Effects of Partial Replacement of Corn with Glycerin on Ruminal Fermentation in a Dual-Flow Continuous Culture System

Megasphaera elsdenii and Saccharomyces Cerevisiae as direct fed microbials during an in vitro acute ruminal acidosis challenge

This study aimed to evaluate the effects of Saccharomyces cerevisiae and Megasphaera elsdenii as direct fed microbials (DFM) in beef cattle finishing diets to alleviate acute ruminal lactic acidosis in vitro. A dual-flow continuous culture system was used. Treatments were a Control, no DFM; YM1, S. cerevisiae and M. elsdenii strain 1; YM2, S. cerevisiae and M. elsdenii strain 2; and YMM, S. cerevisiae and half of the doses of M. elsdenii strain 1 and strain 2. Each DFM dose had a concentration of 1 × 108 CFU/mL. Four experimental periods lasted 11 days each. For the non-acidotic days (day 1-8), diet contained 50:50 forage to concentrate ratio. For the challenge days (day 9-11), diet contained 10:90 forage to concentrate ratio. Acute ruminal acidosis was successfully established. No differences in pH, D-, L-, or total lactate were observed among treatments. Propionic acid increased in treatments containing DFM. For N metabolism, the YMM treatment decreased protein degradation and microbial protein synthesis. No treatment effects were observed on NH3-N concentration; however, efficiency of N utilization by ruminal bacteria was greater than 80% during the challenge period and NH3-N concentration was reduced to approximately 2 mg/dL as the challenge progressed.

Effects of lactic acid-producing bacteria as direct-fed microbials on the ruminal microbiome

The objective of this study was to evaluate ruminal microbiome changes associated with feeding Lactobacillus plantarum GB-LP1 as direct-fed microbials (DFM) in high-producing dairy cow diets. A dual-flow continuous culture system was used in a replicated 4 × 4 Latin square design. A basal diet was formulated to meet the requirements of a cow producing 45 kg of milk per day (16% crude protein and 28% starch). There were 4 experimental treatments: the basal diet without any DFM (CTRL); a mixture of Lactobacillus acidophilus, 1 × 10⁹ cfu/g, and Propionibacterium freudenreichii, 2 × 10⁹ cfu/g [MLP = 0.01% of diet dry matter (DM)]; and 2 different levels of L. plantarum, 1.35 × 10⁹ cfu/g (L1 = 0.05% and L2 = 0.10% of diet DM). Bacterial samples were collected from the fluid and particulate effluents before feeding and at 2, 4, 6, and 8 h after feeding; a composite of all time points was made for each fermentor within their respective fractionations. Bacterial community composition was analyzed through sequencing the V4 region of the 16S rRNA gene using the Illumina MiSeq platform. Sequenced data were analyzed on DADA2, and statistical analyses were performed in R (RStudio 3.0.1, https://www.r-project.org/) and SAS 9.4 (SAS Institute Inc.); orthogonal contrasts were used to compare treatments. Different than in other fermentation scenarios (e.g., silage or beef cattle high-grain diets), treatments did not affect pH or lactic acid concentration. Effects were mainly from overall DFM inclusion, and they were mostly observed in the fluid phase. The relative abundance of the phylum Firmicutes, family Lachnospiraceae, and 6 genera decreased with DFM inclusion, with emphasis on Butyrivibrio_2, Saccharofermentans, and Ruminococcus_1 that are fibrolytic and may display peptidase activity during fermentation. Lachnospiraceae_AC2044_group and Lachnospiraceae_XPB1014_group also decreased in the fluid phase, and their relative abundances were positively correlated with NH₃-N daily outflow from the fermentors. Specific effects of MLP and L. plantarum were mostly in specific bacteria associated with proteolytic and fibrolytic functions in the rumen. These findings help to explain why, in the previous results from this study, DFM inclusion decreased NH₃-N concentration without altering pH and lactic acid concentration.

Residual feed intake and the inclusion of crude glycerin in the diet of feedlot-finished Nellore cattle

Context The beef market faces an increasing demand for an environmentally friendly production system with high-quality final products. The use of strategies that improve system efficiency without detriment on quality are desired for both producers and consumer. Aims This study aimed to evaluate the effects of residual feed intake (RFI) and dietary inclusion of crude glycerin on carcass and meat quality traits of feedlot-finished Nellore cattle. Methods Nellore bulls selected for growth and classified as high (n = 14) and low (n = 14) RFI, with average liveweight of 328 kg and age of 552 days were used. Bulls received a high-concentrate diet for 96 days before slaughter and were randomly allocated to two experimental diets in a 2 × 2 factorial arrangement: RFI class (low or high) and dietary inclusion (CG) or not (WCG) of crude glycerin (20% on dry-matter basis). Data were analysed with the SAS MIXED procedure considering RFI class and diet as fixed effects and selection line as a random effect. Key results There were no significant differences between RFI classes for dry-matter intake during finishing or production traits. Dry-matter intake tended to be reduced by 16% in CG bulls, without alterations in production. Dietary glycerin inclusion tended to increase the protein content in the Longissimus muscle and significantly reduced the fat content. In low-RFI bulls, shear force was higher in unaged beef, and shear force and myofibrillar fragmentation index tended to be higher in meat aged for 14 days. RFI class did not affect Longissimus muscle fatty acid profile, which was highly influenced by dietary glycerin inclusion. Bulls allocated to the CG treatment had a reduction in saturated fatty acids, an increase in odd-chain fatty acids, and a trend towards increased omega-3 fatty acids, which significantly increased the omega-3:omega-6 ratio. Conclusions The use of Nellore bulls classified as low-RFI and crude glycerin inclusion in finishing diets of Nellore cattle do not compromise production, carcass traits or beef properties. Implications This approach increases the efficiency and sustainability of the production process and improves the nutritional characteristics of beef for human consumption.

Low-purity crude glycerin as a nutrient substitute for corn: the effect on yields of goat organs and viscera

This study was conducted to evaluate the effects of the inclusion of low-purity crude glycerin (CG, 63.1% of glycerol) in the diets of feedlot-finished goats on the weights and yields of the non-carcass components, with are frequently used in regionals dishes (buchada and panelada). Forty castrated male goats with the initial mean body weight of 19.70 ± 2.30 kg were used. Experimental treatments consisted of inclusion of CG at levels of 0, 6, 12, and 18%, based on dry matter. The weights of the lungs, spleen, total organs (TWO), and TWO yield, as a function of the slaughter body weight, decreased linearly. It was shown that the rumen portion of the weight showed a quadratic effect, at the level of 10.71% of CG, with a minimum point of 0.37 kg. Similar behavior was observed for the reticulum, with a minimum point of 0.08 kg, at the level of 7.5% of CG. The weights and yields of the buchada and panelada were negatively influenced by the experimental diets. Low-purity crude glycerin may partially replace corn and be included in up to 6% of the dry matter of the finished goats' feedlot diet without adversely affecting weights and yields of organs, viscera, and regional dishes, such as buchada and panelada.

Linseed and glycerol in forage diets effect methane production and rumen fermentation parameters in a Rusitec semi-continuos system

Context The use of oilseeds as a feed ingredient has been proposed to improve fatty acid profiles and reduce methane (CH4) emissions. Glycerol has been used as a common additive in ruminant feeding systems with variable effects on CH4 production. The effects of the combination of these ingredients remain unknown. Aims The aim of this study was to assess the effects of feeding linseed and increasing concentrations of glycerol in forage diets supplemented with corn grain on nutrient disappearance, CH4 production and rumen fermentation parameters. Methods Experimental diets were: control (70:30% hay:corn); linseed (70:15 :15% hay:corn:linseed); 5% glycerol (70:10:15:5% hay:corn:linseed:glycerol); 10% glycerol (70:5:15:10% hay:corn:linseed:glycerol). Diets were incubated in a completely randomised design with four replicates per treatment in a Rusitec apparatus for 15 days (10 days adaptation, 5 days sampling). Key results Total VFA production (VFA, mmol/day) was quadratically increased due to glycerol concentration in the diets (P = 0.009). Acetate:propionate (A:P) decreased by the inclusion of linseed (P < 0.001) and glycerol into the diets (P < 0.001). Linseed inclusion in the diet reduced CH4 production, mg/DM disappeared (P = 0.004) by up to 36%. These effects were not altered by the addition of glycerol into the diets. Ammonia nitrogen (NH3-N) production increased 2-fold in the linseed-added diets, but this effect was partially reverted by increasing glycerol concentrations in the diets (P < 0.001). Crude protein (CP) disappearance increased (P < 0.001) in the linseed added diets, with no effect of glycerol addition. Neutral detergent fibre (aNDFom; P = 0.005) disappearance was increased by the addition of linseed to the diet. Conclusions The use of linseed in ruminant diets reduces CH4 emissions but increases NH3-N production in a Rusitec system. This latter effect is partially reverted by glycerol inclusion in the diet. Propionate production increases with the inclusion of glycerol, but does not alter CH4 production. Including linseed increases the in vitro CP disappearance without affecting DM total disappearance. Implications Care should be taken with the use of oilseeds in ruminant diets as it can reduce CH4 emissions but may cause important increases in NH3 emissions. Inclusion of glycerol may partially overcome this latter issue.

In vitro evaluation of Lactobacillus plantarum as direct-fed microbials in high-producing dairy cows diets

The objectives of this study were: 1) to compare the effects of live yeast (LY), yeast fermentation product (YFP), a mix of Lactobacillus acidophilus and Propionibacterium freudenreichii (MLP), and Lactobacillus plantarum included as additives in dairy cows’ diets on in vitro ruminal fermentation and gas production (GP); and 2) to evaluate the effects of L. plantarum as direct-fed microbials (DFM) in dairy cows’ diets on in vitro ruminal fermentation, GP, nutrient digestibility, and N metabolism. Three experiments were carried out: Exp. 1 had the objective to compare all additives regarding ruminal fermentation parameters: an Ankom GP system was used in a completely randomized design, consisting of four 48 h incubations, and eight replications per treatment. There were eight treatments: a basal diet without additive (CTRL) or with one of the following additives: LY, YFP, MLP, or L. plantarum at four levels (% of diet Dry Matter (DM)): 0.05% (L1), 0.10% (L2), 0.15% (L3), and 0.20% (L4). In Exp. 2, a batch culture was used to evaluate ruminal fermentation, and CO₂ and CH₄ production using the same treatments and a similar experimental design, except for having 16 replications per treatment. Based on Exp. 1 and 2 results, Exp. 3 aimed at evaluating the effects of the L. plantarum on ruminal true nutrient digestibility and N utilization in order to evaluate the use of L. plantarum as DFM. The treatments CTRL, MLP, L1, and L2 were used in a replicated 4 × 4 Latin square design using a dual-flow continuous culture system. Data were analyzed using linear and nonlinear regression; treatment means were compared through contrasts, and L treatments in Exp. 1 and 2 were tested for linear, quadratic, and cubic effects. In Exp. 1, all treatments containing additives tended to reduce OM digestibility as well as reduced total volatile fatty acids (VFA) concentration and total GP. The YFP had greater OM digestibility than LY, and MLP treatment had greater total VFA concentration compared to L. plantarum treatments. In Exp. 2, additives reduced CO₂ production, and there were no major differences in CH₄. In Exp. 3, all additives reduced NH₃-N concentration. In conclusion, pH and lactate concentration were not affected in all three experiments regardless of additive tested, suggesting that these additives may not improve ruminal fermentation by pH modulation; and L. plantarum may improve ruminal N metabolism when used as DFM in high-producing dairy cows’ diets, mainly by reducing NH₃-N concentration.

Unveiling the relationships between diet composition and fermentation parameters response in dual-flow continuous culture system: a meta-analytical approach

The objective of this study was to investigate the functional form of the relationship between diet composition (dietary crude protein [CP] and neutral detergent fiber [NDF]) and amount of substrate (fermenter dry matter intake [DMI]) with microbial fermentation end products in a dual-flow continuous culture system. A meta-analysis was performed using data from 75 studies. To derive the linear models, the MIXED procedure was used, and for nonlinear models, the NLMIXED procedure was used. Significance levels to fit the model assumed for fixed and random effects were P ≤ 0.05. Independent variables were dietary NDF, CP, and fermenter DMI, whereas dependent variables were total volatile fatty acids (VFA) concentration; molar proportions of acetate, propionate, and butyrate; true ruminal digestibilities of organic matter (OM), CP, and NDF; ammonia nitrogen (NH₃-N) concentration and flows of NH₃-N; non-ammonia nitrogen; bacterial-N; dietary-N; and efficiency of microbial protein synthesis (EMPS). Ruminal digestibilities of OM, NDF, and CP decreased as fermenter DMI increased (P < 0.04). Dietary NDF and CP digestibilities were quadratically associated (P < 0.01). Total VFA linearly increased as DMI increased (P < 0.01), exponentially decreased as dietary NDF increased (P < 0.01), and was quadratically associated with dietary CP (P < 0.01), in which total VFA concentration was maximized at 18% dietary CP. Molar proportion of acetate exponentially increased (P < 0.01) as dietary NDF increased. Molar proportion of propionate linearly increased and exponentially decreased as DMI and dietary NDF increased, respectively (P < 0.01). Bacterial-N quadratically increased and dietary-N exponentially increased as DMI increased (P < 0.01). Flows of bacterial-N and dietary-N linearly decreased as dietary NDF increased (P < 0.02), and dietary-N flow was maximized at 18% CP. The EMPS linearly increased as dietary CP increased (P < 0.02) and was not affected by DMI or dietary NDF (P > 0.05). In summary, increasing fermenter DMI increased total VFA concentration and molar proportion of propionate, whereas, dietary NDF increased the molar proportion of acetate. Dietary CP increased bacterial-N flow and was positively associated with NH₃-N concentration. Overall, the analysis of this dataset demonstrates evidences that the dual-flow continuous culture system provides valuable estimates of ruminal digestibility, VFA concentration, and nitrogen metabolism.

Does partial replacement of corn with glycerin in beef cattle diets affect in vitro ruminal fermentation, gas production kinetic, and enteric greenhouse gas emissions?

Five in vitro experiments were conducted with the following objectives: 1) To evaluate the ruminal fermentation of three different single ingredients: corn, glycerin, and starch (Exp. 1 and 2); 2) To assess effects of partially replacing corn with glycerin in beef cattle diets on ruminal fermentation pattern (Exp. 3 and 4); and 3) To evaluate the effects of glycerin inclusion on the extension of ruminal DM digestibility of feeds with high (orchard hay) and low (corn) fiber content (Exp. 5). For Exp. 1 and 2, two in vitro systems (24-bottle AnkomRF and 20-serum bottles) were used in four consecutive fermentation batches to evaluate gas production (GP), fermentation profiles, enteric methane (CH4), and carbon dioxide (CO2) of corn, glycerin, and starch. The 24 h total GP, acetate concentration, and acetate: propionate ratio decreased only when glycerin was added to the diet (P < 0.01). The 48-h total GP and metabolizable energy were greatest for corn (P < 0.01), and similar between glycerin and starch. The starch treatment had the lowest total volatile fatty acids concentration (P = 0.01). Glycerin had greatest CH4 production, lag time, and maximum gas volume of the first pool (P < 0.05). However, the maximum gas volume of the second pool was greatest for corn (P < 0.05), and similar between glycerin and starch. The starch treatment had the greatest specific rates of digestion for first and second pools (P < 0.05). Production of CO2 (mL/g) was greater for corn (P < 0.01), but similar for glycerin and starch. For Exp. 3 and 4, the same systems were used to evaluate four different levels of glycerin [0, 100, 200, and 300 g/kg of dry matter (DM)] replacing corn in beef cattle finishing diets. Glycerin levels did not affect 24 and 48 h total GP, CH4, and CO2 (P > 0.05). The inclusion of glycerin linearly decreased acetate concentration (P = 0.03) and acetate: propionate ratio (P = 0.04). For Exp. 5, two DaisyII incubators were used to evaluate the in vitro dry matter digestibility (IVDMD) of the following treatments: orchard hay; corn; orchard hay + glycerin; and corn + glycerin. Glycerin inclusion decreased orchard hay IVDMD (P < 0.01) but did not affect corn IVDMD (P > 0.05). We concluded that, under these experimental conditions, glycerin has similar energy efficiency when used in replacement of corn and included at up to 300 g/kg in beef cattle diets.

Effect of replacing calcium salts of palm oil with camelina seed at 2 dietary ether extract levels on digestion, ruminal fermentation, and nutrient flow in a dual-flow continuous culture system

Camelina is a drought- and salt-tolerant oil seed, which in total ether extract (EE) contains up to 74% polyunsaturated fatty acids. The objective of this study was to assess the effects of replacing calcium salts of palm oil (Megalac, Church & Dwight Co. Inc., Princeton, NJ) with camelina seed (CS) on ruminal fermentation, digestion, and flows of fatty acids (FA) and AA in a dual-flow continuous culture system when supplemented at 5 or 8% dietary EE. Diets were randomly assigned to 8 fermentors in a 2 × 2 factorial arrangement of treatments in a replicated 4 × 4 Latin square design, with four 10-d experimental periods consisting of 7 d for diet adaptation and 3 d for sample collection. Treatments were (1) calcium salts of palm oil supplementation at 5% EE (MEG5); (2) calcium salts of palm oil supplementation at 8% EE (MEG8); (3) 7.7% CS supplementation at 5% EE (CS5); and (4) 17.7% CS supplementation at 8% EE (CS8). Diets contained 55% orchardgrass hay, and fermentors were fed 72 g of dry matter/d. On d 8, 9, and 10 of each period, digesta effluent samples were taken for ruminal NH₃, volatile fatty acids, nitrogen metabolism analysis, and long-chain FA and AA flows. Statistical analysis was performed using the MIXED procedure (SAS Institute Inc., Cary, NC). We detected an interaction between FA source and dietary EE level for acetate, where MEG8 had the greatest molar proportion of acetate. Molar proportions of propionate were greater and total volatile fatty acids were lower on CS diets. Supplementation of CS decreased overall ruminal nutrient true digestibility, but dietary EE level did not affect it. Diets containing CS had greater biohydrogenation of 18:2 and 18:3; however, biohydrogenation of 18:1 was greater in MEG diets. Additionally, CS diets had greater ruminal concentrations of trans-10/11 18:1 and cis-9,trans-11 conjugated linoleic acid. Dietary EE level at 8% negatively affected flows of NH₃-N (g/d), nonammonia N, and bacterial N as well as the overall AA outflow. However, treatments had minor effects on individual ruminal AA digestibility. The shift from acetate to propionate observed on diets containing CS may be advantageous from an energetic standpoint. Moreover, CS diets had greater ruminal outflow of trans-10/11 18:1 and cis-9,trans-11 conjugated linoleic acid than MEG diets, suggesting a better FA profile available for postruminal absorption. However, dietary EE at 8% was deleterious to overall N metabolism and AA outflow, indicating that CS can be fed at 5% EE without compromising N metabolism.

Nutritional evaluation and ruminal fermentation patterns of kochia compared with alfalfa and orchardgrass hays and ephedra and cheatgrass compared with orchardgrass hay as alternative arid-land forages for beef cattle in two dual-flow continuous culture system experiments

The objective was to evaluate the ruminal fermentation patterns of forage kochia (FK) compared with alfalfa hay (AH) and orchardgrass hay (OH) (Exp. 1), and ephedra (EPH) and immature cheatgrass (CG) compared with OH (Exp. 2), using a dual-flow continuous culture system. Two in vitro experiments were conducted, and in each experiment, treatments were randomly assigned to six dual-flow fermenters (1,223 ± 21 mL) in a replicated 3 × 3 Latin square design, with three consecutive periods of 10 d each, consisting of 7 d for diet adaptation and 3 d for sample collection. Each fermenter was fed a total of 72 g/d (DM basis) and treatments were as follows: Exp. 1: 1) 100% OH, 2) 100% AH, and 3) 100% dried FK. Exp. 2: 1) 100% OH, 2) 100% dried CG, and 3) 100% dried EPH. On day 8, 9, and 10, samples of solid and liquid effluent from each fermenter were taken for digestibility analysis, and subsamples were collected for NH3-N, VFA, and bacterial N determinations. Data were analyzed using the MIXED procedure of SAS. In Exp. 1, treatments did not affect DM, OM, and NDF digestibilities, total VFA and molar proportions of acetate, propionate, butyrate, and branched-chain VFA. True CP digestibility, ruminal NH3-N concentration, and total N, NH3-N, NAN, and dietary N flows (g/d) were greater (P < 0.05) for FK compared with the other forages. However, treatments did not affect bacterial efficiency. In Exp. 2, DM, OM, and CP digestibilities were greater (P = 0.01) for EPH, and NDF digestibility was greater (P < 0.05) for EPH and CG compared with OH. Ephedra had the highest (P < 0.05) pH and acetate:propionate ratio and the lowest (P < 0.05) total VFA concentration. Total VFA, ruminal NH3-N concentration, and NH3-N flow (g/d) were highest (P < 0.05) for CG. Total N flow and bacterial efficiency were highest (P < 0.05) for OH and CG, while the flows (g/d) of NAN, bacterial N, and dietary N were greater (P < 0.05) for OH compared with the other forages. Results indicate that when compared with AH and OH (Exp. 1), FK has similar ruminal fermentation patterns and may be an adequate alternative for beef cattle producers. Furthermore, when compared with OH (Exp. 2), immature CG may also be an adequate forage alternative. This is especially important for areas in which conventional forages may not grow well such as the U.S. arid-land. However, EPH should not be used as the sole forage due to its poor ruminal fermentation as evidenced by the lowest total VFA concentration and propionate molar proportion.

Effects of partial replacement of maize in the diet with crude glycerin and/or soyabean oil on ruminal fermentation and microbial population in Nellore steers

The objective of this study was to determine whether a combination of crude glycerin (CG) and soyabean oil (SO) could be used to partially replace maize in the diet of Nellore steers while maintaining optimum feed utilisation. Eight castrated Nellore steers fitted with ruminal and duodenal cannulas were used in a double 4×4 Latin square design balanced for residual effects, in a factorial arrangement (A×B), when factor A corresponded to the provision of SO, and factor B to the provision of CG. Steers feed SO and CG showed similar DM intake, DM, organic matter and neutral-detergent fibre digestibility to that of steers fed diets without oil and without glycerine (P>0·05). Both diets with CG additions reduced the acetate:propionate ratio and increased the proportion of iso-butyrate, butyrate, iso-valerate and valerate (P<0·05). Steers fed diets containing SO had less total N excretion (P<0·001) and showed greater retained N expressed as % N intake (P=0·022). SO and CG diet generated a greater ruminal abundance of Prevotella, Succinivibrio, Ruminococcus, Syntrophococcus and Succiniclasticum. Archaea abundance (P=0·002) and total ciliate protozoa were less in steers fed diets containing SO (P=0·011). CG associated with lipids could be an energy source, which is a useful strategy for the partial replacement of maize in cattle diets, could result in reduced total N excretion and ruminal methanogens without affecting intake and digestibility.

Camelina Seed Supplementation at Two Dietary Fat Levels Change Ruminal Bacterial Community Composition in a Dual-Flow Continuous Culture System

This experiment aimed to determine the effects of camelina seed (CS) supplementation at different dietary fat levels on ruminal bacterial community composition and how it relates to changes in ruminal fermentation in a dual-flow continuous culture system. Diets were randomly assigned to 8 fermenters (1,200–1,250 mL) in a 2 × 2 factorial arrangement of treatments in a replicated 4 × 4 Latin square with four 10-day experimental periods that consisted of 7 days for diet adaptation and 3 days for sample collection. Treatments were: (1) no CS at 5% ether extract (EE, NCS5); (2) no CS at 8% EE (NCS8); (3) 7.7% CS at 5% EE (CS5); and (4) 17.7% CS at 8% EE (CS8). Megalac was used as a control to adjust EE levels. Diets contained 55% orchardgrass hay and 45% concentrate, and fermenters were equally fed a total of 72 g/day (DM basis) twice daily. The bacterial community was determined by sequencing the V4 region of the 16S rRNA gene using the Illumina MiSeq platform. Sequencing data were analyzed using mothur and statistical analyses were performed in R and SAS. The most abundant phyla across treatments were the Bacteroidetes and Firmicutes, accounting for 49 and 39% of the total sequences, respectively. The bacterial community composition in both liquid and solid fractions of the effluent digesta changed with CS supplementation but not by dietary EE. Including CS in the diets decreased the relative abundances of Ruminococcus spp., Fibrobacter spp., and Butyrivibrio spp. The most abundant genus across treatments, Prevotella, was reduced by high dietary EE levels, while Megasphaera and Succinivibrio were increased by CS supplementation in the liquid fraction. Correlatively, the concentration of acetate was decreased while propionate increased; C18:0 was decreased and polyunsaturated fatty acids, especially C18:2 n-6 and C18:3 n-3, were increased by CS supplementation. Based on the correlation analysis between genera and fermentation end products, this study revealed that CS supplementation could be energetically beneficial to dairy cows by increasing propionate-producing bacteria and suppressing ruminal bacteria associated with biohydrogenation. However, attention should be given to avoid the effects of CS supplementation on suppressing cellulolytic bacteria.

Effects of carbohydrate and nitrogen supplementation on fermentation of cheatgrass () in a dual-flow continuous culture system

Cheatgrass (CG; ), an introduced winter annual grass, is an aggressive invader of the sagebrush community in the Western United States. Because of its greater flammability, mature CG constitutes a fire hazard leading to repeated wildfires. One fuel-reduction strategy is livestock grazing. The objective of this study was to evaluate the effects of urea, molasses, or a combination of urea and molasses supplementation of a CG-based diet on digestibility, microbial fermentation, bacterial protein synthesis, and nutrient flow using a dual-flow continuous culture system. Eight fermenters were used in a replicate 4 × 4 Latin square design with four 10-d experimental periods. Experimental treatments (DM basis) were 1) forage only (CON), 2) CG plus urea alone (URE; 1.36% urea), 3) CG plus molasses alone (MOL; 15.9% molasses), and 4) CG plus urea and molasses combined (URE+MOL; 1.28% urea plus 19.3% molasses). Each fermenter was fed 72 g/d of DM, and data were analyzed using the GLIMMIX procedure of SAS (SAS Inst. Inc., Cary, NC). The true digestibilities of NDF and ADF were not affected by diets ( > 0.05). Molasses-containing diets had greater true digestibility of OM ( = 0.02). However, true digestibility of CP was increased when molasses was fed alone ( < 0.01). Molasses-containing diets had lower pH ( < 0.01) and greater VFA concentrations ( < 0.01) compared to those of the other diets. The URE+MOL diet resulted in a greater VFA concentration ( < 0.01). Propionate concentration increased ( < 0.01), whereas acetate concentration decreased ( < 0.01) when molasses alone or in combination with urea was added to the diets. Supplying molasses alone resulted in greater ( = 0.03) total branched-chain VFA compared to the other diets. The concentration of NH-N and total N flow increased ( < 0.01) in response to urea supplementation and was greater ( < 0.01) when urea alone was supplemented in the diet. On the other hand, molasses-supplemented diets yielded more non-ammonia N ( < 0.01) and bacterial N ( = 0.04). Supplementation had no effect ( = 0.83) on bacterial efficiency. Results from this study indicate that the addition of urea and molasses in a CG-based diet could improve nutrient supply to animals, notably VFA supply and microbial N supply; however, in the levels tested in this study, it did not improve CG utilization as assessed by NDF digestion.

Effects of replacing soybean meal with canola meal differing in rumen-undegradable protein content on ruminal fermentation and gas production kinetics using 2 in vitro systems

Previous research indicated that there were significant differences in rumen-undegradable protein (RUP) among canola meals (CM), which could influence the nutritional value of CM. The objectives of this study were to (1) evaluate the effects of feeding CM with different RUP contents on ruminal fermentation, nutrient digestion, and microbial growth using a dual-flow continuous culture system (experiment 1) and (2) evaluate ruminal gas production kinetics, in vitro organic matter (OM) digestibility, and methane (CH4) production of soybean meal (SBM) and CM with low or high RUP in the diet or as a sole ingredient using a gas production system (experiments 2 and 3). In experiment 1, diets were randomly assigned to 6 fermentors in a replicated 3 × 3 Latin square. The only ingredient that differed among diets was the protein supplement. The treatments were (1) solvent-extracted SBM, (2) low-RUP solvent-extracted CM (38% RUP as a percentage of crude protein), and (3) high-RUP solvent-extracted CM (50% RUP). Diets were prepared as 3 concentrate mixtures that were combined with 25% orchardgrass hay and 15% wheat straw (dry matter basis). Experiments 2 and 3 had the same design with 24 bottles incubated 3 times for 48 h each. During the 48-h incubation, the cumulative pressure was recorded to determine gas production kinetics, in vitro OM digestibility, and CH4 production. In experiment 1, N flow (g/d), efficiency of N use, efficiency of bacterial N synthesis, total volatile fatty acids (mM), and molar proportion of acetate, propionate, and isobutyrate were not affected by treatments. There were tendencies for a decrease in ruminal NH3-N and an increase in molar proportion of butyrate for the SBM diet compared with both CM diets. The molar proportion of valerate was greater in both CM diets, whereas the molar proportion of isovalerate and total branched-chain volatile fatty acids was lower for the CM diets compared with the SBM diet. In experiments 2 and 3, the SBM diet had a greater gas pool size than both CM diets. The SBM diet increased in vitro OM digestibility; however, it also tended to increase CH4 production (mM and g/kg of DM) compared with both CM diets. Based on the results of this study, CM with RUP varying from 38 to 50% of crude protein does not affect ruminal fermentation, nutrient digestion, and microbial growth when CM is included at up to 34% of the diet.

Effects of flaxseed and chia seed on ruminal fermentation, nutrient digestibility, and long-chain fatty acid flow in a dual-flow continuous culture system

Flaxseed (FS) and chia seed (CS) are oilseeds rich in omega-3 fatty acids, which may change meat and milk composition when added to ruminants' diets and may have health benefits for humans. Literature on the effects of CS supplementation on ruminal metabolism is nonexistent. A dual-flow continuous culture fermenter system consisting of 6 fermenters was used to assess the effect of FS and CS supplementation in an alfalfa hay-based diet on ruminal fermentation, nutrient digestibility, microbial protein synthesis, and long-chain fatty acid flow. Diets were randomly assigned to fermenters in a replicated 3 × 3 Latin square design, with 3 consecutive periods of 10 d each, consisting of 7 d for diet adaptation and 3 d for sample collection. Each fermenter was fed a total of 72 g of DM/d divided in 6 equal portions. Treatments were 1) alfalfa hay + calcium soaps of palm oil fatty acid (MEG; 69.3 g DM/d of alfalfa hay plus 2.7 g DM/d of calcium soaps of palm oil fatty acid), 2) alfalfa hay + FS (FLAX; 68.4 g DM/d of alfalfa hay plus 3.6 g DM/d of ground FS), and 3) alfalfa hay + CS (CHIA; 68.04 g DM/d of alfalfa hay plus 3.96 g DM/d of ground CS). Dietary treatments had similar amounts of total fat, and fat supplements were ground to 2-mm diameter. Effluents from the last 3 d of incubation were composited for analyses. Data were analyzed using the MIXED procedure of SAS. Ruminal apparent and true nutrient digestibility of all nutrients did not differ ( > 0.05) among treatments. Compared with MEG, FLAX and CHIA increased the flows of C18:3 -3, C20:4 -6, and total PUFA ( < 0.01). Both CHIA and FLAX treatments had greater ruminal concentrations of C18:0, indicating that both CS and FS fatty acids were extensively biohydrogenated in the rumen. The NH-N concentration, microbial N flow, and efficiency of microbial protein synthesis were not affected ( > 0.05) by treatments. Lastly, there were no differences ( > 0.05) among diets for total VFA concentration and molar proportions of individual VFA. Results from this study indicate that FS and CS supplementation did not impair ruminal fermentation, digestibility, microbial efficiency, and ruminal N metabolism. Overall, CS appears to be as effective as FS as a fat source when added to ruminants' diets using a dual-flow continuous culture system.

Effects of Static or Oscillating Dietary Crude Protein Levels on Fermentation Dynamics of Beef Cattle Diets Using a Dual-Flow Continuous Culture System

The objective of this study was to evaluate the effects of increasing dietary crude protein (CP) levels and also comparing the effects of static versus oscillating dietary CP on ruminal nutrient digestibility, ruminal fermentation, nitrogen (N) metabolism, and microbial efficiency in beef cattle diets using a dual-flow continuous culture system. Eight fermenters (1,223 ± 21 mL) were used in a replicated 4 x 4 Latin square design with periods lasting 12 d each (8 d for adaptation and 4 d for sampling). Dietary treatments were: 1) 10% CP, 2) 12% CP, 3) 14% CP, and 4) 10 and 14% CP diets oscillating at 48-h intervals. Experimental diets consisted of 50% orchard hay and 50% concentrate. Fermenters were fed 72 g/d and solid and liquid dilution rates were adjusted to 5.5 and 11%/h, respectively. Data were analyzed using the MIXED procedure in SAS with α = 0.05. Apparent and true ruminal digestibilities of dry matter and organic matter were not affected (P > 0.05) by increasing dietary CP, nor by oscillating dietary CP. Total volatile fatty acids concentration and molar proportions of acetate, propionate, butyrate, valerate, iso-butyrate and iso-valerate were not affected (P > 0.05) by increasing or oscillating dietary CP. Ruminal NH₃-N concentration increased linearly (P < 0.01) in response to increasing dietary CP. Total N, non-ammonia N, and rumen undegraded protein flows did not differ among treatments or between oscillating dietary CP and static 12% CP. Microbial N and NH₃-N flows and microbial efficiency did not differ when comparing oscillating versus static CP (P > 0.05). However, there was a quadratic effect (P < 0.05) for these variables when dietary CP was increased. These results indicate that either ruminal microorganisms do not respond to oscillating CP levels or are capable of coping with 48-h periods of undernourishment.

Partial Replacement of Ground Corn with Glycerol in Beef Cattle Diets: Intake, Digestibility, Performance, and Carcass Characteristics

The objective of this study was to evaluate the effects of replacing dry ground corn with crude glycerol on intake, apparent digestibility, performance, and carcass characteristics of finishing beef bulls. A completely randomized block design experiment with 25 d for adaptation and 100 d for data collection was conducted, in which 3,640 Nellore bulls (367 ± 36.8 kg; 18 ± 3 mo) were blocked by body weight and assigned to 20 pens. Bulls were randomly assigned to one of four treatments: 0, 5, 10, and 15% (dry matter basis) of crude glycerol in the diet. Initially, 20 bulls were slaughtered to serve as a reference to estimate initial empty body weight, which allowed for carcass gain calculation. Bulls were weighed at the beginning, at two-thirds, and at the end of the experiment for performance calculations. Carcass measurements were obtained by ultrasound. Fecal output was estimated using indigestible neutral detergent fiber as an internal marker. Data were analyzed using the mixed procedures in SAS 9.2 (SAS Institute Inc., Cary, NC). Intake of dry matter, organic matter, and neutral detergent fiber decreased linearly (P < 0.05) with crude glycerol inclusion. However, crude glycerol levels did not affect (P > 0.05) intakes of crude protein, non-fiber carbohydrates, and total digestible nutrients. Digestibility of dry matter, organic matter, neutral detergent fiber, and total digestible nutrients increased quadratically (P < 0.05) with the inclusion of crude glycerol in the diet. Crude glycerol inclusion did not change the intake of digestible dry matter, average daily gain, final body weight, carcass gain, carcass dressing, gain-to-feed ratio, Longissimus thoracis muscle area, and back and rump fat thicknesses (P > 0.05). These results suggest that crude glycerol may be included in finishing beef diets at levels up to 15% without impairing performance and carcass characteristics.