In vitro estimations of the rate and extent of ruminal digestion of starch-rich feed fractions compared to in vivo data

An experiment was conducted to study the rumen digestion characteristics of whole feeds (WF) and the neutral detergent fibre (aNDF) and neutral detergent soluble (NDS) fractions of a range of starch-rich feeds using an automated in vitro gas production (GP) technique. In addition, the ruminal digestibility values predicted from the GP data were compared to previously acquired in vivo data. Nine feeds with starch concentrations ranging from 389 to 712 g/kg dry matter and with known in vivo digestibilities were subjected to neutral detergent extraction. The GP for each WF and the corresponding aNDF fractions were measured in duplicate in buffered rumen fluid during 72 h on two occasions. The fermentation residues were collected and analyzed for aNDF concentration to estimate their true organic matter (OM) and NDF digestibility. The GP from the NDS fraction was calculated by subtracting the GP from the aNDF fraction from the GP of the WF. A three-pool Gompertz model was fitted to the GP profiles (R² = 0.99) and a two compartment, mechanistic and dynamic rumen model was used to predict the digestibility of the potentially digestible feed fraction and the effective digestion rate (k_d). The true OM and NDF digestibility determined for the WF ranged from 0.804 to 1.011 and from 0.362 to 1.107, respectively. The NDF digestibility determined for the aNDF fraction ranged from 0.410 to 0.985. The effective k_d values estimated using GP data varied from 0.118 to 0.282/h for the WF and from 0.123 to 0.301/h for the NDS fraction, and were less (P<0.05) for maize compared to small grains (SG) but did not differ between barley and wheat (P>0.05). The effective k_d values for the aNDF fraction ranged from 0.039 to 0.082/h and did not differ (P>0.05) either between maize and SG or between barley and wheat. The predicted ruminal NDS digestibility determined using GP data closely matched the in vivo data describing starch digestion (R² = 0.81). The effective k_d values for the WF were strongly related (R² = 0.94) to those for the NDS fractions. The results indicate that when measured with the GP technique, the differences in the digestion characteristics of maize and small grains are less than those previously reported in studies using the in situ method. It is concluded that the predicted NDS digestibility determined using GP data corresponded well to the in vivo starch digestibility. Our results also suggest that the first order digestion rates of NDS (starch) in starch-rich feeds can be accurately determined by incubating WF samples in the GP system and using the GP kinetic data in a dynamic, mechanistic rumen model.     

In vitro evaluation of the fermentation characteristics of the carbohydrate fractions of hulless barley and other cereals in the gastrointestinal tract of pigs

An in vitro model was used to study the fermentation characteristics of carbohydrate fractions of hulless barley (hB), in comparison to hulled barley (HB), hulled oat and oat groats (OG) in the pig intestine. For this purpose, 6 hulless barley cultivars (hB), varying in β-glucan content (36–99 g/kg DM), were compared to 3 HB cultivars, 2 oat groat samples (OG), 3 oat varieties and a reference sample of wheat. The residue of a pepsin–pancreatin hydrolysis was incubated in a buffered mineral solution inoculated with pig faeces. Gas production, proportional to the amount of fermented carbohydrates, was measured for 48 h and kinetics modelled. The fermented solution was subsequently analyzed for microbial production of short-chain fatty acids (SCFA) and ammonia. In vitro dry matter degradability varied according to ingredient (P<0.001). Higher values were observed for OG, ranging from 0.88 to 0.99 as compared to oat, hB and HB, for which degradability ranged from 0.63 to 0.73, 0.68 to 0.80 and 0.69 to 0.71, respectively. A “cereal type” effect (P<0.05) was observed on fermentation kinetics parameters. Total gas production was higher (P<0.05) with hB (224 ml/g DM incubated) than with HB and oat (188 and 55 ml/g DM incubated, respectively). No difference was observed between hB cultivars (P>0.05) for total gas production but differences (P<0.001) were found for lag time and the fractional rate of degradation. Hulless barley cultivar CDC Fibar (waxy starch) and CDC McGwire (normal starch) started to ferment sooner (lag time of 0.7 and 0.9 h, respectively) than SH99250 (high amylose starch; 1.7 h). The fractional rate of degradation was similar in both hB and OG (0.15/h on average), which was higher than that of HB (0.12/h). The production of SCFA was also higher (P<0.05) with hB (6.1 mmol/g DM incubated, on average) than with HB and oat (4.9 and 2.9 mmol/g DM incubated, respectively). Similar trends were found for SCFA production expressed per g fermented carbohydrates, with higher butyrate and lower acetate ratio. In contrast, oat fermentation generated higher (P<0.05) ammonia concentration (1.4 mmol/g DM incubated, on average) than hB (1.0 mmol/g DM incubated). In summary, hulless barleys, irrespective of cultivar type had higher in vitro fermentability and produced more SCFA and less ammonia than hulled barley and oat. Thus, hulless barleys have a better potential to be used in pig nutrition to manipulate the fermentation activity in the intestine of pigs.     

Amylolytically-resistant tapioca starch modified by combined treatment of branching enzyme and maltogenic amylase

Tapioca starch was modified using branching enzyme (BE) isolated from Bacillus subtilis 168 and Bacillus stearothermophilus maltogenic amylase (BSMA), and their molecular fine structure and susceptibility to amylolytic enzymes were investigated. By BE treatment, the molecular weight decreased from 3.1 × 10⁸ to 1.7 × 10⁶, the number of shorter branch chains (DP 6–12) increased, the number of longer branch chains (DP >25) decreased, and amylose content decreased from 18.9% to 0.75%. This indicated that α–1,4 linkages of amylose and amylopectin were cleaved, and moiety of glycosyl residues were transferred to another amylose and amylopectin to produce branched glucan and BE-treated tapioca starch by forming α–1,6 branch linkages. The product was further modified with BSMA to produce highly-branched tapioca starch with 9.7% of extra branch points. When subject to digestion with human pancreatic α-amylase (HPA), porcine pancreatic α-amylase (PPA) and glucoamylase, highly-branched tapioca starch gave significantly lowered α-amylase susceptibility (7.5 times, 14.4 times and 3.9 times, respectively), compared to native tapioca starch.     

In vitro evaluation of starch degradation from feeds with or without various heat treatments

An in vitro method was used to evaluate starch degradation from various feeds with or without heat treatments in four studies. The method was based on incubation of feed samples with a buffered rumen fluid solution and subsequent enzymatic analysis of the remaining starch. In all studies, heat treatment of the feed samples increased rate or extent of starch degradation to glucose. In Study 1, measurements of remaining starch, after 5 h in vitro incubations, demonstrated substantial effects of cooking on starch degradation in potatoes, and a trend to faster degradation from autoclaving peas. Up to 0.60 of the starch remaining after a 5 h of incubation was not recovered by centrifugation at 3000 × g for 10 min. In Study 2, cooking increased in vitro starch degradation rate from isolated potato starch (from 0.038 to 0.197/h). Intact starch in barley and wheat grain had similar rates of degradation (0.117 and 0.109/h, respectively). In Study 3, both autoclaving time (15, 30, 60 min) and temperature (115, 130 and 145°C) affected in vitro starch degradation rates in peas, and, in no case did autoclaving for only 15 min increase degradation rates. For the 30 min autoclaving time, only the highest temperature (145°C) increased the degradation rate of the pea starch compared to the untreated peas (0.175 versus 0.110/h). When autoclaving for 60 min, both 130 and 145°C resulted in a considerable increase in starch degradation rate (0.211 and 0.193/h, compared to 0.110/h for the untreated peas). In Study 4, the proportion of starch degraded at 8 h of in vitro incubation was increased by heat treatment of pure potato starch (0.155 versus 0.870), peas (0.491 versus 0.815), barley (0.686 versus 0.913) and maize (0.351 versus 0.498). Measurements of volatile fatty acid production in the fermentation tubes showed a lower acetate:propionate ratio for the faster fermenting heat-treated feeds. Heat treatment generally increased starch degradation in vitro.     

Interpretation of rumen degradability of concentrate feeds with a Gompertz model

An investigation of the kinetics and synchronicity of rumen crude protein and starch degradability was performed for maize, flaked maize, ensiled maize cob, barley, flaked barley, wheat, oat, sorghum and triticale grain, using the in situ polyester bag technique. Kinetics of rumen degradability were corrected for particle losses from the bag before degradation. Washing losses were measured by shaking feed samples in polyester bags in tap water at 20°C for 1 h and recovering the particle losses in fibre glass filter. Mean washing losses of dry matter were 442 g/kg DM (soluble fraction 17%); mean washing losses of nitrogen were 446 g/kg nitrogen, with 52% being water soluble. Starch escaped to a higher extent from the bags in the washing machine (average washing losses were 581 g/kg starch, with a soluble fraction of 7%). Degradability data for dry matter, nitrogen and starch measured at each time of incubation were corrected for the respective particle losses and fitted with both first order and Gompertz (sigmoidal) models. The difference between the estimated parameters obtained with the two models was negligible, although differences occurred for the immediately soluble fraction (a) of dry matter and starch and for total degradable fractions of dry matter, nitrogen and starch. No differences were observed between effective degradabilities, independent of rumen outflow rate (0.04 and 0.08/h), apart for the mean effective degradability of nitrogen at 0.08/h, which was higher for the first order model (577 versus 564 g/kg, P < 0.001). The advantage of using the Gompertz model to interpret the kinetics of rumen degradability of cereals was due to the possibility of studying synchronicity of nitrogen and starch released into the rumen and ranking feeds according to their degradability pattern, which required the calculation of the first derivatives of the Gompertz model for nitrogen and starch and weighted for their respective amounts in the feeds. The difference of these ratios from the optimum value of 30 mg N per 1 g starch gives the instantaneous synchronicity of the cereals. Maize, flaked maize, maize cob and sorghum had negative and almost constant values during the first 8 h of incubation. Barley, flaked barley, wheat, triticale and oat changed from an initially negative value to a positive value from about 4 h onwards; oats had a similar pattern, but a positive value was observed only after 6 h.     

Partial replacement of barley grain for corn grain: Associative effects on lambs’ growth performance

Our objective was to study the positive effects of partial replacement of barley grain for corn in high concentrate diets on growth performance of growing lambs, and to determine the minimum amount of corn needed to produce such effects. Thirty-three male Awassi lambs weaned at 60 days of age were divided into three groups of 11 according to their live weight and offered three isonitrogenous diets. The control diet (B) contained 81 and 14% barley grain and wheat straw, respectively (DM basis). Corn grain replaced barley grain at 10 and 20% of dietary DM for low (LC) and high (HC) corn diets, respectively. Barley had a higher (P < 0.05) rate of digestion (11.5%/h) compared with corn (8.3%/h). The in vitro 30-h digestion extent was also higher (P < 0.05) for barley. The digestion rate for the B diet was higher (P < 0.05) compared with the HC diet, whereas the value for the LC diet was intermediate. Lambs fed LC and HC diets consumed more (P > 0.05) DM (average = 855 g/day) compared with lambs fed B diet (757 g/day). DM and CP digestibilities were similar among diets and averaged 67.0 and 64.2%, respectively. Final BW, BW change and average daily gain (ADG) for lambs fed HC were higher (P < 0.05) compared with B and LC. Moreover, lambs that consumed LC tended (P = 0.12) to grow faster than lambs fed B. Feed to gain ratio was lower (P < 0.05) for lambs fed HC (4.6) compared with B and LC (5.2). In summary, positive associative effects of partial replacement of barley with corn in high concentrate diets for fattening sheep were detected. However, a minimum of 20% replacement of dietary DM from barley with corn was needed to positively improve both performance and feed efficiency.     

Optimization of multiple shoot induction and plant regeneration in Indian barley (Hordeum vulgare) cultivars using mature embryos

Barley is the fourth most important crop in the world. Development of a regeneration system using immature embryos is both time consuming and laborious. The present study was initiated with a view to develop a regeneration system in six genotypes of Indian barley (Hordeum vulgare) cultivars as a prerequisite to transformation. The mature embryos were excised from seeds and cultured on MS medium supplemented with high and low concentrations of cytokinins and auxins respectively. The MS medium containing 3 mg/L N⁶-benzylaminopurine (BA) and 0.5 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) was found to be the most effective for multiple shoot formation in HOR7231 cultivar that could produce 12 shoots per explant. The other cultivars HOR4409 and HOR3844 produced a minimum number of adventitious shoots (1.33 and 1.67 respectively) on MS medium supplemented with 1 mg/L BA and 0.3 mg/L 2,4-D. The elongated shoots were separated and successfully rooted on MS medium containing 1 mg/L indole-3-acetic acid (IAA). The response of different barley cultivars was found to be varying with respect to multiple shoot production. This is the first report of multiple shoot induction and plantlet regeneration in Indian cultivar of barley which would be useful for genetic transformation.     

Evaluation of a two-stage in vitro technique for estimating digestibility of equine feeds using horse faeces as the source of microbial inoculum

To develop a two-stage in vitro technique that simulates both pre-caecal and hind gut digestion processes, four enzymatic pre-digestion treatments by pepsin and α-amylase (ET0 = control, ET1 = 2 h pepsin + 2 h amylase, ET2 = 2 h pepsin + 4 h amylase, ET3 = 8 h pepsin + 16 h amylase) were tested on oat hay (OH), barley grain (BG) and soybean meal (SBM). Investigated parameters were enzymatic organic matter digestibility (OMDe), and gas production (G48h, G72h) and OM digestibility (OMD) using horse faeces as a source of microbial inoculum.Enzymatic pre-digestion treatments affected (P<0.05) investigated parameters and their ranking differed among feeds. Only OMD of BG and SBM were higher after the pre-digestion treatment. OMD prior to (ET0) and after ET3 application were, successively, 0.357 versus 0.351 (OH), 0.71 versus 0.79 (BG) and 0.70 versus 0.78 (SBM). Net gas production overestimated fermentation potential of non-pre-digested feeds. G72h (ml/g DM) prior to (ET0) and after ET3 application were, successively, 80.3 versus 58.0 (OH), 151.7 versus 30.4 (BG) and 110.6 versus 37.7 (SBM).It was concluded that the enzymatic pre-digestion treatments effects varied among tested feeds, and that the suggested procedure be extended and validated with a large array of feeds of known digestibility values.     

Fibre digestibility in large herbivores as related to digestion type and body mass — An in vitro approach

The coexistence of different ungulate species in a given ecosystem has been the focus of many studies. Differences between ruminant foregut fermenters and hindgut fermenters were remarkable for example in the way they ingest and digest high fibre diets. Digestion trials based on total collections are difficult to conduct or are sometimes even not possible for wild animals in the field or in zoos. To gain information on the fibre digestion achieved by these animals and the influence of body mass (BM) thereon, a method using spot sampling is desirable. In this study, in vitro fermentation of faecal neutral detergent fibre (NDF) was used as a measure of fibre digestion in large ungulates. Food and faecal samples of 10 ruminant foregut fermenting and 7 hindgut fermenting species/breeds were collected. All animals received 100% grass hay with ad libitum access. The NDF of food and faeces was fermented in vitro in a Hohenheim gas test (HGT) for 96 h. The digestion type generally had an effect on the gas production (GP) of faecal NDF in the HGT with hindgut fermenters showing higher values than ruminant foregut fermenters. At any time interval of incubation, BM had no influence on GP. The results are in accordance with both findings that ruminant foregut fermenters have longer mean retention times and more comprehensive particle reduction and findings of a lack of influence of BM on digesta mean retention time. It can be stated that the HGT (96 h) is a useful and quick method to show also small differences within groups in fibre digestion.     

Debranching enzyme concentration effected on physicochemical properties and α-amylase hydrolysis rate of resistant starch type III from amylose rice starch

The effect of debranching enzyme concentration on physicochemical properties and α-amylase hydrolysis rate of resistant starch type III from high amylose rice starch were studied. The pullulanase enzyme (8, 10, 12, 14 and 16 U/g starch) was introduced to modify amylopectin molecules of 15% (w/w) gelatinized rice starches at 55 °C for 16 h. The debranched starches with different degrees of hydrolysis (0.14–5.27%), and having 66.60–98.82% β-amylolysis limit were then induced at 4 °C for 16 h, afterward a one cycle of freeze–thaw process (?10/30 °C) was applied. The results showed that a pullulanase hydrolysis improved the degree of syneresis (51.64–54.85% from 8 to 16 U/g starch). Resistant starch content increased sharply as the amount of the enzyme increased, reaching the highest (19.81%) for a 12 U/g starch and decreased to 13.16% by 16 U/g starch. α-Amylase hydrolysis rate showed that incompletely-debranched had a lower estimated glycemic index than completely debranched rice starches. Microstructure of the selected RS III samples using X-ray diffraction and scanning electron microscopy revealed a crystal pattern change from A- to V-type pattern and formed a coarse honeycomb-like and a filamentous network structure.     

Effects of urea and aqueous ammonia treatment on the composition and nutritive value of maize residues

Two trials were conducted to investigate changes in chemical composition and nutritive value of maize residues treated with urea and aqueous ammonia. In Experiment I, maize stalks, husks and cobs were chopped into pieces of approximately 1 cm length. Aqueous NH₃ (3%) and feed grade urea equivalent to 3% NH₃ were sprayed into 100 g duplicate samples on DM basis, thoroughly mixed, stored in plastic containers and kept for 3 week at ambient temperature (25–27 °C). Proximate composition and in vitro dry matter digestibility of test materials were determined. In Experiment II, 100 kg batches of the maize residues were chopped and treated as in Experiment I but stored in 205 l drums lined with black polythene sheet. Feed intake and nutrient digestibility of treated materials were evaluated with 18 mature WAD sheep averaging 19.8 kg BW. Treatment improved (P < 0.05) intake and digestion coefficients for N, DM, NDF, ADF and OM but there were no differences (P > 0.05) between aqueous NH₃ and urea treatments. Feed grade urea or the equivalent weight of fertilizer grade urea can be used to improve the nutritional value of maize residues for small ruminant feeding during off season periods.     

Cultivar and age of regrowth effects on physical,chemical and in sacco degradation kinetics of vegetative perennial ryegrass (Lolium perenne L.)

Perennial ryegrass is the principal component of diets fed to ruminants in New Zealand. Selection for ryegrass improvement should incorporate measures relating to feeding value (i.e. quality × intake) for sheep and cattle. This study was designed to measure the variation in characteristics of nutritive value of three ryegrass cultivars harvested at different stages of regrowth. The cultivars were Grasslands Greenstone (Greenstone; tetraploid), Grasslands Samson (Samson; diploid) and Quartet (tetraploid). They were grown as pure swards with leafy regrowth harvested after 2, 3, 4, 5, 6 and 7 weeks for measurement of chemical composition, physical parameters (i.e. shear force and energy required for mincing), degradation kinetics and distribution of constituents between the immediately degradable (A), potentially degradable (B) and undegradable (C) fractions. Analyses showed that age of regrowth resulted in larger differences in composition and degradation kinetics than cultivar, and emphasised the need to harvest material in a similar condition to that grazed by animals. Cultivar differences were best indicated by chemical composition and ratios of crude protein (CP):neutral detergent fibre (aNDF) in the dry matter (DM), the proportion of CP in the ‘A’ fraction as well as degradation of DM in the ‘B’ fraction. The CP:aNDF ratios averaged for the three cultivars at 2, 3, 4, 5, 6, and 7 weeks were 0.82, 0.76, 0.71, 0.55, 0.48 and 0.42, respectively, with averages at weeks 5 and 6 for Greenstone, Samson and Quartet of 0.59, 0.49 and 0.48, respectively. The ratio differed between ages (P<0.001) and across cultivars (P<0.05). The DM fractional degradation rates (k) tended to decline from 0.18 to 0.12/h with maturity (P<0.05) and after weeks 5 and 6 of regrowth averaged 0.17, 0.16 and 0.14/h for the respective cultivars. Both the concentration of lignin(sa) in DM and shear force were weakly associated with regrowth and cultivar and appeared to be less important than chemical composition for indicating nutritive value of leafy ryegrass.     

Effects of total nonstructural carbohydrates and nitrogen balance on voluntary intake of goats and digestibility of gamagrass hay harvested at sunrise and sunset

We evaluated differences in composition of Iuka gamagrass (Tripsacum dactyloides L.) hay harvested at 06:00 (AM harvest) or 18:00 h (PM harvest), and measured how protein supplementation and time of harvest interact to affect the voluntary intake, digestibility, and N balance of goats. Boer cross wethers (n = 28; 24 kg) were randomly assigned to be fed supplement (310 g/kg of crude protein (CP), fed at 110 g/kg of dry matter (DM) intake, 14 goats) or no supplement (14 goats). Within supplemented or not supplemented groups, goats were randomly assigned to a crossover design of AM harvest (seven goats) or PM harvest (seven goats), and housed individually in metabolism crates with free access to water and mineral blocks. They were fed twice daily, with supplement offered 30 min prior to the morning feedings. After a 7-d adaptation, voluntary intake (goats were offered 1100 g/kg of previous day's intake) was measured for 14 d, followed by a 4-d adjustment phase to equalize DM offered between periods, and finally a 5-d digestion and balance phase. After Period 1, goats were switched to their new hay harvest times, and the protocol was repeated. Compared to the AM harvest, the PM harvest had higher (P<0.03) proportions of total nonstructural carbohydrates (TNC, 70.8 g/kg DM versus 59.0 g/kg DM), monosaccharides (37.0 g/kg DM versus 28.6 g/kg DM), di- and polysaccharides (18.5 g/kg DM versus 15.4 g/kg DM) and less neutral detergent fiber (NDF, 700 g/kg versus 710 g/kg). Crude protein (79 g/kg DM) and starch (15.2 g/kg DM) were similar for the PM and AM harvest. Dry matter digestibility was higher (P<0.03) for the PM versus AM harvests (555 g/kg DM versus 531 g/kg DM) and for supplemented versus not supplemented (563 g/kg DM versus 522 g/kg DM). Voluntary gamagrass DM intake (550 g/d versus 548 g/d) and calculated total digestible DM intake (327 g/d versus 313 g/d) were similar for the PM and AM harvest. However, total digestible DM intake during the digestion and balance phase was higher (P<0.01) for the PM versus AM harvest (317 g/d versus 299 g/d). Time of harvest did not affect N intake, digestion, or calculated retention. Compared to no supplementation, the supplement improved (P<0.01) N digestion (6.1 g/d versus 3.7 g/d) and retention (2.2 g/d versus 1.1 g/d). The PM harvest increased DM digested, largely TNC and digestible DM intake by goats due to increased TNC and not because of a 2% increase in DM intake. Providing a protein supplement had very limited effects on intake and digestibility of gamagrass.     

Effect of the supplementation of a high-concentrate diet with sunflower and fish oils on ruminal fermentation in sheep

This study was conducted to test the hypothesis that the supplementation of a high-concentrate diet with lipids, reportedly a good strategy for improving the nutritional value of ruminant-derived products, may not necessarily be associated with detrimental effects on ruminal fermentation in sheep. Four ruminally cannulated adult ewes were fed a high-concentrate diet, with no oil (Control diet), for a 14-day adaptation period. Afterwards, they were fed the same basal diet but supplemented with sunflower oil [20 g/kg fresh matter (FM)] and fish oil (10 g/kg FM) (SOFO diet) for a further 11 days, to investigate the impact of the addition of oils on the ruminal fermentation of the diet. On days 0 (Control), 3 and 10 of the experimental period rumen fluid was sampled at 0, 1.5, 3, 6 and 9 h after the morning feeding, for analysis of pH, and ammonia, lactate and total volatile fatty acid (VFA) concentrations. Alfalfa hay was incubated in situ, using the nylon bag technique, for 12 and 24 h to examine the effect of oil supplementation on ruminal disappearance of dry matter (DM), crude protein (CP) and neutral-detergent fibre (NDF). On days 0 and 11, rumen fluid was collected just before the morning feeding and used to incubate alfalfa hay and the Control and SOFO diets by means of the in vitro gas production technique. The mean concentrations of acetate (87.8 mmol/L vs. 73.7 mmol/L) and butyrate (21.2 mmol/L vs. 17.7 mmol/L) were reduced by oil supplementation (P < 0.05) and the total VFA showed a tendency (P = 0.098) to be lower with the SOFO diet (139.0 mmol/L vs. 122.1 mmol/L). However, none of the other in vivo ruminal fermentation parameters were affected by the treatment (P > 0.10). The oil supplementation affected neither in situ rumen disappearance of DM, CP and NDF of alfalfa hay, nor rates of gas production (P > 0.10). On the other hand, a little, but significant reduction in cumulative gas production was observed when the experimental diets were incubated with rumen fluid derived from animals fed the oil-rich diet (P < 0.05).Overall, the results suggest that the supplementation of high-concentrate diets with sunflower oil (20 g/kg FM) plus fish oil (10 g/kg FM) had little effect on ruminal fermentation and therefore its use to improve the nutritional value of ruminant-derived products cannot be precluded.     

Effect of rare earth elements on in vitro rumen microbial fermentation and feed digestion

The objectives of this study were to investigate the effects of rare earth elements (REEs) on in vitro rumen fermentation, gas production, microbial protein synthesis and nutrient digestion using in vitro batch culture and continuous culture technique. A mixture of REE containing (g/kg) 380 g of LaCI₃·6H₂O, 521 g of CeCI₃·6H₂O, 30 g of PrCI₃·6H₂O and 69 g chlorides of other light REEs. The experimental diet consisted of 885 g/kg barley grain, 84 g/kg barley silage and 31 g/kg supplement (dry matter (DM) basis). Diet supplemented with different dosages of REE (control, no additional REE; low, 400 mg/kg REE; and high, 800 mg/kg REE, DM basis) were incubated for 4, 8, 14 and 24 h in diluted rumen fluid. At the end of 24 h of incubation, gas production and concentration of volatile fatty acid (VFA) linearly increased with increasing REE supplementation; whereas, influence of REE supplementation on VFA profile was marginal. Dry matter disappearance was not affected (P>0.10). Six dual-flow continuous culture fermenters were used in a replicated 3 × 3 Latin square with same treatments and same diet used in the batch culture. Mean ruminal pH (5.71) and total VFA (93.6 mM) concentration were not affected by supplementation of REE. The molar proportion (mol/100 mol) of acetate (39.1) and propionate (50.5) was similar among the treatments. However, the proportion (mol/100 mol) of butyrate was higher with the high REE (6.6) than with low REE (5.3) or the control (5.8). Ruminal true digestibilities of organic matter (OM) (0.785, 0.811 and 0.828), acid detergent fibre (0.360, 0.431 and 0.432) and crude protein (0.496, 0.590 and 0.589) for control, low and high REE, respectively, linearly increased with increasing REE supplementation, whereas, the increase in ruminal digestibility from low to high dosage of REE was minimal. Microbial nitrogen (N) production (g/day) and microbial efficiency (g N/kg of truly fermented OM) were not affected by treatments. Improvement of ruminal digestibility of OM due to REE supplementation was attributed to the increase in digestibility of fibre and degradability of protein. The results suggest that REE supplementation improved ruminal fibrolytic and proteolytic activities.     

The impact of single and dual hydrothermal modifications on the molecular structure and physicochemical properties of normal corn starch

Effect of single and dual hydrothermal modifications with annealing (ANN) and heat-moisture treatment (HMT) on molecular structure and physicochemical properties of corn starch was investigated. Normal corn starch was modified by ANN at 70% moisture at 50 °C for 24 h and HMT at 30% moisture at 120 °C for 24 h as well as by the combination of ANN and HMT. The apparent amylose content and swelling factor (SF) decreased on ANN and HMT, but amylose leaching (AML) increased. These changes were more pronounced on dual modification. The crystallinity (determined by X-ray diffraction), the gelatinization enthalpy (determined by differential scanning calorimetry) and ratio of 1047 cm^?1/1022 cm^?1 (determined by Fourier transform infrared spectroscopy) slightly increased on ANN and decreased on HMT. The ANN and subsequent HMT (ANN-HMT) resulted in the lowest crystallinity, gelatinization enthalpy and ratio of 1047 cm^?1/1022 cm^?1. The gelatinization temperature range decreased on ANN but increased on HMT. However, the gelatinization range of dually modified starches (ANN-HMT and HMT-ANN) was between ANN starch and HMT starch. Birefringence remained unchanged on ANN but slightly decreased on HMT as well as dual modification. Average chain length and amount of longer branch chains (DP ≥ 37) remained almost unchanged on ANN but decreased on HMT and dual modifications (ANN-HMT and HMT-ANN). HMT and dual modifications resulted in highly reduced pasting viscosity. ANN and HMT as well as dual modifications increased RDS content and decreased SDS and RS content.     

Comparison of bovine rumen liquor and bovine faeces as inoculum for an in vitro gas production technique for evaluating forages

Two experiments were undertaken using the in vitro gas production technique of Theodorou et al. [Anim. Feed Sci. Technol. 48 (1994) 185] to compare rumen liquor (RL) and faeces (FA) as inocula for fermenting gramminaceous forages over 96 h periods. Experiment 1 used 12 forages of differing in vivo digestibility (ammonia treated wheat straw, field-cured hay (Lolium perenne) and 10 artificially dried grasses (L. perenne) harvested at different maturities). Experiment 2 used seven maize-silage based forages (whole plant, stover, leaf, lower stem, middle stem, upper stem and husk). In both experiments, rumen liquor and faeces were obtained from two cows in early lactation, each fed daily with 9.4 kg DM of grass silage and 9.0 kg DM of concentrate. Rumen contents were sampled through the fistula, before morning feeding; faeces were sampled from the rectum, immediately afterwards. Rumen liquor (250 ml) was prepared by straining contents through two layers of muslin, adding the solids after blending with 250 ml of buffer and re-straining. Faeces were prepared by mixing (300 ml) with 150 ml of buffer and straining through two layers of muslin and adding a homogenate of the solids and 150 ml of buffer after straining. Data were fitted to the model of France et al. [J. Theor. Biol. 163 (1993) 99]. All model parameters showed FA to have a poorer fermentation capacity than RL. In both experiments, potential gas production volumes (A) were lower (on average 52.9 ml (18.5%)) and lag times longer (on average 2.9 h) for FA compared to RL. Fractional rate of fermentation at half asymptote (T/2) was generally greater for RL than FA (overall means, 0.042, 0.028) and the time required to T/2 being less (overall means, 21.9, 35.4 h). However, potential gas production (A) was highly correlated between RL and FA: Experiment 1 (r²=0.94, 11 forages, excluding ammonia treated straw) and Experiment 2 (r²=0.83, six forages, excluding middle stem). In Experiment 1, organic matter digestibility in vivo (OMD_IV) was also highly correlated with both OMD_FA (r²=0.77, 11 forages) and OMD_RL (r²=0.89, 11 forages); OMD_RL and OMD_FA were also highly correlated (r²=0.81). Similar correlations occurred in Experiment 2. It is concluded that faeces have potential as an alternative inoculum to rumen liquor for in vitro gas production techniques, but methods of overcoming the longer lag phase with faeces require further research.     

Mycophenolic acid production in solid-state fermentation using a packed-bed bioreactor

Mycophenolic acid (MPA) was produced from Penicillium brevicompactum by solid-state fermentation (SSF) using pearl barley, and submerged fermentation (SmF) using mannitol. It was found that SSF was superior to SmF in terms of MPA concentration (1219 mg/L vs. 60 mg/L after 144 h fermentation), and the product yields were 6.1 mg/g pearl barley for SSF and 1.2 mg/g mannitol for SmF. The volumetric productivities were 8.5 and 0.42 mg/L h for SSF and SmF, respectively.The optimum solid substrate of SSF for MPA production was pearl barley, producing 5470 mg/kg compared with wheat bran (1601 mg/kg), oat (3717 mg/kg) and rice (2597 mg/kg). The optimum moisture content, incubation time and inoculum concentrations were 70%, 144 h and 6%, respectively. Neither the addition of mannitol or (NH4)₂HPO₄ nor adjustment of media pH within the range of 3–7 significantly enhanced MPA production.MPA production by SSF using a packed-bed bioreactor was performed and an increased maximum production of MPA 6.9 mg/g was achieved at 168 h incubation time. The higher volumetric productivity and concentrations makes SSF an attractive alternative to SmF for MPA production.     

Milk fatty acid composition of dairy cows grazing at two pasture allowances and supplemented with different levels and sources of concentrate

Milk fatty acid (FA) composition of dairy cows from two grazing studies was examined. In the first study, effects of concentrate supplementation and pasture allowance were evaluated using 20 multiparous Holstein cows in five 4 × 4 Latin squares. The four treatments resulted from the combination of two pasture allowances (i.e., low, 25 versus high, 40 kg dry matter/cow/day) and two concentrate supplementation levels (i.e., 0 versus 1 kg concentrate/4 kg milk). No interactions occurred between concentrate supplementation and pasture allowance for milk FA composition. Concentrate supplementation increased short-chain FA content, and reduced the content of long-chain FA, trans11 C18:1, and cis9, trans11 conjugated linoleic acid (CLA) (1.36 versus 1.18 g/100 g). Concentrate supplementation increased saturated FA (58.6 versus 54.0 g/100 g) and reduced unsaturated FA content (39.9 versus 43.8 g/100 g). Grazing at high pasture allowance increased short-, medium-, and long-chain FA content, without affecting cis9, trans11 CLA content. Saturated FA content was higher (57.1 versus 55.6 g/100 g), and unsaturated FA content was lower (41.3 versus 42.5 g/100 g), when cows grazed at high pasture allowance. Concentrate supplementation reduced unsaturated FA and cis9, trans11 CLA in milk of dairy cows grazing at two pasture allowances. In the second study, two experiments evaluated effects of different energy supplements in grazing dairy cows. In Experiment 1, 25 multiparous Holstein cows were assigned to a cracked corn (CC) or a steam flaked corn (SFC) supplement containing 667 g/kg of corn grain plus a pelleted protein/mineral supplement. In Experiment 2, 22 multiparous Holstein cows were assigned to a ground corn grain (GC) or a non-forage fiber (NFF) supplement. The GC supplement contained 850 g/kg of corn grain, and the NFF supplement contained 440 g/kg of non-forage fiber sources (i.e., beet pulp, soyhulls, wheat middlings) that partially replaced corn grain. Milk FA composition was not affected by corn processing or carbohydrate source. The content of short-, medium-, long-chain FA, and cis9, trans11 CLA (2.5 g/100 g in Experiment 1; 2.1 g/100 g in Experiment 2) was similar between supplements in both experiments. The type of supplement did not affect the content of saturated (62.6 g/100 g in Experiment 1; 65.4 g/100 g in Experiment 2) and unsaturated FA (37.5 g/100 g in Experiment 1; 34.6 g/100 g in Experiment 2). Supplementation with supplements differing in the rate and extent of ruminal carbohydrate digestion did not affect the milk FA composition of grazing dairy cows.     

The hydrolysate of barley straw containing inhibitors can be used to produce cephalosporin C by solvent extraction using ethyl acetate

When the solvent extraction of the hydrolysate from barley straw was performed using ethyl acetate (EA), the logarithm of the partition coefficient (log P) of the phenols and furans for EA was found to be more than 1.00, which means that more than 90% of the inhibitors were removed from the hydrolysate layer. Cephalosporin C (CPC) was produced from the hydrolysate of dilute acid pretreatment (DAP) by Acremonium chrysogenum M35. A. chrysogenum M35 was cultured using the hydrolysate and the amount of CPC produced was found to be 10.35 g/L at 144 h. Also, the dry cell weight was about 101.5 g/L at 120 h. The utilization of the hydrolysate for CPC production was effective and the solvent extraction method for the removal of inhibitory substances could contribute to the biorefinery process.