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

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

Fecal nitrogen to estimate intake and digestibility in grazing ruminants

This study aimed at evaluating forage intake and digestibility in ruminants using fecal nitrogen content, as well as validating a non-linear model to estimate digestibility in ruminants. A total of 58 conventional metabolism trials, carried out with sheep fed 27 forages (offered pure or in mixture) used in Rio Grande do Sul (RS) during the period 1969–1989 was analyzed. OM intake and OM digestibility (OMD) results were regressed linearly against fecal N, and OMD was also estimated from fecal crude protein (N × 6.25) content by a non-linear regression model. Fecal nitrogen excretion estimated forage intake in sheep with an R² = 0.73, whereas a low R² value of 0.36 was observed for OMD estimates. The equation obtained using the non-linear model was OMD = 0.7326 ? 0.3598 exp [(?0.9052 CP (g/kg OM))/100]. The parameters a (0.7326) and b (0.3598) estimated by the equation for all forages were significant (P<0.00001) and there was no effect of type of forage (P=0.38). The mean prediction error (MSPE), was 0.2379, indicating that the equation fit well to the data. The difference between estimated and observed organic matter digestibility was mainly caused by random variation (0.9765). The results indicated that the equation using the non-linear model developed with all forages can be used with enough precision to estimate the OM digestibility of forage consumed by sheep in Rio Grande do Sul.     

Nitrogen in vivo digestibility and in situ degradability data for estimation of lower tract N digestibility with or without correction for microbial contamination

In situ degradability and in vivo (by difference) digestibility trials were conducted to estimate lower tract residual N digestibility (LTRND) of five protein supplements. Efforts were also made to improve the in situ method of measuring protein degradability. For in situ degradability trials, soybean meal (SBM), corn gluten meal (CGM), cotton seed cake (CSC), wheat bran (WB) and corn gluten feed (CGF) were weighed into Dacron bags and incubated in the rumen of three cannulated Chios ewes. SBM, CGF and WB were degraded significantly, while CGM and CSC were least degraded. Microbial contamination (MC) resulted in a 5.3–28.3% artificially decrease in effective ruminal protein degradation of supplements. Total tract digestibility was measured using five rams in an in vivo, by difference, trial using a 5 × 5 Latin-square design. SBM had higher CP digestibility compared to WB, CGF and CSC, and higher N free extract (NFE) digestibility compared to the other feeds. CGM showed higher CP digestibility compared to WB, CGF or CSC, while CGF had higher organic matter (OM) and crude fibre (CF) digestibility compared to WB. CSC was the protein source with the lowest digestibility of OM, CP and NFE in comparison with the other feeds. LTRND was predicted as 0.928, 0.806, 0.227, 0.540, and 0.498 for SBM, CGM, CSC, WB, and CGF, respectively, or 0.931, 0.803, 0.147, 0.364, and 0.316 when the correction for MC was applied. Lower tract N digestibility could be predicted via a combination of in situ degradability and in vivo apparent digestibility data. This approach yields significant data regarding LTRND estimation of protein supplements, while diminishing animal suffering by avoiding small intestinal fistulation.     

Ammonia fiber expansion (AFEX) treatment of eleven different forages: Improvements to fiber digestibility in vitro

With the increased attention to bioenergy and especially cellulosic ethanol, there are concerns regarding potential competition for available land between biofuels and feeds/foods. Ammonia fiber expansion (AFEX), a pretreatment process for cellulosic ethanol, may also be used to improve ruminant digestibility of feedstuffs not traditionally used as forages. Eleven forages – including traditional forages, agricultural residues, and dedicated energy crops – were AFEX treated and digested in vitro with rumen inoculum. AFEX treatment improved 48-h neutral detergent fiber (aNDFom) digestion for several moderately indigestible forages compared to untreated samples, but showed no improvement for highly digestible samples. Of particular interest are corn stover and late-harvest switchgrass, as AFEX treatment improved digestibility by 52% and 128% over untreated material, whereas the improvement was 74% and 70% over conventional ammonia treatment, respectively. The crude protein content of all treated samples increased to more than 100 g/kg dry forage. This research strongly suggests that AFEX-treated feedstuffs can be competitive with traditional forages, and thus offer expanded options for ruminant feeding.     

Partitioning of energy and degradability of browse plants in vitro and the implications of blocking the effects of tannin by the addition of polyethylene glycol

The gas production in vitro method was used to evaluate the degradability and gas production of browse plants in the absence or presence of polyethylene glycol 8000 (PEG). Substrates (leguminous and browse plants; 500 mg) were incubated for 24 h and the accumulated gas produced recorded. The incubation contents of the syringes were transferred into nylon bags and the undegraded residues weighed after washing and drying to constant weight (syringe-nylon bag (SNB) method). Substrates were also incubated in the rumen in nylon bags for 24 h to determine in sacco degradability. Gas production ranged between 10.3 and 64.4 ml whereas dry matter degradation ranges between 27.3 and 70.9%. Addition of PEG, which minimised the inhibitory effects of tannin on microbial fermentation resulted in an increase in both gas production and degradability in vitro, which ranged from 25.7 to 64.2 ml and 34.2 to 75.0%, respectively. Correlation analysis of the DM degradability estimated by the SNB method and in sacco method was greater in the presence of PEG (y=0.71x+14.9; r²=0.92) compared with absence of PEG (y=0.59x+15.0; r²=0.72). Partitioning factor (PF) of substrate to gas, which was expressed as mg DM degraded/ml gas, reflects the variation in microbial biomass yield. The PF figures, which varied from 4.94–11.05 to PF_+PEG values of 4.74–6.84 upon the addition of PEG, indicate the inhibitory effects of tannins on gas production. This suggests the presence of tannin has a potentially beneficial effect to protein nutrition of the host animal by altering partitioning of nutrients towards higher microbial yield rather than short chain fatty acids. PF values of browse plants determined both in the absence and presence of PEG may indicate the relative importance of tannins in different plant species on substrate degradability and partitioning of nutrients.     

Influences of flavomycin,ropadiar, and saponin on nutrient digestibility,rumen fermentation,and methane emission from sheep

This study focused on the effects of three additives given together with a hay/concentrate-based diet on nutrient digestibility, rumen fermentation, and methane emission from sheep. The basal diet consisted of 1.29 kg mixed hay and 0.43 kg concentrate mixture based on dry matter (DM). Treatments consisted of control (no additive), flavomycin⁴⁰ (250 mg/d), ropadiar from an oregano extract (250 mg/d), and saponin in the form of a yucca schidigera extract (170 mg/d). Results indicated that intake and digestibility were unaffected by treatments (P>0.05). The NH₃-N concentration of rumen liquor was lower (P<0.05) for additive treatments versus the control treatment. Higher concentrations of volatile fatty acid (VFA) were observed in the saponin (75.8 mmol/L) and ropadiar (73.1 mmol/L) treatments. The proportion of individual fatty acid of rumen liquor was unchanged, whereas lower ratio of acetate to propionate in the saponin treatment was observed (P<0.05). The average methane production expressed on digested organic matter (OM) and neutral detergent fiber (aNDFom) basis were decreased by approximately 3.3 and 12.0 g/kg, respectively in saponin, and 4.2 and 11.9 g/kg in ropadiar treatment compared to the control. Methane production was positively correlated with the concentrations of NH₃-N, and negatively correlated with total VFA and the proportion of propionate of rumen liquor (P<0.05). The study found that saponin and ropadiar could have the potential to reduce rumen methanogenesis in sheep.     

Prediction of the digestibility of ruminant feeds from their solubility in enzyme solutions

The solubility of 24 diets containing grain and 23 forages was measured in solutions of either cellulase, pepsin or amylase. Sequential incubations in pepsin and cellulase (from Aspergillus niger) yielded solubility values which were significantly correlated with the dry matter digestibility in vivo of the diets containing grain (r = 0.85) and the forages (r = 0.82). When cellulase from Trichoderma viride was used instead of the cellulase from Aspergillus niger, the correlation was lower for the feeds containing grain (r = 0.60) but not for the forages (r = 0.84). The former method was comparable in accuracy to the two-stage technique for measuring digestibility in vitro with rumen fluid and pepsin, for which correlation coefficients of 0.89 and 0.83 were observed for the diets containing grain and the forages, respectively.     

Effect of elemental nano-selenium on feed digestibility,rumen fermentation,and purine derivatives in sheep

The objective of this experiment was to study the effect of elemental nano-selenium (NS) on feed digestibility, rumen fermentation, and urinary purine derivatives in sheep. Eight male ruminally cannulated sheep (42.5 ± 3.2 kg of body weight, BW) were used in a replicated 4×4 Latin square experiment in four 20 day periods. Depending on treatment designation, sheep were fed the basal diet supplemented with 0 (control), 0.3, 3 and 6 g of nano-Se/kg dry matter (DM). Ruminal pH (range of 6.68–6.80) and ammonia N concentration (range of 9.95–12.49 mg/100 mL) was decreased (P<0.01), and total VFA concentration (range of 73.63–77.72 mM) was increased linearly (P<0.01) and quadratically (P<0.01) with increasing nano-Se supplementation. The ratio of acetate to propionate was linearly (P<0.01) and quadratically (P<0.01) decreased due to the increasing of propionate concentration. In situ ruminal neutral detergent fiber (aNDF) degradation of Leymus chinensis and crude protein (CP) of soybean meal were linearly (P<0.01) and quadratically (P<0.01) improved by feeding nano-Se. Similarly, nutrients digestibility in the total tract and urinary excretion of purine derivatives were also quadratically (P<0.01) changed by increasing nano-Se supplementation. The present results indicated that nano-Se supplementation in basal diet improved rumen fermentation and feed utilization. Nano-Se could also stimulate rumen microbial activity, digestive microorganisms or enzyme activity. The optimum dose of nano-Se was about 3.0 g/kg dietary DM in sheep.     

Evaluation of green forage intake and digestibility in ruminants using near infrared reflectance spectroscopy (NIRS): Developing a global calibration

The objective of this study was to evaluate the potential of near infrared reflectance spectroscopy (NIRS), applied to forage and/or faeces, to estimate the in vivo organic matter digestibility (OMD) and the organic matter voluntary intake (OMVI, g/kg metabolic weight [BW^0.75]) for a wide range of temperate forages. Two different databases, in terms of forage species and development stages were studied. The first one included two grass species and two forage mixtures for which OMD and OMVI were continuously measured during the grass-growing seasons (spring and summer). The second one contained a large set of grass and legume species and forage mixtures (142 trials) for which OMD and OMVI were measured.Forage and faeces samples were submitted to NIRS analysis and predictive calibrations were developed from forage spectra, faeces spectra, forage and faeces subtracted spectra, and faeces and forage concatenated spectra. Working on faecal spectra (alone or concatenated) enabled us to develop the best calibration equations for both OMD and OMVI estimation. The coefficient of determination (R²) was greater than 0.8. The standard error of cross validation (SECV) for OMD and OMVI was 0.021 and 4.51 g/kg BW^0.75, respectively, and the accuracy was similar to that obtained with other predictive methods. With regard to the faecal spectra (second derivative mode), the fat absorbency at wavelengths of 1730, 2310 and 2350 nm was higher when the corresponding forage was highly digestible and ingestible.In conclusion, applying NIRS to faeces is a rapid and easy analytical method that could be an interesting tool for managing grazing ruminants and optimising their performance.     

Rumen degradability and intestinal digestibility of brewers' grains as affected by origin and heat treatment and of barley rootlets

The rumen degradability and intestinal digestibility of dry matter (DM) and nitrogen (N) of three samples of brewers' grains (BG) and three of barley rootlets (BR) were determined. Rumen degradability was determined by the nylon bag technique in three rumen fistulated wethers. Intestinal digestibility was determined by the mobile nylon bag technique in two duodenal fistulated wethers. N content ranged from 41.2 to 46.4 g/kg DM for BG, and from 42.8 to 53.7 g/kg DM for BR. N effective degradability (NED), calculated for rumen outflow rates determined in each sheep, ranged from 57.2% to 70.9% for BG and from 79.0% to 84.0% for BR. N intestinal digestibility (NID) determined on 8 h-rumen incubated residues, ranged from 84.9% to 89.8% for BG and from 67.3% to 81.3% for BR. Lower rumen degradability was partially compensated by higher intestinal digestibility, resulting in a smaller variation in the estimated amount of digestible bypass N, which ranged from 24.7% to 36.7% for BG and from 10.8% to 17.1% for BR. One BG sample was selected to study the effects of heat treatment (HT) on its chemical composition, rumen degradability and intestinal digestibility. The BG sample was either freeze-dried (UBG) or dried at 50°C (50BG), 100°C (100BG), 135°C (135BG) and 175°C (175BG). Total N content was not affected by HT, but the acid–detergent insoluble N (expressed as percentage of total N content) increased from 13.7% to 54.1%. HT reduced the NED (from 76.5% to 25.6%) and, as a consequence, the supply of undegraded N to the duodenum was increased by 1.2, 1.8, 2.4 and 3.2 times for 50BG, 100BG, 135BG and 175BG, respectively. Drying at 50°C and 100°C had no adverse effects on the NID determined on 8 h-rumen incubation residues (mean value of 84.3%), but drying at 135 and 175°C decreased it to values of 80.1 and 51.6%, respectively. As a consequence, the estimated amount of digestible bypass N was increased by 1.2, 1.8, 2.3 and 1.9 times when drying at 50°C, 100°C, 135°C and 175°C, respectively.     

Effect of supplementation with pelleted citrus pulp on digestibility and intake in beef cattle fed a tropical grass-based diet (Cynodon nlemfuensis)

Citrus pulp is an important by-product for sub-tropical and tropical ruminant animal production. In this study, three steers (average body weight = 324 ± 16 kg) were randomly assigned to three levels of pelleted citrus pulp (PCP) supplementation (0, 1.25, and 2.5 kg animal⁻¹ d⁻¹; as-fed) in a 3 × 3 Latin square design to evaluate its effects on forage intake, digestion, and ruminal pH. The basal diet was stargrass (Cynodon nlemfuensis) harvested and chopped every day and fed fresh. Supplementation with increasing amounts of PCP tended (P≤0.10) to result in a linear increase in digestibility of total diet dry matter (DM) and organic matter (OM), but no effects were noticed for digestibility of forage DM or total diet neutral detergent fiber. Forage DM intake decreased linearly (P=0.03) with increasing PCP supplementation, although the decrease tended (quadratic; P=0.08) to be of greater magnitude at the highest level of supplementation. Both a linear increase (P<0.01) and a quadratic trend (greatest increase with first level of supplementation; P=0.09) were also observed for intake of total digestible OM. Average ruminal pH was between 6.6 and 7.2 and was not affected (P=0.29) by supplementation treatment. Although supplementation with PCP depressed forage consumption somewhat, little effect on forage digestion was observed. The provision of digestible OM in the form of supplement was greater than that lost via depressed forage consumption, resulting in an overall increase in energy supply. Our results suggest that high levels of citrus pulp to beef cattle can lower forage intake, but increase total energy intake. High levels of citrus pulp supplementation could be beneficial in combination with forages high in rumen dagradable protein. Systems using grasses with higher ruminally degradable protein content than we used, may benefit from this extra supply of energy which should be tested in a further experiment.     

Chemical composition,digestibility and in situ degradability of dried and ensiled apple pomace and maize silage

The nutritive value of the dried and ensiled apple pomace (DAP and EAP), taken from two processing factories in Urmia city, was compared with maize silage (MS). For EAP, 1 tonnes of AP was mixed with 100 kg of wheat straw and 5 kg of urea (on fresh weight basis). The chemical composition of all feedstuffs was determined by laboratory analysis. Additionally, pH and the concentration of ammonia-N and volatile fatty acids (VFA) were measured in the EAP and MS silages. An in vivo digestibility study was undertaken with three Gezel wether sheep to determine the digestible organic matter content in the dry matter (DOMD) and to estimate the metabolisable energy (ME) content. The dry matter (DM) and protein effective degradabilities (ED) of the feedstuffs were assessed using a nylon bag method. The mean values of the DM, OM, CP, acid detergent fibre (ADF), neutral detergent fibre (NDF), lignin and acid detergent insoluble nitrogen (ADIN) were, respectively, 749 g/kg fresh weight, 929, 64, 405, 473, 10 and 5.6 g/kg DM for DAP, 284 g/kg fresh weight, 925, 72, 460, 567, 20 and 6.5 g/kg DM for EAP and 429 g/kg fresh weight, 936, 260, 463, 44 and 4.4 g/kg DM for MS. No butyric acid was found in EAP and MS, which indicate good preservation for these silages. However, ammonia-N was higher in MS than EAP. The DOMD values were 690, 654 and 580 g/kg DM for DAP, MS and EAP, respectively. The DOMD and ME values for DAP and MS were significantly higher than those of EAP. The dry matter ED of EAP was significantly lower than that of DAP and MS and there was a significant difference among all feedstuffs in the protein ED where MS was the highest and EAP the lowest. The nutritive value of AP was reduced by the addition of wheat straw. However, ensiling apple with straw is a practical method to preserve such high moisture by-product.     

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

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

Intake,digestibility and rumen characteristics in cattle offered whole-crop wheat or barley silages of contrasting grain to straw ratios

The effects of varying the grain (G) to straw (S) ratio (G:S) of whole-crop wheat and barley silages on intake and digestibility and whole-crop barley silage on rumen fermentation characteristics were examined in two parallel studies. For the intake and digestibility study, eight Aberdeen Angus cross-bred steers (mean bodyweight 407 kg (S.D. 24.2)) were used in two (barley and wheat) 4 × 4 Latin Square designed experiments. The dietary treatments were four G:S ratios: 0:100, 30:70, 60:40 and 90:10. Intake of grain linearly increased (P<0.001) while that of straw decreased (P<0.001) as the ratio of G:S increased for both cereals. No effect (P>0.05) was observed in total dry matter (DM) intake (DMI) or in DMI per kg liveweight. There was a positive linear (P<0.001) effect on the digestibility of the DM and organic matter (OM) and a negative linear effect on neutral detergent fibre (aNDFom) digestibility (P<0.01) as the G:S ratio increased for both cereals. Both a positive linear (P<0.05) and quadratic (P<0.01) effect were observed for the G:S ratio on nitrogen (N) digestibility of barley and a corresponding positive linear increase (P<0.01) for wheat. A negative linear effect was found for digestibility of starch (P<0.01) and a positive linear effect for faecal grain content (P<0.01) with increasing G:S ratio. Four Holstein–Friesian steers (mean bodyweight 659 kg (S.D. 56.9)) fitted with rumen cannulae were used in the rumen study. A negative linear effect of G:S ratio was found on rumen pH (P<0.001) while a positive linear effect was found on rumen ammonia (P<0.001) and total volatile fatty acid (VFA) concentration (P<0.01) with increasing G:S ratio. A negative linear effect (P<0.01) was found on the molar proportion of acetic acid. However, this decrease was offset by linear increases in the molar proportions of iso- and n-butyric acid, iso- (P<0.01) and n- (P<0.05) valeric acid, and to a lesser extent in propionic acid (P<0.01). No effect of treatment was found on rumen pool sizes of DM or its constituents. A positive linear effect (P<0.01) was found on the effective degradability (ED) of the DM, OM, N and starch while it was found to be negative in aNDFom (P<0.05). No effect (P>0.05) was found on the fractional clearance rates of DM, OM, aNDFom or starch or on liquid passage rate. It is concluded that increasing the G:S ratio in whole-crop wheat or barley silage linearly increased the intake of digestible nutrients for both wheat and barley and increasing the G:S ratio for whole-crop barley increased the concentration of fermentation products (total VFA, ammonia and the molar proportions of the VFAs, except acetic acid) in the rumen.     

Nutrient composition,digestion and rumen fermentation in sheep of wheat straw treated with calcium oxide,sodium hydroxide and alkaline hydrogen peroxide

This study tested the effect of calcium oxide (CaO), sodium hydroxide (NaOH) and NaOH plus hydrogen peroxide (H₂O₂; AHP) on cell wall composition, digestion and fermentation of wheat straw (straw) in sheep. Treated straws were prepared by mixing straw either with water followed by dusting with CaO at 160 g kg⁻¹ DM or with a NaOH solution alone at 3 l kg⁻¹ DM to supply 80 g NaOH kg⁻¹ DM (Na) or pre-soaked with Na exactly as in the previous treatment for 27 h followed by mixing with 130 g H₂O₂ kg⁻¹ DM (AHP) for 6 h. After 14 days of storage, the treated straws and an untreated straw (U) were fed automatically every 2 h to four individually housed sheep together with a supplement in a 4×4 latin square experiment. Each kilogram supplement DM contained 422 g CP and 10.8 MJ ME. NDF (p<0.001) and hemicellulose (p<0.01) contents were significantly reduced whereas cellulose was increased (p<0.001) in treated compared to untreated straw. ADL was reduced in Ca (p<0.05) but increased (p<0.05) in Na and AHP compared with U. The rumen and total tract digestibility were significantly (p<0.001) greater in sheep fed treated compared with untreated straw. Significant differences (p<0.05) between treatments for pH, NH₃ and VFA were also observed. All treatments improved the nutritive value of straws compared with untreated through modification of cell wall with a subsequent increase in digestibility by sheep. Although the digestibility for Ca was lower than that for Na despite reduction in cell wall, its use to treat straws may be more safe and cost effective than Na. AHP was the most effective and could also improve the energy value of other low quality forages for ruminants. However, the need of AHP for a large amount of NaOH to achieve highly alkaline pH limits its farm scale application. Therefore, further studies should either consider reducing the amount of NaOH or finding alternative alkalis that are cost effective and user-friendly.     

Effects of vitreousness and particle size of maize grain on ruminal and intestinal in sacco degradation of dry matter,starch and nitrogen

We assessed the effects of vitreousness and particle size of maize grain on ruminal and intestinal in sacco degradation of dry matter, starch and nitrogen. Six maize grain (Zea mays) genotypes characterized by differing vitreousness (proportion of vitreous in total endosperm) were ground (3-mm screen; Gr, ground particles, mean particle size (MPS): 526 μm) and cracked with a roller mill using two gap width settings (CS, cracked small particles, MPS: 1360 μm; CL, cracked large particles, MPS: 2380 μm). The ruminal and intestinal in sacco degradation of dry matter, starch and nitrogen was measured on three dry Holstein cows, fitted with rumen, proximal duodenum and terminal ileum cannulas, fed maize silage ad libitum twice daily. The ruminal starch degradability and intestinal digestibility differed among genotypes (P<0.001) and decreased as particle size increased (P<0.001). For the same particle size, starch ruminal degradability decreased (P<0.05) and intestinal digestibility decreased (P<0.002) with vitreousness. Particle size and vitreousness of maize grain are efficient factors for manipulating the amount of starch escaping rumen degradation, but may be limiting for the amount of starch digested in the small intestine.     

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

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

Effects of sun-drying and exogenous enzymes on nutrients intake,digestibility and nitrogen utilization in sheep fed Atriplex halimus foliages

This study was conducted to assess effects of sun-drying and/or addition of an exogenous enzyme (ENZ) preparation on intake, digestibility of nutrients and recovery values of secondary metabolites (SM) in the gastrointestinal tract of sheep fed Atriplex halimus (AH) foliages. A randomized block design for 28 d was used for four experimental treatments based on either fresh (AH-F) or sun-dried (AH-S) A. halimus foliages in the absence (?ENZ) or presence (+ENZ) of 10 g/sheep/d of the exogenous of ZADO^® enzyme preparation. Three adult sheep weighing 51 ± 2.7 kg were fed for each experimental treatment. The ENZ was added daily with a small amount of concentrate to help balance the dietary metabolizable energy concentration. Nutrient intake and digestibility, N balance and recovery of SM (i.e., total phenolics (TP), saponins (SP), alkaloids (AK), aqueous fraction (AF)) in the gastrointestinal tract were determined. Levels of most nutrients did not differ between AH-F and AH-S foliages, but the AH-S contained less than half of the SM in AH-F. Drying of A. halimus and ENZ addition increased (P=0.001) intake as well as OM and NDFom digestibility (P=0.02). Feed intake and digestibility were higher (P=0.01) in AH-S with ENZ addition. Intake of N by sheep fed the treatment diets depended on DM intake as the dietary concentration of N in the diets was similar. Thus AH-S sheep supplemented with ENZ had higher (P=0.001) N intake. Digestibility of N was similar to DM and OM digestibility, and was higher (P=0.03) in AH-S sheep supplemented with ENZ. Drying and ENZ addition to the diet increased (P=0.004) recovery of all SM. The fate of these compounds in the rumen needs to be evaluated considering that SM have been implicated in fiber and protein degradation in the rumen. The study showed that there are beneficial impacts of sun-drying and/or dietary exogenous enzyme addition for sheep fed A. halimus.     

The effect of replacing rice straw with dry wormwood (Artemisia sp.) on intake,digestibility, nitrogen balance and ruminal fermentation characteristics in sheep

This study examined the effect of substituting dry wormwood (Artemisia sp.) for rice straw in sheep diets on intake and apparent digestibility in vivo, nitrogen (N) balance and ruminal fermentation characteristics. Four Corriedale×Polwarth sheep (51.7 ± 1.3 kg) were individually housed in metabolism cages and fed diets (ad. libitum) with a 70:30 forage to concentrate ratio (DM basis), in which the basal rice straw was substituted with 0 (Control), 30 (LW), 50 (MW) or 100 (HW) g/kg of dry wormwood. The experimental design was a 4×4 latin square design in which 10 days of dietary adaptation was followed by 6 days of total feces and urine collection in each period. Rumen fluid was collected from a stomach tube at −0.5, 0.5, 1, 2, 4, and 8 h after the morning feed on day 6 of each collection period and analyzed for volatile fatty acids (VFA). The intakes of dry matter (DM), organic matter intake (OM), crude protein (CP), ether extract (EE), neutral detergent fibre (NDF) and acid detergent fibre (ADF) were higher (P<0.05) in sheep fed diets containing wormwood, than those fed the Control diet. Compared to the Control diet, CP digestibility was higher (P<0.05) in sheep fed MW and N intake, retained N, EE digestibility, urinary purine derivatives and microbial N yield were higher (P<0.05) in sheep fed diets, containing wormwood. Rumen pH was unaffected by treatment. Rumen NH₃-N and VFA concentrations were similar across treatments except that most values for diets containing wormwood were higher (P<0.05) than those for the control diet within the first 2 h of feeding. The non-glucogenic acid ratio was also similar across Control, LW and MW treatments, but it was generally lower in MW versus the Control treatment. In conclusion, substituting wormwood for rice straw in the sheep diets increased feed intake, rumen fermentation, in vivo digestibility, N retention and microbial N yield, particularly at the medium and high levels of wormwood inclusion.     

In vitro and in sacco digestibility of wheat straw treated with calcium oxide and sodium hydroxide alone or with hydrogen peroxide

A series of five factorial experiments examined the effects of sodium hydroxide (NaOH) and calcium oxide (CaO) alone or together with hydrogen peroxide (H₂O₂, 27.5% w/w) at pH of about 11.5 (AHP) on in vitro (IVDMD) and in sacco (ISDMD) dry matter digestibility of wheat straw. The effects of different temperatures (20°C, 40°C and 60°C), various times (2, 3, 4, 6 and 27 h), pre-soaking, filtration and washing on the efficacy of the above levels of chemicals in improving IVDMD and ISDMD were tested in separate experiments. AHP improved IVDMD (P<0.001) of straws when pH was regulated to around 11.5 using NaOH. In contrast, AHP was ineffective or depressive (P<0.001) when CaO was used to regulate pH to around 11.5. However, CaO alone increased IVDMD to a similar extent as did NaOH. Washing, filtration and temperature were ineffective in improving the IVDMD of CaO-treated straw. AHP was most effective when 130 g H₂O₂ was applied to each kg DM of straw after soaking it with 3 l solution containing 80 g NaOH for a period of 27 h. The nutritional value of low quality forages can be enhanced for ruminants by using alkalis provided conditions as described above are maintained during alkali treatments.