Variation of lupin protein degradation in ruminants studied in situ and using chemical protein fractions.

The main objective of this study was to evaluate the variability in in situ CP degradation characteristics of 15 batches lupin grains from nine genotypes in a standardised approach. This study also investigated whether differences in CP degradation can be described by protein fractionation using the Cornell Net Carbohydrate and Protein System (CNCPS) and also whether thermal processing of lupins has an effect on CP degradation in the rumen and analysed protein fractions. The rising political and consumer demand for milk products from dairy production systems based on domestic protein sources and the wide range of lupin types and varieties that can be chosen as protein feed in dairy nutrition requires research to determine the variability in CP degradation characteristics in the rumen. For CP degradation measurements, ground grains were incubated in the rumen of three lactating Jersey cows fitted with a ruminal cannula for different times from 2 to 48 h, and the washing loss of non-incubated samples was also measured. Protein fractions were analysed according to CNCPS and used for the estimation of ruminally degraded protein. In situ CP degradation parameters varied widely between untreated samples. The mean value for the washout fraction was 29.3% (from 16.4% to 43.6%). The potentially degradable fraction averaged 70.5% (from 55.6% to 83.7%), hence maximal degradation of CP was close to completeness. Mean degradation rate was 16.6%/h (from 12.6 to 21.0%/h). Variation in estimated parameters led to variation in the effective degradation (ED) averaging 76.6% (from 67.3% to 83.0%) when calculated assuming a ruminal outflow of 8%/h. Thermal treatment of lupins induced changes in degradation characteristics, primarily by lowering degradation rates, and also led to a significant reduction in ED. The ED calculated from analysed protein fractions averaged 10 percentage points higher than ED calculated from in situ parameters for untreated grains. The ED based on protein fractionation was also reduced by heat treatment, but the correlation with in situ based ED was poor. It can be concluded that the variation in ED indicates a potential to increase the amount of rumen undegraded protein without additional chemical or physical treatment and the effect of genetic factors and agronomic practices on ED of lupin grains should be investigated in systematic studies in the future.

Prediction of CP and starch concentrations in ruminal in situ studies and ruminal degradation of cereal grains using NIRS.

Ruminal in situ incubations are widely used to assess the nutritional value of feedstuffs for ruminants. In in situ methods, feed samples are ruminally incubated in indigestible bags over a predefined timespan and the disappearance of nutrients from the bags is recorded. To describe the degradation of specific nutrients, information on the concentration of feed samples and undegraded feed after in situ incubation ('bag residues') is needed. For cereal and pea grains, CP and starch (ST) analyses are of interest. The numerous analyses of residues following ruminal incubation contribute greatly to the substantial investments in labour and money, and faster methods would be beneficial. Therefore, calibrations were developed to estimate CP and ST concentrations in grains and bag residues following in situ incubations by using their near-infrared spectra recorded from 680 to 2500 nm. The samples comprised rye, triticale, barley, wheat, and maize grains (20 genotypes each), and 15 durum wheat and 13 pea grains. In addition, residues after ruminal incubation were included (at least from four samples per species for various incubation times). To establish CP and ST calibrations, 620 and 610 samples (grains and bag residues after incubation, respectively) were chemically analysed for their CP and ST concentration. Calibrations using wavelengths from 1250 to 2450 nm and the first derivative of the spectra produced the best results (R 2 Validation=0.99 for CP and ST; standard error of prediction=0.47 and 2.10% DM for CP and ST, respectively). Hence, CP and ST concentration in cereal grains and peas and their bag residues could be predicted with high precision by NIRS for use in in situ studies. No differences were found between the effective ruminal degradation calculated from NIRS estimations and those calculated from chemical analyses (P>0.70). Calibrations were also calculated to predict ruminal degradation kinetics of cereal grains from the spectra of ground grains. Estimation of the effective ruminal degradation of CP and ST from the near-infrared spectra of cereal grains showed promising results (R 2>0.90), but the database needs to be extended to obtain more stable calibrations for routine use.

In situ and in vitro evaluation of crude protein degradation and utilisable crude protein content of barley, rye and triticale grains for ruminants.

Rations for dairy cows are comprised of high proportions of cereal grains. Thus, despite their low crude protein (CP) content, grains can contribute considerably to the CP intake of dairy cows. This study was conducted to describe and compare ruminal CP degradation of a broad range of barley, rye and triticale genotypes in situ and in vitro and different methods to estimate the utilisable CP at the duodenum (uCP). Twenty samples each of rye, barley and triticale were incubated in situ and in vitro. Exponential regression analyses were used to estimate in situ degradation parameters. Further, the effective degradability (ED), ruminal undegraded CP (UDP) and uCP for ruminal passage rates of 5% and 8% per hr were estimated. The uCP was estimated in vitro and based on two different approaches using in situ UDP data and estimates of microbial synthesised protein (based on fermented organic matter [fOM] or equations of the Gesellschaft für Ernährungsphysiologie). The degradation rate declined from rye (43% per hr) to triticale (27% per hr) to barley (20% per hr), and it exhibited remarkable variation between the genotypes of a single species. The maximal degradable CP fraction also differed between the species, but was overall very high (94%-99%). The lowest washout fraction (26%) and the highest variation in ED (77%-86% and 69%-80% for a passage rate of 5% and 8% per hr, respectively) were found in barley. The in situ uCP content (estimated using fOM) was lower for barley than for rye and triticale at ruminal passage rates of 5% and 8% per hr (barley: 157 g/kg DM at both passage rates; rye and triticale: 168 (at 5% per hr) and 169 (at 8% per hr) g/kg DM). In vitro estimations of uCP did not differ between the grain species and uCP estimated according to GfE was higher for triticale than for barley and rye, which did not differ. The low variation within a single grain species and the weak correlations between ruminal CP degradation and nutrient concentrations suggested that differentiation of ED and uCP between the genotypes of a single grain species is not necessary.

Ruminal phytate degradation of maize grain and rapeseed meal in vitro and as affected by phytate content in donor animal diets and inorganic phosphorus in the buffer.

The ruminal disappearance of phytate phosphorus (InsP6 -P) from maize grain and rapeseed meal (RSM) was determined in two in vitro studies. In experiment 1, two diets differing in phosphorus (P) and InsP6 -P concentration were fed to the donor animals of rumen fluid (diet HP: 0.49% P in dry matter, diet LP: 0.29% P). Maize grain and RSM were incubated in a rumen fluid/saliva mixture for 3, 6, 12 and 24 h. In experiment 2, a diet similar to diet HP was fed, and the rumen fluid was mixed with artificial saliva containing 120 mg inorganic P/l (Pi) or no inorganic P (P0). Maize grain and RSM were incubated with either buffer for 3, 6, 12 and 24 h. Total P (tP) and InsP6 concentration were analysed in the fermenter fluids and feed residues. The disappearance of InsP6 -P from maize was completed after 12 h of incubation in both experiments. From RSM, 93% (diet LP) and 99% (diet HP) of the InsP6 -P in experiment 1 and 80% (Pi) and 89% (P0) in experiment 2 had disappeared after 24 h of incubation. InsP6 -P disappearance was higher when diet HP was fed (maize: 3 and 6 h; RSM: 6 and 24 h of incubation) and when rumen fluid was mixed with buffer P0 (maize: 6 h; RSM: 12 and 24 h of incubation). InsP6 -P concentration in the fermenter fluids was higher for maize, but no accumulation of InsP6 -P occurred, indicating a prompt degradation of soluble InsP6 . These results confirmed the capability of rumen micro-organisms to efficiently degrade InsP6 . However, differences between the feedstuffs and diet composition as well as the presence of inorganic P in the in vitro system influenced the degradation process. Further studies are required to understand how these factors affect InsP6 degradation and their respective relevance in vivo.

Effect of dietary mineral phosphorus and phytate on in situ ruminal phytate disappearance from different concentrates in dairy cows.

The first objective of this study was to determine the influence of dietary composition on the in situ disappearance of phytate (InsP6) from wheat, corn, soybean meal, and rapeseed meal [solvent-extracted, without (RSM) or with (hRSM) heat treatment] in the rumen of dairy cows. The second objective was to assess the primary degradation products of InsP6 in the rumen. Three diets differing in phosphorus and InsP6 concentration (basal diet = 0.38% P in dry matter; high-P diet = 0.56% P; high-InsP6 diet = 0.39% P) were fed to 3 ruminally fistulated lactating Jersey cows in a 3 × 3 Latin square. Ground concentrates (sieve size = 2 mm) were incubated in polyester bags in the rumen for 2, 4, 8, 16, and 24 h. The bag residues were analyzed for P, InsP6, isomers of lower inositol phosphates (InsP5, InsP4, InsP3), and crude protein. The InsP6 disappeared more rapidly from cereal grains than from oilseed meals; however, after 24 h of incubation ≥95% InsP6 had disappeared from all concentrates except hRSM (57%; diet average). Feeding the high-InsP6 diet increased InsP6 disappearance for oilseed meals, but not for corn and wheat. The predominant InsP5 isomer in all bag residues was Ins(1,2,4,5,6)P5 followed by Ins(1,2,3,4,5)P5 and Ins(1,2,3,4,6)P5. A further InsP5 isomer [Ins(1,3,4,5,6)P5] was detected in both rapeseed meal bag residues. Feeding the high-InsP6 diet led to lower concentrations of Ins(1,2,4,5,6)P5 and Ins(1,2,3,4,5)P5, whereas an interaction between diet, concentrate, and time occurred for Ins(1,2,3,4,6)P5 and Ins(1,3,4,5,6)P5. The results confirm the high potential of rumen microorganisms to hydrolyze InsP6; however, increasing the amount of InsP6 in the diet can further enhance InsP6 hydrolysis, which may be relevant when concentrates with slowly degradable InsP6, such as RSM or heat-treated concentrates, are fed to dairy cows. Based on the concentrations of InsP5 isomers, 3 and 6 phytases appear to play a major role in the rumen. Conversely, intrinsic plant phytase activity appears to be less relevant as the percentage of its primary hydrolysis product, Ins(1,2,3,4,5)P5, changed only slightly upon using wheat known for high intrinsic phytase activity instead of the other concentrates. Additional information regarding the factors influencing the extent of ruminal InsP6 disappearance will require further studies to determine the phytase activity of rumen microorganisms and the characteristics of their respective phytases.

In situ and in vitro ruminal starch degradation of grains from different rye, triticale and barley genotypes.

In recent years, advances in plant breeding were achieved, which potentially led to modified nutritional values of cereal grains. The present study was conducted in order to obtain a broad overview of ruminal digestion kinetics of rye, triticale and barley grains, and to highlight differences between the grain species. In total, 20 genotypes of each grain species were investigated using in situ and in vitro methods. Samples were ground (2 mm), weighed into polyester bags, and incubated in situ 1 to 48 h in three ruminally cannulated lactating dairy cows. The in vitro gas production of ground samples (1 mm) was measured according to the 'Hohenheim Gas Test', and cumulative gas production was recorded over different time spans for up to 72 h. There were significant differences (P<0.05) between the species for most parameters used to describe the in situ degradation of starch (ST) and dry matter (DM). The in situ degradation rate (c) and effective degradability (assuming a passage rate of 8%/h; ED8) of ST differed significantly between all grains and was highest for rye (rye: 116.5%/h and 96.2%; triticale: 85.1%/h and 95.0%; barley: 36.2%/h and 90.0% for c and ED8, respectively). With respect to DM degradation, the ranking of the species was similar, and predicted c values exhibited the highest variation within species. The in vitro gas production rate was significantly higher (P<0.05) for rye than for triticale and barley (rye: 12.5%/h; triticale: 11.5%/h; barley: 11.1%/h). A positive relationship between the potential gas production in vitro and the maximal degradable DM fraction in situ was found using all samples (r=0.84; P<0.001) as well as rye (P=0.002) and barley (P<0.001) alone, but not for triticale. Variation in ruminal in situ degradation parameters within the grain species resulted from the high c values, but was not reflected in the ED estimates. Therefore, the usage of mean values for the ED of DM and ST for each species appears reasonable. Estimated metabolisable energy concentrations (ME, MJ/kg DM) and the estimated digestibility of organic matter (dOM, %) were significantly lower (P<0.05) for barley than for rye and triticale. Rye and triticale dOM and ME values were not significantly different (P=0.386 and 0.485).

In situ starch and crude protein degradation in the rumen and in vitro gas production kinetics of wheat genotypes.

The objective of this study was to determine the variation of in situ ruminal degradation characteristics of dry matter (DM), crude protein (CP) and starch (ST), and to determine the effective degradation (ED) of wheat genotypes. Further, multivariate associations of these in situ values with their corresponding in vitro gas production (GP) kinetics and laboratory measurements were evaluated using correlation and multiple linear regression analyses. Grains of 20 genotypes of wheat were characterized by proximate constituents, amino acid (AA) composition and physical characteristics. Ruminal degradation kinetics were determined by in situ degradation of DM, CP and ST, and subsequent evaluation of in vitro GP relative to time courses. In situ and GP measurements were fitted to an exponential equation, and ED was calculated using passage rates in the rumen of 5%/h (ED5) and 8%/h (ED8). To predict ED8 of CP (EDCP8) and ST (EDST8), correlations were evaluated and stepwise multiple linear regression analyses were applied. Estimated degradation parameters varied considerably between wheat genotypes irrespective of the nutrient tested. Variance in a, b and c was not reflected in the variation of the ED, due to high degradation rates (c). The assumed passage rate also impacted estimation of the ED minimally. Estimated GP parameters varied only slightly among wheat genotypes. Nevertheless, regression models explained up to 80 and 99% of the variance in EDCP8 and EDST8, respectively, and associations between EDST8 and EDCP8 and chemical and physical characteristics of grains were detected. As ST is the primary nutrient in wheat grains and can comprise substantial portions of dairy rations, the total amount of ST as well as its ED in the rumen should be taken into account when wheat is incorporated into dairy rations. Conversely, variance in wheat grain CP degradation was very low and can largely be neglected in practical ration formulation for ruminants.

The effects of a ration change from a total mixed ration to pasture on rumen fermentation, volatile fatty acid absorption characteristics, and morphology of dairy cows.

To investigate the effect of the change from a concentrate and silage-based ration (total mixed ration, TMR) to a pasture-based ration, a 10-wk trial (wk 1-10) was performed, including 10 rumen- and duodenum-fistulated German Holstein dairy cows (182±24 d in milk, 23.5±3.5kg of milk/d; mean ± standard deviation). The cows were divided in either a pasture group (PG, n=5) or a confinement group (CG, n=5). The CG stayed on a TMR-based ration (35% corn silage, 35% grass silage, 30% concentrate; dry matter basis), whereas the PG was gradually transitioned from a TMR to a pasture-based ration (wk 1: TMR only; wk 2: 3 h/d on pasture wk 3 and 4: 12 h/d on pasture wk 5-10: pasture only). Ruminal pH, volatile fatty acids (VFA), NH3-N, and lipopolysaccharide (LPS) concentrations were measured in rumen fluid samples collected medially and ventrally on a weekly basis. Ruminal pH was continuously recorded during 1 to 4 consecutive days each week using ruminal pH measuring devices. In wk 1, 5, and 10, rumen contents were evacuated and weighed, papillae were collected from 3 locations in the rumen, and subsequently a VFA absorption test was performed. In the PG, mean rumen pH and molar acetate proportions decreased, and molar butyrate proportions increased continuously over the course of the trial, which can most likely be ascribed to an increased intake of rapidly fermentable carbohydrates. During the first weeks on a full grazing ration (wk 5-7), variation of rumen pH decreased, and in wk 5 a lower rumen content, papillae surface area, and potential for VFA absorption were observed. In wk 8 to 10, variation of rumen pH and total VFA concentrations increased again, and acetate/propionate ratio decreased. In wk-10 rumen content, papillae area and VFA absorption characteristics similar to initial levels were observed. Although continuous rumen pH assessments and LPS concentrations did not reveal an increased risk for subacute rumen acidosis (SARA) during the adaption period, histopathology of rumen papillae and potential for VFA absorption indicated a possible risk for rumen health. An increased risk for SARA was observed in wk 9 and 10 in the PG, but rumen LPS concentrations and histopathology were not adversely affected. Results of the present study suggest that after behavioral and metabolic adaptation to the transition from a TMR to a pasture-based ration, no adverse effects on rumen morphology and absorption capacity occurred, although rumen pH after adaptation to pasture indicated increased risk of SARA.

Effects of different forms and origins of oilseeds on dynamics of ruminal biohydrogenation of long-chain fatty acids in vitro.

Dietary unsaturated fatty acids (FA) are intensively hydrogenated in the rumen, resulting in reduced amount of poly-unsaturated fatty acids (PUFA) and accumulation of several biohydrogenation (BH) products. In this study, BH of PUFA originating from different oilseeds (linseed, soya beans, sunflower seed and rapeseed) present in crushed oilseeds or their free oils were assessed in vitro. The assay substrates were incubated in buffered rumen fluid for 0, 6, 12 and 24 h. After incubation, the FA pattern of the incubated samples was analysed using gas chromatography. Biohydrogenation is defined as disappearance of double bonds (DB) calculated from the contents of unsaturated FA. After 24-h incubation, the DB contents of all oilseeds were reduced (p < 0.001) by 40-60%. The reduction was higher (p < 0.001) for the crushed form compared with the oil form. In addition, linseed and sunflower seed known as oilseeds with high contents of linolenic acid C18:3 c9,12,15 (LNA) and linoleic acid C18:2 c9,12 (LA), respectively, showed a higher (p < 0.001) accumulation of the BH intermediates conjugated linoleic acid (CLA, isomer C18:2 c9t11) and vaccenic acid (C18:1 t11) for the crushed form, when compared with the oil. These results suggest an inherent effect of the physical form of the assay oilseeds on in vitro BH. Changes in FA pattern during BH in vitro can be attributed to both source and physical form of the assay oilseeds. However, further investigations are warranted to ensure whether the observed in vitro effects on ruminal BH can be confirmed in vivo.

Effects of long-term supplementation of chestnut and valonea extracts on methane release, digestibility and nitrogen excretion in sheep.

The long-term effects of adding chestnut (CHE; Castanea sativa) and valonea (VAL; Quercus valonea) tannin-rich extracts to sheep feed were investigated. In Experiment 1, sheep (65 kg BW) were fed 842 g/day of a ryegrass-based hay. The control-treated animals (CON) received 464 g/day of concentrate, and tannin-treated animals received the same amount of concentrate additionally containing 20 g of the respective tannin-rich extract. Hay and concentrates were offered together in one meal. After the onset of treatment, methane release was measured in respiration chambers for 23.5-h intervals (nine times) in a 190-days period. Faeces and urine were collected three times (including once before the onset of the tannin treatment) to assess digestibility and urinary excretion of purine derivatives. Based on the results obtained from Experiment 1, a second experiment (Experiment 2) was initiated, in which the daily tannin dosage was almost doubled (from 0.9 (Experiment 1) to 1.7 g/kg BW0.75). With the exception of the dosage and duration of the treatment (85 days), Experiment 2 followed the same design as Experiment 1, with the same measurements. In an attempt to compare in vitro and in vivo effects of tannin supplementation, the same substrates and tannin treatments were examined in the Hohenheim gas test. In vitro methane production was not significantly different between treatments. None of the tannin-rich extract doses induced a reduction in methane in the sheep experiments. On the 1st day of tannin feeding in both experiments, tannin inclusion tended to decrease methane release, but this trend disappeared by day 14 in both experiments. In balance period 3 of Experiment 1, lower dry matter and organic matter digestibility was noted for tannin treatments. The digestibility of CP, but not NDF or ADF, was reduced in both experiments. A significant shift in N excretion from urine to faeces was observed for both tannin-rich extracts in both experiments, particularly in Experiment 2. In balance period 2 of Experiment 2, an increased intake of metabolisable energy for VAL was observed. The urinary excretion of purine derivatives was not significantly different between treatments, indicating that microbial protein synthesis was equal for all treatments. Thus, we concluded that both tannin-rich extracts temporary affect processes in the rumen but did not alter methane release over a longer period.

Effect of feeding dried distillers' grains with solubles on milk yield and milk composition of cows in mid-lactation and digestibility in sheep.

We evaluated the effect of three sources of dried distillers' grains with solubles (DDGS) in diets of mid-lactating dairy cows on milk production and milk composition and on digestibility in sheep. DDGS from wheat, corn and barley (DDGS1 ), wheat and corn (DDGS2 ) and wheat (DDGS3 ) were studied and compared with a rapeseed meal (RSM). RSM and DDGS were characterized through in situ crude protein (CP) degradability. Nutrient digestibility was determined in sheep. Twenty-four multiparous cows were used in a 4 × 4 Latin square design with 28-day periods. Treatments included total mixed rations containing as primary protein sources RSM (control), DDGS1 (D1), DDGS2 (D2) or DDGS3 (D3). RSM contained less rapidly degradable CP (fraction a), more potentially degradable CP (fraction b) and more rumen undegradable CP (UDP) than the three DDGS. In vivo digestibility of RSM organic matter was similar to DDGS. Calculated net energy for lactation (NEL ) was lower for RSM (7.4 MJ/kg DM) than for DDGS, which averaged 7.7 MJ/kg DM. Cows' dry matter intake did not differ between diets (21.7 kg/day). Cows fed D1 yielded more milk than those fed D3 (31.7 vs. 30.4 kg/day); no differences were found between control and DDGS diets (31.3 vs. 31.1 kg/day). Energy-corrected milk was similar among diets (31.2 kg/day). Diets affected neither milk fat concentration (4.0%) nor milk fat yield (1.24 kg/day). Milk protein yield of control (1.12 kg/day) was significantly higher than D3 (1.06 kg/day) but not different form D1 and D2 (1.08 kg/day each). Feeding DDGS significantly increased milk lactose concentration (4.91%) in relation to control (4.81%). DDGS can be a suitable feed in relation to RSM and can be fed up to 4 kg dry matter per day in rations of dairy cows in mid-lactation. However, high variation of protein and energy values of DDGS should be considered when included in diets of dairy cows.

In situ ruminal degradation of amino acids and in vitro protein digestibility of undegraded CP of dried distillers' grains with solubles from European ethanol plants.

The objectives of this study were to compare the in situ ruminal degradation of CP and amino acids (AAs) of dried distillers' grains with solubles (DDGS), and to estimate intestinal digestibility (ID) of undegradable crude protein (UDP) with the in vitro pepsin-pancreatin solubility of CP (PPS), using either DDGS samples (DDGS-s) or DDGS residues (DDGS-r) obtained after 16 h ruminal incubation. Thirteen samples originating from wheat, corn, barley and blends were studied. Lysine and methionine content of DDGS-s varied from 1.4 to 4.0 and 1.3 to 2.0 g/16 g N, respectively. The milk protein score (MPS) of DDGS-s was low and ranged from 0.36 to 0.51, and lysine and isoleucine were estimated to be the most limiting AAs in DDGS-s and DDGS-r. DDGS-r contained slightly more essential AAs (EAAs) than did the DDGS-s. Rumen degradation after 16 h varied from 44% to 94% for CP, from 39% to 90% for lysine and from 35% to 92% for methionine. Linear regressions showed that the ruminal degradation of individual AAs can be predicted from CP degradation. The PPS of DDGS-s was higher than that of DDGS-r and it varied from 70% to 89% and from 47% to 81%, respectively. There was no significant correlation between the PPS of DDGS-s and PPS of DDGS-r (R 2=0.31). The estimated intestinally absorbable dietary protein (IADP) averaged 21%. Moderate correlation was found between the crude fibre (CF) content and PPS of DDGS-r (R 2=0.43). This study suggests an overestimation of the contribution of UDP of DDGS to digestible protein supply in the duodenum in some currently used protein evaluation systems. More research is required and recommended to assess the intestinal digestibility of AAs from DDGS.

Effects of different tannin-rich extracts and rapeseed tannin monomers on methane formation and microbial protein synthesis in vitro.

Tannins, polyphenolic compounds found in plants, are known to complex with proteins of feed and rumen bacteria. This group of substances has the potential to reduce methane production either with or without negative effects on digestibility and microbial yield. In the first step of this study, 10 tannin-rich extracts from chestnut, mimosa, myrabolan, quebracho, sumach, tara, valonea, oak, cocoa and grape seed, and four rapeseed tannin monomers (pelargonidin, catechin, cyanidin and sinapinic acid) were used in a series of in vitro trials using the Hohenheim gas test, with grass silage as substrate. The objective was to screen the potential of various tannin-rich extracts to reduce methane production without a significant effect on total gas production (GP). Supplementation with pelargonidin and cyanidin did not reduce methane production; however, catechin and sinapinic acid reduced methane production without altering GP. All tannin-rich extracts, except for tara extract, significantly reduced methane production by 8% to 28% without altering GP. On the basis of these results, five tannin-rich extracts were selected and further investigated in a second step using a Rusitec system. Each tannin-rich extract (1.5 g) was supplemented to grass silage (15 g). In this experiment, nutrient degradation, microbial protein synthesis and volatile fatty acid production were used as additional response criteria. Chestnut extract caused the greatest reduction in methane production followed by valonea, grape seed and sumach, whereas myrabolan extract did not reduce methane production. Whereas chestnut extract reduced acetate production by 19%, supplementation with grape seed or myrabolan extract increased acetate production. However, degradation of fibre fractions was reduced in all tannin treatments. Degradation of dry matter and organic matter was also reduced by tannin supplementation, and no differences were found between the tannin-rich extracts. CP degradation and ammonia-N accumulation in the Rusitec were reduced by tannin treatment. The amount and efficiency of microbial protein synthesis were not significantly affected by tannin supplementation. The results of this study indicated that some tannin-rich extracts are able to reduce methane production without altering microbial protein synthesis. We hypothesized that chestnut and valonea extract have the greatest potential to reduce methane production without negative side effects.

Variation of in situ rumen degradation of crude protein and amino acids and in vitro digestibility of undegraded feed protein in rapeseed meals.

In this study, 10 samples of rapeseed meal (RSM) from 10 different oil plants in Germany were examined. In situ rumen degradation of CP was determined by incubation over 1, 2, 4, 8, 16, 32 and 72 h in duplicate per time point using three rumen fistulated dry cows. Degradation kinetics were estimated by an exponential model and effective CP degradation was calculated. Degradation was corrected for small particle loss as the difference between washing loss and water-soluble fraction. Amino acid analysis was carried out in the samples and in the residues after 8 and 16 h of incubation in situ and degradation of individual amino acids was calculated for these incubation times. In vitro pepsin-pancreatin digestibility of CP (IPD) was determined in the samples as well as in the 8 and 16 h residues. Effective CP degradation for a rumen outflow rate of 8%/h (ED8) averaged 54.3% with a considerable variation among samples ranging from 44.3% to 62.7%. A multiple regression equation containing acid detergent insoluble N, total glucosinolates and petroleum ether extract as independent variables predicted ED8 with satisfying accuracy (R 2 = 0.74; RSD = 6.4%). Degradation of amino acids was different from that of CP for most amino acids studied, especially after 8 h of incubation. Compared with CP, degradation of essential amino acids was predominantly lower while degradation of non-essential amino acids was higher in most cases. However, for lysine and methionine no distinct difference with CP degradation was found. Degradation of individual amino acids was predicted from CP degradation with high accuracy using linear regression equations. Average IPD of RSM was 79.8 ± 2.6%. IPD was lower in the incubation residues and decreased with longer incubation time and increasing rumen degradation, respectively.

In vitro fermentation characteristics and effective utilisable crude protein in leaves and green pods of Moringa stenopetala and Moringa oleifera cultivated at low and mid-altitudes.

This study was conducted to assess the in vitro nutrient digestibility and utilisation of leaves and green pods of two Moringa species in supplementing the feed of ruminant animals during the dry season. Samples were analysed for proximate nutrients using official methods. The metabolisable energy (ME), organic matter digestibility (OMD) and effective utilisable crude protein (uCP) were estimated using the Hohenheim in vitro gas test method. Gas volume in Moringa stenopetala leaves and green pods was generally higher than those of Moringa oleifera. Gas volume for leaves was similar between low and mid-altitudes but was higher for green pods at mid-altitude. M. stenopetala leaves contained significantly higher ME (9.8 MJ/kg DM) and OMD (75%) than those of M. oleifera. Similarly, M. stenopetala green pods had higher ME and OMD values than those of M. oleifera. For green pods, the ME and OMD values were significantly higher at mid-altitude than those at low altitude although these values for leaves were similar between both altitudes. Moringa oleifera leaves had higher effective uCP than those of M. stenopetala. Nevertheless, the effective uCP was higher for green pods of M. stenopetala than those of M. oleifera. The effective uCP for leaves cultivated at mid-altitude was slightly higher than those at low altitude. This study suggested that leaves and green pods could be used as alternative energy and protein supplements for tropical ruminants, particularly during dry periods. It was further concluded that leaves were generally better in nutrient compositions and in vitro nutrient digestibility characteristics than green pods.

Modeling the adequacy of dietary fiber in dairy cows based on the responses of ruminal pH and milk fat production to composition of the diet.

The main objective of this study was to develop practical models to assess and predict the adequacy of dietary fiber in high-yielding dairy cows. We used quantitative methods to analyze relevant research data and critically evaluate and determine the responses of ruminal pH and production performance to different variables including physical, chemical, and starch-degrading characteristics of the diet. Further, extensive data were used to model the magnitude of ruminal pH fluctuations and determine the threshold for the development of subacute ruminal acidosis (SARA). Results of this study showed that to minimize the risk of SARA, the following events should be avoided: 1) a daily mean ruminal pH lower than 6.16, and 2) a time period in which ruminal pH is <5.8 for more than 5.24 h/d. As the content of physically effective neutral detergent fiber (peNDF) or the ratio between peNDF and rumen-degradable starch from grains in the diet increased up to 31.2 +/- 1.6% [dry matter (DM) basis] or 1.45 +/- 0.22, respectively, so did the daily mean ruminal pH, for which a asymptotic plateau was reached at a pH of 6.20 to 6.27. This study also showed that digestibility of fiber in the total tract depends on ruminal pH and outflow rate of digesta from reticulorumen; thereby both variables explained 62% of the variation of fiber digestibility. Feeding diets with peNDF content up to 31.9 +/- 1.97% (DM basis) slightly decreased DM intake and actual milk yield; however, 3.5% fat-corrected milk and milk fat yield were increased, resulting in greater milk energy efficiency. In conclusion, a level of about 30 to 33% peNDF in the diet may be considered generally optimal for minimizing the risk of SARA without impairing important production responses in high-yielding dairy cows. In terms of improvement of the accuracy to assessing dietary fiber adequacy, it is suggested that the content of peNDF required to stabilize ruminal pH and maintain milk fat content without compromising milk energy efficiency can be arranged based on grain or starch sources included in the diet, on feed intake level, and on days in milk of the cows.

Effects of varying dietary forage particle size in two concentrate levels on chewing activity, ruminal mat characteristics, and passage in dairy cows.

The objective of this study was to investigate the effects of varying dietary forage particle size on chewing activity, ruminal mat characteristics, passage, and in situ ruminal and total tract digestion in dairy cows at a low- and high-concentrate inclusion. The experiment was designed as a 4 x 4 Latin square with a 2 x 2 factorial arrangement of treatments. Four ruminally cannulated late-lactating dairy cows were restrictively fed (17 kg of dry matter/d), in four 23-d periods, 1 of 4 different diets varying in the theoretical particle size (6 and 30 mm) of hay (56.6% NDF of dry matter) and in the levels (approximately 20 and 60%, dry matter basis) of a cereal-based concentrate. Ingredients of the ration were offered separately to the cows; dietary hay and low-level concentrate were offered twice daily at 0800 and 1600 h, whereas concentrate of the high-level treatment was offered in 4 meals a day at 0800, 1200, 1600, and 1900 h. This study showed that altering the forage particle size from 6 to 30 mm in a low-concentrate diet significantly increased the rumination time and ruminal mat consistency without affecting ruminal fermentation and passage. Further, particle breakdown and proportion of mat in the rumen increased, and in situ hay dry matter degradability improved, which in turn indicated a higher capacity of ruminal digesta to degrade fiber. On the other hand, increasing the forage particle size in a diet containing a high amount of concentrate increased the proportion of dry matter retained on a 1.18-mm screen from 37.5 to 42.0% and extended the rumination time by 100 min/d, as well as increasing the ruminal mat consistency. However, ruminal particle breakdown, short-term ruminal pH, fibrolytic capacity of the digesta, and proportion of mat in the rumen decreased. This was also reflected in a higher bailable liquid pool, increased fractional passage rate of solid digesta from the reticulorumen, and increased retention time in the hindgut, which in turn indicated a shift of fiber digestion from the rumen to the lower digestive tract. This study showed that the response of chewing or ruminating activity alone seemed to be insufficient to assess the dietary physical effectiveness or fiber adequacy in limit-fed dairy cows when high-concentrate diets were fed separately. Based on the results of this study, we concluded that inclusion of coarsely chopped hay in the high-concentrate diet did not appear to further improve rumen conditions and digestion when the rations were formulated to exceed the fiber requirements in limit-fed dairy cows.

Relationship between thiamine concentration and fermentation patterns in the rumen fluid of dairy cows fed with graded concentrate levels.

The objective of this study was to investigate the relationship between the thiamine concentration and the fermentation patterns [pH, concentration of short-chain fatty acids (SCFA)] in the free liquid (FRL) and particle-associated liquid (PARL) of the rumen in dairy cows fed with graded concentrate levels in the diet. Four ruminally cannulated Holstein cows in mid lactation were fed [semi-ad libitum, 18 kg dry matter (DM)/day] diets consisting of hay (H) and slowly degradable concentrate (C), offered in five different H:C ratios (% DM basis) in the following sequence: period 1, 30:70; period 2, 40:60; period 3, 50:50; period 4, 60:40 and period 5, 75:25. A negative quadratic relationship was observed between thiamine concentration in FRL and intake of dietary thiamine (R(2) = 0.36), of concentrate (R(2) = 0.38) and of digestible non-fibre carbohydrates (R(2) = 0.37). The thiamine concentration in PARL was higher (p < or = 0.05) compared to FRL. The ruminal thiamine concentration correlated negatively to pH and positively to concentrations of SCFA and propionate in the rumen. R(2) of these relationships varied markedly (0.002 and 0.77), depending on time after feeding and fluid digesta compartment. The higher R(2) were observed at 8 and 11 h after the morning feeding for FRL (R(2) 0.46-0.71) and PARL (R(2) 0.41-0.77), respectively.

Effects of physically effective fiber on digestive processes and milk fat content in early lactating dairy cows fed total mixed rations.

Data from recent research studies were analyzed quantitatively, and the random effect of experiment was assessed to define the physiological responses of dairy cows in early lactation to intake of physically effective neutral detergent fiber (peNDF). All studies were conducted with lactating Holstein cows (84.8 +/- 3.54 days in milk) in Latin square designs, and feeds were offered ad libitum as total mixed rations (TMR). The peNDF was estimated by 2 measurement techniques, the NDF content of TMR multiplied by amount of dry matter (DM) retained on a 1.18-mm screen (peNDF(> 1.18)) and NDF content of TMR multiplied by the proportion of DM retained by 19- and 8-mm Penn State Particle Separator screens (peNDF(> 8)). Other factors, including concentrations of NDF, forage NDF, non-fiber carbohydrates, the amount of digestible organic matter of forages (FDOM), and the intake of ruminally degradable starch (RDSI) from grain in the diet were also investigated. The studied animal response variables included feed intake, ruminal fermentation, chewing activity, fiber digestibility, and milk production and composition. The ruminal pH (day mean) in this study ranged from 5.30 to 6.59. Using peNDF(> 1.18) approach, the requirements for physically effective fiber in high-yielding dairy cows fed TMR in an ad libitum intake were estimated to be about 19% of ration DM or 4.1 kg/d or 0.6 kg/100 kg of body weight to maintain a ruminal pH of about 6.0. When peNDF was measured as peNDF(> 8), ruminal pH responded in a quadratic fashion but the confidence of estimation was lower (R(2) = 0.27) compared with the peNDF(> 1.18) approach (R(2) = 0.67). Results of these data analyses showed that peNDF(> 1.18) provided a satisfactory estimation of the mean ruminal pH (R(2) = 0.67) and NDF digestibility (R(2) = 0.56). Furthermore, peNDF(> 1.18) was poorly, although positively, correlated to daily chewing (R(2) = 0.17), and rumination (R(2) = 0.24) activity. On the other hand, results from these analyses showed that milk parameters are less sensitive to the effects of dietary peNDF than other variables, such as ruminal pH, chewing activity, and fiber digestibility. Dietary FDOM correlated positively (moderately) to ruminal pH (R(2) = 0.24), daily chewing (R(2) = 0.23), and rumination (R(2) = 0.29) activity, whereas the daily RDSI from grain correlated negatively to ruminal pH (R(2) = 0.55) and positively to total volatile fatty acids (R(2) = 0.27). Inclusion of FDOM and RDSI from grain along with peNDF(> 1.18) in the models that predict rumen pH further improved the accuracy of prediction. This approach appeared to further complement the concept of peNDF that does not account for differences in ruminal fermentability of feeds.

Digesta characteristics of dorsal, middle and ventral rumen of cows fed with different hay qualities and concentrate levels.

The influence of fibre content of hay (H) and concentrate level (C) on local differences in the composition of ruminal digesta (ratio of solid to fluid digesta, DM, NDF, ADF and ADL content), particle size (MPL), specific gravity (SG) and fermentation (pH and concentrations of SCFA and bicarbonate) have been tested on two ruminally cannulated Friesian cows (520 kg BW) which were fed restricted, using individual cows as experimental units. Digesta samples were collected via cannula from three rumen layers: 5 to 10 cm (top) and 25-35 cm beneath the top of the particle mat (middle) and 5-10 cm above the rumen floor (bottom). For a main plot treatment (H x C), repeated samples were collected at four time intervals (1 h before and 2, 5 and 10 h after morning feeding) on each of two days. From top to bottom rumen the share of solid digesta mass (SM), DM and NDF contents of squeezed digesta fluid (SRF) and concentration of SCFA decreased (P < 0.05); pH and bicarbonate concentration increased (P < 0.05), while DM, NDF, ADF and ADL contents in SM, MPL and SG did not differ. Higher NDF content of hay (from 47-62%) increased SM, fibre fractions in SM, MPL, pH and concentration of bicarbonate in ruminal digesta, especially when 50% concentrate was given, while SG decreased. When the concentrate level was enhanced from 20 to 50%, digesta SM, MPL and the content of DM and NDF in SRF increased, while pH, concentrations of SCFA and acetate decreased when low-fibre hay was given. With longer time after feeding the digesta SM was reduced and fibre content in SM increased. The increase of the fibre content of hay reduced the possible negative effect of high concentrate level on the stratification of ruminal digesta. The decrease of the fibre content of hay promised better conditions for fibre digestion in the rumen when concentrate availability is limited.