The DMACA–HCl Protocol and the Threshold Proanthocyanidin Content for Bloat Safety in Forage Legumes

A protocol using HCl-acidified 4-dimethylaminocinnamaldehyde (DMACA) was developed for screening proanthocyanidins (PA) in plants. Individual PA-containing cells could be observed following staining of decolourised leaves with DMACA. The quantitative assay using DMACA-HCl to detect soluble PA and butanol–HCl to detect insoluble PA could detect PA content lower than 0·4 mg g⁻¹ dry matter (DM). The DMACA–HCl protocol is recommended for PA detection in low-PA plants because of its higher sensitivity than vanillin–acid protocols. Twenty-two forage legume species, most of which had been reported free of leaf PA but bloat-safe, were re-examined using the DMACA–HCl protocol. PA-positive cells were observed in leaves of 15 species. Measurable amounts of PA were detected in leaves of seven species, with the PA content ranging from 0·6 to 11 mg g⁻¹ DM. White clover ( Trifolium repens L), red clover ( T pratense L) and lucerne ( Medicago sativa L) were also found to have PA-positive leaf trichomes. By analysis of these data and the literature, the threshold PA content for bloat safety in forage legumes was estimated to be 1–5 mg PA g⁻¹ DM.     

A Simple Method for Estimation of Neutral Detergent-Soluble Fibre

A method was developed to estimate the neutral detergent-soluble fibre (NDSF) content of feeds. Citrus pulp, sugar beet pulp, soybean hulls, separated leaves and stems from mature and immature alfalfa, red clover, reed canarygrass and timothy were analysed. Half-gram samples were stirred at room temperature for 4 h with 100 ml of 90:10 (v/v) ethanol/water to extract low molecular weight substances, crude protein (CP) and ash to produce ethanol-insoluble residues (EIR). Samples were refluxed for 1 h with neutral detergent solution and heat stable α-amylase to extract low molecular weight substances, NDSF, starch, CP and ash to produce neutral detergent residues (NDF). The EIR and NDF were analysed for organic matter (OM; EIROM; NDFOM) and CP (EIRCP; NDFCP), and EIR was analysed for starch. Values were expressed as proportions of the original sample dry matter. The NDSF was calculated as the difference in OM mass between EIR and NDF after correction for CP and starch by the equation: EIROM-NDFOM-EIRCP+NDFCP-EIR starch. Extractions with 90:10 (v/v) ethanol/water gave a higher yield of EIR and NDSF than did 80: 20 (v/v) ethanol/water. The method gave good precision and is convenient for assessing NDSF content of feeds. © 1997 SCI.     

In vitro degradability of three forages: fermentation kinetics and gas production of NDF and neutral detergent‐soluble fraction of forages

The fermentation of the neutral detergent‐soluble (NDS) fraction of three forages (alfalfa hay, Italian ryegrass + oats hay and corn silage) was measured using a curve subtraction technique with in vitro gas production data from the whole forage (WF) and the isolated neutral detergent fibre (NDF). NDF disappearance and volatile fatty acid (VFA) production were determined. There was no significant difference between the VFA patterns from the whole forage and the isolated NDF. There were significant (P < 0.001) linear correlations between the volume of gas and moles of VFA produced and the mass of fibre digested in the NDF samples. Using the monophasic curve model, maximum gas production rates (R_M) for the whole forages and the isolated NDF and NDS fractions can be calculated. For all three forages we obtained R_M‐NDS > R_M‐WF > R_M‐NDF. Trends in the rates of gas and VFA production were similar in the whole forages. The NDF showed a high superimposition between substrate degradability and VFA production. Our experiment confirmed the curve subtraction technique as a simple method to obtain information on the size and digestion kinetics of the NDS fraction, which helps in understanding the nutritional significance of this important fraction of the forages studied. © 2001 Society of Chemical Industry     

Isolation of grass cell walls as neutral detergent fibre increases their fermentability for rumen micro‐organisms

Cell wall isolated from grasses as neutral detergent fibre (NDF) is fermented more readily than cell wall in the unfractionated forage by rumen organisms in vitro. In several experiments with Heteropogon contortus and Astrebla squarrosa the NDF digestibility at 48 h for the isolated cell wall was 8–18 units higher than for the unfractionated forage, with most of the difference appearing in the first 24 h of fermentation. Similar in vitro increases were obtained for Sorghum sp, wheat hay, bagasse and Lolium perenne and less so for Panicum maximum. The difference was not significant for Chloris gayana, nor for the tropical legumes Stylosanthes hamata, Clitoria ternatea and Lablab purpureus. For those grasses in which the above effect was statistically significant there was a significant relationship between NDF content of the unfractionated grass (x) and the ratio of NDF digestibility of isolated NDF to that of the unfractionated grass, as described by y=0.018x (P<0.01). For H contortus, kinetic analysis of gas produced from 0 to 48 h of in vitro incubation with rumen microbes showed an increased (from 0.016 to 0.020 h ⁻¹, P<0.001) rate of production from the slowly‐digested pool. Spear grass NDF incubated in the rumen in polyester bags had a higher NDF loss than unfractionated forage between 9 and 24 h and the difference was maintained after 24 h. Treatments in which amorphous silica was precipitated within NDF or leached from a grass substrate indicated that the enhanced rate in grasses was not due to removal of biogenic silica by the neutral detergent treatment. © 1999 Society of Chemical Industry     

In vitro fermentation kinetics of carbohydrate fractions of fresh forage,silage and hay of Avena sativa

The objective of this experiment was to evaluate the influence of preservation methods on the fermentation kinetics of carbohydrate fractions of fresh forage, hay and silage of oats, which have been harvested at the milky stage of grain ripening. Samples of unfractionated forage (WF), residue insoluble in 90% ethanol (EIR) and isolated neutral detergent fibre (NDF) were fermented in vitro and the gas production was monitored. To obtain the gas production and fermentation kinetics of the ethanol‐soluble fraction (A fraction) the gas produced from the EIR fermentation was subtracted from the WF gas at each time point. The same approach was used to obtain the gas production and fermentation kinetics of the fraction insoluble in 90% ethanol but soluble in neutral detergent solution (B₁ fraction), by subtracting the isolated NDF gas curve from the corresponding EIR curve. The fractional maximum rate of gas production (R_M) was lower for both preserved forages (p < 0.01 for silage; p < 0.05 for hay) than for fresh forage. Ensiling did not change the size of the A fraction but reduced by 40% its R_M (p < 0.01) compared with fresh forage. The potential gas production from the B₁ fraction and its R_M were reduced by 19% (p < 0.01) and 44% (p < 0.05), respectively. R_M of both A and B₁ fractions was the same for hay and fresh forage. The curve subtraction technique may be used to obtain an estimation of the rate for neutral detergent‐soluble fractions and to determine changes due to ensiling and haymaking on the rate of gas produced. Copyright © 2005 Society of Chemical Industry     

The Condensed Tannin Content of a Range of Subtropical and Temperate Forages and the Reactivity of Condensed Tannin with Ribulose- 1,5-bis-phosphate Carboxylase (Rubisco) Protein

A series of subtropical grasses and temperate grasses, herbs and legumes were analysed for the presence of extractable and bound condensed tannin (CT) using colorimetric analysis by the butanol–HCl method. Condensed tannins are routinely purified using affinity chromatography with Sephadex LH-20 as a matrix. Therefore, Sephadex LH-20 extracts were further analysed for the presence of CT by ¹³C nuclear magnetic resonance, for anthocyanidin formation after butanol–HCl treatment and for their ability to precipitate ribulose-1,5-bisphosphate carboxylase (Rubisco) protein from lucerne, at pH 7·0. Criteria for the presence or absence of CT were defined. Trace amounts of CT (0·2–2·5 g kg⁻¹ dry matter; DM) were identified and confirmed in summer grass (Digiteria sanguinalis), perennial ryegrass (Lolium perenne) and red clover (Trifolium pretense), with chicory (Chicorium intybus), lucerne (Medicago sativa) and plantain (Plantago lanceolata) identified as probably containing CT. It was concluded that the subtropical grasses kikuyu (Pennisetum clandestinum), paspalum (Paspalum diatatum), smooth witchgrass (Panicum dichotomiflorum) and crowfoot (Eleusine indica) and the temperate grass, Yorkshire fog (Holcus lanatus) probably did not contain CT. Analysis of the extractable fractions by vanillin–HCl gave higher values for CT than analysis by butanol–HCl and wrongly identified some forages as containing trace levels of CT. It was concluded that vanillin–HCl was not specific enough for the detection of trace levels of CT in forages. These results raise the possibility of plant selection programmes to increase the level of CT in grazed forages to approximately 5 g kg⁻¹ DM, the suggested minimum level required to prevent bloat in cattle and to increase wool growth in sheep. It is suggested that this be considered for perennial ryegrass, chicory, red clover and lucerne.     

Utilization of kura clover-reed canarygrass silage versus alfalfa silage by lactating dairy cows

The mixture of kura clover (Trifolium ambiguum M. Bieb.) and reed canarygrass (Phalaris arundinacea L.) has proven to be extremely persistent in the northern United States, but information about dairy cow performance on this mixture is lacking. Twenty lactating Holstein cows were used in a crossover design to compare dry matter (DM) intake and milk production from diets containing kura clover-reed canarygrass silage (KRS) or alfalfa (Medicago sativa L.) silage (AS). Forages were cut, wilted, ensiled in horizontal plastic bags, and allowed to ferment for at least 50 d before beginning the feeding experiment. The KRS was approximately 40% kura clover and 60% reed canarygrass. Treatments were total mixed rations formulated with either 57% of total DM from 1) AS or 2) KRS. Experimental periods were 28 d, with the first 14 d for diet adaptation and the last 14 d for measurement of intake and milk production. The neutral detergent fiber (NDF) concentrations of AS and KRS were 37.3 and 47.3%, respectively. The fermentation analyses indicated that both silages underwent a restricted fermentation, producing primarily lactic acid and some acetic acid. Dry matter intake (24.2 vs. 22.8 kg) and 4% fat-corrected milk (32.8 vs. 30.9 kg) were significantly higher for cows fed AS than for cows fed KRS. Cows consumed less NDF (6.7 vs. 8.0 kg) and less digestible NDF (3.0 vs. 4.4 kg) when fed AS diets compared with KRS diets, but the pool of ruminally undegraded NDF was similar (3.7 kg) between diets. Cows produced 1.5 kg of milk/kg of DM consumed regardless of the diet, indicating that digestible NDF of KRS was utilized with similar efficiency as the cell wall constituents of AS, but the intake of cows fed KRS may have been limited by rumen fill. Milk fat concentration tended to be higher for cows fed AS, but the milk true protein concentration and yields of fat and protein did not differ by treatment. Milk urea nitrogen content was higher when cows consumed AS (16.4 mg/ dL) compared with KRS (13.4 mg/dL). The cows fed KRS consumed more NDF but less total DMI, based on the results from this trial with diets formulated to contain approximately 60% of DM as forage, resulting in slightly lower milk yields than cows fed excellent-quality AS. This grass-legume mixture has the potential to be a source of quality forage for dairy cows in regions where alfalfa persistence is a problem.     

A comparison of the insoluble residues produced by the Klason lignin and acid detergent lignin procedures

Two methods—Klason lignin (KL) and acid detergent lignin (ADL)— for determining lignin concentration in plants were compared using stem material from lucerne (Medicago sativa L), cocksfoot (Dactylis glomerata L) and switchgrass (Panicum virgatum L), at three stages of maturity, and leaf samples from lucerne and cocksfoot. For all forages, KL values were higher than ADL values. Lucerne samples, which had crude protein levels twice that of the grass species, had KL values that were only 30–40% higher than ADL values; in grasses, KL values were 200–300% greater than ADL values. The addition of nitrogenous materials (bovine serum albumin, lysine, and ammonium sulfate) to commercial xylan and cellulose did not result in additional KL residue. Pyrolysis-GC-MS revealed that both residues appeared to be similar to the orginal plant lignin and did not appear to be contaminated with carbohydrate or protein. The higher values for grass KL residues were not due to protein con- tamination or incomplete hydrolysis of carbohydrates, but were more likely due to the solubilization of lignin components by the ADL treatment. KL values may give a more accurate quantification of the total lignin within forage plants.     

Relationship between Phenolic Acids Formed During Rumen Degradation of Maize Samples andin vitroDigestibility

The organic matter (OMD) and cell wall (CWD) digestibility of stalks of 25 different maize samples were determined in an in vitro assay using rumen fluid. The stalk OMD and CWD varied between 62–80% and 44–62%, respectively. The free phenolic acids formed in the liquid phase during fermentation in in vitro incubations were assessed by HPLC and ¹H NMR. The following nine phenolic acids could be demonstrated to be present: p -hydroxybenzoic (HBA), p -hydroxyphenylacetic (HPAA), vanillic (VA), syringic (SYRA), 3-(4-hydroxyphenyl)propionic (HPPA), p -coumaric (PCA), ferulic (FA), phenylacetic (PAA) and 3-phenylpropionic (PPA) acids. Large variation was observed among the maize samples for all phenolic acids identified. The most abundant phenolic acids, PPA, PAA and HPAA were present in concentrations ranging from 0·57 to 1·41 mM, 0·32 to 0·46 mM, and 71 to 105 μM, respectively, and were present as free monomeric molecules. HBA concentrations ranged from 6·9 to 21·1 μM and this acid was also present as free molecules. The other phenolic acids could only be observed after NaOH treatment of the liquid phase and were detected in minor amounts (0 to 12 μM). Correlation studies revealed a negative relation between digestibility and NaOH labile esters in the medium (ie PCA, FA, VA and SYRA esters) and a positive relationship between digestibility and PPA and PAA. When path analysis was applied, an inverse effect of PCA esters in the medium on both OMD and CWD ( r =-0·71 and −0·56, respectively) was observed and a high positive effect of PPA acid on CWD ( r =+0·67). Principal component analysis revealed close associations between released phenolic acid esters, neutral detergent fibre, and cell wall esters of PCA and FA.     

The study of Clitoria Ternatea L. hay as a forage alternative in tropical countries. Evolution of the chemical composition at four different growth stages

The nutrients and the total carotenoids of samples of Clitoria rernatea L. hay harvested at four different stages of growth were analysed. Yields were also estimated. The results were: protein (N × 6.25), 23–19%; crude fibre, 29–38%; ether extract, 4.4–3.4%; Ash, 9–7%; neutral detergent fibre (NDF), 42–54%; acid detergent fibre (ADF), 38–47%; permanganate lignin, 14–16%; cellulose, 21–29%. Moreover, after being stored for 6 months, the samples have a carotenoids content of 587–400 mg kg^?1. All data refer to DM content. First year results reveal that the forage plant can give high annual yields of hay, (18–29 t ha^?1) with good palatability, readily accepted by cattle. In certain warm areas with low rainfall it could replace lucerne (alfalfa) Medicago sativa L.     

Modification of in-vitro digestibility and cell-wall composition of cocksfoot,ryegrass and timothy by imazethapyr

Recent studies have shown that the compound imazethapyr (5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid) possesses growth regulatory activity and can be used to enhance nutritive value of grasses. However, little is known about possible effects of this material on fibre composition or potential fibre utilisation by ruminants. The objective of this research was to examine imazethapyr-treated cocksfoot (Dactylis glomerata L), ryegrass (Lolium perenne L × L multiflorum Lam), and timothy (Phleum pratense L) for possible treatment-induced changes in in-vitro digestibility and in concentrations of selected fibre constituents. Replicated field plots treated with imazethapyr at 0 (control) or 100 g ai ha^?1 during the vegetative (pre-elongation) stage of growth were harvested when controls were in the early stage of inflorescence emergence. Samples taken from treated plots 4 weeks post-treatment had higher in-vitro dry matter disappearance (IVDMD), lower neutral detergent fibre (NDF), lower acid detergent fibre (ADF), lower cellulose, lignin, and higher hemicellulose concentrations compared with controls. Imazethapyr treatment also reduced the concentration of p-coumaric acid in NDF, but had no effect on ferulic acid. The treatment effect on in-vitro NDF disappearance, however, was inconsistent among the grass species and was statistically non-significant (P = 0·10), implying that, under the conditions of this study, imazethapyr-related enhancements in IVDMD can be attributed primarily to a reduction in the amount of NDF and its associated constituents, as opposed to qualitative differences in NDF composition.     

Chemical characterisation and ruminal nutrient degradability of hulled and hull-less oats

The objectives of this study were to determine the chemical and ruminal nutrient degradability characteristics of two hulled (Calibre and AC Mustang) and one hull-less (AC Belmont) oat varieties. Ruminal nutrient degradability characteristics of the oat varieties were determined relative to barley using one ruminally fistulated cow. Neutral (NDF) and acid (ADF) detergent fibre levels were higher (P < 0·05) in hulled than hull-less oats. Hulled AC Mustang had higher (P < 0·05) NDF and ADF content than hulled Calibre. Starch content was higher (P < 0·05) in AC Belmont (590 g kg⁻¹) than Calibre (457 g kg⁻¹) and was higher in Calibre than AC Mustang (415 g kg⁻¹). Crude protein was higher (P < 0·05) in hull-less than hulled oat. Both hulled varieties had similar CP content (average 124 g kg⁻¹). Estimated digestible energy value was highest (P < 0·05) for AC Belmont (16·94 MJ kg⁻¹), intermediate for Calibre (14·18 MJ kg⁻¹) and lowest for AC Mustang (13·34 MJ kg⁻¹). Ruminal dry matter and NDF degradability were higher (P < 0·05) in hull-less than barley and was higher in barley than hulled oats. Ruminal starch degradability exceeded 900 g kg⁻¹ for all tested feeds and had the order AC Belmont = barley > Calibre = AC Mustang. It was concluded that oat varieties used in this study varied considerably in their chemical composition and ruminal degradability. When compared with barley, hulled oats had lower while hull-less oats had higher ruminal degradability. © 1998 SCI.     

Ergovaline occurrence in grasses infected by fungal endophytes of semi‐arid pastures in Spain

Ergovaline is a mycotoxin produced by fungal endophytes belonging to Neotyphodium and Epichloë spp in several host grass species. Owing to the production of this alkaloid, the ingestion of endophyte‐infected grasses causes toxicosis in grazing animals. The aim of this work was to determine if ergovaline is produced in several grasses (Agrostis castellana Boiss and Reuter, Brachypodium phoenicoides (L) Roemer and Schultes, Dactylis glomerata L, Festuca arundinacea Schreb, Festuca arundinacea Schreb subsp fenas (Lag) Arcangeli, Festuca ovina L, Festuca rubra L, Holcus lanatus L and Lolium perenne L) infected by fungal endophytes in ‘dehesa’ pastures in Spain. Forage and seed samples of several ecotypes of these grass species were analysed for their ergovaline content by HPLC with fluorescence detection. The ergovaline content ranged between 0.03 and 0.85 µg g^?1 in forage and 0.28 and 3.17 µg g^?1 in seed samples of F arundinacea, between 0.00 and 0.08 µg g^?1 in forage and 0.02 and 0.19 µg g^?1 in seed samples of F rubra, between 0.00 and 0.02 µg g^?1 in forage samples of H lanatus, and was 0.11 µg g^?1 in one ecotype of F ovina. All nine ecotypes of F rubra had ergovaline in seed samples, but in three ecotypes the alkaloid was not detected in forage samples. No ergovaline was detected in the other four endophyte‐infected grasses analysed. The ergovaline content should be considered as an anti‐quality parameter to be measured when the nutritional quality of these pastures is evaluated. © 2003 Society of Chemical Industry     

Factors affecting ANKOM™ fiber analysis of forage and browse varying in condensed tannin concentration

BACKGROUND: Browse species containing condensed tannins (CTs) are an important source of nutrition for grazing/browsing livestock and wildlife in many parts of the world, but information on fiber concentration and CT–fiber interactions for these plants is lacking. RESULTS: Ten forage or browse species with a range of CT concentrations were oven dried and freeze dried and then analyzed for ash‐corrected neutral detergent fiber (NDFom) and corrected acid detergent fiber (ADFom) using separate samples (ADFSEP) and sequential NDF‐ADF analysis (ADFSEQ) with the ANKOM^? fiber analysis system. The ADFSEP and ADFSEQ residues were then analyzed for nitrogen (N) concentration. Oven drying increased (P < 0.05) fiber concentrations with some species, but not with others. For high‐CT forage and browse species, ADFSEP concentrations were greater (P < 0.05) than NDFom values and approximately double the ADFSEQ values. Nitrogen concentration was greater (P < 0.05) in ADFSEP than ADFSEQ residues, likely due to precipitation with CTs. CONCLUSION: Sequential NDF‐ADF analysis gave more realistic values and appeared to remove most of the fiber residue contaminants in CT forage samples. Freeze drying samples with sequential NDF‐ADF analysis is recommended in the ANKOM^? fiber analysis system with CT‐containing forage and browse species. Copyright © 2010 Society of Chemical Industry     

Biodegradation of cell wall components of maize stover colonized by white-rot fungi and resulting impact on in-vitro digestibility

Treatment of crop residues with some species of white-rot fungi can enhance digestibility. This study was conducted to investigate changes in in-vitro dry matter disappearance (IVDMD) and degradation of cell wall constituents in maize (Zea maize L) stover treated with three white-rot fungi: Cyathus stercoreus, Phlebia brevispora and Phanerochaete chrysosporium. Solid fermentation of maize stover for 28 days at 27°C improved IVDMD from 409 g kg^?1 (control) to 514 g kg^?1 for P brevispora and 523 g kg^?1 for C stercoreus. In contrast, growth of P chrysosporium reduced IVDMD from 409 to 298 g kg^?1. All fungi degraded cell wall p-coumaric acid (PCA) and ferulic acid (FA), but P chrysosporium was the least effective in degrading PCA and FA. Conversely, P chrysosporium degraded lignin 1·6 times more effectively than C stercoreus and 1·4 times more than P brevispora, indicating that lignin degradation alone cannot account for the IVDMD enhancement and that degradation of PCA and FA may be important. Hemicelluloses were preferentially and highly utilized by all the fungi. Cellulose was extensively degraded only by P chrysosporium (69% lost after 28 days of incubation), while substrate colonized by the other two fungi retained more than 84% original cellulose. Incubation of C stercoreus and P brevispora decreased the concentrations of both xylose and arabinose, but increased glucose concentration, whereas P chrysosporium removed less xylose and decreased glucose concentration. Preferential removal of arabinose over xylose by the fungi caused an increase in the xylose to arabinose ratio of the treated residues. Enhanced digestibility may have resulted from cleavage of lignin-carbohydrate bonds. Results of this study suggest that digestibility enhancement of maize stover colonized by white-rot fungi is regulated by a complex combination of various factors, including the degradation of structural carbohydrates, cell wall phenolic acids and lignin.     

Effect of palmitic acid-enriched supplements containing stearic or oleic acid on nutrient digestibility and milk production of low- and high-producing dairy cows

We evaluated the effects of fatty acid (FA) supplement blends containing 60% palmitic acid (C16:0) and either 30% stearic acid (C18:0) or 30% oleic acid (cis-9 C18:1) on nutrient digestibility and milk production of low- and high-producing dairy cows. Twenty-four multiparous Holstein cows [118 ± 44 d in milk (DIM)] were divided into 2 blocks by milk production and then randomly assigned to treatment sequence in four 3 × 3 Latin squares within production level, balanced for carryover effects in three consecutive 21-d periods. Cows were blocked by milk yield and assigned to 1 of 2 groups (n = 12 per group): (a) low group (42.5 ± 3.54 kg/d; 147 ± 42 DIM) and (b) high group (55.8 ± 3.04 kg/d; 101 ± 34 DIM). Commercially available fat supplements were combined to provide treatments that consisted of the following: (1) control (CON; diet with no supplemental FA), (2) FA supplement blend containing 60% C16:0 and 30% C18:0 (PA+SA), and (3) FA supplement blend containing 60% C16:0 and 30% cis-9 C18:1 (PA+OA) The FA blends were fed at 1.5% of dry matter (DM) and replaced soyhulls from CON. Preplanned contrasts were (1) overall effect of FA treatments [CON vs. the average of the FA treatments (FAT); 1/2 (PA+SA + PA+OA)], and (2) effect of FA supplement (PA+SA vs. PA+OA). Regardless of production level, overall FAT reduced DMI compared with CON. Also, regardless of level of milk production, PA+OA increased total-tract FA digestibility compared with PA+SA. Treatment by production level interactions were observed for neutral detergent fiber (NDF) digestibility, total FA intake, and the yields of 3.5% fat-corrected milk (FCM), energy-corrected milk (ECM), and milk fat. In low-producing cows, FAT increased DM and NDF digestibility compared with CON. In high-producing cows PA+SA increased DM and NDF digestibility compared with PA+OA. In low-producing cows, PA+SA increased 3.5% FCM, ECM, and milk fat yield compared with PA+OA. However, in high-producing cows PA+OA tended to increase 3.5% FCM compared with PA+SA. In conclusion, low-producing cows responded better to a FA blend containing 60% C16:0 and 30% C18:0, whereas high-producing dairy cows responded more favorably to a FA blend containing 60% C16:0 and 30% cis-9 C18:1. However, further research is required to validate our observations that higher-yielding cows have improved production responses when supplemented with cis-9 C18:1 compared with C18:0.     

Ensiling characteristics and ruminal degradation of Italian ryegrass and lucerne silages treated with cell wall-degrading enzymes

Two experiments were carried out to investigate the effect of added cell wall-degrading enzymes at ensiling on the fermentation and in situ degradation of grass and legume silages. Primary growths of Italian ryegrass (Lolium multiflorum Lam) and lucerne (Medicago sativa L) were wilted and ensiled in laboratory-scale silos with or without enzymes. Silages were opened at 2, 5, 15 and 45 days after storage; the fermentation quality and the contents of cell wall components (NDF, ADF, ADL) were determined. The 45 day silages were subjected to in situ incubation experiments, and the kinetics of DM and NDF degradation was estimated. The enzyme treatment enhanced the lactic acid production (P < 0.01) and reduced the pH value (P < 0.01) of both Italian ryegrass and lucerne silages. The contents of cell wall components, however, were not affected by enzymes, except for NDF of Italian ryegrass silage. The in situ incubation experiments revealed that added enzymes increased the rapidly degradable DM (P < 0.01) and appeared to decrease the rate of degradation of DM and NDF of Italian ryegrass silage. The rapidly degradable DM was not altered when lucerne was treated, but the rate of degradation of NDF was significantly reduced (P < 0.05). These results suggest that although added cell wall-degrading enzymes could improve the preservation of grass and legume silages, the effects on ruminal degradation may be different according to the herbage treated. Enzymatic hydrolysis during ensilage may be restricted to easily digestible cell walls, leaving relatively less digestible components that would be retained in treated silages. © 1999 Society of Chemical Industry     

Effect of lignin linkages with other plant cell wall components on in vitro and in vivo neutral detergent fiber digestibility and rate of digestion of grass forages

The objective of this study was to correlate in vitro and in vivo neutral detergent fiber (NDF) digestibility (NDFD) with the chemical composition of forages and specific chemical linkages, primarily ester- and ether-linked para-coumaric (pCA) and ferulic acids (FA) in forages fed to dairy cattle. The content of acid detergent lignin (ADL) and its relationship with NDF does not fully explain the observed variability in NDFD. The ferulic and p-coumaric acid linkages between ADL and cell wall polysaccharides, rather than the amount of ADL, might be a better predictor of NDFD. Twenty-three forages, including conventional and brown midrib corn silages and grasses at various stages of maturity were incubated in vitro for measurement of 24-h and 96-h NDFD. Undigested and digested residues were analyzed for NDF, acid detergent fiber (ADF), ADL, and Klason lignin (KL); ester- and ether-linked pCA and FA were determined in these fractions. To determine whether in vitro observations of ester- and ether-linked pCA and FA and digestibility were similar to in vivo observations, 3 corn silages selected for digestibility were fed to 6 ruminally fistulated cows for 3 wk in 3 iso-NDF diets. Intact samples and NDF and ADF residues of diet, rumen, and feces were analyzed for ester- and ether-linked pCA and FA. From the in vitro study, the phenolic acid content (total pCA and FA) was highest for corn silages, and overall the content of ester- and ether-linked pCA and FA in both NDF and ADF residues were correlated with NDF digestibility parameters, reflecting the competitive effect of these linkages on digestibility. Also, Klason lignin and ADL were negatively correlated with ether-linked ferulic acid on an NDF basis. Overall, esterified FA and esterified pCA were negatively correlated with all of the measured fiber fractions on both a dry matter and an NDF basis. The lignin content of the plant residues and chemical linkages explained most of the variation in both rate and extent of NDF digestion but not uniformly among forages, ranging from 56 to 99%. The results from the in vivo study were similar to the in vitro data, demonstrating the highest total-tract aNDF digestibility (70%; NDF analysis conducted with α-amylase and sodium sulfite) for cows fed the corn silage with the lowest ester- and ether-linked pCA content in the NDF fraction. In this study, digestibility of forage fiber was influenced by the linkages among lignin and the carbohydrate moieties, which vary by hybrid and species and most likely vary by the agronomic conditions under which the plant was grown.     

Cell-Constituents,Tannin Levels by Chemical and Biological Assays and Nutritional Value of Some Legume Foliage and Straws

Twenty six straw and 15 foliage samples of Lathyrus sativus , Vicia narbonensis , V sativa and V ervilia were analysed for ash, crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), extractable phenols (Pe), extractable tannins (Te), extractable condensed tannins (CTe), protein precipitation capacity (PPC) and in vitro characteristics predicted from Hohenheim gas test. The content of crude protein in the foliage was significantly higher than that of the straws (152·6 vs 64·5 g kg⁻¹), while ash (82·8 vs 116·8 g kg⁻¹), NDF (332·7 vs 523·5 g kg⁻¹) and ADF (205·2 vs 369·9 g kg⁻¹) were significantly lower. For straws of L sativus , V narbonensis and V sativa , there was no significant difference in the protein and ADF contents, whereas ash and NDF contents were significantly lower and higher respectively in L sativus as compared to V narbonensis or V sativa . Predicted from gas volumes, the organic matter digestibility (OMD: 70 vs 56%) and metabolisable energy (ME: 9·7 vs 7·3 MJ kg⁻¹) were significantly higher for the foliage compared to straws. The OMD of L sativus straws was significantly lower compared to the straws of V narbonensis and V sativa . The OMD and ME of the straws of second year was significantly lower than those of the first year. The CP, OMD and ME of V sativa foliage were higher than that of V narbonensis . There was no difference in the cell constituents, OMD and ME of foliage samples of V sativa harvested in May 1992 and June 1992. The contents of Pe, Te and CTe of straws were 1·08%, 0·43% and 0·33%, respectively, and those of foliage were 2·27%, 1·30% and 1·63%, respectively. PPC was not detected for any of the foliage and straw samples. The results suggested that the tannin levels of legume straws investigated are negligible and those of the legume foliage are very low. This does not appear to adversely affect their nutritive value since the maximum decrease in OMD by the tannins was about 3% units.     

Lipid and flavour quality of stored breast meat from broilers fed marine algae

In the current study, broilers were fed either 2·8 or 5·5% natural golden marine algae (MA) or 2·1% menhaden oil in an effort to produce an n-3 fatty acid (FA) enriched broiler breast product with acceptable flavour and lipid quality. Previously cooked or raw breast samples were stored at -23°C for 82 d and evaluated at intervals for flavour and TBA values. All treatments significantly increased breast n-3 FA content compared to samples from control-fed birds. The greatest n-3 FA deposition (212 mg kg⁻¹) was achieved by feeding 5·5% MA. All dietary n-3 FA significantly reduced flavour scores compared to samples from control-fed birds, although 2·8% MA samples were still considered acceptable by consumer panelists. Deterioration of flavour quality during storage of previously cooked samples was accelerated by all n-3 FA treatments except 2·8% MA. The rate of TBA production during storage of cooked breast meat was increased by n-3 FA, but this was curtailed by storing samples raw. These data indicate that 2·8% MA is useful for enhancing poultry tissue n-3 FA with minimal compromise in flavour or lipid quality, thus yielding a product that may serve as a substitute for fish in the diet. © 1988 Society of Chemical Industry