PSVIII-28 Dietary impacts on rumen, vaginal, and uterine environments in beef heifers

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 322-322
Author(s):  
Autumn Pickett ◽  
Reinaldo F Cooke ◽  
Alice Brandão ◽  
Eduardo Colombo ◽  
Shea Mackey ◽  
...  
Keyword(s):  
Measurement Data ◽  
Latin Square ◽  
Experimental Unit ◽  
Beef Heifers ◽  
Ruminal Ph ◽  
Rumen Ph ◽  
Vaginal Ph ◽  
Grass Hay ◽  
Uterine Fluid ◽  
Dietary Treatments

Abstract This experiment examined the effects of diet composition on rumen, vaginal, and uterine environments in beef heifers. Fifteen rumen-cannulated, pubertal Angus-influenced heifers were used in a replicated 3 x 3 Latin square design (28-d periods and 21-d washout intervals). Dietary treatments included (as-fed) diets based on 100% grass hay (HF), 61% grass hay + 39% corn-based concentrate (INT), or 25% grass hay + 75% corn-based concentrate (HG). Treatments were offered individually to heifers once daily at 2% of their body weight. Heifers also received 280 g/d of a mineral mix containing melengestrol acetate. Rumen, vaginal, and uterine fluid samples were collected on d 0 and 28 of each period for pH measurement. Data were analyzed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC) using results from d 0 as independent covariates, and heifer as the experimental unit. Rumen pH on d 0 did not differ (P = 0.97) among treatments (7.197, 7.194, and 7.188 for HF, INT, and HG, respectively; SEM = 0.038). Ruminal pH on d 28 was greater (P ≤ 0.01) in HF compared with INT and HG (6.805, 6.628, and 6.380, respectively; SEM = 0.049), and greater (P < 0.01) in INT compared with HG. Vaginal and uterine pH on d 0 did not differ (P ≥ 0.24) among HF, INT, and HG (6.914, 6.965, 6.780 of vaginal pH, respectively, SEM = 0.082; 6.644, 6.760, 6,592 of uterine pH, respectively, SEM = 0.079). Uterine and vaginal pH on d 28 also did not differ (P ≥ 0.64) among HF, INT, and HG heifers (6.926, 6.937, 6.918 of vaginal pH, respectively, SEM = 0.051; 6.567, 6.507, and 6.457 of uterine pH, respectively, SEM = 0.084). Therefore, dietary composition impacted rumen pH of beef heifers as expected, but without consequences to their vaginal and uterine pH.

scholarly journals 172 Enteric methane emissions from pregnant beef heifers as affected by multiple mitigation strategies

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 131-131
Author(s):  
Rhea E Teranishi ◽  
E J McGeough ◽  
Karin Wittenberg ◽  
Gary Crow ◽  
Kim Ominski
Keyword(s):  
Low Cost ◽  
Average Daily Gain ◽  
Latin Square ◽  
Dietary Treatment ◽  
Mitigation Strategies ◽  
Beef Heifers ◽  
Ch4 Emissions ◽  
Enteric Methane ◽  
Grass Hay ◽  
Dietary Treatments

Abstract This study was conducted to determine if enteric methane (CH4) emissions from pregnant beef heifers could be reduced by using multiple dietary mitigation strategies. The trial was designed as a 4 x 4 Latin square consisting of a 21-d adaptation phase followed by a 21-d data collection phase. Forty Aberdeen Angus cross pregnant beef heifers were randomly assigned to one of the four dietary treatments (n = 10): i) low protein grass hay (L; 6.1% CP; 1.9% fat); ii) adequate protein grass hay (AD; 10.8% CP; 1.9% fat); iii) AD supplemented with sunflower screenings (ADSS; 9.8% CP; 5.6% fat); and iv) above adequate protein legume grass mix hay (AAD; 12.8% CP; 1.7% fat). Total dry matter intake (DMI) was 32%, 27% and 39% greater (P < 0.0001) for AD, ADSS and AAD respectively, relative to the L diet (6.5 kg d-1). Average daily gain (ADG; kg d-1) was influenced by dietary treatment (P < 0.0001), as heifers offered L, AD, ADSS and AAD diets gained 0 ± 0.2, 0.6 ± 0.2, 0.5 ± 0.2 and 0.7 ± 0.2 kg d-1, respectively. Enteric CH4 emissions (L d-1), were influenced by dietary treatment (P < 0.0001) with 184 ± 18.9, 214 ± 19.0, 204 ± 19.1 and 232 ± 19.1 L d-1 for heifers offered L, AD, ADSS and AAD diets, respectively. Further, heifers offered AD, ADSS and AAD diets emitted 19%, 22% and 14% less (P=0.03) enteric CH4 (% GEI) relative to diet L, respectively. This study demonstrates that supplementation to meet nutrient requirements for protein or increasing the fat content of forage-based diets using low-cost by-products such as sunflower screenings can decrease enteric CH4 emissions without adversely impacting total DMI and ADG.

Effect of leucaena supplementation level, and provision of urea, on utilisation by sheep of Rhodes grass hay

2001 ◽  
Vol 41 (2) ◽  
pp. 155 ◽  
Author(s):  
I. W. Karda ◽  
G. McL. Dryden
Keyword(s):  
Organic Matter ◽  
Rumen Fluid ◽  
Latin Square ◽  
Rhodes Grass ◽  
Microbial Nitrogen ◽  
Grass Hay ◽  
Digestible Organic Matter ◽  
Ruminal Degradation ◽  
Chloris Gayana ◽  
Dietary Treatments

Tarramba leucaena (Leucaena leucocephala cv. Tarramba) foliage had per kilogram dry matter, 169 g protein and 29.8 g condensed tannins. Its value as a supplement, given either with or without urea, to sheep given a low-quality Callide Rhodes grass (Chloris gayana cv. Callide) hay was studied. Six rumen fistulated sheep (mean s.d. liveweight, 34 1.4 kg) were used to compare 6 dietary treatments in an incomplete latin square design. Rhodes grass hay was given ad libitum either alone, or with urea 7 g/day (U), or with leucaena 150 g/day (L150), or leucaena with urea (L150U), or leucaena 300 g/day (L300), or leucaena with urea (L300U). Digestible organic matter intake was increased significantly by leucaena supplementation although digestibility of the whole diet did not alter. Rumen fluid ammonia-N was not altered by leucaena supplementation, but was increased by urea. This suggests that Tarramba foliage protein has some resistance to ruminal degradation. Liquid and solids passage rates were not affected by the treatments. Microbial nitrogen supply to the intestine (g/day), and the efficiency of microbial nitrogen synthesis (g/kg organic matter apparently digested in the rumen), were increased by leucaena supplementation (P<0.01). Microbial protein synthesis was the only response in which 300 g/day air-dry Tarramba foliage gave improved results over 150 g/day.

scholarly journals Effect of stage of maturity at harvest for forage pea (Pisum sativum L.) on eating behavior, ruminal fermentation, and digestibility when fed as hay to yearling beef heifers

2019 ◽  
Vol 4 (1) ◽  
pp. 149-158 ◽  
Author(s):  
Alex A Pursley ◽  
Bill Biligetu ◽  
Tom Warkentin ◽  
Herbert A Lardner ◽  
Gregory B Penner
Keyword(s):  
Pisum Sativum ◽  
Eating Behavior ◽  
Latin Square ◽  
Neutral Detergent Fiber ◽  
Starch Digestibility ◽  
Ruminal Fermentation ◽  
Beef Heifers ◽  
Passage Rate ◽  
Ruminal Ph ◽  
Pisum Sativum L

Abstract The objective of this study was to evaluate the stage of maturity at harvest for pea hay (Pisum sativum L., c.v. CDC Horizon) on dry matter intake (DMI), eating behavior, ruminal fermentation, and digestibility when fed to beef heifers. Pea hay was cut at EARLY (defined to occur when flat pods were on one or more nodes), MID (when seeds filled the pods at one or more nodes and the leaves were changing from green to gold), and LATE (yellow dry seeds filled pods on most or all of the nodes and the pods and leaves had a yellow color) phases, and was cured in the field and baled. Six ruminally-cannulated Speckle Park heifers were used in a replicated 3 × 3 Latin square design with three 18-d periods including 12 d for adaptation, 2 d for measurement of ruminal pool sizes, and 4 d for the collection of eating behavior, ruminal pH, ruminal digesta, and feces. For all treatments, the respective pea hay was included at 40% of the dietary DM. Stage of maturity at harvest for pea hay did not affect total DMI, pea hay DMI, or the total short-chain fatty acid concentration in ruminal fluid with averages of 8.6 kg/d, 3.2 kg/d, and 96.55 mM, respectively. The duration of time spent ruminating decreased with advancing pea hay maturity when reported as min/d, min/kg DMI, and min/kg neutral detergent fiber (NDF) (P ≤ 0.01). Mean ruminal pH also decreased with advancing pea maturity (P &lt; 0.01). The ruminal DM and undigested NDF corrected for OM pools were not affected by stage of maturity (P ≥ 0.55) nor was the rate of digestion for NDF. However, NDF passage rate decreased by 0.21%/h with advancing pea hay maturity (P = 0.02). Apparent total tract digestibility of NDF (average = 16.30%, P = 0.41) was not affected, but starch digestibility decreased from 96.10% to 93.08% with advancing pea hay maturity (P = 0.07). Overall, stage of maturity at harvest for pea hay does not appear to affect DMI or NDF digestibililty but decreases chewing activity, apparent total tract starch digestibility, ruminal pH, and ruminal NDF passage rate.

scholarly journals 223 Effects of high protein DDGS in SFC or DRC-based diets on nutrient digestibility and ruminal fermentation characteristics

2019 ◽  
Vol 97 (Supplement_2) ◽  
pp. 128-128
Author(s):  
Lauren Ovinge ◽  
Mitch Norman ◽  
Kaylee Wheeler ◽  
Galen E Erickson
Keyword(s):  
Latin Square ◽  
Ammonia Concentration ◽  
Nutrient Digestibility ◽  
High Protein ◽  
Starch Digestibility ◽  
Experimental Unit ◽  
Ruminal Fermentation ◽  
Dried Distillers Grains ◽  
Ruminal Ph ◽  
Treatment Design

Abstract The effect of high protein dried distillers grains plus solubles in steam flaked corn (SFC) or dry rolled corn (DRC)-based diets on rumen fermentation and nutrient digestion was evaluated. Six ruminally and duodenally cannulated heifers were utilized in a 6×6 Latin Square experiment using a 2×3 factorial treatment design. One factor was SFC or DRC-based diets, and the other factor was a control with no DGS (CON), regularly produced DDGS (DDGS), or High Protein DDGS (HiPro) included at 30% in the diet (DM basis). Data were analyzed using the MIXED procedure of SAS, with individual steer within period as the experimental unit. There was an interaction of apparent total tract starch digestibility (P 0.01), as including either DDGS or HiPro reduced starch digestibility in DRC-based diets and tended (P = 0.06) to reduce starch digestibility in SFC-based diets. Digestibility of starch was greater (P < 0.01) for SFC versus DRC-based diets across distillers treatments. Dry matter and OM apparent total tract digestibility was lowest (P < 0.01) for HiPro and DDGS was intermediate. There was no difference in molar acetate proportions (P > 0.43) between treatments. Dry rolled corn tended (P = 0.08) to have greater propionate proportion than SFC (44 vs 38%; respectively). Ammonia concentration was greater (P < 0.01) for DRC-based diets, and greatest for CON (P < 0.01) over DDGS and HiPro treatments. Average ruminal pH was unaffected by treatment (P > 0.16). Digestible energy (Mcal/kg) tended (P = 0.08) to be greater for CON over HiPro and DDGS. The use of HiPro did not affect apparent total tract nutrient digestibility as compared to DDGS in SFC or DRC-based diets. The use of either distillers product did result in a reduction in energy intake and digestibility, without affecting ruminal metabolic parameters.

scholarly journals PSI-3 Effect of stage of maturity of forage pea cultivar (Pisium sativum L.) in hay on palatability, ruminal fermentation, and digestibility when fed to beef cattle

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 290-290
Author(s):  
Alex Pursley ◽  
Bill Biligetu ◽  
Tom Warkentin ◽  
Bart Lardner
Keyword(s):  
Beef Cattle ◽  
Eating Behavior ◽  
Latin Square ◽  
Starch Digestibility ◽  
Ruminal Fermentation ◽  
Beef Heifers ◽  
Passage Rate ◽  
Ruminal Ph ◽  
Yellow Color ◽  
Late Stages

Abstract The objective of this experiment was to evaluate stage of maturity at harvest for pea hay on DMI, eating behavior, ruminal fermentation, and digestibility when fed to beef heifers. Pea hay was harvested at early, mid, and late stages of maturity. Early was defined as observing flat pods at one or more nodes. Mid stage was defined as seeds filling the pods at one or more nodes and leaves beginning to turn from green to gold. Late stage was defined as yellow, dry seeds filling pods on most or all of the nodes, with a yellow color to the leaves and pods. Six ruminally-cannulated Speckle Park heifers were used in a replicated 3 × 3 Latin square design with 3 18-d periods with pea hay included at 40% of the dietary DM. Stage of maturity did not affect DMI or ruminal total SCFA concentration with averages of 3.2 kg/d and 96.55 mM, respectively. Time spent ruminating decreased with advancing maturity when reported as min/d, min/kg DMI, and min/kg NDF (P ≤ 0.01). Mean ruminal pH also decreased with advancing pea maturity (P &lt; 0.01). The ruminal DM and uNDFOM pools were not affected by stage maturity (P ≥ 0.55). While the rate of digestion for NDF was not affected, NDF passage rate decreased by 0.21 %/h with advancing maturity (P = 0.02). Apparent total tract digestibility of NDF (average = 16.30%, P = 0.41) was not affected but starch digestibility tended to decrease from 96.10 to 93.08% with advancing maturity (P = 0.07). Overall, stage of maturity at harvest for pea hay does not appear to impact DMI, fermentation, or digestibility.

scholarly journals Comparison of monensin sodium sources for finishing beef cattle

2021 ◽  
Author(s):  
Taylor C Husz ◽  
Wyatt N Smith ◽  
Caleb G Lockard ◽  
Megan N Homolka ◽  
Peter T Anderson ◽  
...  
Keyword(s):  
Fixed Effects ◽  
Methane Concentration ◽  
Rumen Fluid ◽  
Latin Square ◽  
Experimental Unit ◽  
Ruminal Fermentation ◽  
Ruminal Ph ◽  
Grain Processing ◽  
Significant Difference

Abstract The objective of this study was to evaluate the ruminal fermentation characteristics of ruminally fistulated beef steers consuming a steam-flaked corn (SFC) or dry-rolled corn (DRC) based diet containing either Rumensin 90 (RUM; Elanco, Greenfield, IN), or Monovet 90 (MV; Huvepharma, Peachtree City, GA). Six ruminally fistulated steers (657.7 kg ± 72.6) housed individually were used in a 6 × 6 Latin square design with 2 × 3 factorial treatment arrangement. Each of the 6 periods were 15 d with 14 d for diet adaptation and 1 d of rumen fluid collections. Dietary treatments were DRC without monensin sodium (DRC-C), SFC without monensin sodium (SFC-C), DRC with Rumensin 90 (DRC-R), DRC with Monovet 90 (DRC-MV), SFC with Rumensin 90 (SFC-R), and SFC with Monovet 90 (SFC-MV). Rumen contents and fluid were collected through the fistula of each animal at 0, 3, 6, 12, and 24 h on d 15 of each period. Rumen fluid collected at 6 h post-feeding each period was used for in vitro analyses. Steer was the experimental unit and the model included fixed effects of grain processing, additive, and grain processing × additive. Total gas produced was composited from each in vitro bottle into a gas collection bag for the 48-h determination of methane concentration. No differences were detected for DMI (P = 0.81). Ruminal pH did not differ for the control or additive treatments (P = 0.33). However, ruminal pH was lower (P &lt; 0.01) with SFC compared to DRC. There was a significant difference in acetate to propionate ratio for grain type (P = 0.01) and a tendency for additive inclusion (P = 0.06). Additive inclusion reduced methane proportion of total gas compared to control treatments (P ≤ 0.01). Overall, monensin sodium reduced methane concentration though source had no effect on DMI or ruminal pH.

33 Comparison of Monensin Sodium Sources for Finishing Beef Cattle

2021 ◽  
Vol 99 (Supplement_1) ◽  
pp. 34-35
Author(s):  
Taylor C Husz ◽  
Wyatt Smith ◽  
Caleb Lockard ◽  
Megan Homolka ◽  
Pete Anderson ◽  
...  
Keyword(s):  
Fixed Effects ◽  
Methane Concentration ◽  
Rumen Fluid ◽  
Latin Square ◽  
Experimental Unit ◽  
Ruminal Ph ◽  
Grain Processing ◽  
Significant Difference ◽  
Fluid Collections

Abstract The objective of this study was to evaluate the digestive characteristics of ruminally cannulated beef steers consuming a steam-flaked corn (SFC) or dry-rolled corn (DRC) based diet containing either Rumensin 90 (R) or Monovet 90 (MV). Six ruminally fistulated steers (657.7 kg ± 72.6) housed individually were used in a 6 × 6 Latin square design with a factorial treatment arrangement. Each of the 6 periods were 15 d with 14 d for diet adaptation and 1 d of rumen fluid collections. Six 15-d periods consisted of 14 d diet adaptation prior to rumen fluid collections. Dietary treatments were DRC without monensin sodium (DRC-C), SFC without monensin sodium (SFC-C), DRC with Rumensin 90 (DRC-R), DRC with Monovet 90 (DRC-MV), SFC with Rumensin 90 (SFC-R), and SFC with Monovet 90 (SFC-MV). Rumen contents and fluid were collected through the fistula of each animal at 0, 3, 6, 12, and 24 h on d 15 of each period. Rumen fluid was collected 6 h postfeeding each period for in vitro analyses. Steer was the experimental unit and the model included fixed effects of grain processing, additive, and grain processing × additive. Total gas produced was composited from each in vitro bottle into a gas collection bag for the 48-h determination of methane concentration. No differences were detected for DMI (P = 0.81). Ruminal pH did not differ for the control or additive treatments (P = 0.33). However, ruminal pH was lower (P &lt; 0.01) with SFC relative to DRC There was a significant difference in acetate to propionate ratio for both additive (P = 0.04) and grain type (P ≤ 0.01). Additive inclusion reduced methane proportion of total gas relative to control treatments (P ≤ 0.01). Monensin sodium reduced methane concentration though source had no effect on DMI or ruminal pH.

251 Effects of Roughage Source on Rumination Time and Ruminal Ph in Steers Fed a Steam-flaked Corn Finishing Diet

2021 ◽  
Vol 99 (Supplement_1) ◽  
pp. 127-127
Author(s):  
Wyatt Smith ◽  
Catherine Lockard ◽  
Caleb Lockard ◽  
Megan Homolka ◽  
Kendall Karr ◽  
...  
Keyword(s):  
Latin Square ◽  
Neutral Detergent Fiber ◽  
Beef Steers ◽  
Finishing Diets ◽  
Ruminal Ph ◽  
Penn State ◽  
Dietary Treatments ◽  
Particle Separator ◽  
Finishing Beef Cattle ◽  
Different Sources

Abstract Research is limited on how physically effective fiber from various roughage sources aids in rumination time and ruminal pH of finishing beef cattle. This experiment’s objective was to evaluate rumination time and ruminal pH of beef steers consuming finishing diets with varying roughage sources (corn stalks, cotton burrs, or wheat silage). We hypothesized that roughage type would not impact rumination time and ruminal pH if different sources provide similar dietary neutral detergent fiber (NDF). Ruminally cannulated steers (n = 6; average BW = 644.56 + 13.15 kg) were used in a 3 × 3 replicated Latin square with 3 dietary treatments and 3, 21-d periods (20-d diet adaptation, 1-d sampling). Steers consumed a steam-flaked corn-based finishing diet containing corn stalks (CS), cotton burrs (CB), or wheat silage (WS) included at 7% (DM basis) of the diet. Dietary NDF was similar across treatments. Steers were fitted with a sensory collar to record daily rumination (Allflex Livestock Intelligence). Ruminal pH was measured using a handheld pH probe on d-21 at 0, 3, 6, 12, 24 hr postprandial. The NDF and dry matter intake (DMI) were greatest for steers consuming the WS diet (P &lt; 0.01) while CS and CB diets did not differ (P = 0.81). While dietary NDF and estimated physically effective NDF (peNDF) were similar among roughage sources, CB had the lowest actual peNDF, consistent with lower rumination time (P &lt; 0.01) and lower ruminal pH (P = 0.29). This experiment’s results indicate that roughage source impacted rumination time despite feeding steers a steam-flaked corn-based finishing diet with similar roughage and NDF levels. Using rumination time (min/d) to determine peNDF was a better indicator of rumen function parameters than particle size measured via the Penn State Particle Separator equation.

PSX-A-12 Late-Breaking: Effects of Renergy™ on ruminal fermentation in steers fed a high-grain diet

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 375-375
Author(s):  
Jeff S Heldt ◽  
Harrison Hallmark ◽  
Huey Yi Loh ◽  
Sara Crane ◽  
Briana V Tangredi ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Rumen Fluid ◽  
Lactate Production ◽  
Experimental Unit ◽  
Adaptation Period ◽  
Ruminal Fermentation ◽  
Acetate Production ◽  
Ruminal Ph ◽  
Post Feeding ◽  
Dietary Treatments

Abstract Renergy™ is a proprietary blend of organic acids with a proposed mode of action of increasing ruminal propionate production. Little is known about the efficacy of Renergy™ supplementation in modifying ruminal fermentation in beef cattle consuming high-grain diets. Therefore, eight Angus steers (BW 531.7 ± 20.4 kg) fitted with ruminal cannulae were used to determine the effects of Renergy™ on ruminal fermentation characteristics. Steers were fed a high concentrate diet (DM basis: 13.6% CP, 1.38 Mcal/kg NEg, and 2.02 Mcal/kg NEm) with no monensin sodium or tylosin phosphate added to the diet for 30 d prior to the initiation of the experiment. Treatments consisted of control (CON; no supplemental Renergy™) and Renergy (REN) fed at 27.6 g.animal-1.d-1 (n = 4 steers/treatment; experimental unit = animal). Following the 30 d diet adaptation period, dietary treatments were initiated for 28-d. On day 28, rumen fluid was collected at 3 h post feeding and analyzed for VFA, pH, and NH3. Ruminal pH (P = 0.62) and NH3 (P = 0.56) were unaffected by treatment. However, total VFA (P = 0.05) and propionate (P = 0.03) production were increased by Renergy, 13.3% and 25.7% respectively. There was a tendency (P = 0.14) for acetate production to be increased 10.9% in steers supplemented with Renergy™. Butyrate was unaffected (P = 0.51) by treatment. However, isobutyrate production was lower (P &lt; 0.01) in steers receiving Renergy™. Feeding Renergy™ also resulted in 25% less (P = 0.07) L-lactate production. Under conditions of this experiment, results indicate that supplementing Renergy™ for 28d to beef cattle consuming high concentrate diets impacts ruminal fermentation 3 h post feeding.

scholarly journals 413 Effect of chitosan inclusion and dietary crude protein level on rumen fermentation in beef heifers fed a total mixed ration

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 166-167
Author(s):  
Stuart Kirwan ◽  
Tommy Boland ◽  
Eleonora Serra ◽  
Gaurav Rajauria ◽  
Karina Pierce
Keyword(s):  
Crude Protein ◽  
Volatile Fatty Acids ◽  
Rumen Fluid ◽  
Rumen Fermentation ◽  
Ruminal Fermentation ◽  
Beef Heifers ◽  
Total Mixed Ration ◽  
Ruminal Ph ◽  
Dietary Crude Protein ◽  
Dietary Treatments

Abstract Chitosan (N-acetyl-D-glucosamine polymer) is a natural biopolymer, which is the second most abundant organic compound on earth, found in lower plants and some arthropods and crustaceans. Studies with ruminants have shown that supplementing with chitosan can alter ruminal fermentation, including higher propionate concentration and lower acetate to propionate ratio, improving the energy efficiency within the rumen though data on nitrogen metabolism is lacking. Therefore, the objective of this study was to evaluate the effects of chitosan with different dietary crude protein (CP) inclusion on rumen fermentation in beef heifers. Eight ruminally cannulated Belgian Blue x Holstein Friesian heifers (752 ± 52Kg BW) were allocated one of four dietary treatments in a 2 x 2 factorial Latin Square design (n = 8). Diets were offered as total mixed ration (TMR) consisting of grass silage plus concentrate. Diets were offered once daily ad libitum. Dietary treatments were as follows: high CP (16%) +/- chitosan (10g kg-1 DMI) supplementation (HP+) or (HP-) and low CP (12%) +/- chitosan supplementation (LP+) or (LP-). Experimental periods were 25d in duration (14 d dietary adaptation and 10 d sampling). Rumen fluid was collected via cannula every 2 h post feeding for analysis of ruminal pH, ammonia (NH3) and volatile fatty acids (VFA) over a 48-hour period. Data was analysed using Proc Mixed procedure in SAS. Significant differences were considered when P &lt; 0.05. Dietary treatment had no effect on ruminal pH (P &gt; 0.05). Chitosan supplementation had no effect on ruminal NH3 and VFA concentrations (P &gt; 0.05), whereas, animals offered 16% CP had higher concentrations of ruminal NH3 (P &lt; 0.001). In conclusion, supplementing a TMR diet fed to beef heifers with chitosan had no effect on rumen fermentation. However, reducing dietary CP concentration fed to beef animals resulted in lower rumen NH3 concentrations.

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