Comparison of dry matter and neutral detergent fibre degradation of fibrous feedstuffs as determined with in situ and in vitro gravimetric procedures

Comparison of in situ ruminal straw fiber degradation and bacterial community between buffalo and Holstein fed with high-roughage diet

Buffalo exhibits great efficiency in utilizing low-quality roughage, which can be due to the combined effect of host physiological feature and roughage diet fed. The present study was designed to compare the ruminal fiber degradation and the bacterial community attached to straws in buffalo and Holstein when fed with the same high-roughage diet using in situ ruminal incubation technique. Rice and wheat straws were selected as the incubation substrates and sampled at 0, 4, 12, 24, 48, 72, 120, and 216 h of incubation time to measure the kinetics of dry matter (DM) and neutral detergent fiber (NDF) disappearance. Additional two bags were incubated and sampled at 4 and 48 h of incubation time to evaluate the bacterial community attached to straws. The results showed that buffalo exhibited a greater (p ≤ 0.05) fraction of rapidly soluble and washout nutrients and effective ruminal disappearance for both DM and NDF of straw than Holstein, together with a greater (p ≤ 0.05) disappearance rate of potentially degradable nutrient fraction for NDF. Principal coordinate analysis indicated that both host and incubation time altered the bacterial communities attached to straws. Buffalo exhibited greater (p ≤ 0.05) 16S rRNA gene copies of bacteria and greater (p ≤ 0.05) relative abundance of Ruminococcus attached to straw than Holstein. Prolonging incubation time increased (p ≤ 0.05) the 16S rRNA gene copies of bacteria, and the relative abundance of phyla Proteobacteria and Fibrobacters by comparing 4 vs. 48 h of incubation time. In summary, buffalo exhibits greater ruminal fiber degradation than Holstein through increasing bacterial population and enriching Ruminococcus, while prolonging incubation time facilitates fiber degradation through enriching phyla Proteobacteria and Fibrobacteres.

The Effect of the Stirring Speed on the In Vitro Dry Matter Degradability of Feeds

In vitro methods have been standardized and tested to correctly simulate the rumen environment and fermentation process. A few studies have verified that the feed degradability achieved as a result of stirring the samples is higher when the samples are incubated under continuous stirring than when they are only stirred twice daily. The objective of this study has been to verify the effect of the speed of stirring on feed degradability during In vitro incubation. For this purpose, the apparent and true dry matter degradability (ADMD and TDMD) of grass hay, pelleted alfalfa, corn silage, barley meal, straw, and a total mixed ration (TMR) were measured after 48 h of incubation in jars under different rotation speeds. The same types of feed were placed in the four jars of each instrument, and the rotation system of the machine was modified to ensure the simultaneous rotation of a pair of original jars (which sometimes stopped and/or rotated slowly and irregularly) together with a pair of modified jars under regular and continuous rotation. A rev counter data logger was mounted onto the jars, and the rotation speeds of the original and modified jars were measured and compared under different conditions (empty jars, jars with liquid, jars with rumen fluid, and sample bags). The modifications to the instruments stabilized the rotation of the jars, thereby making the stirring more regular during incubation. The degradability was partly influenced by the regular stirring, albeit with just one instrument, and for grass hay, barley meal, corn silage, and TMR. In short, it has been found that the regular stirring of sample bags is not essential to obtain reliable degradability measurement during incubation, although it is better to maintain a constant rotation to ensure a regular and standardized In vitro incubation process and therefore to allow reproducibility and comparisons of the results on feed degradability.

Variability among Animals and Incubation Protocols for Ruminant In Situ Degradation Studies with Tropical Feeds

Simple Summary

The knowledge on the nutritive value of feeds is essential to feed animals with adequate diets and to optimize production with minimal environment impact. In situ degradation is an important tool for nutritionists because it is a reliable, cheap, and fast way to assess information on feed digestion in ruminants. However, the lack of standards procedures for in situ trials with cattle in the tropics may compromise the reliability of information obtained from those studies. Thus, we aimed to generate useful information for animal scientists on how to perform that kind of study using adequate and minimal resources yet keeping accuracy to interpret feed characteristics. Our findings indicated an important variation among animals on the estimates of the rumen degradation rate of feeds, and taking into account that variation can allow for a more adequate comparison among feeds. On the other hand, we also found that an in situ trial cannot be performed using fewer than three animals, otherwise the risk of obtained biased and imprecise information increases. Minimum sets of incubation times were defined and evaluated. They can be used to decrease the costs and the labor when tropical feeds are evaluated through in situ trials with cattle.

Abstract

Our objectives were to evaluate the variability among animals regarding to the degradation rate of the potentially degradable fraction of dry matter, crude protein, and neutral detergent fiber, as well as to establish the minimum number of animals and provide a standardized design of sampling times for in situ ruminal degradation assays of tropical feeds with cattle. Seven feeds were evaluated, four concentrates and three forages. The incubations were performed using five rumen-cannulated Nellore heifers (328 ± 9.8 kg of body weight). The complete sets of incubation sampling times encompassed 16 time points for forage samples (0–240 h) and 13 time points for concentrate samples (0–144 h). The profiles were adjusted using both fixed and mixed model approaches. When the variation among animals on the degradation rate was considered using the mixed model approach, the precision of the adjusted degradation profiles was increased. Moreover, the utilization of a low number of animals increases the probability to obtain biased estimates of degradation rate and increased random variances. A minimum of three animals is recommended for in situ trials with cattle. Minimum designs of sampling times regarding number and position of incubation times were proposed, discussed, and recommended to assess the dynamics of tropical feed degradation.

Effects of Exogenous Fibrolytic Enzyme Derived from Trichoderma reesei on Rumen Degradation Characteristics and Degradability of Low-Tannin Whole Plant Faba Bean Silage in Dairy Cows

The objectives of this study were to (1) determine the effect of exogenous fibrolytic enzyme derived from Trichoderma reesei on dry matter (DM) and neutral detergent fibre (NDF) degradability of whole plant faba bean silage (Snowbird), (2) evaluate the effects of fibrolytic enzyme (FETR) on DM and NDF degradation kinetics of whole plant faba bean silage, and (3) compare the difference between in the vitro approach (DaisyII incubation method) and the in situ assay-biological approach (nylon bag technique) in the determination of degradability of dry matter (DMD) and neutral detergent fibre (NDFD). The fibrolytic enzyme from Trichoderma reesei was a mixture of xylanase and cellulase. The whole plant faba bean silage was treated with seven doses of fibrolytic enzyme, with 0 as a control and 0.25, 0.5, 0.75, 1, 1.25 and 1.5 mL of FETR/kg DM of silage. The results obtained from the in situ method show that fibrolytic enzyme cubically (p < 0.05) affected DMD and quadratically (p < 0.01) affected NDFD with increasing level of enzyme application. In vitro DM and NDF degradability were quadratically and cubically (p < 0.01) affected by the increasing dosage of enzyme. Correlation analysis between the in situ assay-biological approach and the In vitro DaisyII approach showed a strong correlation (r = 0.98, p < 0.01) on overall DMD and also a satisfactory relationship (r = 0.84, p < 0.01) was found on overall NDFD. The enzyme application showed a great impact on NDF rumen degradation kinetics by decreasing the undegradable fraction and increasing the potential degradable fraction and the effective degradable content of fiber. The washable (W) and potential degradation fraction (D) were linearly (p = 0.05) increased by the enzyme treatments. Therefore, the undegradable fraction was linearly decreased (p = 0.05) with increasing dosage of enzyme. Both bypass (BNDF) and effective degradable NDF (EDNDF) were cubically (p = 0.05) affected by fibrolytic enzyme. In conclusion, the exogenous fibrolytic enzyme derived from Trichoderma reesei highly impacted rumen degradation characteristics and degradability of whole plant faba bean silage and could be used to improve fibre digestion of whole plant faba silage in dairy cows.

Potential Valorization of Organic Waste Streams to Valuable Organic Acids through Microbial Conversion: A South African Case Study

The notion of a “biobased economy” in the context of a developing country such as South Africa (SA) necessitates the development of technologies that utilize sustainable feedstocks, have simple and robust operations, are feasible at small scale and produce a variety of valuable bioproducts, thus fitting the biorefinery concept. This case study focuses on the microbial production of higher-value products from selected organic waste streams abundant in the South African agricultural sector using microbes adapted to utilize different parts of biomass waste streams. A ruminant-based carboxylate platform based on mixed or undefined anaerobic co-cultures of rumen microorganisms can convert the carbohydrate polymers in the lignocellulosic part of organic waste streams to carboxylic acids that can be upgraded to biofuels or green chemicals. Furthermore, yeast and fungi can convert the simpler carbohydrates (such as the sugars and malic acid in grape and apple pomace) to ethanol and high-value carboxylic acids, such as lactic, fumaric, succinic and citric acid. This review will discuss the combinational use of the ruminal carboxylate platform and native or recombinant yeasts to valorize biomass waste streams through the production of higher-value organic acids with various applications.

Quantifying non-fibrous carbohydrates, acid detergent fiber and cellulose of forage through an in vitro gas production technique

BACKGROUND

The in vitro gas production (GP) technique has been useful for evaluating the potential degradability of feedstuffs in ruminal environments; GP is related to the components of feedstuff ingredients.

RESULTS

Linear models were generated and validated as alternatives of quantifying neutral detergent-soluble fiber, starch (St)/hemicellulose (Hem) and cellulose (Cel) through GP. Residuals of models obtained from the peaks of GP [0-8 h (GP-8), > 8-24 h (GP-24), > 24-48 h (GP-48) and > 24-81 h (GP-81)] of 0.02, 0.04, 0.08, 0.12 and 0.20 g of glucose (Glu), St and Cel respectively. The incubations were analyzed in mixtures of Glu, St and Cel. The best fitting models (r² from 0.709 to 0.935) were tested on corn stover (CS) to quantify rapid fermentation fractions (RF; equivalent to Glu), medium fermentation fractions (MF; equivalent to St) and low fermentation fractions (LF48; equivalent to Cel); in CS, RF, MF and LF models had standardized residuals < 0.09. The analysis with Leucaena (Leucaena leucocephala Lam. de Wit) and star grass (Cynodon nlemfuensis Vanderyst) consider high-protein ingredients.

CONCLUSION

The in vitro GP of RF, MF and LF48 fractions equivalent to Glu, St and Cel are affected by maturity and harvest time even when the chemical composition remains similar, and so RF, MF and LF48 should be considered during the design of ruminant diets. In vitro GP could be used to quantify the components of some forages, although further studies are necessary. © 2020 Society of Chemical Industry.

In Vitro Techniques Using the DaisyII Incubator for the Assessment of Digestibility: A Review

Simple Summary

The Ankom Daisy^II incubator (AD^II; Ankom Technology Corporation Fairport, NY, USA) has gained acceptance as an alternative to traditional in vitro procedures. It reduces the labour requirement and increases the number of determinations that can be completed by a single operator. The apparatus allows for the simultaneous incubation of several feedstuffs in sealed polyester bags in the same incubation vessel, which is rotated continuously at 39.5 °C. With this method, the material that disappears from the bag during incubation is considered digestible. The method, which was first developed to predict the digestibility of feedstuffs for ruminants, has been modified and adapted to improve its accuracy and prediction capacity. Modifications used by various researchers include the use of different inocula, buffer solutions, and sample weights. Recently, attempts have been made to adapt the method to determine nutrient digestibility of feedstuff in non-ruminant animals, including pets.

Abstract

This review summarises the use of the Ankom Daisy^II incubator (AD^II; Ankom Technology Corporation Fairport, NY, USA), as presented in studies on digestibility, and its extension to other species apart from ruminants, from its introduction until today. This technique has been modified and adapted to allow for different types of investigations to be conducted. Researchers have studied and tested different procedures, and the main sources of variation have been found to be: the inoculum source, sample size, sample preparation, and bag type. In vitro digestibility methods, applied to the AD^II incubator, have been reviewed, the precision and accuracy of the method using the AD^II incubator have been dealt with, and comparisons with other methods have been made. Moreover, some hypotheses on the possible evolutions of this technology in non-ruminants, including pets, have been described. To date, there are no standardised protocols for the collection, storage, and transportation of rumen fluid or faeces. There is also still a need to standardise the procedures for washing the bags after digestion. Moreover, some performance metrics of the instrument (such as the reliability of the rotation mechanism of the jars) still require improvement.

Comparison of ruminal digestibility of Origanum onites L. leaves in dairy buffalo and cows

This experiment evaluated the ruminal digestibility of Turkish oregano leaves in dairy buffalo and cows. Ruminally cannulated, multiparous Brown Swiss cows (n = 3) and water buffalo (Bubalus bubalis; n = 3) were used in the experiment. The ad libitum basal diet was balanced to NRC requirements for a dry, nonpregnant multiparous dairy cow (680 kg) and consuming 12.8 kg of DM/day. Air-dried, ground, weighed oregano leaves were inserted in the rumen of all animals before the morning feeding within heat-sealed nylon bags (4 replicates per treatment and time point). After incubation (4, 8, 24, 48, and 72 h), dry matter (DM), crude protein (CP), aNDFom, and ADFom concentrations were determined and compared to initial leaf chemical composition. The means for in situ disappearance (ISD, %) of DM, aNDFom, and ADFom did not differ between the species, but ISD of CP was greater in buffalo than the cows (P = 0.05) after 72 h incubation. The lag time of kinetic degradation curves, the potentially degradable fraction (b), hourly degradation rate (c), and undegradable fraction were similar between species. The immediately degraded fraction (a) and effective digestibility (ED) of CP were greater in buffalo than the cows (P = 0.04), but the a fraction and ED of other nutrients showed no differences between the species. In conclusion, CP of oregano leaves are degraded more rapidly in the rumen of dairy buffalo than cows, primarily due to a large difference in the rapidly soluble CP fraction in the buffalo.

Valorisation of the invasive species, Prosopis juliflora, using the carboxylate platform to produce volatile fatty acids

Biomass derived from low-value, high-volume invasive plant species is an attractive, alternative feedstock to produce biofuels and biochemicals. This study aimed to use the carboxylate platform to valorize the invasive leguminous shrub, Prosopis juliflora (Mesquite), by utilizing in vitro rumen fermentations without chemical pretreatment to produce volatile fatty acids. The three fractions of the mesquite: leaves (ProL), stems (ProS) and branches (ProB) were compared regarding chemical composition, neutral detergent fiber (NDF) digestibility at 7 time points and VFA production after 72 h with sugarcane bagasse (SCB) as a reference. NDF digestibility was significantly (P < 0.05) higher in ProL (35.8%) than ProS (30.4%) and ProB (20.9%) compared to SCB (21.9%). VFA concentrations from 20 g biomass L^-1 showed significant differences with 8.07, 6.71 and 6.51 g L^-1 for ProL, ProS and ProB respectively, while SCB yielded 4.02 g L^-1. These concentrations were comparable with other platforms that employ chemically pretreated biomass for VFA production.

Effects of sample size on neutral detergent fiber digestibility of triticale forages using the Ankom DaisyII Incubator system

Accurate and precise determinations of fiber digestibility are essential for proper diet formulation for dairy cows. Our objectives were 3-fold: (1) regress in vitro neutral detergent fiber digestibility (NDFD) values from 48 triticale forages determined at multiple endpoints ranging from 12 to 240 h with Ankom Daisy^II Incubator system (Ankom Technology Corp., Macedon, NY) methods using 0.25- or 0.50-g sample sizes on concentrations of fiber-related analytes or growth stage; (2) directly compare NDFD values determined with 0.25- or 0.50-g sample sizes by Ankom methods after 12-, 24-, 30-, 48-, 144-, or 240-h incubations; and (3) compare NDFD values determined by Ankom methods after 30 and 48 h of incubation with those determined by traditional sealed-tube procedures obtained from a commercial laboratory. Generally, plant growth stage, which was quantified with a linear model suitable for serving as an independent regression variable, proved to be a better predictor variable for NDFD than neutral detergent fiber or acid detergent lignin. For direct comparisons of 0.25- and 0.50-g sample sizes using Ankom methods, the regression relationship for a 30-h incubation was explained by a linear model [Y = 1.206x - 1.1; coefficient of determination (R²) = 0.933], in which the slope differed from unity, but the intercept did not differ from 0. After a 48-h incubation, a linear model (Y = 1.014x + 7.1; R² = 0.964) indicated that the slope did not differ from unity, but the intercept was >0. A linear regression (Y = 1.040x - 1.8; R² = 0.861) of the 30-h incubation results obtained by Ankom methods using the 0.25-g sample size on those from the commercial laboratory indicated the slope and intercept did not differ from unity or 0, respectively. A similar relationship was obtained from the 48-h incubation (Y = 1.021x - 3.4; R² = 0.866). Relationships were poorer when the 0.50-g sample size was used by Ankom methods, particularly for the 30-h incubation, where the slope (0.824) was less than unity. Generally, NDFD values were greater for the 0.25-g sample size by Ankom methods, especially with 24-, 30-, and 48-h incubation times, and agreement with traditional sealed-tube methods was improved with the smaller sample size. Synchronization of results between Ankom and traditional methods needs to be further verified across a wider range of forages and harvest/preservation methods before definitive recommendations can be made.

Effects of conservation method on condensed tannin content, ruminal degradation, and in vitro intestinal digestion of purple prairie clover (Dalea purpurea Vent.)

In situ and in vitro experiments were conducted to evaluate the effect of forage conservation method on the chemical composition, ruminal degradation, and intestinal digestion of purple prairie clover (PPC), which was conserved as freeze-dried forage (FD), silage (SIL), or hay (Hay). In situ dry matter (DM), neutral detergent fiber (NDF), and crude protein (CP) degradabilities were determined by incubating the forages in three rumen-cannulated heifers for 0, 1, 2, 4, 8, 24, 48, and 72 h. Intestinal DM and CP digestions were estimated by incubating 12 h ruminal in situ residues in a modified three-step in vitro procedure. Ensiling decreased (P < 0.001) extractable condensed tannins (CT) but increased (P < 0.001) protein- and fiber-bound CT compared with FD and Hay. The ruminal disappearance of CP at 8 and 24 h was affected by conservation method (P < 0.001), ranked as SIL > FD > Hay. The effective degradability of DM was lower (P < 0.001) for Hay than for FD and SIL. Ensiling lowered (P < 0.001) whereas haymaking increased (P < 0.001) intestinal digestion of CP compared with the fresh PPC. There were no differences in intestinal DM digestion among the three conserved forages. The results suggest that PPC conserved as Hay may conserve the biological activity of CT via preserving extractable CT more than as SIL, thus having the potential to improve protein utilization in ruminants.

Effects of calcium oxide treatment at varying moisture concentrations on the chemical composition, in situ degradability, in vitro digestibility and gas production kinetics of anaerobically stored corn stover

The objective of this study was to determine the optimum conditions for calcium oxide (CaO) treatment of anaerobically stored corn stover by in situ and in vitro methods. Four ruminally cannulated, non-lactating, non-pregnant Holstein cows were used to determine the in situ effective degradabilities of dry matter (ISDMD), organic matter (ISOMD), neutral detergent fibre (ISNDFD), in vitro organic matter disappearance (IVOMD) and gas production in 72 h (GP72h ) of corn stover. A completely randomized design involving a 3 × 3 factorial arrangement was adopted. Ground corn stover was treated with different levels of CaO (3%, 5% and 7% of dry stover) at varying moisture contents (40%, 50% and 60%) and stored under anaerobic conditions for 15 days before analysis. Compared with untreated corn stover, the CaO-treated stover had increased ash and calcium (Ca) contents but decreased aNDF and OM contents. The moisture content, CaO level and their interaction affected (p < 0.01) the content of aNDF, ash and OM, and the ratio of aNDF/OM. The greatest ISDMD, ISOMD and ISNDFD were observed when stover was treated with 7% CaO and 60% moisture, while no differences (p > 0.01) in these in situ degradability parameters were observed between the stover treated with 5% CaO at 60% moisture content and those treated with 7% CaO at 60% moisture content. Corn stover treated with 5% CaO at 50% moisture had the maximum IVOMD and GP72 h among the treatments, and there was no difference (p > 0.01) between 50% and 60% moisture. Results from this study suggested that 5% CaO applied at 60% moisture could be an effective and economical treatment combination.

True dry matter digestibility of feeds evaluated in situ with different bags and in vitro using rumen fluid collected from intact donor cows

The aim of the study was to determine the comparability of the true dry matter digestibility (TDMd) achieved in situ with either traditional nylon bags (IS nylon) or synthetic filter bags (IS filter), and in vitro with either conventional bottles (CB) or the DaisyII incubation technique, using rumen fluid collected by oro-ruminal suction from intact cows. The four TDMd results were compared by linear regression. For each method, 11 feeds were incubated for 48 h in two separate incubations. The reproducibility of TDMd measurements was 97.9%, 95.1%, 98.8% and 96.0% for IS nylon, IS filter, CB and DaisyII, respectively. The determination coefficient, the slope (b), and the significant difference of the slope from unity, of the linear relationship between TDMd values (g/kg DM) were as follows: IS nylon v. IS filter, R2 = 0.97, b = 0.86, P = 0.02; IS nylon v. CB, R2 = 0.90, b = 1.02, P = 0.27; IS nylon v. DaisyII, R2 = 0.90, b = 1.06, P < 0.01; and IS filter v. DaisyII, R2 = 0.95, b = 0.98, P = 0.13. In situ filter bags and DaisyII underestimated the TDMd values compared with IS nylon bags and CB, respectively. In situ, the replacement of nylon with filter bags could simplify the procedure of analysis, with less manipulation of residuals and less labour, and offers the possibility to increase the number of samples analysed simultaneously. The close relationships found among methods suggest that rumen fluid collected from intact cows can produce in vitro estimates of TDMd at 48 h well correlated with those obtained in situ.