of total fermentation acids. The ridge regression technique was used to reduce collinearity problems and produce stable equations. The best prediction equations for water intake involved a combination of both animal and analytical information: diet DM concentration, milk yield and silage pH. The use of fermentation information, whether from titration or high-performance liquid chromatography did not describe real variation in water intake beyond that described by silage pH. Free water intake was higher with higher diet DM concentrations, higher milk yields and higher silage pH.

Effect of duration of wilting on the conservation of silage and on gains in body components by steers

ABSTRACTFour silages were prepared from a sward of perennial ryegrass (Lolium perenne cv. Melle). Two were ensiled directly either without (UWN) or with formic acid at 31 1/t fresh material (UWA). The remaining herbage was left undisturbed in the swath for 43 h (WL) or was spread and harvested after 19 h (WS). The dry matter (DM) concentrations at harvest for the unwilted herbage were 229 (UWN) and 238 g DM per kg (UWA) and wilting increased DM concentration to a similar extent for both treatments (WS, 339 v. WL, 346 g DM per kg).Forty British Friesian steers initially 3·5 months of age and 105 kg live weight were used for the trial. Eight steers were allocated to an initial slaughter group and the remainder were offered the four silages at a restricted level to give 940 kJ digestible energy per kg M0·75. These animals were slaughtered after 112 days to estimate the incremental increases in the components of the body.Loss of DM in the field by respiration increased from 22·2 to 40·6 g/kg DM cut with increased length of wilting. In silo losses were greater with unwilted (UWN, 222, UWA 183 g/kg DM ensiled) than with wilted silage (WS, 133 WL, 122 g/kg DM ensiled). All silages were well preserved. Wilting was more effective than formic acid in reducing total fermentation acids but a lower proportion of these acids was in the form of lactic acid.Live-weight gain was lower for the steers given the control (UWN) silage (398 g/day) than for those given silages UWA (463 g/day), WS (476 g/day) and WL (470 g/day). However, a lower proportion of the gain by steers given UWN was in the form of gut contents so that gains in fat, protein and energy were not significantly affected by treatment. In conclusion, when steers were given similar amounts of digestible energy and unwilted silage was well preserved, neither the use of formic acid nor wilting influenced gains in protein and energy. Further, the duration of wilting, in the absence of any differences in DM content, had no effect on animal performance.

Effect of sodium acrylate and calcium and sodium hydroxides on the fermentation, digestibility, chemical composition and aerobic deterioration of whole-crop maize silage

Whole-crop maize was harvested at a dry matter (DM) content of 33.2% and ensiled in polythene bag silos containing, on average, 2.75 kg DM, without additive (C) or with the addition of sodium acrylate (SA), calcium hydroxide (CH) or sodium hydroxide (SH), at intended application rates of 12.5, 50 and 50 g kg −1 of crop DM, respectively. After 60 days, all the silages were apparently well preserved and only the CH silage contained a trace of butyric acid; none of the silages contained more than 5% of the nitrogen in the form of ammonia. Bacterial fermentation was restricted by the addition of SA and enhanced by the use of CH and SH. Total fermentation acids formed 5.24, 3.25, 10.28 and 11.68% of the silage DM for C, SA, SH and CH silages, respectively. Ethanol production was relatively high when bacterial fermentation was restricted. The digestibility of organic matter was increased by SH from 72.5 for the C silage to 80.0%. All silages heated when exposed to air, an effect which was lowest for SA. The SH and CH silages heated extensively and after 14 days of exposure had lost over 30% of the original DM. It is concluded that SA may have a place in ensiling whole-crop maize, but that SH and CH do not.

The effect of paraformaldehyde on the fermentation quality and feeding value of ryegrass and lucerne silages

SUMMARYCrops of perennial ryegrass and lucerne were each ensiled without additives and after the addition of paraformaldehyde to provide about 0·1, 0·2 or 0·4% HCHO/t crop fresh weight. The ryegrass and lucerne silages were offered ad libitum to sheep in separate experiments of identical design.All theryegrass silages were well preserved with low pH values, the level of butyric acid was very low and ammonia-N comprised less than 8% of total N. The lucerne silage made without additive had a pH of 5 and acetic acid comprised the major part of the total fermentation acids. Ammonia-N comprised over 12% of total N. All levels of paraformaldehyde addition restricted fermentation in both crops and led to an increase in the proportion of total N which was insoluble in hot water.Voluntary intake of organic matter (OM) was higher for the lucerne than for the ryegrass silages but digestible organic matter (DOM) intake was higher for the ryegrass. Intakes of OM and DOM were not significantly affected by paraformaldehyde treatment. The addition of paraformaldehyde significantly depressed apparent digestibility of OM and cellulose with the ryegrass but had less effect with the lucerne. Nitrogen digestibility was significantly depressed in both crops at all paraformaldehyde levels. Paraformaldehyde addition resulted in increased faecal N output and decreased urinary N, but retention of N was not significantly affected.The lack of response in feeding value to paraformaldehyde treatment may have been due to the relatively high intake and N retention of the untreated silages which were fairly well preserved.

Milk production from diets of silage and dried forage. 3. Effect of formalin-treated ryegrass silage of high digestibility givenad libitumwith and without urea

ABSTRACT1. Young adult and adult lactating British Friesian female cattle (heifers and cows) were individually fedad libitumon perennial ryegrass silage (F) made with an additive of formic acid (3·41 of 85% acid/t fresh grass) or on a silage (FF) made from the same crop with an additive of 9·01/t of a mixture of equal volumes of formic acid and formalin (35% w/w solution of formaldehyde). Silage F was supplemented with a concentrate containing 50% dried grass and 50% barley at a low (L) or high (H) level of feeding; silage FF was supplemented with the same concentrate at the lower level only, either with urea at 2·0% of the silage DM (FFLU) or without urea (FFL).2. Silage F had a lower pH (P&lt; 0·001) and contained more lactic, acetic and total fermentation acids (P&gt;&lt;0·001). The DOMDin vivoof the diet was lower (by up to 3 units) for treatment FFL than for the other treatments (P&lt;0·05 in weeks 17 and 18).3. Over weeks 4 to 18 of lactation the mean dry-matter intakes (DMI) of silage on treatments FL and FFL were similar, but silage DMI was 12 to 13% greater on treatment FFLU than on FL or FFL (P&lt;0·05). Digestible OM intake was greater with FFLU than with FFL (P&lt;0·01) and with FL (P&lt;0·05).4. Milk yields did not differ significantly between treatments and metabolic blood profiles were normal.

Performance of Dairy Cattle on Wilted Formic Acid Silages

Abstract Orchardgrass and alfalfa-orchardgrass were made into wilted silages that had been ensiled either without treatment or with treatment by formic acid. Formic acid increased energy recovery as silage by 5 percentage units and reduced total fermentation acids by 3 percentage units. It increased sugar recovery and decreased protein degradation. Energy digestibility was not affected by formic acid. Daily milk production increased 3%. Milk production per ton of harvested forage increased 9%. Daily gains of dairy heifers increased 30% with no increase in energy intake but with improved partial feed conversion. Gain per ton of harvested forage increased 31%. Concentrations of plasma of valine, isoleucine, leucine, and phenylalanine in growing heifers increased, but concentrations of serine and glycine decreased.

Anaerobic Excretion of Fermentation Acids by Hymenolepis diminuta during Development in the Definitive Host

Succinic, acetic, and lactic acids are the major anaerobic fermentation acids excreted in vitro by Hymenolepis diminuta. In parasites recovered from immature (6-day) infections in white rats that were fed ad lib. in the dark for 12 hr, approximately equal amounts of succinic and lactic acids, and less acetic acid, were excreted. In the succeeding 12-hr period of fasting in the light, production of succinic and acetic acids from endogenous glycogen reserves was unaffected, whereas that of lactic acid decreased markedly. The pattern was different in parasites recovered from 10and 14-day infections, in that quantitative differences in acid excretion during feeding and fasting periods were not observed, lactic acid production was relatively small, and succinic acid constituted about half of the total excreted acids. An active pyruvate decarboxylase enzyme complex presumably accounted for the formation of acetate from pyruvate. The existence of lactate dehydrogenase, and a phosphoenolpyruvate carboxykinase leading to succinate production were already known. A calculation of the carbon content of excreted acids in terms of ,moles phosphoenolpyruvate carbon/mg protein showed that the rates of excretion of fermentation acids in 6and 14-day infections did not differ. Succinic, acetic, and lactic acids comprise most of the total fermentation acids excreted in vitro by Hymenolepis diminuta recovered from patent (15 day) infections in rats (Fairbairn et al., 1961). It is known that phosphoenolpyruvate is a key intermediate in the formation of these acids since it reacts with carbon dioxide in the presence of phosphoenolpyruvate carboxykinase and GDP or IDP to form oxaloacetate and thence succinic acid, and is also converted to pyruvate by pyruvate kinase (Bueding and Saz, 1968) and hence to L(+) lactate by lactate dehydrogenase (Walkey and Fairbairn, 1973). Acetic acid is presumably formed by oxidative decarboxylation of pyruvate, although the existence of this enzyme complex has not been studied. Different isoenzymes of L(+) -lactate dehydrogenase occur in the anterior regions of the mature tapeworm strobila or in immature (6 day) parasites, and in infective eggs obtained from mature proglottids (Walkey and Fairbairn, 1973). Similar observations have been made on pyruvate kinase (Carter and Fairbairn, unpublished). There is reason to believe, therefore, that quantitative differences in the forReceived for publication 11 February 1974. * This work was supported by Grants AI-08491 and 5 TOI AI-226 from the NIH, Bethesda, Maryland 20014. t Present address: The Wellcome Research Laboratories, Beckenham, Kent BR3 3BS, England. mation and excretion of succinic, acetic, and lactic acids may exist in different regions of the strobila, or in parasites at different stages of development in the definitve host. This is not surprising, as the strobila of H. diminuta contains hundreds of proglottids representing all stages of continuous growth and differentiation. In the present investigation we have compared the in vitro anaerobic excretion of succinic, acetic, and lactic acids by H. diminuta recovered from infected rats after 6 and 14 days, respectively, and have demonstrated the decarboxylation of pyruvate by a pyruvate decarboxylase enzyme complex. MATERIALS AND METHODS In order to make possible a comparison of the present experiments with other recently completed experiments (Carter and Fairbairn, unpublished), white, male Sprague-Dawley rats (Holtzman strain) weighing about 150 g each were infected with 30 cysticercoids of H. diminuta injected into the stomach through a catheter. After ensuring that all cysticercoids had been delivered from the catheter, the rats were caged in pairs and maintained on a 12 hr light-12 hr dark daily photoperiod. Food (commercial pellets) was provided only during the dark half of the cycle, from 8:00 PM to 8:00 AM. Rats harboring parasites to be recovered on the 10th or 14th day after infection were maintained in this manner. When parasites were to be recovered after infection for 6 days the procedure was the same except that greater numbers of rats were infected, each with 300 to 500 cysticercoids, in order that sufficient weight of tissue would be available for

Formic acid as a silage additive

SummaryPure swards of cocksfoot and perennial ryegrass cut on three occasions and of lucerne cut on two occasions were ensiled in test-tube silos after three treatments: (i) unwilted without additive, (ii) unwilted after the addition of formic acid at 0-23 % of fresh weight, and (iii) wilted to a water content of about 70 %, with no additive. Replicate silos were opened at intervals up to 105 days in order to follow the course of fermentation.Silages from the final sampling could be divided into two clearly defined groups. Those where the lactic acid content, expressed as a percentage of total fermentation acids (L %T), was over 60 (19 silages) were considered stable while those with a value less than 20 (5 silages) were considered unstable.The addition of formic acid resulted in a reduction in pH of the ensiled material from 5–86 + 0–12 to 4–60 ±0–11. This value changed little during the first 6 days after ensiling but then fell as lactic and acetic acids were formed. Stable silages made from unwilted crops without additive contained more lactic acid than those made with formic acid, but the converse was true for unstable silages. The ammonia content of silages made from unwilted material was always lower when formic acid had been applied. Wilting before ensiling gave stable silages from all crops.