True Organic Matter Digestibility Research Articles

Effect of different levels of added selenium without or with arsenic on rumen fermentation parameters in buffaloes under in vitro conditions

Studies were conducted to find the effect of addition of different levels of selenium (Se) without or with arsenic (As) on rumen fermentation parameters viz., in vitro gas production (IVGP), true organic matter digestibility (TOMD), microbial biomass production (MBP), total volatile fatty acids (TVFA) and individual volatile fatty acids (IVFA) under in vitro conditions. Basal substrate (200 mg) comprising of paddy straw and concentrate mixture (40: 60) alongwith different levels of Se (0, 2, 4, 8, 10, 12 and 14μg/200 mg substrate or per syringe) was incubated in 100 ml glass syringes. Arsenic, an antagonist of Se in form of sodium arsenite, was used @ 0, 10, 20, 40, 80 and 100 μg levels added to the substrate (200 mg). The inhibitory effect on TOMD, IVGP, MBP and TVFA was observed at 12 μg added Se level. Addition of As at 10 or 20 μg level to the substrate (200 mg) containing 12 μg Se improved rumen fermentation parameters under in vitro system, however, further addition of As (40, 80 or 100 μg) showed negative effects on these parameters.

Nutritional evaluation of wheat straw treated with Crinipellis sp. in Sahiwal calves

Wheat straw was subjected to solid-state fermentation (SSF) with lignolytic white-rot fungus (WRF) Crinipellis sp. for 5days to improve the nutritive value and digestibility. The fungal treatment caused a significant (P < 0.05) decrease in cell wall constituents viz., neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose, lignin, and cellulose to the extent of 10.4, 11.2, 8.7, 8.7, and 12.1%, respectively, with increase (P < 0.05) in crude protein (CP) (51.6%) and ash (25.8%) contents in fungal treated wheat straw (FT-WS) than untreated wheat straw (UT-WS). Further, in vitro gas production, in vitro true dry matter digestibility and in vitro true organic matter digestibility at 48h, metabolizable energy (ME) content, microbial biomass production, and short-chain fatty acids synthesis were significantly (P < 0.05) higher in FT-WS. In vivo feeding trial in 10 Sahiwal calves (8-12 months) comprised of (1) control group (T1) fed with ad libitum chopped UT-WS and (2) treatment group (T2) offered with ad libitum chopped FT-WS, in addition to supplementation of groundnut cake and green berseem (Trifolium alexandrium) forage to both groups. Digestibility of nutrients for dry matter (DM), organic matter, CP, NDF, ADF, hemicellulose, cellulose, and total carbohydrates were significantly (P < 0.05) higher in T2 compared to T1. Moreover, daily DM (P < 0.05), digestible crude protein (P < 0.01), and ME intakes were also higher (P < 0.05) in group T2 with higher (P < 0.05) nitrogen (N) retention, which resulted in significantly (P < 0.05) higher average daily gain in body weight (135 vs. 102 g/day). It was concluded that SSF with WRF Crinipellis sp. holds potential in upgrading the nutritional worth of wheat straw for feeding growing calves.

Nutritive value, in vitro fermentation and methane production of perennial pastures as affected by botanical composition over a growing season in the south of Chile

Permanent pastures have been shown to produce similar herbage masses and nutrient contents to perennial ryegrass pastures. To the best of our knowledge, little research has been conducted on the ruminal fermentation of permanent pastures. Our objective was to evaluate the effect of botanical composition of four perennial pastures during a growing season in the south of Chile [winter, September 2010 ‘S1’; spring, November 2010 ‘S2’; and summer, January 2011 ‘S3’]: on in vitro fermentation products using a batch culture system. The perennial pastures studied included: permanent (PP), permanent fertilised (PFP) and renovated pastures (Lolium perenne and Trifolium repens pasture ‘RGWC’; Bromus valdivianus, Dactylis glomerata, Holcus lanatus, L. perenne and T. repens ‘MIXED’). There were strong interactions between pasture type and regrowth period for true organic matter, nitrogen (N) and neutral detergent fibre digestibility; total gas and volatile fatty acid (VFA) production; ammonia and microbial N. In general, all pasture treatments showed a high true organic matter digestibility (&gt;800 g/kg), and tended to decrease in S3. In vitro fermentation of PFP and RGWC produced the highest total VFA concentration during S1 and S2, and no differences among pastures were observed in summer. Propionate proportion of total VFA was affected by pasture type and regrowth period, being higher for RGWC and S1, respectively. In vitro microbial N was higher for MIXED in S1, and PFP in S2 and S3. No pasture and regrowth period effects were observed for methane production and its proportion of total gas production. These results indicate that the in vitro fermentation products of a permanent fertilised pasture reach similar levels to those obtained from a sown pasture, and thus may be considered as a sustainable alternative for grazing livestock systems.

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 712g/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 72h 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 (kd). 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 kd 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 kd 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 kd 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.

Development of an in vitro method for determination of methane production kinetics using a fully automated in vitro gas system—A modelling approach

The objective of the present study was to estimate methane production using the kinetic parameters from an automated in vitro gas production (GP) system in a mechanistic, dynamic rumen model. Four sample sizes [300mg (5g/l), 600mg (10g/l), 900mg (15g/l) and 1200mg (20g/l)] of timothy hay were incubated in 60ml buffered rumen fluid in an automated in vitro system to determine methane and total gas production. A logarithmic model (R2>0.99) was fitted to methane data to estimate methane concentrations at time intervals of 0.2h. The first-order gas production rates were not different (P=0.18) with values of 0.072, 0.061, 0.061 and 0.059/h for the sample size of 300, 600, 900 and 1200mg, respectively. The methane production rates were 0.052, 0.046, 0.046 and 0.045/h, respectively. Predicted methane production decreased linearly (PLIN<0.01) as the sample size increased from 300 (36.9ml/g dry matter, DM) to 1200mg (28.2ml/g DM). After 48h of incubation total volatile fatty acids (VFA) production decreased (PLIN<0.01) as the sample size increased from 300 to 1200mg (4.41mmol/g DM and 3.82mmol/g DM, respectively). Neutral detergent fibre digestibility (aNDFomD), apparent organic matter digestibility (AOMD) and true organic matter digestibility (TOMD) decreased (PLIN=0.01) as the sample size increased (0.479, 0.433 and 0.681 for 300mg, and 0.369, 0.379 and 0.614 for 1200mg of sample size, respectively). Actual methane production (24 and 48h of incubation) was strongly correlated (R2=0.97) with the methane production predicted from VFA stoichiometry (VFA measured at 24 and 48h of incubation). It is concluded that in vitro GP measurements can be successfully used to estimate kinetic parameters of methane production and consequently to predict methane production. It seems that sample size did not affect the first-order production rate of methane and therefore, it is possible to use greater amounts of substrate in the in vitro GP system up to 1000mg (16.6g/l).

In vitro study of the effects of condensed tannins in sainfoin on the digestive process in the rumen at two vegetation cycles

One approach to reducing enteric production of greenhouse gases (GHG; i.e., nitrous oxide and methane) is to feed tanniniferous forage plants such as sainfoin. The objective of this study was to investigate, in vitro, effects of the content and structural characteristics of condensed tannins (CT) in the whole plant, leaves and stems of sainfoin ( Onobrychis viciifolia) on the digestive process in the rumen. Sainfoin, studied during the first vegetation cycle at the end of flowering, and during the second vegetation cycle at the start of flowering, was incubated in serum bottles containing buffered rumen fluid for 3.5 and 24 h. To assess effects of CT, incubations were with and without added polyethylene glycol (PEG), to neutralise CT effects. Biological activity and prodelphinidin (PD) content were higher (P<0.001) in leaves than in stems, but cis value was lower (P<0.01). At 3.5 h of incubation, gas production was higher for stems than leaves (P<0.05), but at 24 h only tended to be higher for leaves than stems (P=0.096), at the end of flowering. The presence of PEG at both short and long fermentation times increased gas production of leaves, stems and whole plant (P<0.001). At 3.5 h, PEG addition resulted in higher CH 4 values for stems and leaves at two vegetation cycles (P<0.01). The CO 2:CH 4 ratio was lower (P<0.01) at 3.5 h and higher at 24 h (P<0.01) with added PEG. No effect of PEG on whole plant CH 4 production, or the CO 2:CH 4 ratio, at either 3.5 or 24 h of incubation. At both incubation periods, in vitro true organic matter digestibility (IVTOMD) was higher for leaves than stems (P<0.001), and decreased with added PEG at 24 h (P<0.001). For the whole plant, PEG had no effect on IVTOMD at either 3.5 or 24 h of incubation. At 3.5 h, PEG resulted in higher N disappearance (ND) at both vegetation cycles (P<0.01), whereas values were higher at the second one (P<0.001). Mean volatile fatty acid production was higher for leaves than stems (P<0.01) and increased with PEG (P<0.001) for both vegetation cycles at 3.5 and 24 h of incubation. For both incubation periods, PEG increased (P<0.001) NH 3–N for leaves and stems in both vegetation cycles. For the whole plant, PEG resulted in higher NH 3–N content (P<0.001) at both 3.5 and 24 h of incubation. Utilisation of sainfoin curbs CH 4 production without altering its organic matter digestibility and N value, but research on the nutritional impact of CT must not only be based on CT content in plant tissue, but include structure-activity considerations of CT.

Negative effects of tropospheric ozone on the feed value of rice straw are mitigated by an ozone tolerance QTL

High surface ozone concentrations are recognized as an emerging threat to food security in Asia. This study aimed at determining the effects of ozone on the nutritive quality of rice straw, a by-product of rice grain production and a major feed resource for ruminant livestock. Further, the question was addressed whether negative effects of ozone can be mitigated through molecular breeding. Rice plants from three different genotypes were exposed to four different ozone treatments in fumigation chambers from transplanting to maturity. These genotypes were (i) IR64, one of the most wide spread indica varieties in the world, (ii) Nipponbare, a typical japonica variety, and (iii) SL41, an ozone tolerant breeding line that carried chromosomal inserts at the ozone tolerance QTL OzT9 in the genetic background of Nipponbare. The treatments consisted of (i) charcoal filtered air, (ii) simulated ambient ozone concentration, (iii) 2 × ambient ozone concentration, and (iv) 2.5 × ambient ozone concentration. The effects of ozone on the chemical composition of straw were clearly dependent of the ozone level, and were significant even at ambient ozone concentration. Increases in crude ash, lignin and phenolics concentration adversely affected the digestibility as demonstrated in incubation experiments simulating rumen digestion in vitro. Negative ozone effects included reductions in the rate and extent of gas production due to inhibition of microbial fermentation, reduced formation of short chain fatty acids (SCFA), and a decrease in the true organic matter digestibility. The ozone tolerant genotype SL41 was less responsive to ozone than its more susceptible recurrent parent Nipponbare in terms of lignin and phenolics formation, organic matter digestibility and SCFA production. These data demonstrate that the feed quality of rice straw is affected by ozone even at ambient concentration, and that these negative effects are mitigated by the ozone tolerance QTL OzT9.

Effects of timing of corn silage supplementation on digestion, fermentation pattern, and nutrient flow during continuous culture fermentation of a short and intensive orchardgrass meal

Using a dual-flow continuous culture fermenter system, this study evaluated the effect of timing of corn silage supplementation on ruminal digestion and nutrient flows following a short and intensive orchardgrass herbage meal. Treatments included 28g dry matter (DM) of corn silage added either 9h (9BH; 0700h) or 1h (1BH; 1500h) before adding 42g DM orchardgrass herbage or no corn silage (control; 70g DM herbage). Herbage was fed as follows: 66% of the total herbage meal at 1600h, 22% at 1720h, and the remaining 12% at 1840h. Effluent was analyzed for organic matter (OM), crude protein (CP), and neutral detergent fiber (NDF). Purine concentrations in effluent and bacterial isolates were used to estimate the partition of effluent N flow into bacterial and nonbacterial fractions, and to calculate true OM digestibility. Fermenters were sampled for pH, volatile fatty acids (VFA), and NH3-N at 0730, 1100, 1530, 1600, 1720, 1840, and 2000h on d 10. Data were analyzed as a 3×4 Latin square experimental design. True digestibilities for OM (average of 78.5%) and CP (average of 84.6%), and apparent NDF digestibility (average of 82.7%) were not affected by treatment. Mean ruminal pH was lower for 9BH than for 1BH, averaging 5.6 and 6.5, respectively. Molar proportions of acetate were not affected by treatment. Propionate concentration was greater for 9BH than for 1BH, averaging 20.5 and 18.1mM, respectively. Diurnal patterns of pH, NH3-N, and acetate:propionate ratio were affected by treatment: 9BH had the lowest values for all measurements as the day progressed. The NH3-N concentration and effluent NH3-N flow were higher for 1BH (11.4mg/100mL and 0.26g/d, respectively) than for 9BH (8.8mg/100mL and 0.20g/d, respectively). Effluent NH3-N flow (as a % of total N flow) was the lowest for 9BH. Bacterial efficiency was not affected by treatments, with a mean of 10.5g of N/kg of OM truly digested. Under the same resource allocation (pasture plus supplement), a simple change in timing of corn silage feeding (9 rather than 1h before an orchardgrass herbage meal) may alter ruminal fermentation pattern. These changes could increase the glucogenic nutrient supply and improve N utilization by reducing ammonia N losses.

Quantifying ruminal digestion of organic matter and neutral detergent fiber using the omasal sampling technique in cattle—A meta-analysis

A data set from 32 studies (122 diets) was used to evaluate the accuracy and precision of the omasal sampling technique by investigating the relationships between ruminal and total digestion of neutral detergent fiber (NDF), between intake and apparent and true ruminal digestion of organic matter (OM), and between omasal NAN flow and milk protein yield. A mixed model regression analysis with random study effect was used to evaluate the relationships. The data were obtained when feeding North American diets (n=36) based on alfalfa silage, corn silage, and corn grain and North European diets (n=86) comprising grass silage supplemented with barley-based concentrates. In all studies, digesta flow was quantified using a triple-marker approach. Standard deviations of ruminal NDF and true OM digestibility were smaller than typically reported in duodenal sampling studies using only chromic oxide as a flow marker. The relationship between total and ruminal NDF digestion was consistent, indicating little variation in the proportion of total-tract NDF digestion that occurred in the rumen. Furthermore, the slope of this regression indicated that 94.7% (±2.7%) of total NDF digestion occurred in the rumen. The slopes of mixed model regression equations between OM intake and amount digested indicated that 42% (±2.4%) and 74% (±3.1%) of OM was apparently and truly digested in the rumen, respectively. The contribution of the rumen to total-tract apparent OM digestion was 62% (±2.6%). The close relationship between omasal flow of nonammonia crude protein and milk protein yield (with adjusted residual mean squared error=31g) provided further confidence in the reliability of omasal flow measurements.

Dose–response effects of chitosans on in vitro rumen digestion and fermentation of mixtures differing in forage-to-concentrate ratios

The in vitro gas production technique was used to study the dose–response effects of three chitosans on rumen fermentation of three mixtures differing in their forage-to-concentrate ratio (80:20, 50:50 and 20:80). Four concentrations (0, 325, 750 and 1500 mg/l of culture fluid) for each chitosan (CHI1, CHI2, and CHI3) were incubated for 24 h in diluted ruminal fluid with three different mixtures. Samples were collected to determine pH, volatile fatty acid (VFA) and ammonia–N concentrations. Methane concentration was estimated stoichiometrically, and in vitro true organic matter digestibility (IVOMD) was calculated. In the high-forage mixture, no differences were found between additives except for propionate molar proportion, for which CHI1 showed a lower proportion than CHI2 or CHI3. Increasing doses of chitosans did not affect total VFA or acetate molar proportions, but decreased IVOMD as well as butyrate and branch-chained volatile fatty acid (BCVFA) molar proportions, and increased propionate molar proportion as well as ratios of C3:C2 and VFA to truly degraded substrate (VFA:TDS). In the medium-forage mixture, no differences were found between additives. Increasing doses of chitosan did not affect total VFA or acetate molar proportions or methane production compared to control, but decreased IVOMD as well as butyrate and BCVFA molar proportions, and increased propionate molar proportion as well as C3:C2 and VFA:TDS ratios. In the low-forage mixture, increasing doses did not reduce total VFA, but decreased IVOMD, acetate, butyrate, and BCVFA molar proportions and methane production, and increased propionate molar proportion as well as C3:C2 and total VFA:TDS ratios compared to control. No differences were found between additives in IVOMD or butyrate molar proportion, but differences were found in acetate molar proportion, with CHI1 showing a higher proportion than CHI2 or CHI3. Differences between additives were also found for propionate molar proportion, C3:C2 ratio, and methane production, and an additive × dose effect was found, with CHI1 showing a weaker response than CHI2 or CHI3 at all tested doses. Differences were found between additives for BCVFA molar proportion, with CHI1 and CHI2 showing greater production than CHI3, and for VFA:TDS ratio, with CHI1 showing a higher ratio than CHI2 or CHI3. These results indicate that chitosans affect rumen microbial fermentation in a dose-dependent manner and that the optimum dose depends on the nature of the incubated substrate and the chitosan's characteristics.

Evaluation of nutritive value and palatability by goats and sheep of selected browse foliages from semiarid area of Kenya

ABSTRACTThe feeding value of five browse foliages (Acacia brevispica, Acacia mellifera, Berchemia discolor, Zizyphus mucronata and Maerua angolensis) grown in semiarid area of Kenya were evaluated. Their chemical composition including polyphenolics and in vitro gas production characteristics were determined. The biological activity of the polyphenolics was assessed as the increases in gas production profiles and in vitro true dry matter (DM) and organic matter (OM) digestibility after in vitro incubation with or without addition of polyethylene glycol (PEG) as a tannin binding reagent. The intake and palatability ranking of the browse foliages by goats and sheep were also investigated. The browse foliages had variable crude protein content (149.5–248.6 g/kg DM) and variable content of neutral detergent fiber (205.1–424.0 g/kg DM). The content of total extractable tannins was generally low (2.4–34.8 g/kg DM). At 24 h of incubation, Z. mucronata produced the highest gas volume, while after 48 h of incubation, B. discolor produced the highest gas volume. M. angolensis had the least gas production potential within the browse foliages. Addition of PEG increased gas production except in A. mellifera and M. angolensis. However, PEG addition did not have any significant effect on in vitro true DM and OM digestibility except in B. discolor, which decreased. The rank order of preference (highest to least) for goats was A. brevispica, Z. mucronata, B. discolor, A. mellifera and M. angolensis while the rank order of preference for sheep was A. brevispica, B. discolor, A. mellifera, Z. mucronata and M. angolensis. The goats had higher intakes of all the browse foliages than sheep. The result of this study highlights the higher feeding value of the browse species as supplemental feed with low quality basal diet with both of animal species except M. angolensis.

Effect of chitosans on in vitro rumen digestion and fermentation of maize silage

The gas in vitro technique was used to study the effects of six types of chitosans, each having different molecular weights and acetylation degrees, on rumen microbial fermentation. In a first trial, a separate concentration of 750 mg/l of culture fluid for each of the six chitosans (CHI1, CHI2, CHI3, CHI4, CHI5, and CHI6) was incubated for 24 h in diluted ruminal fluid with maize silage as the substrate. The ionophore antibiotic monensin (MON) was used as a positive control, and a negative control with no chitosan (CTR) was also included. Each treatment was tested in triplicate for three different periods. At the end of the trial, samples were collected to determine volatile fatty acid (VFA) and ammonia N concentrations, and pH and gas production values were recorded. Methane concentration was estimated stoichiometrically. In vitro true organic matter digestibility (IVOMD) and partitioning factor (PF, mg OM truly degraded/ml gas produced) were also calculated. In a second trial, a separate concentration of 750 mg/l of each of the six chitosans was incubated for 144 h in diluted ruminal fluid with maize silage as the substrate, to study the effects of these compounds on fermentation kinetics. All six chitosans decreased the IVOMD and PF values. Chitosan inclusion did not affect the fermentation of the substrate's soluble fraction, but did reduce the fermentation kinetics of the insoluble but fermentable fraction. However, only CHI5 and CHI6 decreased total VFA concentration. CHI3 and CHI6 decreased the molar proportion of acetate and increased the molar proportion of propionate, thus increasing the propionate-to-acetate ratio. Chitosan inclusion did not affect molar proportions of butyrate. With the exception of CHI2, the molar proportion of branch-chained VFA was lowered by all of the chitosan treatments. Most of the treatments also decreased methane production, also with the exception of CHI2. In conclusion, chitosan extracts may enable the manipulation of rumen microbial fermentation, but further research is required to elucidate the effect of chitosans on ruminal fermentation parameters in commercial diets as well as the adaptability of rumen microflora to these additives.

Intake, rumen fermentation and nutrient flow to the omasum in beef cattle fed grass silage fortified with sucrose and/or supplemented with concentrate

The objective was to determine the relative effects of a specific increase in grass silage sucrose concentration, or a specific supplement of a starch-based concentrate, on rumen fermentation and nutrient supply to the omasum in beef cattle. Four ruminally cannulated Holstein–Friesian steers were fed grass silage only (G), G plus 3 kg concentrates/day (GC), G plus 90 g sucrose/kg dry matter (DM) (GS) and G plus 90 g sucrose/kg DM plus 3 kg concentrates/day (GCS) in a 4 × 4 Latin Square design experiment. Omasal flow was estimated using Co-EDTA, Yb-acetate and indigestible neutral detergent fibre (INDF) as digesta flow markers and purine bases as microbial markers. Concentrate supplementation reduced ( P < 0.01) silage and increased ( P < 0.001) total DM intake whereas sucrose had no effect. There was a sucrose × concentrate interaction ( P < 0.05) for rumen pH whereby addition of sucrose to grass silage alone decreased pH and to grass silage plus concentrate had no effect. Rumen ammonia N ( P < 0.01), total volatile fatty acid (VFA) concentration ( P < 0.05) and the molar proportions of valerate ( P < 0.05) and butyrate ( P < 0.001) increased with concentrate supplementation whereas, sucrose supplementation had no effect on rumen fermentation parameters. Organic matter (OM) intake, omasal OM flow, the quantities of OM apparently (OMAD) and truly digested (OMTD) in the rumen ( P < 0.001) and total tract OM digestibility ( P < 0.01) increased, and apparent and true ruminal OM digestibility decreased ( P < 0.05) with concentrate supplementation. Supplementation with concentrate decreased ( P < 0.05) ruminal neutral detergent fibre (aNDFom) digestibility and increased ( P < 0.05) aNDFom omasal flow. There was a tendency for addition of sucrose to increase ( P < 0.1) ruminal OMAD and OMTD, while there was no effect of sucrose addition on intake or digestion of aNDFom. Concentrate supplementation increased ( P < 0.001) N intake, flows of N, non-ammonia N (NAN), microbial N (MN) ( P < 0.05) and non-ammonia non-microbial N (NANMN) ( P < 0.01) and apparent total tract digestibility of N ( P < 0.01), whereas sucrose reduced ( P < 0.05) N intake and apparent ruminal N digestibility. There was no effect of concentrate or sucrose on N use efficiency or efficiency of microbial protein synthesis. Concentrate supplementation increased ( P < 0.001) plasma β-hydroxybutyrate levels. In comparison to supplementing unwilted, well preserved grass silage of moderate digestibility with 3 kg starch-based concentrate per day, the limited response to the rate of sucrose supplementation employed suggests that increasing the water-soluble carbohydrate (WSC) concentration of grass silage through agronomic and/or ensiling practices will have relatively little effect on intake, rumen digestion or efficiency of microbial N synthesis.

Effects of Patterns of Suboptimal pH on Rumen Fermentation in a Dual-Flow Continuous Culture System

Low ruminal pH affects rumen fermentation, with the effects being larger as the time at suboptimal pH increases. Eight 1,325-mL dual-flow continuous culture fermenters were used to examine the hypothesis that the negative effects of a single cycle of 12h (experiment 1) or 8h (experiment 2) at pH 5.5 can be reduced by splitting it into several cycles. Temperature (39°C), diet (97 g/d of a 60:40 forage:concentrate diet), and solid (5%/h) and liquid (10%/h) dilution rates were kept constant. In experiment 1, treatments were a constant pH 6.4 (H); 1 cycle of 12h at pH 5.5 (L12); 2 cycles of 6h at pH 5.5; and 3 cycles of 4h at pH 5.5. In experiment 2, treatments were a constant pH 6.4 (H); 1 cycle of 4h at pH 5.5 (L4); 1 cycle of 8h at pH 5.5 (L8); or 2 cycles of 4h at pH 5.5. During the rest of the day, pH was maintained at 6.4. Each experiment consisted of 2 replicated periods of 8 d (5 d for adaptation and 3 d for sampling). Within period, treatments were randomly assigned to fermenters. Data were analyzed as a randomized complete block using PROC MIXED of SAS and differences declared at P<0.05 using the Tukey's test. In experiment 1, L12 reduced neutral detergent fiber (NDF) digestion, acetate proportion, and the acetate:propionate ratio, increased propionate proportion, and tended to reduce ammonia N concentration, compared with H, but had no effect on the flow of dietary or microbial N, crude protein degradation, efficiency of microbial protein synthesis, or the flow of total, essential, and individual amino acids. Dividing the 12h at suboptimal pH into 2 or 3 cycles reduced true organic matter (OM) degradation compared with H, and did not alleviate the negative effects on NDF digestion and volatile fatty acid profile observed in L12. In experiment 2, L4 tended to reduce true OM digestion, ammonia N concentration, and bacterial N flow, reduced CP degradation, and increased dietary N flow. Treatment L8 reduced OM and NDF digestion, and ammonia N concentration, compared with H. Treatments L4 and L8 also reduced acetate proportion and the acetate:propionate ratio, and increased propionate proportion and the flow of total, essential, and most individual amino acids, but had no effect on efficiency of microbial protein synthesis compared with the H treatment. When the 8h at suboptimal pH was divided into 2 cycles of 4h the effects were not different from L8. Results suggest that the effects of low pH are dependent on the total amount of time that pH is suboptimal and are not reduced by splitting it into various cycles.

Effects of Time at Suboptimal pH on Rumen Fermentation in a Dual-Flow Continuous Culture System

Ruminal pH varies considerably during the day, achieving values below 6.0 when cows consume large amounts of concentrates. Low ruminal pH has negative effects on ruminal fermentation. However, previous studies have indicated that rumen bacteria may resist short periods of low ruminal pH, and it is not clear how long this period may be before rumen microbial fermentation is negatively affected. Seven dual-flow continuous culture fermenters (1,320mL) were used in 3 replicated periods with the same diet (97g of dry matter/d of a 60:40 forage-to-concentrate diet, 18.3% crude protein, 35.9% neutral detergent fiber), temperature (39°C), and solid (5%/h) and liquid (10%/h) dilution rates to study the effects of increasing time at suboptimal pH on rumen microbial fermentation and nutrient flow. Treatments were a constant pH of 6.4 and 6 different intervals of time during the day (4, 8, 12, 16, 20, 24h) at suboptimal pH (5.5), with the rest of the day being at pH 6.4. Polynomial equations were derived using the Mixed procedure of SAS, and linear, quadratic and cubic terms were left in the equation if P<0.10. True organic matter digestion decreased with increasing time at suboptimal pH and was best described by a cubic regression (TOMD=58.5−2.15x + 0.16x2 −0.0037x3; R2=0.74). Digestion of NDF (DNDF=55.1−1.00x; R2=0.75) and digestion of ADF (DADF=56.2−1.33x; R2=0.78) decreased linearly with increasing time at suboptimal pH. Total VFA had a cubic response (VFA=112.7−2.09x + 0.17x2−0.0054x3; R2=0.82). The proportion of acetate decreased linearly (acetate=58.7−0.61x; R2=0.79). The propionate proportion increased (propionate=17.6 + 2.09×−0.044x2; R2=0.85) and branched-chain VFA decreased (BCVFA=4.45 −0.51x + 0.014x2; R2=0.75) quadratically. The ammonia N concentration (NH3-N=5.85−0.13x; R2=0.46) and flow (NH3-N flow=0.18−0.0039x; R2=0.43) decreased linearly as the time at suboptimal pH increased. Crude protein degradation (CPd=41.9−1.60x + 0.060x2; R2=0.71), efficiency of microbial protein synthesis (EMPS=26.6−0.33x + 0.021x2; R2=0.77), microbial N flow (MN flow=1.38−0.036x + 0.0015x2; R2=0.77), and dietary N flow (DN flow=1.49 + 0.041x−0.0015x2; R2=0.65) had a quadratic response. The flow of essential, nonessential, and most individual AA increased linearly with increasing time at suboptimal pH. The effects of pH on rumen fermentation appear to start as soon as pH drops to suboptimal pH.

Performance of beef heifers grazing stockpiled fescue as influenced by supplemental whole cottonseed1

The objectives of this study were to determine the composition of stockpiled fescue from December through February over 2 yr and to determine the performance of heifers grazing stockpiled fescue with or without supplemental whole cottonseed. In early December, 36 heifers (initial BW 277 +/- 0.70 kg, yr 1; 266 +/- 2.2 kg, yr 2; and initial BCS of 5.0 +/- 0.04) were assigned randomly to 6 groups. Each group was assigned randomly to a 2.4-ha tall fescue pasture (98% endophyte infected), which had received 76 kg of N/ha on September 1. Group was the experimental unit for all measures. Forage DM available during grazing (to ground level) averaged 3,913 and 5,370 kg/ha in yr 1 and 2, respectively. The pasture was strip-grazed for 83 d, with daily forage allocation. Three groups were fed whole cottonseed (0.90 kg of DM/heifer; 24.4% CP, DM basis) daily at 0.33% of BW, and a small amount of a corn-based concentrate (0.19 kg of DM/heifer) to assure complete cottonseed consumption. Nutritive value of forage (dry basis) was determined each week by sampling each pasture to the 5-cm target grazing height. Forage disappearance was estimated every 2 wk from pre- and postgraze forage mass. Forage CP was 16.8% in yr 1 and 12.6% in yr 2. In vitro true organic matter digestibility (IVTOMD) was 82.0 and 71.9%, and ADF was 25.9 and 30.7% in yr 1 and 2, respectively. Most indicators of forage quality declined slightly through the winter, although they recovered in late winter in yr 1. The proportion of fescue that was green declined (P < 0.05) from December (79% in yr 1 and 64% in yr 2) to February (62% in yr 1 and 52% in yr 2). Green tissue averaged 20.4 and 15.2% CP, 91 and 87% IVTOMD, and 22.1 and 23.3% ADF in yr 1 and 2, respectively. Brown tissue averaged 10.3 and 8.5% CP, 64 and 62% IVTOMD, and 35.7 and 37.4% ADF in yr 1 and 2, respectively. Shrunk ADG (0.46 vs. 0.56 kg/d in yr 1 and 0.23 vs. 46 kg/d in yr 2) and change in BCS (- 0.03 vs. 0.33 in yr 1 and 0.13 vs. 0.5 in yr 2) was greater (P < 0.05) for supplemented heifers. Supplemented heifers had greater serum urea nitrogen in yr 1 (9.5 vs. 10.5 mg/dL; P < 0.07) and yr 2 (7.2 vs. 8.6 mg/dL; P < 0.01). Forage disappearance was similar between supplemented and unsupplemented heifers (3.19 vs. 3.39 kg.heifer(-1).d(-1) in yr 1 and 4.14 vs. 4.17 kg.heifer(-1).d(-1) in yr 2, respectively). Heifers responded to supplementation, but performance was lower than expected based on forage nutrient content.

Biohydrogenation of Fatty Acids and Digestibility of Fresh Alfalfa or Alfalfa Hay Plus Sucrose in Continuous Culture

The pattern of biohydrogenation of fatty acids from fresh alfalfa or alfalfa hay supplemented with 3 concentrations (0, 4, and 8%) of sucrose was studied at a constant pH of 6.2. Four continuous culture fermenters were used in a 4×4 Latin square design to test the hypothesis that fresh forage would increase flow of vaccenic acid (VA) from the fermenters compared with the same forage in hay form and that this difference would be diminished by adding sucrose to the hay diet by changing the bacterial community profile. Effluent was collected from each of the 4 fermenters during the last 3 d of each 10-d period. Nutrient digestibility, volatile fatty acids (VFA), and fatty acids in the effluent were measured. Flow of bacterial organic matter (OM) and neutral and acid detergent fiber and acid detergent fiber digestibilities were higher for fresh alfalfa than alfalfa hay. True OM digestibility of alfalfa hay tended to linearly decrease with sucrose supplementation. However, microbial efficiency and flow of bacterial OM (g/d) linearly increased with sucrose addition. There was no change in total VFA concentration; however, proportion of acetate linearly decreased and proportion of butyrate linearly increased with sucrose addition. Fresh alfalfa increased total biohydrogenation of fatty acids compared with than hay. Vaccenic acid flow (mg/d) was much higher for fresh alfalfa compared with alfalfa hay (216 vs. 41) and VA was the predominant 18:1 isomer, followed by trans-13 18:1; however, sucrose had no effect on VA flow. The percentage of VA (of total trans-18:1) was not different between fresh alfalfa and hay, whereas percentage of trans-10 18:1 was much lower for fresh alfalfa. Therefore, the ratio of VA to trans-10 18:1 was higher for fresh alfalfa. Flow of trans-12 18:1 linearly increased, whereas flows of cis-12 and total cis-18:1 had quadratic responses to sucrose supplementation. Total biohydrogenation and biohydrogenation of linoleic and linolenic acids linearly decreased with sucrose; however, there was no effect of sucrose on total trans fatty acid flow. Sucrose may be more detrimental to the last step of biohydrogenation of VA. The effects of sucrose on biohydrogenation and concentration of VFA may have been caused by a shift in microbial population by mechanisms that are independent of pH.

Effect of dietary inclusion of hazelnut and soybean meals on microbial protein synthesis

The aim of this study was to compare effects of dietary inclusion of hazelnut meal (HZM) with soybean meal (SBM) on site of digestion and microbial protein synthesis in sheep. Four ruminally and duodenally cannulated female Redkaraman × kıvırcık sheep (initial BW of 44.0 ± 1.02 kg) were utilized in a crossover experiment. Sheep were fed a diet of 60% corn silage (DM basis) and 40% concentrate consisting of barley and SBM or HZM. Feed was fed at 115% of ad libitum intake. Intakes of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were similar between sheep fed SBM or HZM based diets ( P > 0.05). Organic matter intake averaged 1089 (2.37% BW) and 1143 g/day (2.42% BW) for SBM and HZM, respectively. Apparent and true ruminal and total tract DM and OM digestibilities did not differ between diets ( P > 0.05). True ruminal OM digestibility was 74.3 and 74.6% for SBM and HZM based diets, respectively. Total CP entering the duodenum was similar between diets ( P > 0.05). Dietary plus endogenous CP entering the duodenum in grams and as a percentage of total CP was greater ( P < 0.05) for SBM versus HZM. Quantities of microbial protein ( P < 0.15) and NH 3 N ( P < 0.08) flowing to the duodenum tended to be less for SBM versus HZM; percentages of total CP were lower ( P < 0.05) for SBM. Apparent ruminal and total tract CP digestibilities did not differ between diets, but true ruminal CP digestibility and efficiency of microbial protein synthesis tended to be higher in animals fed the HZM based diet compared with the diet based on SBM ( P < 0.13). In conclusion, because total CP entering duodenum did not differ between diets, HZM can be substituted for SBM in sheep fed corn silage and barley based diets with a moderate CP level.

The effect of dietary protein content and hay intake level on the true and apparent digestibility of hay

The digestibility of concentrate feeds has been determined by difference using hay as a basal forage in many institutions. The objective of this experiment was to examine the effect of hay intake level and dietary crude protein (CP) content on hay digestibility. Groups of wether lambs (1 year old) were fed three levels (600, 700 and 800 g/day) of hay each at two CP contents (103 and 182 g CP/kg DM), achieved by using a urea solution. An extra group of lambs were fed hay unsupplemented with urea (42 g CP/kg DM) at a level of 800 g/day. The true organic matter digestibility (True OMD, calculated using two methods: True OMD 1 and 2) and apparent OMD of all treatments fed the 182 g CP/kg DM diets were significantly higher ( P<0.05) than treatments fed the 103 g CP/kg DM diet (OMD: 632.8 g/kg vs. 604.2 g/kg; True OMD 1: 720.6 vs. 694.1 g/kg; True OMD 2: 711.8 vs. 681.0 g/kg). Apparent and true digestibility also increased as hay allowance increased and a significant linear effect was observed for GED. For the three groups fed 800 g/day of hay, significant differences in digestibility due to CP content only occurred between the 182 and the 42 g CP/kg DM diets (with the exception of CP digestibility). Although the effect of CP content was significant in some cases, the magnitude of the observed digestibility response is of little consequence for concentrate feed evaluation.

In vitro and in vivo comparisons of diaminopimelic acid and purines for estimating protein synthesis in the rumen

Means analyses were used to compare estimates of crude protein (CP) degradation (%), true organic matter (OM) digestion (%), efficiency of microbial synthesis (g N kg −1 OM truly digested) and microbial nitrogen (N) flow (g d −1) using diaminopimelic acid (DAPA) and purines as microbial markers for 12 in vitro and four in vivo experiments. In vitro experiments included 268 determinations and in vivo experiments included 80 determinations of microbial activity by each marker. In vitro estimates of ruminal CP degradation, true OM digestion, efficiency of microbial synthesis and microbial N flow by purines (60.5, 52.4, 33.1 and 1.3) were lower ( P < 0.05) than estimates by DAPA (69.9, 55.0, 36.1 and 1.4). Coefficients of variation of estimates of ruminal CP degradation, true OM digestion, efficiency of microbial synthesis and microbial N flow determined by purines (22.0, 12.4, 17.0 and 22.4) or DAPA (22.2, 12.3, 14.2 and 20.5) were similar for in vitro experiments. In vivo estimates of ruminal CP degradation, true OM digestion and microbial N flow by purines (57.2, 53.1 and 137.2) were lower ( P < 0.05) than estimates by DAPA (65.9, 61.1 and 162.2). Estimates of efficiency of microbial synthesis determined using purines (28.4) and DAPA (27.9) were similar. Coefficients of variation for estimates of ruminal CP degradation, true OM digestion, efficiency of microbia l synthesis and microbial N flow determined by purines (21.4, 23.8, 38.6 and 32.4) and DAPA (16.5, 16.7, 37.3 and 33.9) were similar for in vivo experiments. Estimates of CP degradation exceeded 90% on 26 occasions when DAPA was used as the marker, compared with seven occasions when purines were used. Using purines as the microbial marker resulted in lower microbial activity and similar coefficients of variation compared with DAPA. Unrealistic values of CP degradation were observed more frequently using DAPA as the microbial marker.