Natural populations of lactic acid bacteria associated with silage fermentation as determined by phenotype, 16S ribosomal RNA and recA gene analysis

One hundred and fifty-six strains isolated from corn (Zea mays L.), forage paddy rice (Oryza sativa L.), sorghum (Sorghum bicolor L.) and alfalfa (Medicago sativa L.) silages prepared on dairy farms were screened, of which 110 isolates were considered to be lactic acid bacteria (LAB) according to their Gram-positive and catalase-negative characteristics and, mainly, the lactic acid metabolic products. These isolates were divided into eight groups (A-H) based on the following properties: morphological and biochemical characteristics, γ-aminobutyric acid production capacity, and 16S rRNA gene sequences. They were identified as Weissella cibaria (36.4%), Weissella confusa (9.1%), Leuconostoc citreum (5.3%), Leuconostoc lactis (4.9%), Leuconostoc pseudomesenteroides (8.0%), Lactococcus lactis subsp. lactis (4.5%), Lactobacillus paraplantarum (4.5%) and Lactobacillus plantarum (27.3%). W. cibaria and W. confusa were mainly present in corn silages, and L. plantarum was dominant on sorghum and forage paddy rice silages, while L. pseudomesenteroides, L. plantarum and L. paraplantarum were the dominant species in alfalfa silage. The corn, sorghum and forage paddy rice silages were well preserved with lower pH values and ammonia-N concentrations, but had higher lactic acid content, while the alfalfa silage had relatively poor quality with higher pH values and ammonia-N concentrations, and lower lactic acid content. The present study confirmed the diversity of LAB species inhabiting silages. It showed that the differing natural populations of LAB on these silages might influence fermentation quality. These results will enable future research on the relationship between LAB species and silage fermentation quality, and will enhance the screening of appropriate inoculants aimed at improving such quality.     

The response of sheep to big bale grass silage ensiled with,or supplemented separately with,molassed sugar beet feed

Second cut big bale grass silage was prepared with grass ensiled alone or with added pelleted, molassed sugar beet feed (MSBF) at 32 or 64 g MSBF kg⁻¹ fresh weight of grass. Addition of MSBF at ensilage increased silage dry matter (DM), water soluble carbohydrate and lactic acid concentrations and decreased ammonia concentration. When fed to wether lambs, MSBF addition, whether at ensilage or given separately, variably improved DM intake, live-weight gain and feed conversion efficiency. Ruminal concentrations of ammonia were reduced and acetate molar proportion increased in diets supplemented with MSBF separately compared with the silage only control diet. Animal performance was generally improved by MSBF supplementation with responses to silages made with added MSBF comparable to those from silage supplemented with MSBF at feeding. There was little difference in animal performance between silages made with 32 or 64 g kg⁻¹ MSBF added at ensiling.     

Ensilage characteristics of three tropical grasses as influenced by stage of growth and addition of molasses

When molasses was added during ensilage of three tropical grasses [hamil grass (Panicum maximum cv. Hamil), pangola grass (Digitaria decumbens) and setaria (Setaria sphacelata cv. Kazungula)] the final pH, concentration of fermentation acids (except lactic acid) and NH₃–N content were all similar after 100 days of incubation. Pangola grass silage had significantly higher lactic acid content (66 g/kg dry matter) than the other two. Adding either 4 or 8% (w/w) molasses reduced NH₃–N, volatile fatty acid content and pH but increased lactic acid content in the final silages. Numbers of lactic acid bacteria remained approximately constant during the course of the fermentation, although large differences were noted in the species composition of the populations. At the time of ensiling, only Pediococcus spp. and Leuconostoc spp. were detected. By 5 days, the homo-fermentative population, notably Lactobacillus plantarum, dominated (43%) and remained dominant. Hetero-fermentative rods were only detected in the 100-day silage, where they represented 29% of the strains isolated. Homo-fermenters were more abundant in pangola (60%) and setaria (47%) silages than hamil (27%) silages. Homo-fermenter populations were lowest in the 12-week forage. Molasses additions increased homo-fermenter populations. Pangola grass gave the best quality silage but, since the water-soluble carbohydrate content in the grasses was insufficient to promote a strong lactic fermentation, the addition of 20 to 30 kg molasses/tonne should achieve satisfactory preservation.M. Tjandraatmadja and B.W. Norton are with the Department of Agriculture, The University of Queensland, Queensland, 4072, Australia; I.C. Mac Rae is with the Department of Microbiology, The University of Queensland, Queensland, 4072, Australia.     

Effects of Bacillus subtilis and its metabolites on corn silage quality

Cellulolytic micro-organisms are potent silage inoculants that decrease the fibrous content in silage and increase the fibre digestibility and nutritional value of silage. This study aimed to evaluate the effects of Bacillus subtilis CCMA 0087 and its enzyme β-glucosidase on the nutritional value and aerobic stability of corn silage after 30 and 60 days of storage. We compared the results among silage without inoculant (SC) and silages inoculated with B. subtilis 8 log₁₀ CFU per kg forage (SB8), 9 log₁₀ CFU per kg forage (SB9) and 9·84 log₁₀ CFU per kg forage + β-glucosidase enzyme (SBE). No differences were observed in the levels of dry matter, crude protein and neutral detergent fibre due to the different treatments or storage times of the silos. Notably, the population of spore-forming bacteria increased in the SB9-treated silage. At 60 days of ensiling, the largest populations of lactic acid bacteria were found in silages treated with SB8 and SBE. Yeast populations were low for all silages, irrespective of the different treatments, and the presence of filamentous fungi was observed only in the SBE-treated silage. Among all silage treatments, SB9 treatment resulted in the highest aerobic stability.     

Feed consumption and performance of dairy cows with alternate feedings of grass silage and maize silage

A feeding experiment was conducted with 10 dairy cows of the Fleckvieh breed and the cross Red Holstein Friesian × Fleckvieh, to study whether feeding with grass silage at the morning meal and maize silage at the evening meal (treatment B: alternating forage allocation) affects forage intake and milk production, in comparison with combined feeding with these two silages at each meal (treatment A). In order to prevent a selective forage consumption in treatment A, the two silages were given as a homogeneous mixture of nearly equal portions (51.6% maize silage, 48.4% grass silage) of dry matter (DM). The experiment was of switch-back design, with the treatment sequences ABA and BAB, and three experimental periods of 6 weeks.The daily forage consumption averaged 12.3 kg DM when the silages were given as a mixture and was significantly higher than the total forage consumption of 11.8 kg DM (P < 0.05) during the alternating allocation of the silages. In treatment B, daily intake of maize silage (7.10 kg DM) was greater than that of grass silage (4.70 kg DM/day). Furthermore, variation between cows in forage intake was significantly higher in this treatment than in treatment A. Average daily milk yield for treatment A was 18.75 kg with 3.84% fat and 3.70% protein, and 18.10 kg with 3.76% fat and 3.68% protein for treatment B. Production was significantly higher (P < 0.05), by 0.65 kg milk or 0.90 kg FCM, for treatment A.     

The effect of some pre-ensiling treatments on silage composition and nitrogen disappearance in the rumen

Ryegrass, harvested before ear emergence, was ensiled in triplicate in laboratory silos with and without pre-ensiling treatments. These were: 4.7 M sulphuric acid (39 and 79 g kg^?1 DM); formalin (28 and 58 g kg^?1 DM); ‘Add-F’ (22.5 M formic acid; 36 and 71 g kg^?1 DM); formalin (28 and 58 g kg^?1 DM); ‘Farmline’, a commercial additive containing acids and formalin (31 g kg^?1 DM); heat (30 and 60°C for 1 h); and Lactobacillus plantarum inoculum + glucose (4.6 g kg^?1 DM). The ensilage period was 120 days. Samples of each silage were incubated, in artificial fibre bags, in the rumens of four Hereford-cross steers fitted with permanent rumen cannulae. Total nitrogen (TN) disappearance was measured after incubation periods of 1, 2, 4, 7, 12 and 24 h.Hydrochloric acid and the heating pre-treatments had no significant effect (P > 0.05) on the pH, water-soluble carbohydrates and fermentation acid values compared with those of the control. Fermentation acid production was suppressed to an increasing extent by formalin (28 g kg^?1 DM), sulphuric acid (79 g kg^?1 DM), formic acid (36 g kg^?1 DM), formalin (58 g kg^?1 DM) and formic acid (71 g kg^?1 DM).The application of L. plantarum + glucose increased fermentation acids from 90.3 g kg^?1 DM in the control to 227 g kg^?1 DM, owing to a 10-fold increase in lactic acid content from 21.7 to 202 g kg^?1 DM.All treatments, with the exception of 30°C heating, produced silages with significantly (P < 0.001) more total nitrogen as protein than the control. This ranged from 334 g kg^?1 TN (60°C heating) to 748 g kg^?1 TN (formalin; 58 g kg^?1 DM).All treatments significantly (P < 0.05) reduced TN loss, compared with the control silage values, after a 7-h incubation period in the rumen. After 24 h, however, TN disappearance from the treated silages was not significantly different from that of the control with the exception of the two silages treated with formalin alone. With these silages, the proportion of TN disappearing was 55.0 and 40.0% for the low and high application rates, respectively, compared with a value of 74.0% for the control.     

Characterization and Identification of Pediococcus Species Isolated from Forage Crops and Their Application for Silage Preparation

Pediococcus species isolated from forage crops were characterized, and their application to silage preparation was studied. Most isolates were distributed on forage crops at low frequency. These isolates could be divided into three (A, B, and C) groups by their sugar fermentation patterns. Strains LA 3, LA 35, and LS 5 are representative isolates from groups A, B, and C, respectively. Strains LA 3 and LA 35 had intragroup DNA homology values above 93.6%, showing that they belong to the species Pediococcus acidilactici. Strain LS 5 belonged to Pediococcus pentosaceus on the basis of DNA-DNA relatedness. All three of these strains and strain SL 1 (Lactobacillus casei, isolated from a commercial inoculant) were used as additives to alfalfa and Italian ryegrass silage preparation at two temperatures (25 and 48°C). When stored at 25°C, all of the inoculated silages were well preserved and exhibited significantly (P < 0.05) reduced fermentation losses compared to that of their control in alfalfa and Italian ryegrass silages. When stored at 48°C, silages inoculated with strains LA 3 and LA 35 were also well preserved, with a significantly (P < 0.05) lower pH, butyric acid and ammonia-nitrogen content, gas production, and dry matter loss and significantly (P < 0.05) higher lactate content than the control, but silages inoculated with LS 5 and SL 1 were of poor quality. P. acidilactici LA 3 and LA 35 are considered suitable as potential silage inoculants.     

Fermentation patterns of forage sorghum ensiled under different environmental conditions

The effects of temperature, aerobic and anaerobic conditions in the silo and plant characteristics [water-soluble carbohydrate (WSC) contents, growing season] on the fermentation characteristics of a tropical forage species, Sorghum bicolor cv. sugar-drip, were investigated. Silages fermented in oxygen-impermeable bags were well preserved and had low pH (3.7), high lactic acid [72 g kg^–1 dry matter (DM) 80% of total acids], and low butyric acid (0.12 g kg^–1 DM) and ammonia nitrogen (NH₃–N) (57 g kg^–1 total nitrogen contents. Conversely, the use of oxygen-permeable bags as silos allowed aerobic decomposition of the ensiled forages. Increasing the incubation temperature lowered the population of lactic acid bacteria, reduced lactic acid production and caused the pH to rise. The heterofermentative Leuconostoc spp. predominated on fresh forages but homofermentative Lactobacillus plantarum began to dominate after 5 and 8 days of fermentation. Heterofermentative lactobacilli, notably Lactobacillus brevis, were dominant among the isolates obtained from 100-day silages. Varying the WSC contents, by crushing and/or chopping the forage, and growing season did not significantly affect the fermentation quality of the resulting silages. It was concluded that the maintenance of anaerobic conditions is essential if good quality silage is to be produced from tropical forage species.     

Viability of Cryptosporidium parvum during ensilage of perennial ryegrass

The survival of Cryptosporidium parvum during ensilage of perennial ryegrass was examined in laboratory silos with herbage prepared in one of three different ways; either untreated, inoculated with a strain of Lactobacillus plantarum or by direct acidification with formic acid. The pH values of all silages initially fell below 4.5, but only formic acid-treated silage remained stable at less than pH 4 after 106 d, with the pH of the untreated and inoculant-treated silages rising to above 6. The formic acid-treated silage had a high lactic acid concentration (109 g kg^-1 dry matter (DM)) and low concentrations of propionic and butyric acids after 106 d. However, the untreated and inoculant-treated silages showed an inverse relationship, with low lactic acid concentrations and high concentrations of acetic, propionic and butyric acids. These silages also contained ammonia-N concentrations in excess of 9 g kg^-1 DM. In terms of the viability of Cryptosporidium parvum oocysts very few differences were seen after 14 d of ensilage with ca 50% remaining viable, irrespective of treatment and total numbers had declined from the initial level of 5.9 × 10⁴ to 1 x 10⁴ g^-1 fresh matter. Total oocyst numbers remained approximately the same until the end of the ensiling period, with the percentage of viable oocysts declining to 46, 41 and 32% respectively for formic acid, inoculant and untreated silages. The results are discussed in terms of changes occurring during the silage fermentation, in particular the products which may influence the survival of Cryptosporidium and implications for agricultural practice and the health of silage fed livestock.     

Fate of Escherichia coli O26 in corn silage experimentally contaminated at ensiling, at silo opening, or after aerobic exposure, and protective effect of various bacterial inoculants

Shiga toxin-producing Escherichia coli (STEC) strains are responsible for human illness. Ruminants are recognized as a major reservoir of STEC, and animal feeds, such as silages, have been pointed out as a possible vehicle for the spread of STEC. The present study aimed to monitor the fate of pathogenic E. coli O26 strains in corn material experimentally inoculated (10⁵ CFU/g) during ensiling, just after silo opening, and after several days of aerobic exposure. The addition of 3 bacterial inoculants, Propionibacterium sp., Lactobacillus buchneri, and Leuconostoc mesenteroides (10⁶ CFU/g), was evaluated for their abilities to control these pathogens. The results showed that E. coli O26 could not survive in corn silage 5 days postensiling, and the 3 inoculants tested did not modify the fate of pathogen survival during ensiling. In the case of direct contamination at silo opening, E. coli O26 could be totally eradicated from corn silage previously inoculated with Leuconostoc mesenteroides. The combination of proper ensiling techniques and the utilization of selected bacterial inoculants appears to represent a good strategy to guarantee nutritional qualities of cattle feed while at the same time limiting the entry of pathogenic E. coli into the epidemiological cycle to improve the microbial safety of the food chain.     

Gnotobiotic Silage

Selected strains of lactic acid bacteria isolated from grass silage were found to flourish when inoculated into irradiation-sterilized forage under gnotobiotic conditions. The acid content and pH of these silages resembled naturally fermented silage. Inoculation of gnotobiotic silage with Clostridium sporogenes and C. tyrobutyricum failed to cause any noticeable deterioration of silage quality.     

Inhibition of Listeria monocytogenes by defined lactic microflora in gnotobiotic silages of lucerne,fescue, ryegrass and maize — Influence of dry matter and temperature

The development of L. monocytogenes was studied in gnotobiotic silages of four plant species (ryegrass, fescue, lucerne, maize) with various dry matter concentrations and incubation temperatures. The microflora of these silages was perfectly defined and included Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus casei, Pediococcus spp., Enterobacter liquefaciens and Clostridium tyrobutyricum. The results show that in silages of good quality not only is there no development of L. monocytogenes, but the cells initially present are eliminated. It is therefore most unlikely that a silage of good quality with a pH lower than 5 plays a contaminating role. The hypothesis according to which silages, especially those of bad quality, contain factors favouring contamination seems to be more plausible.     

Effect of NaCl-tolerant lactic acid bacteria and NaCl on the fermentation characteristics and aerobic stability of silage

NaCl-tolerant lactic acid bacteria (LAB) strains LC-10 ( Lactobacillus casei ) and LP-15 ( Lact. plantarum ) and NaCl were used as additives to sorghun ( Sorghum bicolor ). Numbers of LAB were significantly ( P < 0·05) higher in all the additive-treated silages than in the control silage at an early stage of ensiling. During the fermentation process, addition of NaCl or LAB effectively inhibited the growth of aerobic bacteria and clostridia, but not yeasts. All the additive-treated silages had significantly ( P < 0·05) lower pH, ammonia nitrogen content, dry matter loss and gas production but significantly ( P < 0·05) higher lactic acid content and residual water soluble carbohydrates compared with the control silage. The improvement in silage quality was in the order : LAB > NaCl > control. Yeast counts were high in all additive-based silages and they increased during the exposure of the silages to air. As a result, these silages suffered aerobic deterioration, whereas the control silage was stable. The results confirmed that the NaCl or LAB improved fermentation quality but did not prevent aerobic deterioration of the silage.     

Effects of silage from maize crops differing in maturity at harvest,grass silage feed value and concentrate feed level on performance of finishing lambs

The effects of (i) medium and high feed value (MFV and HFV) maize silages and (ii) MFV and HFV grass silages, each in combination with a range of concentrate feed levels, on the performance of finishing lambs were evaluated using 280 Suffolk-X lambs (initial live weight 36.1 kg). The MFV and HFV maize silages represented crops with dry matter (DM) concentrations of 185 and 250 g/kg, respectively, at harvest, and had starch and metabolisable energy (ME) concentrations of 33 and 277 g/kg DM and 9.6 and 11.0 MJ/kg, respectively. HFV and MFV grass silages had DM and ME concentrations of 216 and 294 g/kg and 11.0 and 11.5 MJ/kg DM, respectively. A total of 13 treatments were involved. The four silages were offered ad libitum with daily concentrate supplements of 0.2, 0.5 or 0.8 kg per lamb. A final treatment consisted of concentrate offered ad libitum with 0.5 kg of the HFV grass silage daily. Increasing the feed value of grass silage increased (P < 0.001) forage intake, daily carcass and live weight gains, final live weight and carcass weight. Increasing maize silage feed value tended to increase (P = 0.07) daily carcass gain. Increasing concentrate feed level increased total food and ME intakes, and live weight and carcass gains. There was a significant interaction between silage feed value and the response to concentrate feed level. Relative to the HFV grass silage, the positive linear response to increasing concentrate feed level was greater with lambs offered the MFV grass silage for daily live weight gain (P < 0.001), daily carcass gain (P < 0.01) and final carcass weight (P < 0.01). Relative to the HFV maize silage, there was a greater response to increasing concentrate feed level from lambs offered the MFV maize silage in terms of daily carcass gain (P < 0.05) and daily live weight gain (P = 0.06). Forage type had no significant effect on the response to increased concentrate feed level. Relative to the MFV grass silage supplemented with 0.2 kg concentrate, the potential concentrate-sparing effect of the HFV grass silage, and the MFV and HFV maize silages was 0.41, 0.09 and 0.25 kg daily per lamb, respectively. It is concluded that increasing forage feed value increased forage intake and animal performance, and maize silage can replace MFV grass silage in the diet of finishing lambs as performance was equal to or better (depending on maturity of maize at harvest) than that for MFV grass silage.     

The effect of temperature and Lactobacillus amylovorus and Lact. plantarum, applied at ensiling, on wheat silage

The effects of applying Lactobacillus plantarum and Lact. amylovorus at ensiling on wheat silage stored at 25 and41 °C was studied under laboratory conditions. The inoculants were applied at 10⁶ cfu g⁻¹.Silages with no additives served as controls. Three jars per treatment were sampled on days 2, 8 and 60 after ensiling, for chemical and microbiological analyses. After the ensiling period, the silages were subjected to an aerobic stability test. The control and Lact. plantarum inoculated wheat fermented faster at 25 than at 41 °C, whereas silages inoculated with Lact. amylovorus fermented faster at 41 °C. This was apparent from the rate of pH decrease and from the contents of residual sugars and lactic acid in the final silages. The numbers of lactobacilli in the control and Lact. plantarum silages at 41 °C after 2 and 8 days of ensiling were lower than in the corresponding silages at 25 °C. For the Lact. amylovorus silage the opposite held true. The control silages at both temperatures and the Lact. plantarum silage at 41 °C were the most stable silages under aerobic exposure.     

Bacterial and fungal communities of wilted Italian ryegrass silage inoculated with and without Lactobacillus rhamnosus or Lactobacillus buchneri

Aims: To understand the effects of lactic acid bacteria (LAB) inoculation on fermentation products, aerobic stability and microbial communities of silage. Methods and Results: Wilted Italian ryegrass was stored in laboratory silos with and without inoculation of Lactobacillus rhamnosus and Lactobacillus buchneri. The silos were opened after 14, 56 and 120 days and then subjected to aerobic deterioration for 7 days. Intensive alcoholic fermentation was found in untreated silage; the sum of ethanol and 2,3‐butanediol content at day 14 was about 7 times higher than that of lactic and volatile fatty acids. Alcoholic fermentation was suppressed by L. rhamnosus and L. buchneri inoculation and lactic acid and acetic acid became the dominant fermentation products, respectively. Silages were deteriorated in untreated and L. rhamnosus‐inoculated silages, whereas no spoilage was found in L. buchneri‐inoculated silage. Enterobacteria such as Erwinia persicina, Pantoea agglomerans and Rahnella aquatilis were detected in untreated silage, whereas some of these bacteria disappeared or became faint with L. rhamnosus treatment. When silage was deteriorated, Lactobacillus brevis and Bacillus pumilus were observed in untreated and L. rhamnosus‐inoculated communities, respectively. The inoculated LAB species was detectable in addition to untreated bacterial communities. Saccharomyces cerevisiae and Pichia anomala were the main fungi in untreated and L. rhamnosus‐inoculated silages; however, P. anomala was not visibly seen in L. buchneri‐inoculated silage either at silo opening or after exposure to air. Conclusion: Inoculation with L. rhamnosus can suppress alcoholic fermentation of wilted grass silage with elimination of enterobacteria at the beginning of fermentation. Addition of L. buchneri may improve aerobic stability, with distinct inhibitory effect observed on P. anomala after silo opening. Significance and Impact of the Study: Bacterial and fungal community analyses help us to understand how inoculated LAB can function to improve the fermentation and aerobic stability of silage.     

The effects of using lactic acid bacteria inoculants in maize silage on the formation of biogenic amines

Silages from five ripened varieties of silage maize with dry matter contents ranging between 275 and 410 g/kg were prepared in five laboratory experiments. Whole-plant maize was fermented at 22°C and silages were then stored at the same temperature for 4 months. Spontaneously fermented silages were prepared as control variants and compared with silages inoculated with commercial strains of Lactobacillus plantarum, Lactobacillus buchneri and a mixed preparation Microsil containing L. plantarum, Lactobacillus casei, Enterococcus faecium and Pediococcus pentosaceus. The starter cultures were applied at doses 5·10⁵ and 5·10⁶ CFU/g of chopped maize. Seven biogenic amines and polyamines were extracted from silages with perchloric acid and determined as N-benzamides by micellar electrokinetic capillary chromatography. Common chemical criteria of silage quality were also determined. All three inoculants, mainly at the higher dose, decreased significantly contents of tyramine, putrescine and cadaverine, three undesirable amines occurring at the highest levels. L. plantarum was the most effective. Contents of histamine and tryptamine were low in all experimental silages. Also relatively low were levels of polyamines spermidine and mainly of spermine.     

Effects of replacing grass silage with maize silages differing in inclusion level and maturity on the performance,meat quality and concentrate-sparing effect of beef cattle

The effects of maturity of maize at harvest, level of inclusion and potential interactions on the performance, carcass composition, meat quality and potential concentrate-sparing effect when offered to finishing beef cattle were studied. Two maize silages were ensiled that had dry matter (DM) concentrations of 217 and 304 g/kg and starch concentrations of 55 and 258 g/kg DM, respectively. Grass silage was offered as the sole forage supplemented with either 4 or 8 kg concentrate/steer daily or in addition with one of the two maize silages at a ratio 0.5 : 0.5, on a DM basis, maize silage : grass silage supplemented with 4 kg concentrate daily. The two maize silages were also offered as the sole forage supplemented with 4 kg concentrate/steer daily. The forages were offered ad libitum. The six diets were offered to 72 steers (initial live weight 522 s.d. 23.5 kg) for 146 days. There were significant interactions (P < 0.05) between maize maturity and inclusion level for food intake, fibre digestibility and daily gain. For the grass silage supplemented with 4 or 8 kg concentrate, and the maize silages with DM concentrations of 217 and 304 g/kg offered as 0.5 or 1.0 of the forage component of the diet, total DM intakes were 8.3, 9.8, 8.9, 8.2, 9.2 and 9.8 kg DM/day (s.e. 0.27); live-weight gains were 0.74, 1.17, 0.86, 0.71, 0.88 and 1.03 kg/day (s.e. 0.057); and carcass gains were 0.48, 0.73, 0.56, 0.46, 0.56 and 0.63 kg/day (s.e. 0.037), respectively. Increasing the level of concentrate (offered with grass silage), maize maturity and level of maize inclusion reduced (P < 0.05) fat b* (yellowness). The potential daily concentrate-sparing effect, as determined by carcass gain, for the maize silages with DM concentrations of 217 and 304 g/kg offered as 0.5 and 1.0 of the forage component of the diet were 1.3, −0.3, 1.3 and 2.4 kg fresh weight, respectively. It is concluded that the response, in animal performance, including maize silage is dependent on the stage of maturity and level of inclusion in the diet. Maize silage with a DM of 304 g/kg offered ad libitum increased carcass gain by 31%, because of a combination of increased metabolizable energy (ME) intake and improved efficiency of utilization of ME, and produced carcasses with whiter fat.     

Fermentative profile and lactic acid bacterial dynamics in non-wilted and wilted alfalfa silage in tropical conditions

This study was conducted to evaluate the fermentative profile and microbial populations of wilted and non-wilted alfalfa silages ensiled with or without inoculant and the population dynamics of lactic acid bacteria (LAB) of wilted alfalfa plant and theirs silage. A 2?×?2?×?6 factorial arrangement was used, with the absence or presence of wilting (W), with and without bacterial inoculant (I) and six fermentation periods (P) (1, 3, 7, 14, 28 and 56 days), in a completely randomized design, with three replicates. The alfalfa was slightly wilted for 6 h and increased the dry matter content from 133.9 to 233.4 g/kg. It was performed the cultivation, followed by the isolation of LAB from samples of alfalfa forage before ensiling and its silage only in non-inoculated silages, after different fermentation periods. DNA was extracted from the isolated strains of LAB; the 16S rRNA gene sequences were amplified by PCR and the sequences were compared to those available from the GenBank database. Wilting provided silages with lower pH, ammonia nitrogen and acetic acid concentrations. The wilting process did not alter the amount of LAB; however, it affected the LAB diversity of the silages. The Lactobacillus plantarum was the predominant species in non-wilted and wilted silages.

     

Effects of lactic acid bacteria in inoculants on changes in amino acid composition during ensilage of sterile and non-sterile ryegrass

A study was carried out on the changes occurring in the amino acid fraction of a hybrid ryegrass during ensilage in laboratory-scale silos to help to establish the relative roles of plant and microbial proteases on protein degradation in the silo. Herbage treatments included (i) normal grass without treatment (ii) lambda-irradiated grass (sterile) without treatment (iii) sterile, inoculated with a strain of Lactobacillus plantarum and (iv) sterile, inoculated with a strain of Lactobacillus paracasei subsp. paracasei. These treatments had a significant effect on silage amino acid profiles. Concentrations of free amino acids and the extent of amino acid catabolism varied with treatment. However, levels were notably higher in control silages after 90 days (free amino acid nitrogen constituting 54% of total amino acid nitrogen compared with 37, 32 and 22% for treatments i, ii and iv, respectively). These results indicate that the extent of protein hydrolysis during ensilage is influenced by factors other than rate of pH decline and plant protease activity, and that microbial proteases play a role.