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1.
Well‐established stands of three ecotypes of Arachis pintoi (CIAT 17434, 18744 and 18748) were harvested from replicated plots (three blocks, each containing three plots for each ecotype) during the two dominant seasons (dry and wet) of the low altitude, humid tropics of Costa Rica. Each plot was further divided into six subplots so that, within each season, samples corresponding to 4, 6, 8, 10, 12 or 14 weeks of regrowth could be collected. For each harvest, dry matter (DM) yield of the leaf, stem and whole plant, and the leaf:stem ratio, were recorded. Samples of the whole plant were analysed for crude protein (CP), rumen‐degradable (RDP) and rumen‐undegradable protein (RUP) concentrations. DM yield of the leaf, stem and whole plant increased with advancing period of regrowth but the effects of period of regrowth varied somewhat among ecotypes and across seasons. Generally, DM yield was greater during the wet than during the dry season. The greatest difference between ecotypes for stem and total DM yields was evident during the dry season. In general, DM contents were low in the whole plant, leaf and stem samples (<220 g kg?1) and increased with increasing period of regrowth. Increases in leaf:stem ratio were most dramatic during the dry season with greater periods of regrowth, although the ratio was fairly constant during the wet season. Whole‐plant CP concentration was relatively high after short periods of regrowth (up to 279 g kg?1 DM) but declined with longer periods of regrowth; the relative decline was much greater during the dry season. The RDP concentration was relatively constant during the wet season (mean 115 g kg?1 DM), but declined with longer periods of regrowth during the dry season (range 194–111 g kg?1 DM). In general, the concentrations of RDP, on a CP basis, were greater during the dry season and ranged from 590 to 700 g kg?1 CP. Season, ecotype and period of regrowth all exerted an effect on RUP concentrations.  相似文献   

2.
Agronomic data on most broad‐leaved species of grasslands are scarce. The aim of this study was to obtain novel information on herbage DM yield and forage quality for several forb species, and on species differences and seasonal patterns across harvests and in successive years. Four non‐leguminous forbs [salad burnet (Sanguisorba minor), caraway (Carum carvi), chicory (Cichorium intybus) and ribwort plantain (Plantago lanceolata)] and three leguminous forbs [yellow sweet clover (Melilotus officinalis), lucerne (Medicago sativa) and birdsfoot trefoil (Lotus corniculatus)] and a perennial ryegrass–white clover mixture were investigated in a small‐plot cutting trial in Denmark during 2009 and 2010. Plots were harvested four times per year. On average, annual herbage yield was highest for lucerne (15·4 t DM) and grass–white clover (12·5 t DM ha?1), and lowest for salad burnet (4·6 t DM ha?1) and yellow sweet clover (3·9 t DM ha?1). Ribwort plantain and lucerne had the highest concentrations of acid detergent fibre (339 and 321 g kg?1 DM respectively) and lignin (78 and 67 g kg?1 DM respectively); contents in other species were similar to grass–white clover (275 and 49 g kg?1 DM respectively). No common feature was found within the functional groups of non‐leguminous forbs and leguminous forbs, other than higher crude protein contents (198–206 g kg?1 DM) in the legumes. DM yield and fibre content were lowest in October. Digestibility declined with higher temperature and increasing fibre content. Results are discussed in terms of the potential of forbs to contribute to forage resources in farming practice.  相似文献   

3.
Various management practices (e.g. wilting, application of silage additives or adding a grass component) can be used to improve silage fermentation of pure red clover (Trifolium pratense L.). Therefore, the aim of this laboratory ensiling study was to investigate the effects of varying proportions of red clover and perennial ryegrass (100/0, 66/33, 33/66, 0/100) on silage quality during two consecutive years. In addition, two wilting levels [target dry matter (DM): 300 vs. 400 g kg?1] in combination with lactic acid bacteria (LAB) additives were tested. Herbage was ensiled, either untreated or inoculated with homofermentative LAB (low wilted) or homo‐ and heterofermentative LAB (high wilted). In most cases, lactic and acetic acid decreased as the proportions of ryegrass were increased. Data concerning ammonia‐N concentrations showed considerable differences between cuts and years. Silages treated with homofermentative LAB generally had high lactic acid and low final pH, whereas acetic acid and 1,2‐propanediol tended to be higher when homo‐ and heterofermentative LAB were applied. Inoculants had a positive effect on DM losses and ammonia‐N in only a few silages. Wilting decreased DM losses and fermentation acids at most cuts, irrespective of the grass/clover ratio in the herbage mixture. There was a strong year effect on the organic matter digestibility (DOM) of the silages. In conclusion, the optimal strategy for successful silage fermentation of red clover is the ensiling in mixtures with ryegrass. Furthermore, herbage should be wilted to a DM content of about 300–350 g kg?1. The application of LAB inoculants did not alter the DOM but did improve silage fermentation.  相似文献   

4.
The effects of a 10-d increase in regrowth interval (35 and 45 d) of a predominantly perennial ryegrass sward harvested in two periods in the autumn in Ireland on feed intake, rumen fermentation, in situ degradability and rumen digesta kinetics was examined using six ruminally cannulated Holstein–Friesian steers in three replicates of a 2 × 2 crossover design. The longer regrowth interval had a higher grass dry-matter (DM) yield of herbage by 615 kg DM ha−1 and a lower crude protein (CP) concentration of herbage by 27 g kg−1 DM. There was no effect of regrowth interval on DM intake, rumen pH, total volatile fatty acid concentration or the molar proportions of acetate, propionate or butyrate in the rumen but the concentration of rumen ammonia (NH3-N) was lower on the longer regrowth interval. The longer regrowth interval had a lower apparent total tract digestibility of DM, organic matter (OM), N and neutral-detergent fibre (NDF). There was no effect of regrowth interval on the in situ degradability of DM, OM, N or NDF. The passage rates ( k p) of DM and OM were higher while the rate of digestion ( k d) of DM and NDF was lower with the longer regrowth interval. The results indicated that, although increasing the regrowth interval by 10 d in autumn reduced the apparent digestibility of the grass herbage, there was no adverse effect on DM intake, rumen fermentation pattern or in situ rumen degradability. The reduction in rumen NH3-N concentrations, reflecting the lower herbage CP concentration in herbage for the longer regrowth interval, may potentially reduce nitrogen excretion to the environment.  相似文献   

5.
The objective of this experiment was to use diurnal and temporal changes in herbage composition to create two pasture diets with contrasting ratios of water‐soluble carbohydrate (WSC) and crude protein (CP) and compare milk production and nitrogen‐use efficiency (NUE) of dairy cows. A grazing experiment using thirty‐six mid‐lactation Friesian x Jersey cows was conducted in late spring in Canterbury, New Zealand. Cows were offered mixed perennial ryegrass and white clover pastures either in the morning after a short 19‐day regrowth interval (SR AM) or in the afternoon after a long 35‐day regrowth interval (LR PM). Pasture treatments resulted in lower pasture mass and greater herbage CP concentration (187 vs. 171 g kg?1 DM) in the SR AM compared with the LR PM but did not affect WSC (169 g kg?1 DM) or the ratio of WSC/CP (1·0 g g?1). Cows had similar apparent DM (17·5 kg DM cow?1 d?1) and N (501 g N cow?1 d?1) intake for both treatments. Compared with SR AM cows, LR PM cows had lower milk (18·5 vs. 21·2 kg cow?1 d?1), milk protein (0·69 vs. 0·81 kg cow?1 d?1) and milk solids (1·72 and 1·89 kg cow?1 d?1) yield. Urinary N concentration was increased in SR AM, but estimated N excretion and NUE for milk were similar for both treatments. Further studies are required to determine the effect of feeding times on diurnal variation in urine volume and N concentration under grazing to predict urination events with highest leaching risk.  相似文献   

6.
Two experiments were carried out with grass silages cut at a leafy (Experiment 1) and a more mature (Experiment 2) stage of growth to evaluate the effect of wilting and chop length on silage intake and performance of store lambs. In each experiment, the herbage was cut with a rotary mower and was either ensiled within 24 h as unwilled silage (U) or wilted for 1–3 d (W). Each silage type was harvested with either a double-chop harvester (D) or a precision-chop harvester (P). All silages were treated with formic acid at 3 1 t?1 and were well preserved. The silages were fed ad libitum to Suffolk crossbred store lambs (twenty-four lambs per treatment) without any supplement over a period of 8 or 9 weeks. Wilting of the silages had little effect on silage intake (797 vs. 809g dry matter (DM) d?1) or on lamb performance in Experiment 1. In Experiment 2, wilting of the D silage increased silage DM intake (589 vs. 534 g DM d?1; +10%) and reduced the extent of liveweight losses. Wilting of the P silage reduced silage intake (770 vs. 791g DM d?1; -3%) and reduced liveweight gains. In Experiment 1 intakes of the D silages were 650–667g DM d?1 and just maintained lamb live weights. Intakes of the P silages were 39–49% higher than the D silages (927–968 g DM d?1) and increased liveweight gains. In Experiment 2 intakes of the D silages were 534–589 g DM d?1 and resulted in a loss in lamb live weight. Precision-chopping increased silage intakes by 31–48% (770–791 DM d?1)in Experiment 2 and improved lamb liveweight gains. Lamb performance was higher on the UP silage than on the WP silage. The rumen retention lime (RRT), estimated from the rumen contents of the lambs at slaughter and their silage intake before slaughter, was much shorter for the lambs fed on the P silages (12.6–20.6 h) than those fed on the D silages (21.4–29.3 h) in each experiment. Silage intake and liveweight gain were positively related to silage in vivo DM digestibility (DMD), whereas RRT was negatively related to DMD. However, there were distinct differences between the P and D silages in the elevation and, to a lesser extent, in the slope of the regression lines, indicating that intake of D silage was limited by factors other than the digestibility of the silage The results of this study show that the chop length of grass silage had a far greater effect on intake and on lamb performance than silage digestibility, whereas wilting had little or no effect.  相似文献   

7.
This study evaluated two potassium sorbate (PS) and sodium benzoate (SB) application rates in improving the aerobic stability of maize silage. Treatments included no additive, the addition of PS at 1 and 2 g kg?1 fresh matter (FM) and the addition of SB at 1 and 2 g kg?1 FM. Four replicates of each treatment were ensiled in 15‐L plastic jars. The silages were analysed for their fermentative characteristics and were subjected to an aerobic stability test with pH and yeast and mould count measurements. Considering fermentation quality and aerobic stability, both additives were effective. The PS was more active against yeasts during aerobic exposure. When the additives were applied at 2 g kg?1, the silages were more stable (256 h, on average) than those with 1 g kg?1 (119 h, on average) and control (61 h). Aerobic deterioration was more pronounced in the controls than in the treated silages. Silages treated at 2 g kg?1 had consistent effects on pH values and yeast counts over 288 h of aerobiosis. Overall, PS and SB applied at 2 g kg?1 were more effective in improving aerobic stability.  相似文献   

8.
Changes in the crude protein (CP) concentration of white clover and perennial ryegrass herbage from a mixed sward were determined on six sampling dates from May to October in each of 2 years. The swards were grown without fertilizer N in an organic farming system and continuously grazed by dairy cows during the grazing season. The annual mean contents of white clover in the dry matter (DM) of the sward were 272·3 and 307·0 g kg−1 in Years 1 and 2. The mean CP concentrations of the white clover and perennial ryegrass herbage were 251·6 and 151·9 g kg−1 DM in Year 1 and 271·9 and 174·0 g kg−1 DM in Year 2 respectively. The CP concentration of the white clover increased significantly during the grazing season from 220·0 to 284·1 g kg−1 DM in Year 1 and from 269·0 to 315·5 g kg−1 DM in Year 2. In the perennial ryegrass herbage the CP concentration increased from 112·2 to 172·6 g kg−1 DM in Year 1 and from 142·7 to 239·5 g kg−1 DM in Year 2. The rate of increase during the season in the CP concentration of the perennial ryegrass herbage was similar to the rate of increase recorded in the white clover herbage.  相似文献   

9.
Protein degradability in forage legumes is of global importance because utilization efficiency of forage has economic and environmental consequences. However, there are no published studies on the effect of legume stand structure on differences in crude protein (CP) fractions. The main objective of the present research was therefore to investigate differences in CP fractions in leaves and stems of lucerne (Medicago sativa L.) during the growing season. Stand traits were measured over 2 years, and forage was sampled at the early bud and early flower stages in the first, second and third cuts. Stems had significantly higher concentrations (in g kg?1 CP) of non‐protein (fraction A: 430 g kg?1 CP) and indigestible nitrogen (fraction C: 92 g kg?1 CP) than leaves and had lower relative content of true protein (fraction B: 478 g kg?1 CP). In the total forage (stems and leaves combined), about 80% of the variation in CP fractions was explained by year, cut and maturity. Year was the most important factor, particularly for the B fractions. Cut was the second‐most important factor; its main effect was that the relative abundance of fraction A declined from 394 g kg?1 CP in the first cut to 293 in g kg?1 CP the third cut. Maturity increased the amounts of indigestible fraction C and protein fractions B1 and B3. This was associated with the leaf weight ratio, which had an inverse relationship with maximal stem length and dry matter yield. Variation partitioning showed that 75% of CP fraction variability associated with cut, maturity and year could be explained by the evaluated stand traits. This research has highlighted the need to consider plant morphological traits when legume CP fractions are evaluated.  相似文献   

10.
The productivity and nutritive value of some cultivated perennial grasses, Bromus inermis (B), Elymus sibricus (S), E. nutans (N), Agropyron cristatum (A), Poa crymophila (P) and mixtures B + N, S + A, B + S + A, S + B + N, N + S + A, B + S + N + A, B + N + A + P, B + S +A + P and S + N + A + P, in the alpine region of the Tibetan Plateau were investigated. Elymus nutans and E. sibricus and the mixtures, B + S + N + A, B + S +A + P and S + N + A + P, were most productive with yields of dry matter (DM) of between 11 000 and 14 000 kg?1 of biomass annually in the second harvest year. Acid‐detergent fibre (ADF) concentrations increased (P < 0·05), and crude protein (CP) concentrations and in sacco DM degradability values decreased (P < 0·05) with the maturity of the cultivated grasses. Swards, based on these species and mixtures, have the potential to be the main choices for cultivation in the Tibetan Plateau because they produce more nutrients than other grass species and mixtures. Late August (flowering stage of dominant grasses) is the optimum time for harvesting as the yield of rumen‐degradable CP is highest that of DM relatively high and the DM degradability is satisfactory.  相似文献   

11.
The effects of ensiling lucerne with graded inclusion of Cistus ladanifer condensed tannins (CT) on in silo fermentative parameters, in vitro organic matter digestibility (IVOMD) and on in situ rumen degradability of dry matter (DM) and crude protein (CP) were studied. Lucerne forage ( Medicago sativa subsp. sativa ) was sprayed with different solutions of C. ladanifer CT extract in 60 ml of water in order for dose 0 (control), 40 (L40), 80 (L80) and 120 (L120) g of CT per kg of lucerne DM and was ensiled in lab‐scale silos. After 35 days, the silages were analysed for chemical composition, and the in situ ruminal degradability was determined in rams. The inclusion of CT in the silages caused an important dose‐dependent reduction in soluble‐N, NH3‐N and a large increase in true protein content and N bound with neutral detergent fibre (NDF‐N), which indicates an effective proteolysis reduction during ensiling. Also, the rumen undegradable protein (RUP) increased linearly (P < 0.01) with CT inclusion. However, a linear decrease (P < 0.02) of 5%, 13% and 22% of IVOMD was observed for the silages L40, L80 and L120 respectively. The results obtained suggest that C. ladanifer CT can be used as silage additives to reduce proteolysis of high‐protein forages during ensiling. A level of CT of 40 g/kg DM seems to be the best compromise between the gains achieved by the protection of CP degradation in silo and in the rumen and the losses associated with the depression of the digestion and absorption.  相似文献   

12.
A field experiment was undertaken between April 2003 and May 2004 in southern Tasmania, Australia, to quantify and compare changes in the nutritive value of perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under a defoliation regime based on stage of leaf regrowth. Defoliation interval was based on the time taken for two, three or four leaves per tiller to fully expand. At every defoliation event, samples were collected and analysed for acid‐detergent fibre (ADF), neutral‐detergent fibre (NDF) and total nitrogen (N) concentrations and to estimate metabolizable energy (ME) and digestible dry matter (DDM) concentrations. Amounts of crude protein (CP) and metabolizable energy (MJ) per hectare values were subsequently calculated. There was a significantly lower (P < 0·001) NDF concentration for perennial ryegrass compared with prairie grass and cocksfoot, and a significantly lower (P < 0·001) ADF concentration for cocksfoot compared with prairie grass and perennial ryegrass, regardless of defoliation interval. The CP concentration of cocksfoot was significantly greater (P < 0·001) compared with the CP concentrations of prairie grass and perennial ryegrass. The estimated ME concentrations in cocksfoot were high enough to satisfy the requirements of a lactating dairy cow, with defoliation at or before the four‐leaf stage maintaining ME concentrations between 10·7 and 10·9 MJ kg?1 DM, and minimizing reproductive plant development. The ME concentrations of prairie grass (10·2–10·4 MJ kg?1 DM) were significantly lower (P < 0·001) than for cocksfoot (as above) and perennial ryegrass (11·4–11·6 MJ kg?1 DM) but a higher DM production per hectare resulted in prairie grass providing the greatest amounts of ME ha?1.  相似文献   

13.
Silage making practices in respect of 130 samples of autumn made grass silages ensiled in bunkers on commercial farms in South Wales during 1983-1985 were analysed to discern the effect of wilting and/or silage additives on fermentation. Silages were primarily made during late September and early October in fine weather from perennial ryegrass pasture which had not been grazed for 6 weeks. On average 13.9 ha of pasture was cut for silage. Analysis of 120 samples of grass showed it contained 176 g kg?1 dry matter (DM) with (g kg?1 DM) 215 protein, 240 modified acid detergent fibre (MADF), 78 water-soluble carbohydrate (WSC) and 95 ash. Most farmers attempted to pre-wilt grass for 1 day prior to ensilage and one quarter of them made unwilted silage. Silage making was usually completed within 6 days of starting to cut and was generally made with a precision-chop machine. Silage additives applied were (kg t?1) formic acid (4·7), formic acid 4-formalin (5·5), sulphuric acid-+ formalin (5·0) sugars (14) and inoculants (0·65). Formic acid significantly reduced pH, and formic acid with or without formalin significantly reduced ammonia nitrogen (N) content of silages compared with other treatments. Protein contents of acid/formalin treated silages were significantly higher and MADF of acid with or without formalin treated silages were significantly lower than other treatments. Pre-wilting grass prior to ensilage did not significantly increase subsequent silage DM content and significantly increased the pH of non-additive treated silages. Unwilted silages treated with formic acid with or without formalin had a significantly lower ammonia-N content and higher residual WSC than other treatments. It is suggested that only formic acid application either alone or in conjunction with formalin to unwilted silage was successful in producing well preserved silages and that a grass WSC content of 17 g kg?1 would be necessary to achieve this.  相似文献   

14.
In change‐over trials, mid‐lactation dairy cows were fed concentrate‐supplemented, isonitrogenous and isofibrous perennial ryegrass–legume silage diets that satisfied energy requirements but were suboptimal with respect to metabolizable protein supply. Legumes were either birdsfoot trefoil with low levels of condensed tannins (typical for hemiboreal conditions), or white clover. Averaged over two experimental years, birdsfoot trefoil–based silage resulted in lower digestibility (P < 0·001) of dry matter (50 g kg?1), organic matter (52 g kg?1), neutral detergent fibre (120 g kg?1) and nitrogen (24 g kg?1) and lower rumen total volatile fatty acid concentration (7 mm ; P = 0·009). Milk protein yield was 36 g d?1 higher with birdsfoot trefoil silage (P = 0·002), while raw milk yield tended to be 0·8 kg d?1 higher (P = 0·06). Rumen ammonia concentration was similar between diets, but milk urea concentration (P < 0·001), urinary urea excretion (P = 0·002) and faecal‐N proportion (P = 0·001) were higher with birdsfoot trefoil silage. The results suggest that grass–birdsfoot trefoil silage produced in hemiboreal areas exhibits a protein‐sparing effect in dairy rations, despite a low condensed tannin content that is further diluted by companion grasses and ration concentrate proportion.  相似文献   

15.
The study aimed at evaluating an effective sterilization–inoculation technique to facilitate silage research on the effect of forage microflora on fermentation variables. The sterilization effect of heating at 60°C for 3 h + 103°C for 15 h was tested on samples of grass, grass–clover, white clover and maize, pre‐dried at 60°C to a dry‐matter (DM) content >900 g kg?1. The ensilability of treated samples, reconstituted to original DM concentration (250–390 g kg?1), was assessed by inoculation with microfloras extracted from the original samples. Microfloral inoculants were obtained by a combination of centrifugation (15 500  g for 40 min) and filtration (0·45 and 0·22 μm pore sizes) of the supernatant. The sterilization treatment effectively sterilized the forage samples but decreased water soluble carbohydrates by 49% and N buffer solubility by 22% and increased the acid detergent insoluble N proportion of total N by 53% (P < 0·05). The reconstituted silages had 18% less lactic acid, 20% less ethanol and 37% less ammonia‐N (P < 0·05), but volatile fatty acids and 2,3‐butanediol did not differ from the untreated silages (P > 0·05). Counts of lactic acid bacteria, enterobacteria, clostridia, yeasts and moulds in the two silage treatments were also similar (P > 0·05). It is concluded that, despite causing chemical and physical alterations, the sterilization–inoculation technique evaluated could be a useful tool for future studies on the effects of microflora on ensiling results.  相似文献   

16.
The pattern of crude protein (CP) fractions with advancing maturity during a primary spring growth of forage legumes was investigated on freeze‐dried samples of fresh forage using the method of chemical CP fractionation according to the ‘Cornell Net Carbohydrate and Protein System’ (CNCPS). The CP of white clover (WC), red clover (RC), lucerne (LU), birdsfoot trefoil (BT) and Kura clover (KC) was separated into five fractions (A, B1, B2, B3 and C), which are assumed to have different rates and extents of ruminal degradation. Ruminally undegraded dietary CP (RUP) was predicted on the basis of the CP fractions using regression equations that were developed for fresh forage assuming ruminal passage rates of 2, 5 and 8% h?1 (RUP2,5,8). Maturity stage did not affect the soluble CP fractions of the legumes but increased fraction B3 in RC and WC and fraction C of all forages except WC. The estimated RUP values of the legumes increased with advancing maturity. The mean values for RUP5 across all harvest dates for WC, RC, LU, BT and KU were 154, 271, 226, 287 and 212 g kg?1 CP respectively. BT and RC had the highest amount of RUP across all harvest dates and passage rates (159–372 and 134–324 g kg?1 CP respectively). This observation may be related to the advanced stage of vegetation of both species at the harvest dates compared with the other legumes and to condensed tannins in BT and to products of polyphenol oxidase activity in RC.  相似文献   

17.
The aim of the experiment was to assess the effect of applying, at commercially recommended rates, formic acid or formic acid/formaldehyde at ensilage upon the subsequent digestion of the silages by cattle. Three wilted grass silages were made from perennial ryegrass ensiled at a DM concentration of 206 g kg−1 after a poor wilting period of 49 h without additive application and with application of 2.5 litres t−1 of formic acid or of 4.5 litres t−1 of a mixture of (gkg−1) 500 formic acid, 200 sulphuric acid and 200 formatin giving an application rate of 15 g formaldehyde kg−1 herbage crude protein (N × 6.25).
The silages were fed to cattle equipped with rumen cannulae and duodenal re-entrant cannulae. Results from analyses of silage composition and from the digestion of organic matter and N showed no major differences between silages. The efficiency of rumen microbial N synthesis, the rumen degradability of silage N (determined in vivo or in sacco ) and in vivo digestion of individual amino acids were also unaffected by additive treatment. These results indicate that poor wilting conditions before ensilage restricted the effectiveness of additive treatment; the ineffectiveness of formaldehyde in reducing the rumen degradability of silage N may also have been related to the low rate of formaldehyde application.  相似文献   

18.
The chemical composition of silage consumed by cattle can influence the subsequent rumen microbial fermentation patterns and methane (CH4) emissions. The objectives of this study were to (i) evaluate the effect of ensilage on the in vitro rumen methane output of perennial ryegrass and (ii) relate the silage fermentation characteristics of grass silages with in vitro rumen methanogenesis. Three pre‐harvest herbage‐conditioning treatments and seven silage‐additive treatments were used in a laboratory‐scale silo experiment to produce a diversity of silage fermentation characteristics. Ensilage reduced (P < 0·01) the in vitro rumen CH4 output (mL CH4 g?1 dry matter (DM) disappeared). This reflected differences in the direction of rumen fermentation (lower acetic (P < 0·05) and higher propionic (P < 0·001) acid proportions in volatile fatty acids) rather than major changes in the extent of in vitro rumen fermentation (i.e. mmol VFA g?1 DM). The magnitude of the decrease in CH4 output (mL g?1 DM incubated) owing to ensilage increased as the extent of silage fermentation, and in particular the lactic acid concentration, increased. In contrast, among silages with relatively similar extents of silage fermentation (i.e. total fermentation products), an increase in the proportion of lactic acid in silage fermentation products led to a more extensive in vitro rumen fermentation and thus to a greater CH4 output (mL g?1 DM).  相似文献   

19.
The objectives of this study were to determine the range of neutral detergent fibre (NDF) digestibility across sugarcane varieties and predict dry‐matter (DM) and NDF digestibility based on morphological and chemical composition. Whole plants of thirty‐two commercial varieties were collected after 12 months regrowth (second cut) and evaluated for morphological traits, chemical composition, in situ digestibility of NDF (NDFD) and of DM (DMD), in vitro NDFD (IVNDFD) and gas production dynamics from isolated NDF. The content of NDF ranged from 404 to 547 g kg?1 DM, DMD was between 593 and 739 g kg?1 and NDFD varied from 270 to 363 g kg?1. Cluster and discriminant analyses for NDFD agglomerated sugarcane genotypes into three groups (high, medium and low NDFD). The contents of NDF and lignin were the best univariate predictors of sugarcane DMD and NDFD respectively. Therefore, associating NDF and lignin improved the accuracy of DMD prediction. Associating lignin concentration with the number of dry leaves and stalk length significantly improved the goodness of fit of NDFD prediction. Contrary to expectations, silicon concentration was not related to NDFD. The principal component analysis patterned the content of neutral detergent solubles, NDFD and variables related to DM yield in different components. Hence, these characteristics would coexist in the same variety. Based on Lucas test and kinetics of gas production from NDF, sugarcane potentially digestible NDF (pdNDF) can be considered almost uniform (pdNDF digestibility = 677 g kg?1). In conclusion, associating chemical composition and morphological traits can successfully improve the screening of sugarcane genotypes for animal nutrition.  相似文献   

20.
Monocultures of thirteen perennial C3 grass species that co‐occur in temperate semi‐natural grassland communities in Europe were compared in a factorial field design of two levels of N supply and two levels of cutting frequency. Above‐ground yield of dry matter (DM), crude protein (CP) concentration and pepsin‐cellulase DM digestibility of herbage were measured in two successive years. Species was the largest source of variability in yield of DM and DM digestibility of herbage, while CP concentration of herbage responded more to management factors. The highest mean DM yields and values of DM digestibility of herbage were achieved in spring for Festuca arundinacea and in autumn for Phleum pratense. Poa trivialis and Festuca rubra had the lowest DM yield and DM digestibility values, respectively, regardless of seasons and treatments. For all species CP concentration in herbage increased in response to an increase in cutting frequency and N supply by an average of 46 and 34 g kg?1 DM respectively. Differences between years and seasons indicated the importance of plant phenology on nutritional variables and the influence of environmental factors on species performance. Species ranking was compared according to their annual digestible DM and CP yields. The results show that some grasses have a nutritive value which is comparable to that of forages selected for high yields.  相似文献   

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