Ensiled Grass Research Articles

Effects of plant species, stage of maturity, and level of formic acid addition on lipolysis, lipid content, and fatty acid composition during ensiling.

Forage type and management influences the nutritional quality and fatty acid composition of ruminant milk. Replacing grass silage with red clover (RC; L.) silage increases milk fat 18:3-3 concentration. Red clover has a higher polyphenol oxidase (PPO) activity compared with grasses, which has been suggested to decrease lipolysis and . The present study characterized the abundance and fatty acid composition of esterified lipid and NEFA before and after ensiling of grass and RC to investigate the influence of forage species, growth stage, and extent of fermentation on lipolysis. A randomized block design with a 2 × 3 × 4 factorial arrangement of treatments was used. Treatments comprised RC or a mixture of timothy ( L.) and meadow fescue ( Huds.) harvested at 3 growth stages and treated with 4 levels of formic acid (0, 2, 4, and 6 L/t). Lipid in silages treated with 0 or 6 L/t formic acid were extracted and separated into 4 fractions by TLC. Total PPO activity in fresh herbage and the content of soluble bound phenols in all silages were determined. Concentrations of 18:3-3 and total fatty acids (TFA) were higher ( < 0.001) for RC than for grass. For both forage species, 18:3-3 and TFA content decreased linearly ( < 0.001) with advancing growth stage, with the highest abundance at the vegetative stage. Most of lipid in fresh RC and grass herbage (97%) was esterified, whereas NEFA accounted for 71% of TFA in both silages. Ensiling resulted in marginal increases in TFA content and the amounts of individual fatty acids compared with fresh herbages. Herbage total PPO activity was higher ( < 0.001) for RC than grass (11 vs. 0.11 μkatal/g leaf fresh weight). Net lipolysis during ensiling was extensive for both forage species (660 to 759 g/kg fatty acid for grass and 563 to 737 g/kg fatty acid for RC). Formic acid application (0 vs. 6 L/t) resulted in a marked decrease ( = 0.026) in net lipolysis during the ensiling of RC, whereas the opposite was true ( = 0.026) for grass. In conclusion, results suggest that formic acid addition during the ensilage of RC decreases lipolysis . For both plant species, total PPO activity was not associated with the extent of lipolysis . However, bound phenols formed via PPO activity appear to have a role in protecting lipid and protein against degradation in grass and lowering proteolysis of RC during ensiling.

Use of a mannitol rich ensiled grass press juice (EGPJ) as a sole carbon source for polyhydroxyalkanoates (PHAs) production through high cell density cultivation

This study demonstrates the use of a mannitol rich ensiled grass press juice (EGPJ) as a renewable carbon substrate for polyhydroxyalkanoates (PHA) production in shaking flask experiments and fed-batch stirred tank reactor cultivations. Fed-batch cultivations of Burkholderia sacchari IPT101 using EGPJ as sole carbon source produced 44.5g/L CDW containing 33% polyhydroxybutyrate (PHB) in 36h, while Pseudomonas chlororaphis IMD555 produced a CDW of 37g/L containing 10% of medium chain length polyhydroxyalkanoates (mcl-PHA) in 34h. PHB and mcl-PHA extracted from B. sacchari IPT101 and P. chlororaphis IMD555, grown on EGPJ, had a molecular weight of 548kg/mol and 115.4kg/mol, respectively. While mcl-PHA can be produced from EGPJ, PHB production is more interesting as there is a 4-fold higher volumetric productivity compared to mcl-PHA.

Ensiling and hydrothermal pretreatment of grass: consequences for enzymatic biomass conversion and total monosaccharide yields

BackgroundEnsiling may act as a pretreatment of fresh grass biomass and increase the enzymatic conversion of structural carbohydrates to fermentable sugars. However, ensiling does not provide sufficient severity to be a standalone pretreatment method. Here, ensiling of grass is combined with hydrothermal treatment (HTT) with the aim of improving the enzymatic biomass convertibility and decrease the required temperature of the HTT.ResultsGrass silage (Festulolium Hykor) was hydrothermally treated at temperatures of 170, 180, and 190°C for 10 minutes. Relative to HTT treated dry grass, ensiling increased the solubilization of dry matter (DM) during HTT and gave increased glucan content, but lower lignin in the insoluble fiber fraction. Ensiling improved glucose yields in the enzymatic hydrolysis of the washed solid fiber fraction at the lower HTT temperatures. At 170°C glucose yield improved from 17 to 24 (w/w)% (45 to 57% cellulose convertibility), and at 180°C glucose yield improved from 22 to 29 (w/w)% (54 to 69% cellulose convertibility). Direct HTT of grass at 190°C gave the same high glucose yield as for grass silage (35 (w/w)% (77% cellulose convertibility)) and improved xylan yields (27% xylan convertibility). The effect of ensiling of grass prior to HTT improved the enzymatic conversion of cellulose for HTT at 170 and 180°C, but the increased glucose release did not make up for the loss of water soluble carbohydrates (WSC) during ensiling. Overall, sugar yields (C6 + C5) were similar for HTT of grass and grass silage at both 170 and 180°C, but at 190°C the overall sugar yield was better for HTT of dry grass.ConclusionsThis study unequivocally establishes that ensiling of grass as a biomass pretreatment method comes with a loss of WSC. The loss of WSC by ensiling is not necessarily compensated for by providing a lower temperature requirement for HTT for high enzymatic monosaccharide release. However, ensiling can be an advantageous storage method prior to grass processing.

Effect of graded levels of saccharum officinarum as an additive to Panicum maximum (JACQ) silage.

An experiment was conducted to evaluate the effect of graded levels of sugar cane (Saccharum officinarum) as an additive to Guinea grass (Panicum maximum) silage. A previously established guinea grass plot, totaling an area of 625m2 was cut back and fertilized with urea at the rate of 200 kgN/ha. The pasture was then harvested at 6-weeks regrowth, chopped (5-10cm long), mixed with chopped sugar cane (1-3cm long) and ensiled in stack silos. Four treatments were formulated as follows: Treatment A = 10%w/w Sugar cane with Panicum maximum; Treatment B = 20%w/w sugar cane with Panicum maximum; Treatment C = 30%w/w sugar cane with Panicum maximum; Treatment D = Panicum maximum without additive; with the fresh Panicum maximum serving as Control. The yield values of 6,169 and 4,850 Kg DM/ha was observed for the fresh and ensiled P. maximum, respectively. The pH values of the ensiled forage were significantly (P&lt; 0.05) highest in Treatment D (5.72) and least in Treatment C (4.20), while Treatments A and B were similar. Results showed significant (P&lt;0.05) reduction in the pH value of the ensiled grass as the content of sugar cane increased. Total cell wall (NDF) contents were similar and significantly reduced in ensiled guinea grass. Crude protein (CP) level was highest (P&lt;0.05) in 30% sugarcane additive silage (Treatment C) but similar in Treatments A, B, D and Control. The Crude fibre (CF) content was highest (P&lt;0.05) in the 10% sugarcane additive silage and lowest (P&lt;0.05) in the fresh un-ensiled guinea grass forage. Nitrogen Detergent Fibre (NDF) of the Control was higher (P&lt;0.05) than the ensiled grass across the treatments, while Acid Detergent Fibre (ADF) values of the ensiled grass increased significantly (P&lt;0.05) with increasing sugarcane inclusion with highest (P&lt;0.05) value recorded for the 30% sugarcane additive silage (Treatment C). It can, therefore, be concluded from this study that sugarcane can serve as an additive in ensiling guinea grass up to the rate of 30% w/w.

Medium chain length polyhydroxyalkanoate (mcl-PHA) production from volatile fatty acids derived from the anaerobic digestion of grass

A two step biological process for the conversion of grass biomass to the biodegradable polymer medium chain length polyhydroxyalkanoate (mcl-PHA) was achieved through the use of anaerobic and aerobic microbial processes. Anaerobic digestion (mixed culture) of ensiled grass was achieved with a recirculated leach bed bioreactor resulting in the production of a leachate, containing 15.3 g/l of volatile fatty acids (VFAs) ranging from acetic to valeric acid with butyric acid predominating (12.8 g/l). The VFA mixture was concentrated to 732.5 g/l with a 93.3 % yield of butyric acid (643.9 g/l). Three individual Pseudomonas putida strains, KT2440, CA-3 and GO16 (single pure cultures), differed in their ability to grow and accumulate PHA from VFAs. P. putida CA-3 achieved the highest biomass and PHA on average with individual fatty acids, exhibited the greatest tolerance to higher concentrations of butyric acid (up to 40 mM) compared to the other strains and exhibited a maximum growth rate (μMAX = 0.45 h⁻¹). Based on these observations P. putida CA-3 was chosen as the test strain with the concentrated VFA mixture derived from the AD leachate. P. putida CA-3 achieved 1.56 g of biomass/l and accumulated 39 % of the cell dry weight as PHA (nitrogen limitation) in shake flasks. The PHA was composed predominantly of 3-hydroxydecanoic acid (>65 mol%).

Effect of maturity at harvest on in vitro methane production from ensiled grass

Controlling the time of harvest to affect grass maturity for silage was evaluated as a methane (CH4) mitigation strategy in a batch culture in vitro with ruminal fluid as inoculum and silage from a mixed timothy (Phleum pretense)-meadow fescue (Festuca pratensis) stand. The stand was cut in May (early maturity [EM]; first cutting), June (late maturity [LM]; first cutting), and August (mid-maturity [MM]; third cutting). Disappearance of neutral detergent fiber (NDF) (EM: 0.58; MM: 0.50; LM: 0.45) and ADF (EM: 0.57; MM: 0.49; LM: 0.45) after 48 h was greater for EM compared to MM and LM, with no difference between the latter two. With advancing maturity, total gas (EM: 166.6; MM: 149.7; LM: 119.3 mL), CH4 production (EM: 21.4; MM: 17.6; LM: 14.8 mL), and methane production per g NDF digested decreased at 48 h (EM: 120; MM: 92; LM: 74 mL/g NDF digested). Ensiling less mature grass resulted in more CH4 per unit of NDF digested.

Use of Avoidance Tests for Investigating Potential of the Earthworm Eisenia fetida to Improve Composting of Grass Clippings

The earthworm Eisenia fetida is the most commonly used worm for worm-supported composting of organic residues. Within the present study, the potential of E. fetida for decomposing grass clippings, an organic waste which usually causes anoxic conditions and thus insufficient degradation in the course of common composting, was investigated. To enable a thorough investigation, the substrate-related requirements of E. fetida were studied using so-called avoidance tests. These tests provide a sensitive method for evaluating the preferences and aversions of soil animals related to substrate ingredients in a sublethal range. E. fetida favored relatively moist soil with about 70% of the WHCmax and the most preferred concentration of fresh grass clippings within soil was 15% (v/v). Pretreatments of the grass clippings like silage, precomposting or inoculation with the fungi Trichoderma viride and Geotrichum klebahnii were investigated and point to an increased tolerance of the worms against pre-composted and inoculated grass whereas ensiled grass and remoistened hay was avoided. The optimum concentration of ammonium for E. fetida was 18 μg NH4+-N g−1 DW soil although the worms could withstand much higher concentrations. Lactic and acetic acid, intermediates that are quickly released from fresh lawn clippings under oxygen lacking conditions, were indicated to be the most important factors for preventing worms from tolerating higher concentrations of grass clippings.

Agrochemical value of the liquid phase of wastes from fermentem during biogas production

We tested the procedure of combined phytomass utilization Integrated Generation of Solid Fuel and Biogas from Biomass (IFBB) proposed for ensiled grass matter from the aspect of suitability of its use for a typical substrate of new Czech biogas stations, a mixture of cattle slurry, maize silage and grass haylage. The agrochemical value of the liquid phase from a biofermenter was also evaluated. We concluded that this procedure is suitable for the tested substrate and improves the agrochemical value of a fugate from biogas production. By chlorine transfer to the liquid phase, it enables to use the solid phase as a material for production of solid biofuels with a reduced threat of the generation of polychlorinated dioxins and dibenzofurans during combustion. However, the concentration of mineral nutrients in the liquid phase during IFBB procedure is extremely low after anaerobic digestion as a result of dilution with water, and so its volume value is negligible.

Simulating the effects of grassland management and grass ensiling on methane emission from lactating cows

SUMMARYA dynamic, mechanistic model of enteric fermentation was used to investigate the effect of type and quality of grass forage, dry matter intake (DMI) and proportion of concentrates in dietary dry matter (DM) on variation in methane (CH4) emission from enteric fermentation in dairy cows. The model represents substrate degradation and microbial fermentation processes in rumen and hindgut and, in particular, the effects of type of substrate fermented and of pH on the production of individual volatile fatty acids and CH4as end-products of fermentation. Effects of type and quality of fresh and ensiled grass were evaluated by distinguishing two N fertilization rates of grassland and two stages of grass maturity. Simulation results indicated a strong impact of the amount and type of grass consumed on CH4emission, with a maximum difference (across all forage types and all levels of DMI) of 49 and 77% in g CH4/kg fat and protein corrected milk (FCM) for diets with a proportion of concentrates in dietary DM of 0·1 and 0·4, respectively (values ranging from 10·2 to 19·5 g CH4/kg FCM). The lowest emission was established for early cut, high fertilized grass silage (GS) and high fertilized grass herbage (GH). The highest emission was found for late cut, low-fertilized GS. The N fertilization rate had the largest impact, followed by stage of grass maturity at harvesting and by the distinction between GH and GS. Emission expressed in g CH4/kg FCM declined on average 14% with an increase of DMI from 14 to 18 kg/day for grass forage diets with a proportion of concentrates of 0·1, and on average 29% with an increase of DMI from 14 to 23 kg/day for diets with a proportion of concentrates of 0·4. Simulation results indicated that a high proportion of concentrates in dietary DM may lead to a further reduction of CH4emission per kg FCM mainly as a result of a higher DMI and milk yield, in comparison to low concentrate diets. Simulation results were evaluated against independent data obtained at three different laboratories in indirect calorimetry trials with cows consuming GH mainly. The model predicted the average of observed values reasonably, but systematic deviations remained between individual laboratories and root mean squared prediction error was a proportion of 0·12 of the observed mean. Both observed and predicted emission expressed in g CH4/kg DM intake decreased upon an increase in dietary N:organic matter (OM) ratio. The model reproduced reasonably well the variation in measured CH4emission in cattle sheds on Dutch dairy farms and indicated that on average a fraction of 0·28 of the total emissions must have originated from manure under these circumstances.

Nutritional regulation of milk fatty acid composition

There is increasing evidence that nutrition plays an important role in the development of chronic diseases in the human population including cancer, cardiovascular disease, insulin resistance and obesity. Developing foods that enhance human health is central to dietary approaches for preventing and reducing the economic and social impact of chronic disease. Numerous studies in human subjects have implicated a high consumption of medium-chain (12:0-16:0) saturated fatty acids (SFA) and trans fatty acids (TFA) as risk factors for cardiovascular disease risk, with emerging evidence of a possible role in the development of insulin resistance and inflammation. Milk and dairy products are a major source of 12:0, 14:0, 16:0 and TFA in the human diet. However, developing public health policies promoting a decrease in milk, cheese and butter consumption ignores the value of these foods as a versatile source of nutrients and bioactive lipids, including 4:0, branch-chain fatty acids, cis-9, trans-11 conjugated linoleic acid (CLA), vitamins A and D, β-carotene and sphingomyelin. Therefore, altering milk fatty acid composition through sustainable, environmental and welfare acceptable means is an integral component of an overall strategy for preventing human chronic disease. Nutrition is the major environmental factor regulating milk fat composition. Strategies for enhancing the nutritional value of milk fat have been directed towards reducing the proportion of 12:0, 14:0 and 16:0, increasing cis monounsaturated fatty acids (MUFA) and polyunsaturated fatty acid (PUFA) content and/or enhancing the concentration of bioactive lipids. Formulation of diets to alter milk fat composition to meet these targets typically involves 1) inclusion of plant oils and oilseeds, 2) supplements of marine lipids, 3) increasing the proportion of dietary energy derived from fresh grass, 4) replacing ensiled grass, maize or whole-crop cereal with forage legumes or 5) inclusion of rumen-protected lipids in the diet. Nutritional strategies for reducing 12:0, 14:0 and 16:0 and enhancing cis-MUFA in milk fat are dependent on increasing the supply of C18 or longer-chain fatty acids to inhibit mammary de novo fatty acid synthesis. Due to incomplete metabolism of dietary unsaturated fatty acids in the rumen, inclusion of oils or oilseeds in the diet also increases milk fat TFA content. Both the concentration and distribution of TFA isomers in milk is dependent on the amount and type of lipid supplement fed, composition of the basal diet and interactions between these factors. Altering the diet of lactating cows can be used as a means to significantly enrich milk fat cis-9, trans-11 CLA content. Increases in the concentration of CLA in milk are reliant, in the most part, on enhancing ruminal trans-11 18:1 outflow for endogenous cis-9, trans-11 CLA synthesis in the mammary gland. The potential to increase n-3 fatty acids in milk is relatively limited. Inclusion of fresh or ensiled red clover in the ruminant diet significantly increases 18:3 n-3 content, while increases in milk 20:5 n-3 and 22:6 n-3 concentrations to marine lipid supplements is relatively limited due to extensive ruminal metabolism of n-3 PUFA. Greater enrichment of 20:5 n-3, 22:5 n-3 and 22:6 n-3 in milk can be achieved using rumen-protected fish oil supplements. Overall, recent research has highlighted the important role of nutrition in attempts to modify milk fat composition for improved long-term human health.

The relative impacts of wilting, chopping, compaction and air infiltration on the conservation characteristics of ensiled grass

SummaryThe chemical composition of baled silage frequently differs from that of comparable conventional silage. The extents of wilting, chopping, compaction and air infiltration potentially contribute to these differences in conservation characteristics. An experiment was organized in a 3 (0, 24 or 48‐h wilting to influence herbage dry‐matter content) × 2 (unchopped or chopped) × 2 (with or without compaction) × 2 (with or without air infiltration) factorial arrangement of treatments, to elucidate the relative effects of these factors on the conservation characteristics of ensiled grass. Dry‐matter content of herbage and infiltration of air had a greater effect on silage conservation characteristics than chopping and compaction. The main interactions were between wilting and air infiltration, wilting and compaction, and compaction and air infiltration. Air infiltration stimulated a secondary fermentation in the unwilted herbage, reflected in a large increase (P &lt; 0·001) in clostridial activity. As wilting progressed, air infiltration facilitated yeast respiration of water‐soluble carbohydrates (WSC) and resulted in an increase (P &lt; 0·001) in in‐silo fresh‐weight losses. Compaction reduced (P &lt; 0·05) silage pore space and, as a result, the extent to which air could penetrate the silage mass. Compaction of the wilted herbage restricted respiration and was reflected in increased (P &lt; 0·05) concentrations of WSC and in a reduction (P &lt; 0·001) in fresh‐weight loss. The rapid achievement and maintenance of adequately anaerobic conditions is the primary requirement for baled silage. This study showed that failure to achieve this will lead to progressively greater losses, especially with drier herbage.

Change in Nitrogen Fractions and Ruminal Nitrogen Degradability of Orchardgrass Ensiled at Various Moisture Contents and the Subsequent Effects on Nitrogen Utilization by Sheep

The effect of various moisture contents of fresh forage on the change in nitrogen (N) fractions, in vitro ruminal N degradability, and the subsequent N utilization of silage in sheep were evaluated. Orchardgrass (Dactylis glomerata L.) with high (HM, 76%), medium (MM, 65%) and low (LM, 40%) moisture contents were ensiled into silos of 120 L capacity for 120 days. A nitrogen balance trial was conducted using a 4×4 Latin square design consisting of four dietary treatments (i.e. fresh forage, HM, MM and LM silages) and four wethers. With respect to N fractions, fraction 1 (buffer solution soluble N), fraction 2 (buffer solution insoluble N- neutral detergent insoluble N), fraction 3 (neutral detergent insoluble N-acid detergent insoluble N), and fraction 4 (acid detergent insoluble N) were determined. The proportion of fraction 1 in silages tended to decrease, while the in vitro ruminal degradability of insoluble N increased (p<0.05) with lower moisture contents at ensiling. Consequently, nitrogen utilization in sheep tended to improve as the moisture content of ensiled grass was decreased, with a negative correlation (p<0.01) between urinary N and the in vitro ruminal degradability of insoluble N. The averaged N retentions for HM, MM, and LM silage treatments were 59, 73 and 79% of that for fresh forage, respectively. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 9 : 1267-1272)

Effects of changes to the stable environment on the exhalation of ethane, carbon monoxide and hydrogen peroxide by horses with respiratory inflammation

The aim of this study was to assess the effects of changes to the stable environment on exhaled markers of respiratory inflammation in six horses with clinical histories of recurrent...

Potential risks when spreading anaerobic digestion residues on grass silage crops – survival of bacteria, moulds and viruses

AbstractThe survival of pathogenic and spoilage micro‐organisms in soil and on grass fertilized with spiked anaerobic digestion residue (ADR) was investigated in a climate chamber during periods of up to 56 d. In addition, the survival of these organisms over time was investigated during ensiling of grass at 390 g dry matter (DM) kg−1 or 610 g DM kg−1. Micro‐organisms included in these studies were: Clostridium tyrobutyricum, Salmonella serotype Typhimurium, Listeria monocytogenes, Campylobacter jejuni, Escherichia coli, Talaromyces emersonii, Byssochlamys nivea, Porcine parvovirus and Swine vesicular disease virus. Soil and grass still contained high numbers of E. coli, Cl. tyrobutyricum and T. emersonii (1·9–5·4 log10) 49 and 56 d after fertilization with spiked ADR. Listeria monocytogenes and S. Typhimurium were generally found in the samples. This indicates that, within this time span, there is a risk of silage contamination by bacteria, moulds and viruses present in ADR spread on grassland. An increase in DM content of the crop decreased its ensilability as measured by pH and short‐chain fatty acid content. However, no clear differences were found in survival of pathogenic and spoilage micro‐organisms between the two silages with different DM contents, regardless of storage time. The lack of moisture and oxygen was probably sufficient to cause the reduction in vegetative bacteria in the 610 g DM kg−1 silage. However, bacterial and fungal spores and the viruses studied were not significantly inactivated by ensiling at these high DM contents and could, therefore, pose a health risk to farm animals fed on the silage if present in ADR applied to crops prior to ensilage.

Comparison of the fatty acid composition of fresh and ensiled perennial ryegrass ( Lolium perenne L.), affected by cultivar and regrowth interval

Two experiments were conducted to evaluate the effects of grass cultivar and regrowth stage on the fatty acid (FA) profile in fresh and ensiled perennial ryegrass ( Lolium perenne L.). The Experiment 1 compared the composition of fresh grass with that of pre-wilted ensiled material of six cultivars, harvested after 25 days of regrowth at a dry matter (DM) yield of approximately 2000 kg DM ha −1. The Experiment 2 compared fresh and ensiled grass of two cultivars, harvested after 23 and 33 days of regrowth. There were genetic differences in fatty acid profiles in fresh grass, but the physiological basis of these differences was not clear as management, growth conditions and leaf blade proportion were similar among cultivars. The concentrations of most FA declined with increasing regrowth stage. In fresh grass, 98% of the fat was present as esterified fatty acids (EFAs) but in silages, 27–73% of the total FA consisted of free fatty acids (FFAs). The largest changes in FA contents took place in the EFA. In pre-wilted ensiled grass, the contents of most FA were lower than in fresh grass, especially of C18:1 and C18:3.

Effects of grass clover-pellets and whole plant maize-pellets on the feed intake and performance of dairy cows

Twenty dual-purpose Simmental dairy cows were used in a 2 × 2 cross-over design to evaluate the effects of feeding, both pelleted vs. ensiled grass clover and whole plant maize on feed intake, milk production and composition, as well as on blood metabolites and some parameters of rumen fermentation. In addition to the pelleted/ensiled forages, all animals were offered grass hay, and, based on the individual milk performance prior to the beginning of the experiment, 1 kg of concentrate for every 2.35 kg energy-corrected milk (ECM) exceeding a daily production of 15 kg ECM. In both groups, the forage was offered so that grass hay, grass clover silage or pellets and whole plant maize silage or pellets would contribute 100, 450 and 450 g kg −1 to total forage dry matter intake (DMI), respectively. Both the treatment periods lasted for seven weeks. Average daily forage DMI was increased from 12.8 up to 18.6 kg when grass clover and whole plant maize were fed in the pelleted form. ECM production was elevated from 18.3 up to 20.3 kg ( p < 0.001). Also, a significant increase was observed for milk protein and lactose level, while content of milk fat and concentration of milk urea were reduced. Rumen pH-values were significantly lower in the pellet-fed cows than in the silage-fed cows. The acetate to propionate ratio was narrowed down from 3.80 : 1 to 3.54 : 1. Concentration of blood serum urea was significantly reduced (0.8 mmol l −1) when pellets were fed. Except for glutamate dehydrogenase (GlDH), all the liver specific enzymes were within normal ranges. The analysis of glucose, protein and ketone bodies in the urine was negative for both the dietary treatments. Pelleted grass clover and whole plant maize proved to be superior to their ensiled counterparts in regard to DMI and milk performance, without having a negative impact on the health status of the animals, but extra milk output in relation to the additional feed intake was very low.

Effluent production from grass silages treated with additives and made in large‐scale bunker silos

Data from twenty experiments, conducted at ADAS Research Centres in England and Wales during 1986–92, were used to determine effluent production from additive‐treated grass silages made in large‐scale bunker silos. The additives compared were formic acid at 4·0 l t–1, rolled barley at 44·0 kg t–1, dried molassed sugar beet feed at 40·0 kg t–1 and liquid inoculants at 2·2 l t–1 together with a non‐additive‐treated control. The silages were made from herbage with an average dry‐matter (DM) content of 177 (s.e. 3·8) g kg–1 and water‐soluble carbohydrate content of 140 g kg–1 DM. Average silage toluene DM content was 213 (s.e. 3·8) g kg–1. The formic acid and sugar beet feed silages were both well fermented, whereas the other silages were less well fermented.Effluent produced was determined as either effluent production (l t–1 grass ensiled) during the 52‐d period in which it was measured or peak flow (l h–1) during the first 2 d of ensilage. Compared with non‐additive‐treated silage, dried molassed sugar beet feed significantly reduced both effluent production (27%) and peak flow (36%). Formic acid significantly increased peak flow (51%), but had little effect upon effluent production, and significantly reduced effluent N and lactic acid content. Barley and inoculant treatment had no significant effect upon effluent production.In general, poor relationships were found between DM content and effluent production. Nevertheless for silages, except those treated with absorbents or formic acid, a significant (P &lt; 0·001) negative relationship between silage effluent production (l t–1 grass ensiled) and the DM (g kg–1) content of the ensiled grass was found.

Metabolisable energy requirements of lactating dairy cows offered a straw/concentrate ration

Previous studies at this Institute (Yan et al., 1997), using regression techniques on calorimetric data obtained with dairy cows offered grass silage based diets, have indicated that the metabolisable energy (ME) requirement for maintenance (MEm) is higher than that predicted using the equations of AFRC (1990). It was hypothesised, (Yan et al., 1997), that this higher MEm may reflect the use of diets containing ensiled grass and, furthermore, that ratio of grass silage:concentrates also influences MEm. In contrast, kl calculated by regression techniques was in line with that predicted using the equations of AFRC (1990). Against this background, the objective of the current study was to establish, using regression techniques, the MEm and kl on a non-grass silage based ration.

Effect of a mixture of salts of carboxylic acids on silage conservation, voluntary intake and growth rate of cattle fed grass silages

A mixture of carboxylic salts (CS) was used to restrict the extent of fermentation in predominantly grass silages. In trial 1, wilted annual ryegrass/red clover [292 g dry matter (DM) kg−1] was ensiled without additive or after application of 8 L carboxylic salts t−1 fresh forage at ensiling. After 5 mo storage in a plastic silo tube, silages were offered to growing Holstein steers ad libitum, either alone or with 2 kg barley d−1 for 70 d. Use of CS restricted the extent of carbohydrate fermentation and protein solubilization compared with the untreated silage. When fed to steers, CS-treated silage resulted in higher intakes and body weight (BW) gains. Barley supplementation increased total DM intake, but reduced silage intake. Feeding barley increased BW gain. Feed conversion efficiency was improved by CS in unsupplemented silages but not in supplemented silages. In trial 2, first-cut, wilted orchardgrass/red clover was ensiled at 283 g DM kg−1 either with formic acid (FA) at 2 L t−1 or CS at 3.5 L t−1 in bunker silos. The regrowth was ensiled at 304 g DM kg−1 either with FA at 4 L t−1 or CS at 5.3 L t−1 in heap silos. Both CS- and FA-treated first-cut silages underwent butyric acid fermentations. Both second-cut silages were well preserved. Relative to the FA treatment, CS had little influence on fermentation or protein solubilization of the ensiled grass. When fed to growing heifers, intake and BW gains were less for first-cut than second-cut silages. There was no effect of additive on DM intake or BW gain, but feed to gain ratio was better in heifers fed CS-treated than FA-treated silage for both cuts. Carboxylic salts were effective at restricting fermentation and protein solubilization in silage which was beneficial to animal performance. Key words: Grass, silage additive, carboxylic salts, growth, beef

Effects of ensilage of grass on performance and nutrient utilization by dairy cattle 2. Nutrient metabolism and rumen fermentation

AbstractA study was carried out to examine the effects of ensiling and pattern of silage fermentation on nitrogen and energy utilization, rumen fermentation and rumen degradation characteristics of forage by lactating dairy cows. Six nonfistulated dairy cows and three rumen fistulated dairy cows were offered fresh grass (G) or grass silage produced from the same sward which had undergone either an extensive (E) or restricted (R) fermentation. Animals offered extensively fermented silage had liigher urinary nitrogen (N) outputs (expressed as a proportion of N intake) than those offered fresh grass (P &lt; 0·05). Corresponding values for animals offered restricted fermented silage were intermediate between those offered grass and extensively fermented silage. Animals offered fresh grass and restricted fermented silage also had higher methane energy losses (P &lt; 0·05), than those offered extensively fermented silage. The ensiling of grass had little effect on metabolizable energy (ME) intake or on the efficiency of utilization of ME for lactation (k1). Animals offered extensively fermented silage had higher proportions of propionate and lower proportions of acetate than those offered fresh grass or restricted fermented silage (P &lt; 0·001). Ensiling resulted in an increase in the soluble (a) fraction and a reduction in the potentially degradable (b) fraction of N.