Evaluation of different inclusion levels of dry live yeast impacts on various rumen parameters and in situ digestibilities of dry matter and neutral detergent fiber in growing and finishing beef cattle

Abstract This study evaluated the effects of supplementing dry live yeast (LY; Saccharomyces cerevisiae) on in vitro gas production (IVGP) fermentation dynamics, pH, and CH4 concentration at 48 h, and in situ rumen parameters and digestibility of DM (DMD) and NDF (NDFD) of growing cattle during 3 feeding phases: grower (GRW) for 17 d (38% steamed-flaked corn; SFC), transition (TRANS) for 15 d (55.5% SFC: 1.2 Mcal/kg NEg), and finisher (FIN) for 13 d (73% SFC: 1.23 Mcal/kg NEg). Twenty British-crossbred, ruminally cannulated steers (183 kg ± 44 kg) 6 mo of age were blocked by weight into 5 pens containing Calan gate feeders and received a control (CON) diet (17.2% CP, 35.8% NDF, 86.7% DM) without LY on days −12 to 0. After that, animals were randomly assigned to treatments (TRT), 5 animals per TRT: CON or LY at inclusion rates of 5 g/d (LY1), 10 g/d (LY2), or 15 g/d (LY3) top dressed every morning at 0800 for 45 d. The DMD and NDFD were assessed during 7 separate collection days using in situ nylon bags containing 5 g of GRW, TRANS, or FIN diets, incubated at 1200 for 48 h. Protozoa counts (PC) were determined during 5 collection periods. Data were analyzed as a repeated measure within a randomized complete block design, assuming a random effect of the pen. For GRW, TRT altered the total gas production of the nonfiber carbohydrate (NFC; P = 0.045) and the fractional rate of degradation (kd) of the fiber carbohydrate (FC) pool (P = 0.001) in a cubic pattern (P ≤ 0.05): LY2 had the most gas production and fastest kd. TRT also influenced DMD (P = 0.035) and NDFD (P = 0.012) with LY2 providing the greatest digestibility. For TRANS, TRT tended to affect the NFC kd (P = 0.078) and influenced pH (P = 0.04) and DMD (P < 0.001) in which LY2 yielded the fastest kd, highest pH, and greatest DMD. For FIN, there was an effect of TRT on total gas production (P < 0.001) and kd (P = 0.004) of the NFC pool, FC kd (P = 0.012), in vitro CH4 concentration (P < 0.001), PC (P < 0.001), DMD (P = 0.039), and NDFD (P = 0.008). LY1 had the highest PC and provided the greatest DMD and NDFD. LY2 had the fastest kd of both the NFC and FC pools and had the least CH4 concentration. LY3 had the greatest NFC gas production. No specific dose–response pattern was observed, but 10 g/d provided the most beneficial result for all diets. We concluded that supplementation with LY affected IVGP as well as ruminal parameters and digestibilities.

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Evaluation of the Nutrient Composition, In Vitro Fermentation Characteristics, and In Situ Degradability of Amaranthus caudatus, Amaranthus cruentus, and Amaranthus hypochondriacus in Cattle

Animals ◽

10.3390/ani11010018 ◽

2020 ◽

Vol 11 (1) ◽

pp. 18

Author(s):

Kim Margarette C. Nogoy ◽

Jia Yu ◽

Young Gyu Song ◽

Shida Li ◽

Jong-Wook Chung ◽

...

Keyword(s):

Crude Protein ◽

Dry Matter ◽

Gas Production ◽

Nutrient Composition ◽

Neutral Detergent Fiber ◽

Amaranthus Cruentus ◽

Amaranthus Caudatus ◽

Amaranthus Hypochondriacus

The amaranth plants showed high potential feed value as forage for ruminants. An in-depth study of this plant, particularly in cattle, will help extend its utilization as an alternative protein and fiber feed source in cattle feeding. In this study, the nutrient compositions of three different species of amaranth, Amaranthus caudatus L., Amaranthus cruentus L., and Amaranthus hypochondriacus L.—two varieties for each species, A.ca 74, A.ca 91, A.cu 62, A.cu 66, A. hy 30, and A. hy 48—were evaluated. The in vitro technique was used to evaluate the fermentation characteristics such as total gas production, total volatile fatty acids (VFA) concentration, pH, and ammonia concentration of the rumen fluid. Moreover, the effective degradabilities of dry matter (EDDM) and crude protein (EDCP) of the amaranth forages were determined through in situ bag technique. The amaranth forages: A. caudatus, A. cruentus, and A. hypochondriacus showed better nutritive value than the locally produced forages in Chungcheong province of Korea. The CP of the amaranth ranged from 11.95% to 14.19%, and the neutral detergent fiber (NDF) and acid detergent fiber (ADF) contents ranged from 45.53% to 70.88% and 34.17% to 49.83%, respectively. Among the amaranth varieties, A. hypochondriacus 48 showed the most excellent ruminant feed nutrient quality (CP, 14.19%; NDF, 45.53%; and ADF, 34.17%). The effective degradabilities of dry matter (EDDM; 33–56%) and crude protein EDCP (27–59%) of the amaranth were lower compared to other studies, which could be due to the maturity stage at which the forages were harvested. Nonetheless, A. hypochondriacus 48 showed the highest EDDM (56.73%) and EDCP (59.09%). The different amaranth species did not differ greatly in terms of total VFA concentration or molar proportions, total gas production, or ammonia-N concentration. The high nutrient composition, and highly effective degradability of dry matter and crude protein, coupled with the favorable fermentation characteristics, suggest that the amaranth forages showed good to excellent feed quality for cattle.

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409 Effects of essential oils on in vitro ruminal fermentation using a high-concentrate substrate

Journal of Animal Science ◽

10.1093/jas/skz258.339 ◽

2019 ◽

Vol 97 (Supplement_3) ◽

pp. 165-165

Author(s):

Nadira J Espinoza-Rock ◽

Andrea O Doblado ◽

Sebastian E Mejia-Turcios ◽

Evandro Dias ◽

Michael Sandes ◽

...

Keyword(s):

Essential Oils ◽

Fixed Effects ◽

Block Design ◽

Random Effect ◽

Gas Production ◽

Experimental Unit ◽

Ruminal Fermentation ◽

Cinnamic Aldehyde ◽

Garlic Oil

Abstract A randomized complete block design was used to determine the effects of 4 concentrations of 4 essential oils (EO) on in vitro ruminal fermentation variables. In vitro fermentation consisted of 0.7 g of high concentrate substrate (86.7% DM) and 50 mL of 2:1 buffer:ruminal fluid inoculum incubated for 24 h for each batch (n = 3; separate days) Treatments were arranged as a 4 × 5 factorial. Factors included 4 EO (eugenol, cinnamic aldehyde, anethole, and garlic oil) at 5 concentrations (0, 10, 75, 200, and 400 mg/L of inoculum). Data were analyzed using the MIXED procedure of SAS with the fixed effects of EO, concentration, and their interaction, and random effect of day (block). Batch was considered the experimental unit. There was an interaction (P < 0.001) for total gas production, where a cubic effect (P ≤ 0.041) was observed for eugenol, cinnamic aldehyde, and anethole, and a quadratic effect (P = 0.001) was observed for garlic oil. No interactions (P > 0.05) were observed for in vitro OM digestibility (IVOMD) or CH4 production. There was an effect of EO (P < 0.001) on IVOMD, where eugenol reduced (P ≤ 0.007) digestibility compared with anethole and garlic oil, which promoted the greatest (P ≤ 0.029) IVOMD. Methane production (mmol/g OM fermented) was affected by EO (P < 0.001), where it was decreased (P ≤ 0.001) by garlic oil compared with all other EO. There was an interaction (P < 0.001) for H2S production (µmol/g OM fermented), where it was linearly decreased (P = 0.003) and linearly increased (P < 0.001) as concentrations of eugenol and garlic oil increased, respectively. These EO had contradictory impacts on in vitro ruminal fermentation, thus combining them could potentially improve multiple aspects of in vitro and in vivo fermentation.

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312 Effects of Bismuth Subsalicylate and Different Sulfate Concentrations on in vitro Ruminal Fermentation Using a Warm-season Perennial Hay Substrate

Journal of Animal Science ◽

10.1093/jas/skab235.305 ◽

2021 ◽

Vol 99 (Supplement_3) ◽

pp. 166-166

Author(s):

Kenneth S Madrid ◽

Andrea M Osorio ◽

Francine M Ciriaco ◽

Kymberly D Coello ◽

Angel A Raudales ◽

...

Keyword(s):

Fixed Effects ◽

Block Design ◽

Random Effect ◽

Gas Production ◽

Experimental Unit ◽

Ruminal Fermentation ◽

In Vitro Fermentation ◽

Bismuth Subsalicylate ◽

H2s Production

Abstract A randomized complete block design was used to evaluate the effects of bismuth subsalicylate (BSS) on in vitro ruminal fermentation with differing concentrations of sulfate. In vitro fermentation consisted of 50 mL of a 4:1 buffer:ruminal fluid inoculum and 0.7 g (pre-dehydrated) of substrate [WW-B Dahl bluestem hay (Bothriochloa bladhii)] incubated for 48 h (39oC). Treatments were arranged as a 3 × 4 factorial with concentration of sulfate (0.2, 2.9, or 5.6 g sulfate/L buffer) and BSS (0.0, 0.165, 0.330, or 0.495% substrate DM) as the main factors. In vitro organic matter digestibility (IVOMD), and CH4, H2S, and total gas production (TGP) were measured. Data were analyzed using the MIXED procedure of SAS with the fixed effects of BSS, sulfate, and their interaction. Incubation day (block) was considered a random effect. The average of 2 bottles within day was considered experimental unit. A BSS × sulfate interaction was observed for TGP (P = 0.040) and H2S production (P < 0.001), where BSS had a larger negative impact on TGP and production of H2S with greater concentrations of sulfate. A linear effect (P < 0.001) of sulfate was observed for CH4 production per gram of incubated OM, where CH4 was decreased as sulfate concentration increased. A quadratic effect of sulfate was observed for IVOMD (P = 0.010) and pH (P = 0.009). Production of H2S linearly decreased (P = 0.001) as BSS concentration increased. The addition of BSS to in vitro incubations did not affect (P > 0.10) any other variables measured. Bismuth subsalicylate does not appear to have negative effects on in vitro fermentation parameters while decreasing H2S production; however, elevated concentrations of sulfate in the buffer appears to have negative impacts on fermentation. Further in vivo research is warranted to support BSS supplementation to cattle with high dietary sulfate.

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The potential of tropical grass as a feed in ruminant by using an in vitro gas production

MATEC Web of Conferences ◽

10.1051/matecconf/201819706005 ◽

2018 ◽

Vol 197 ◽

pp. 06005

Author(s):

Nevyani Asikin ◽

Anuraga Jayanegara ◽

Muhamad Ridla ◽

Anjas Asmara Samsudin

Keyword(s):

Animal Feed ◽

Block Design ◽

In Vitro Study ◽

Proximate Analysis ◽

Gas Production ◽

Neutral Detergent Fiber ◽

In Vitro Gas Production ◽

Significant Difference ◽

Tropical Grass

Pennisetum purpoides is one of the most widely cultivated tropical forages and it is often used as animal feed in Indonesia. However, grass feeding could not fulfill the need of nutrients if served as single feed because it contained of high crude fiber and low protein. In terms of nutritional adequacy, animal feed should contain complete nutritional value in order to achieve an optimum productivity. This experiment aimed to elucidate the potential of tropical grass as a feed in ruminant by using an in vitro gas production technicque. The grasses were determined for proximate analysis, Van Soest fiber fractions (neutral detergent fiber, acid detergent fiber and acid detergent lignin), and in vitro rumen fermentation parameters. This study was conducted from January until April 2018 at Nutrition Laboratory, Department of Animal Science, Faculty of Agriculture, University Putra Malaysia, Serdang Selangor Darul Ehsan, Malaysia. This study used a randomized block design with 3 replications. There were three treatments tested in this study, i.e. (1) Pennisetum purpoides (T1), (2) Setaria splendida (T2), (3) Setaria anceps (T3). Parameters measured in the in vitro study is total gas production. Data were tested using analysis of variance (ANOVA) and continued with Duncan test if there was a significant difference among treatments. The data showed that gas production is not significantly different (P>0,05).

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183 Effect of fermentation temperature on in vitro digestibility of a finishing diet

Journal of Animal Science ◽

10.1093/jas/skz053.140 ◽

2019 ◽

Vol 97 (Supplement_1) ◽

pp. 62-63

Author(s):

Miranda K Stotz ◽

Sebastian E Mejia-Turcios ◽

Andrea M Osorio ◽

Nadira Espinoza ◽

Philip M Urso ◽

...

Keyword(s):

Rumen Fluid ◽

Block Design ◽

Random Effect ◽

Gas Production ◽

In Vitro Digestibility ◽

Ph Change ◽

Fermentation Rate ◽

N Concentration ◽

Effect Of Treatment

Abstract Heat stress (HS) has been indicated to increase ruminal temperature, increase digestibility, and reduce ruminal pH of steers fed high concentrate diets. However, it is unclear if this effect is the result of greater fermentation rate, slower passage rate, or a combination. The effect of ruminal incubation temperature on substrate digestibility and rate of fermentation were evaluated. Four cannulated British-crossbreed steers (BW = 520 kg ± 30 kg) consuming an 87% (DM) concentrate diet were utilized as rumen fluid donors in a randomized complete block design with two incubation treatments (CON=39°C and HS=42°C). Within block, duplicate 125 mL serum bottles containing 200 mg of dietary substrate were inoculated with a 2:1 buffer:ruminal fluid mixture and incubated for 24 h to measure total gas production, fermentation rate, fermentation lag, pH, and ammonia-N concentration. In vitro organic matter digestibility (IVOMD) was measured separately in 100 mL centrifuge tubes. Data were analyzed using the MIXED procedure of SAS using the fixed effect of treatment and random effect of rumen fluid donor (block). There was no treatment effect on total gas production (P = 0.92) or fermentation rate (P = 0.11); however, HS began fermenting substrate sooner than CON (P < 0.005). There was a significant effect of treatment on IVOMD where HS was greater compared to CON (79.3 vs. 70.4%; P = 0.05). Final pH and relative pH change were not different (P ≥ 0.25) likely due to buffering capacity of the in vitro technique Ammonia-N concentration was greater for HS than CON (7.92 vs. 5.33 mM; P < 0.05) and may indicate a temperature effect on ruminal nitrogen availability.In conclusion, it does not appear that incubating at a greater temperature affected the fermentation rate but likely induced a change in fermentation kinetics, which may have contributed to the greater overall IVOMD

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Chemical composition and fatty acid profile of BRS Capiaçu ensiled at different regrowth ages

Semina Ciências Agrárias ◽

10.5433/1679-0359.2021v42n3supl1p1981 ◽

2021 ◽

pp. 1981-2004

Author(s):

Fernando César Ferraz Lopes ◽

◽

Mirton José Frota Morenz ◽

Francisco José da Silva Lédo ◽

Jailton da Costa Carneiro ◽

...

Keyword(s):

Fatty Acid ◽

Chemical Composition ◽

Block Design ◽

Random Effect ◽

Neutral Detergent Fiber ◽

Elephant Grass ◽

Randomized Block Design ◽

Quadratic Effects ◽

Chopped Grass

This study aimed to evaluate the chemical composition and fatty acid (FA) profile of chopped forage and silage of BRS Capiaçu elephant grass at four regrowth ages: 50, 70, 90 and 110 days. A randomized block design with five replications was used. The ensiling was carried out manually in experimental silos without wilting using no additives or bacterial inoculants. The results were analyzed using mixed models (P < 0.05). The model included treatment (regrowth age) as a fixed effect and block as a random effect. Linear and quadratic effects of the treatments were analyzed using orthogonal contrasts. There were linear increases in the dry matter (DM, g kg-1) and lignin (g kg-1 DM) contents and linear reductions in the in vitro DM digestibility (g kg-1) of chopped grass and silage as a function of regrowth age (P < 0.001). Quadratic effects (P ≤ 0.01) were observed for the chopped grass contents (g kg-1 DM) of crude protein (CP), ether extract (EE) and neutral detergent fiber (NDF) as a function of regrowth age. There were linear decreases (P < 0.0001) in the CP content (g kg-1 DM) and pH and linear increases (P < 0.001) in the EE and NDF contents (g kg-1 DM) in the silage as a function of regrowth age. There were linear decreases (P < 0.01) in the chopped grass contents and linear increases (P < 0.05) in the silage contents of total FAs, linoleic and α-linolenic acids (g kg-1 DM) asa function of regrowth age. BRS Capiaçu elephant grass must be harvested at up to 70 days of regrowth to obtain forage with good nutritional value and the highest levels of linoleic and α-linolenic acids (g kg-1 DM). To produce silages with adequate pH values and the highest levels of linoleic and α-linolenic acids (g kg-1 DM), BRS Capiaçu must be harvested between 90 and 110 days of regrowth.

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Rumen In Vitro Fermentation and In Situ Degradation Kinetics of Winter Forage Brassicas Crops

Animals ◽

10.3390/ani9110904 ◽

2019 ◽

Vol 9 (11) ◽

pp. 904 ◽

Cited By ~ 4

Author(s):

Daza ◽

Benavides ◽

Pulido ◽

Balocchi ◽

Bertrand ◽

...

Keyword(s):

Chemical Composition ◽

Degradation Kinetics ◽

Brassica Species ◽

Gas Production ◽

Neutral Detergent Fiber ◽

In Vitro Fermentation ◽

Fermentation Products ◽

In Situ Degradation

The aim of the present study was to evaluate the nutritional value, the rumen in vitro fermentation, and the in situ degradation of Brassica oleracea (L.) ssp. acephala (kales) and Brassica napus (L.) ssp. napobrassica (swedes) for winter use. Five varieties of each brassica were used in three field replicates and were randomized in a complete block nested design. All forage varieties were harvested at 210 days post-sowing to analyze the chemical composition, in vitro gas production, volatile fatty acid (VFA) production and in situ dry matter (DM) and crude protein (CP) degradability. Kales presented higher DM and neutral detergent fiber (NDF) content (p < 0.01), whereas swedes showed higher CP, metabolizable energy (ME), glucose, fructose, total sugars, NFC, and nonstructural carbohydrate (NSC) content (p < 0.01). The kale and swede varieties differed in their CP and sugar concentrations, whereas the kale varieties differed in their DM and raffinose content. The rates of gas production were higher for swedes than for kales (p < 0.01). No differences between the brassica species (p > 0.05) were observed in the total VFA production, whereas kales had a higher proportion of acetate and swedes had higher proportions of butyrate (p < 0.05). Only the swede varieties showed differences in VFA production (p < 0.05). The soluble fraction “a”, potential and effective in situ DM degradability were higher in swedes (p < 0.01), but kales presented greater DM and CP degradation rates. Differences were observed between brassica species in the chemical composition, degradation kinetics, and ruminal fermentation products, whereas differences among varieties within species were less frequent but need to be considered.

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In vitro Fermentation Profile and Methane Production of Kikuyu Grass Harvested at Different Sward Heights

Frontiers in Sustainable Food Systems ◽

10.3389/fsufs.2021.682653 ◽

2021 ◽

Vol 5 ◽

Author(s):

Alejandra Marín ◽

Jérôme Bindelle ◽

Ángel S. Zubieta ◽

Guillermo Correa ◽

Jacobo Arango ◽

...

Keyword(s):

Organic Matter ◽

Methane Production ◽

Block Design ◽

Gas Production ◽

Metabolizable Energy ◽

Neutral Detergent Fiber ◽

Sward Height ◽

Fermentation Profile ◽

Kikuyu Grass

Highly digestible forages are associated with an in vitro low-methane (CH4) rumen fermentation profile and thus the possibility of reducing CH4 emissions from forage-based systems. We aimed to assess the in vitro ruminal fermentation profile, including CH4 production, of the top stratum of Kikuyu grass (Cenchrus clandestinus - Hochst. ex Chiov) harvested at different sward heights (10, 15, 20, 25, and 30 cm). Herbage samples (incubating substrate) were analyzed for their chemical composition, in vitro organic matter digestibility (IVOMD), and morphological components. In vitro incubations were performed under a randomized complete block design with four independent runs of each treatment. Gas production (GP), in vitro dry matter digestibility (IVDMD), CH4 production, total volatile fatty acid (VFA) concentration, and their acetate, propionate, and butyrate proportions were measured following 24 and 48 h of incubation. Herbage samples had similar contents of organic matter, neutral detergent fiber, and crude protein for all treatments. However, a higher acid detergent fiber (ADF) content in taller sward heights than in smaller sward heights and a tendency for metabolizable energy (ME) and IVOMD to decrease as sward height increased were found. Similarly, the stem + sheath mass tended to increase with increasing sward height. Amongst the nutrients, ME (r = −0.65) and IVDMD (r = −0.64) were negatively correlated with sward height (p < 0.001) and ADF was positively correlated with sward height (r = 0.73, p < 0.001). Both the GP and IVDMD were negatively related to the sward height at both incubation times. Sward heights of Kikuyu grass below 30 cm display an in vitro profile of VFAs high in propionate and low in acetate, with a trend toward lower methane production of CH4 per unit of IVDMD. These findings are important to aid decision-making on the optimal sward height of Kikuyu grass and manage animal grazing with the opportunity to reduce CH4 production.

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407 Effects of calcium-ammonium nitrate on in vitro ruminal fermentation using a wheat forage based substrate

Journal of Animal Science ◽

10.1093/jas/skz258.340 ◽

2019 ◽

Vol 97 (Supplement_3) ◽

pp. 165-166

Author(s):

Andrea O Doblado ◽

Sebastian E Mejia-Turcios ◽

Nadira J Espinoza-Rock ◽

Evandro Dias ◽

Michael Sandes ◽

...

Keyword(s):

Ammonium Nitrate ◽

Methane Production ◽

Block Design ◽

Random Effect ◽

Gas Production ◽

Experimental Unit ◽

Ruminal Fermentation ◽

Calcium Ammonium Nitrate ◽

N Concentration

Abstract A randomized complete block design was used to evaluate in vitro ruminal total gas and methane production, N-NH3 concentration, and digestibility of wheat forage when incubated with calcium-ammonium nitrate (CAN). The in vitro fermentation consisted of 50 mL of a 4:1 buffer:ruminal fluid inoculum and 0.7 g of substrate [DM; wheat (Triticum aestivum; 100%) or wheat:corn (88:12)] incubated for 48 h. Batches were incubated on 4 separate days. Treatments included: 1) wheat (W); 2) wheat + corn (WC); 3) WC + 2% CAN in the substrate DM (WCN); and 4) WC + 0.67% UREA in the substrate DM (WCU). Treatments WCN and WCU were isonitrogenous. In vitro organic matter digestibility (IVOMD) was determined after incubation for 48 h with inoculum, followed by a 48 h incubation with HCl and pepsin solutions. Data were analyzed using the MIXED procedure of SAS with the fixed effect of treatment and random effect of day (block). Batch was considered the experimental unit. Total gas production was reduced by WCN compared with WCU (P = 0.049) and WC (P = 0.001). The addition of corn without NPN increased (P = 0.004) total gas production compared to wheat. An increased (P = 0.009) IVOMD was observed for WC compared to W, while no differences (P = 0.416) were observed between WCN and WCU. Ammonia-N concentration was not different (P = 0.463) between WCN and WCU; and the inclusion of NPN increased (P ≤ 0.026) NH3-N concentration compared to W. Methane production (mmol/g OM fermented) was lesser (P < 0.001) for WCN compared to WCU. Total VFA concentration and acetate:propionate were not affected by treatment (P > 0.05). Therefore, CAN can potentially be used as a NPN source with the additional benefit of in vitro methane mitigation without negatively affecting IVOMD or total VFA concentration.

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14 Effect of fermentation temperature on in vitro digestibility of a finishing diet

Journal of Animal Science ◽

10.1093/jas/skz053.026 ◽

2019 ◽

Vol 97 (Supplement_1) ◽

pp. 12-12

Author(s):

Miranda K Stotz ◽

Sebastian E Mejia-Turcios ◽

Andrea M Osorio ◽

Nadira Espinoza ◽

Philip M Urso ◽

...

Keyword(s):

Rumen Fluid ◽

Block Design ◽

Random Effect ◽

Gas Production ◽

In Vitro Digestibility ◽

Ph Change ◽

Fermentation Rate ◽

N Concentration ◽

Effect Of Treatment

Abstract Heat stress (HS) has been indicated to increase ruminal temperature, increase digestibility, and reduce ruminal pH of steers fed high concentrate diets. However, it is unclear if this effect is the result of greater fermentation rate, slower passage rate or a combination. The effect of ruminal incubation temperature on substrate digestibility and rate of fermentation were evaluated. Four cannulated British-crossbreed steers (BW = 520 kg ± 30 kg) consuming an 87% (DM) concentrate diet were utilized as rumen fluid donors in a randomized complete block design with two incubation treatments (CON=39°C and HS=42°C). Within block, duplicate 125 mL serum bottles containing 200 mg of dietary substrate were inoculated with a 2:1 buffer:ruminal fluid mixture and incubated for 24 h to measure total gas production, fermentation rate, fermentation lag, pH, and ammonia-N concentration. In vitro organic matter digestibility (IVOMD) was measured separately in 100 mL centrifuge tubes. Data were analyzed using the MIXED procedure of SAS using the fixed effect of treatment and random effect of rumen fluid donor (block). There was no treatment effect on total gas production (P = 0.92) or fermentation rate (P = 0.11); however, HS began fermenting substrate sooner than CON (P < 0.005). There was a significant effect of treatment on IVOMD where HS was greater compared to CON (79.3 vs. 70.4%; P = 0.05). Final pH and relative pH change were not different (P ≥ 0.25) likely due to buffering capacity of the in vitro technique Ammonia-N concentration was greater for HS than CON (7.92 vs. 5.33 mM; P < 0.05) and may indicate a temperature effect on ruminal nitrogen availability.In conclusion, it does not appear that incubating at a greater temperature affected the fermentation rate but likely induced a change in fermentation kinetics, which may have contributed to the greater overall IVOMD

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