Ruminal parameters and in-situ degradability of rations with wheat middling substitution for corn

This study aimed to evaluate the effect of substituting corn with wheat middling on the in-situ degradability of foods and ruminal parameters of cattle. The experiment was conducted at the Ruminant Studies Unit and the Laboratory of Food Analysis and Animal Nutrition of Londrina State University. Five rumen-fistulated cattle with an average weight of 521 ± 38.22 kg were housed in individual stalls. The experimental design used was a Latin square with five treatments (100% C, 75% C 25% WM, 50% C 50% WM, 25% C 75% WM, and 100% WM) and five periods of 25 days each. The pH and ammoniacal nitrogen (N-NH3) concentration in ruminal fluid was measured before feeding and 2, 4, 6, and 8 h after feeding in subdivided parcels. The in-situ degradability of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) were determined by incubating silage samples and measuring concentrates in the rumen of cattle. The levels of substitution of corn by wheat middling did not alter the pH and N-NH3 values but was influenced by the collection time. The N-NH3 presented quadratic behavior with a point of maximum rumen concentration (5.31 mgdL-1) reached 1.12 h after feeding. The pH presented quadratic behavior with a point of minimum (6.04) reached 4.32 h after feeding. The effective degradability (ED) of DM with 2, 5 and 8%h-1 of passage rate was influenced by the substitution of corn by wheat middling, with increasing linear behavior. The ED 2%h-1 varied from 46.19% to 50.24%, the ED 5%h-1 varied from 33.76% to 38.68%, and the ED 8%h-1 values ranged from 28.16% to 32.92% for the 100% C and 100% WM treatments. Higher values, for treatments with higher levels of substitution of corn by wheat middling, occurred owing to the lower fiber content and to the largest soluble fractions and degradation rate of DM in rations with wheat middling. The ED of CP and NDF with passage rates of 2, 5 and 8%h-1 presented quadratic behavior. The ED 2, 5 and 8%h-1 of CP presented maximums of 75.9%, 77.9%, and 86.2%, with averages of 52.02%, 45.93%, and 42.23%, respectively. The ED 2, 5 and 8%h-1 of NDF presented minimum points of 29.6%, 34.7%, and 35.2%, with averages of 41.60%, 33.43%, and 27.76%, respectively. Wheat middling can be used for total substitution of corn without damaging ruminal pH and N-NH3, in addition to improving the degradability of rations.

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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

Translational Animal Science ◽

10.1093/tas/txz167 ◽

2019 ◽

Vol 4 (1) ◽

pp. 149-158 ◽

Cited By ~ 1

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 < 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.

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Total and partial digestibility, rates of digestion obtained with rumen evacuation and microbial protein synthesis in bovines fed fresh or ensiled sugar cane and corn silage

Revista Brasileira de Zootecnia ◽

10.1590/s1516-35982011000500023 ◽

2011 ◽

Vol 40 (5) ◽

pp. 1104-1113 ◽

Cited By ~ 11

Author(s):

Gustavo Chamon de Castro Menezes ◽

Sebastião de Campos Valadares Filho ◽

Felipe Antunes Magalhães ◽

Rilene Ferreira Diniz Valadares ◽

Lays Débora Mariz ◽

...

Keyword(s):

Calcium Oxide ◽

Sugar Cane ◽

Dry Matter ◽

Latin Square ◽

Nutrient Digestibility ◽

Corn Silage ◽

Neutral Detergent Fiber ◽

Average Weight ◽

Passage Rate ◽

Intestinal Digestibility

It was evaluated intake, rumen and intestinal digestibility and passage and digestion rates in bovines fed diets constituted of corn silage, crushed sugar cane and given fresh, crushed sugar cane and given after 72 hours of storage, ensiled sugar cane with 1% of calcium oxide and with no treatment and a same concentrate fixed at 1% of body weight. All roughage was corrected to contain 10% of crude protein. It was used five rumen-fistulated bovine with average weight of 240 ± 15 kg, distributed in a 5 × 5 Latin square. Abomasum and total fecal collection and two rumen evacuations were carried out in the morning. Animals fed corn silage based diet presented greater rumen digestibility of the protein and intestinal digestibility of the ether extract, greater intake and passage of dry matter, justifying greater intakes of dry matter and neutral detergent fiber corrected for protein and ash (NDFap). The greatest passage rates in animals fed fresh sugar cane based diet justify greater intakes of dry matter and NDFap in relation to the one observed with sugar cane silage supply. Animal consuming corn silage diets present greater dry matter passage rate and NDFap digestion. Diets with fresh sugar cane, stored or not, favor dry matter passage rate and intake, in relation to ensiled sugar cane. The use of calcium oxide in the ensilage does not improve nutrient digestibility neither passage rate of the diet. Sugar cane stored for 72 hours has digestible traits similar to the ones of fresh sugar cane.

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Citrus pulp in lamb diets: intake, digestibility, and ruminal parameters

Semina Ciências Agrárias ◽

10.5433/1679-0359.2015v36n5p3421 ◽

2015 ◽

Vol 36 (5) ◽

pp. 3421 ◽

Cited By ~ 2

Author(s):

Eduardo Lucas Terra Peixoto ◽

Mirton José Frota Morenz ◽

Carlos Elysio Moreira da Fonseca ◽

Elizabeth Dos Santos Moura ◽

Karla Rodrigues de Lima ◽

...

Keyword(s):

Dry Matter ◽

Rumen Fluid ◽

Latin Square ◽

Neutral Detergent Fiber ◽

Average Weight ◽

Corn Meal ◽

Ruminal Fermentation ◽

Ruminal Ph ◽

Citrus Pulp ◽

Fermentation Parameters

This study aimed to evaluate the viability of replacing corn meal with citrus pulp (0, 25, 50, 75, and 100 % dry matter of corn meal) by evaluating several nutritional parameters such as intake and digestibility of nutrients, and ruminal fermentation parameters. The diets were formulated to be isoproteic with a roughage:concentrate ratio of 60:40. Five crossbred lambs with an initial average weight of 26.1 ± 1.8 kg were used and distributed in a 5 x 5 Latin Square design. For digestibility of nutrients was carried out to feed, orts, and feces collection. The evaluated nutrients were dry matter, crude protein, ether extract, ash, neutral detergent fiber, fiber acid detergent and lignin. Were determined nitrogen and carbohydrate fractions, and ruminal fermentation parameters (N-NH 3 and ruminal pH). The results were subjected to analysis of variance and regression analysis (t-test; ? = 0.05). Citrus pulp inclusion in the diets did not affect intake and digestibility of nutrients, or the pH and the NH3-N content of the rumen fluid. Citrus pulp can be used as a total substitute for corn in concentrate or up to 26.5% in the total ration for lambs (dry basis).

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PSX-B-10 Effect of undigested neutral detergent fiber concentration and forage inclusion rate on ruminal pH, reticular motility, and total tract permeability for finishing beef heifers

Journal of Animal Science ◽

10.1093/jas/skab235.811 ◽

2021 ◽

Vol 99 (Supplement_3) ◽

pp. 457-458

Author(s):

Murillo C Pereira ◽

Karen A Beauchemin ◽

Tim A McAllister ◽

Wenzhu Yang ◽

Joyce Van Donkersgoed ◽

...

Keyword(s):

Gastrointestinal Tract ◽

Dry Matter ◽

Latin Square ◽

Barley Grain ◽

Neutral Detergent Fiber ◽

Fiber Concentration ◽

Eating Time ◽

Ruminal Ph ◽

Contraction Duration ◽

Gastrointestinal Permeability

Abstract This study evaluated the effects of undigested neutral detergent fiber (uNDF) concentration and forage inclusion (FI) rate on dry matter (DM) intake, ruminal pH, reticular contractions, and gastrointestinal permeability for finishing beef cattle. Five ruminally cannulated Hereford′Simmental heifers (699±69.1 kg) were used in an incomplete 6×6 Latin square (26-d periods) with a 2×3 factorial treatment arrangement. Barley grain-based diets were formulated using barley silage or wheat straw to provide low or high uNDF (7.1 vs. 8.5% DM) with forage proportions of 5, 10, or 15% of dietary DM. Dry matter intake (P ≥ 0.10) and eating time (P ≥ 0.13) were not affected by uNDF, FI, or uNDF′FI. With low uNDF diets, increasing FI numerically (P = 0.02) increased rumination time (min/d); while, with high uNDF diets, rumination time increased with 5 to 10% FI, but not thereafter (P = 0.03). Mean ruminal pH was not affected by uNDF (6.17 vs. 6.19; P = 0.08), but increased with increasing FI (6.04b, 6.23a, and 6.28a; P = 0.02). Duration of ruminal pH < 5.5 was not affected by uNDF but tended (P = 0.07) to be reduced with increasing FI. High uNDF diet tended to increase the frequency of reticular contractions (1.43 vs. 1.51 contractions/min; P = 0.07) but decreased the contraction duration (13.2 vs. 14.1 sec; P = 0.04). Increasing FI increased contraction frequency (1.39b, 1.50a, and 1.53a contractions/min; P = 0.03) and tended to reduce contraction duration as forage increased from 5 to 10 and 15% (14.3, 13.1, and 13.6 sec; P = 0.07). Feeding high uNDF decreased (P = 0.05) permeability of the gastrointestinal tract based on the appearance of Cr-EDTA in urine following an intra-ruminal dose. Increasing FI tended to reduce gastrointestinal tract permeability (P = 0.06). Limited interactions indicate that uNDF and FI act independently suggesting that increasing dietary uNDF, without increasing FI rate, can stimulate frequency of reticulo-ruminal contractions and reduce gastrointestinal permeability for finishing cattle.

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USE OF THE IN SITU TECHNIQUE AND PASSAGE RATE CONSTANTS IN PREDICTING VOLUNTARY INTAKE AND APPARENT DIGESTIBILITY OF FORAGES BY STEERS

Canadian Journal of Animal Science ◽

10.4141/cjas89-112 ◽

1989 ◽

Vol 69 (4) ◽

pp. 973-987 ◽

Cited By ~ 19

Author(s):

MARINA A. G. VON KEYSERLINGK ◽

G. W. MATHISON

Keyword(s):

Dry Matter ◽

Neutral Detergent Fiber ◽

Passage Rate ◽

Feeding Level ◽

Festuca Hallii ◽

Grass Hay ◽

Medicago Sativa L ◽

Ad Libitum ◽

Voluntary Intake

The in situ bag technique was evaluated as a method of predicting the voluntary intake and digestibility of forages. Nine feedstuffs including three cereal straws, three alfalfa (Medicago sativa L.) and grass hay mixtures, two alfalfa-grass silages, and a prairie (Festuca hallii L.) grass hay were each fed to five steers (350 ± 49.5 kg) at ad libitum and approximately maintenance feeding levels. Hays and silages were also fed at near the twice maintenance feeding level. Voluntary forage dry matter (DM) intakes ranged from 1.00 to 2.85% of body weight. Apparent forage DM digestibilities ranged from 37 to 64%. At the lower feeding level fractional rates of particulate passage through the digestive tract were higher (P < 0.05) for 37% DM silage (0.037 h−1) than for two of the straw-based diets (0.020–0.023 h−1). Particulate passage rates were not (P > 0.05) affected by feeding level. Predictions from in situ results were most accurate when 24 and 36 h degradation values were used to estimate DM digestibility (R2 = 0.92) and intake (R2 = 0.86), respectively. The neutral detergent fiber content of forage was equally well correlated with DM digestibility (R2 = 0.86) and voluntary DM intake (R2 = 0.85). Inclusion of information on rates of passage in prediction equations did not (P > 0.05) improve accuracies of predictions over those obtained using in situ results or chemical feed components. Key words: Steers, in situ, voluntary intake, digestibility, passage rates, prediction

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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

Journal of Animal Science ◽

10.1093/jas/skz258.587 ◽

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 < 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.

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PSXIV-11 Silage source, physically effective neutral detergent fiber, and undigested neutral detergent fiber concentrations affect eating behavior, ruminal pH and reticular motility of finishing heifers

Journal of Animal Science ◽

10.1093/jas/skab235.839 ◽

2021 ◽

Vol 99 (Supplement_3) ◽

pp. 476-477

Author(s):

Murillo C Pereira ◽

Karen A Beauchemin ◽

Tim A McAllister ◽

Wenzhu Yang ◽

Joyce Van Donkersgoed ◽

...

Keyword(s):

Eating Behavior ◽

Latin Square ◽

Barley Grain ◽

Neutral Detergent Fiber ◽

Equal Proportion ◽

Eating Time ◽

Finishing Cattle ◽

Ruminal Ph ◽

Diet Formulation ◽

Carry Over

Abstract This study evaluated the effects of silage source, physically effective neutral detergent fiber (peNDF), and undigested neutral detergent fiber (uNDF) concentrations on eating behavior, ruminal pH, and reticular contractions for finishing beef heifers. Six Hereford′Simmental heifers (579±51.2 kg) were used in a replicated 6×6 Latin square (21-d periods) balanced for carry-over effects with 2×2 + 2 factorial treatment arrangement. Barley grain-based diets included barley (BarS) or wheat silage (WhS) at 10% of dietary DM. Silages were harvested at two chop lengths to yield low (LpeNDF) vs. high peNDF (HpeNDF) silage. For both BarS and WhS, chopped wheat straw was included (5% of DM) by replacing an equal proportion of LpeNDF silages to evaluate low vs. high uNDF (7.3 vs. 8.2% dietary DM) concentrations. Heifers fed HpeNDF WhS had greater DMI (silage′peNDF; P < 0.01) than those fed HpeNDF BarS, but DMI did not differ for LpeNDF treatments. Ruminating and eating time increased for heifers fed HpeNDF WhS relative to LpeNDF WhS, but were not different for BarS (silage′peNDF; P ≤ 0.02). Increasing uNDF increased eating and ruminating times for heifers fed WhS, but not BarS (silage′uNDF; P ≤ 0.03). Mean ruminal pH averaged 5.97 and was not affected by silage, peNDF, uNDF, or the interactions (P ≥ 0.12). Feeding BarS increased the duration (384 vs. 256 min/d; P = 0.02) and area (84.5 vs. 43.8 pH×min/d; P = 0.02) that pH was < 5.5 relative to WhS. Increasing peNDF numerically reduced the frequency of reticular contractions when fed BarS but numerically increased them when fed WhS (silage′peNDF; P < 0.01). Reticular contractions were not affected by dietary uNDF concentration (P ≥ 0.13). These data highlight that at a constant inclusion rate, silage source and chop length interact to affect DMI, eating behavior, ruminal pH, and reticular motility indicating the need to account for silage type, peNDF, and uNDF in diet formulation for finishing cattle.

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Effects of lucerne particle size and source of dietary carbohydrates on in situ degradation and ruminal variables in sheep

Czech Journal of Animal Science ◽

10.17221/1729-cjas ◽

2009 ◽

Vol 54 (No. 6) ◽

pp. 277-285 ◽

Cited By ~ 1

Author(s):

A. Asadi Alamouti ◽

G.R. Ghorbani ◽

M. Alikhani ◽

H.R. Rahmani ◽

A. Teimouri Yansari ◽

...

Keyword(s):

Particle Size ◽

Latin Square ◽

Dietary Carbohydrates ◽

Ruminal Fermentation ◽

Ruminal Ph ◽

Degradation Rate Constant ◽

Beet Pulp ◽

Feeding Diets ◽

Kinetics Of

The effects of altering forage particle size and source of rapidly degradable carbohydrates on in situ degradation and ruminal variables were studied in four Iranian male sheep. The study was designed as a Latin square with a 2 × 2 factorial arrangement of treatments including two carbohydrate sources (pelleted beet pulp vs. maize- and barley-based concentrate) and two lucerne particle sizes (2.38 vs. 0.94 mm). Kinetics of disappearance of lucerne, concentrates and mixed samples was studied in situ. Among feed samples, the degradation rate constant of lucerne dry matter was higher (P < 0.02) and disappearance of lucerne neutral detergent fibre (NDF) in 4 h of incubation was lower (P = 0.06) in diets with reduced particle size. The rapidly degradable fraction of lucerne samples was also affected by treatments. Other degradability components were not affected. The mean ruminal pH was lower in diets containing short hay than in those containing long hay (5.76 vs. 5.86, P < 0.006) and pH values were consistently lower immediately after feeding diets with short lucerne hay. The form of carbohydrates did not affect ruminal pH, however, altering the source of carbohydrates changed the pattern of pH over time. Total volatile fatty acid (VFA) concentration and proportions of individual VFA were similar but numerical differences indicated a lower acetate to propionate ratio in diets with short hay. Most of the affected variables were influenced by the particle size of forage to a larger extent than by the source of rapidly degradable carbohydrates or the interaction between them. So, when sheep diets contain no more than 250 g/kg starch, the source of dietary carbohydrates may not interact with forage particle size to affect DM degradability and ruminal fermentation.

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IN SITU DEGRADABILITY OF BARLEY STRAW IN CATTLE FED A BARLEY STRAW AND CRESTED WHEATGRASS DIET SUPPLEMENTED WITH ISOBUTYRIC ACID

Canadian Journal of Animal Science ◽

10.4141/cjas88-091 ◽

1988 ◽

Vol 68 (3) ◽

pp. 821-829 ◽

Cited By ~ 2

Author(s):

P. S. MIR ◽

Z. MIR

Keyword(s):

Volatile Fatty Acids ◽

Latin Square ◽

Isobutyric Acid ◽

Neutral Detergent Fiber ◽

Barley Straw ◽

Intake Rate ◽

Crested Wheatgrass ◽

Voluntary Intake ◽

Molar Percent

A feeding trial was conducted using a 3 × 3 Latin square design to determine the effects of isobutyric acid (IBA) supplementation of a diet containing 60% barley straw and 37% crested wheatgrass hay, on voluntary intake, rate of passage of solids from the rumen and in situ degradability of barley straw. IBA supplementation at 0, 2 and 4% of dietary dry matter (DM) resulted in voluntary intakes of 6.6, 7.1 and 7.6 kg d−1. Although the rate of passage of solids from the rumen of the diet supplemented with IBA at 4% of DM was 2.82% h−1 and was 1.89 and 1.97 times that of the other two diets, it was not statistically different (P > 0.05). Effective in situ degradability of either DM, neutral detergent fiber (NDF) or acid detergent fiber (ADF) of barley straw was not affected by IBA supplementation. However, potentially digestible DM, NDF and ADF were increased at the 4% level of IBA supplementation. Rumen ammonia levels were similar across all treatments and ranged from 5.33 to 5.93 mg dL−1. Supplementation with IBA did not affect molar percent of the rumen volatile fatty acids other than acetic acid and IBA. Although not significant, supplementation of the diet with 4% of dietary DM with IBA resulted in a 13.7% increase in intake. Key words: Cattle, barley straw, in situ degradability, isobutyric acid

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Processing index of barley grain and dietary undigested neutral detergent fiber concentration affected chewing behavior, ruminal pH, and total tract nutrient digestibility of heifers fed a high-grain diet

Journal of Animal Science ◽

10.1093/jas/skab011 ◽

2021 ◽

Vol 99 (1) ◽

Author(s):

Tao Ran ◽

Atef M Saleem ◽

Karen A Beauchemin ◽

Gregory B Penner ◽

Wenzhu Yang

Keyword(s):

Barrier Function ◽

Latin Square ◽

Barley Grain ◽

Nutrient Digestibility ◽

Neutral Detergent Fiber ◽

Blood Metabolites ◽

Fiber Concentration ◽

Finishing Cattle ◽

Ruminal Ph ◽

Grain Processing

Abstract The objective of this study was to investigate the effects of processing index (PI) of barley grain and dietary undigested neutral detergent fiber (uNDF) concentration on dry matter (DM) intake, chewing activity, ruminal pH and fermentation characteristics, total tract digestibility, gastrointestinal barrier function, and blood metabolites of finishing beef heifers. The PI was measured as the density after processing expressed as a percentage of the density before processing, and a smaller PI equates to a more extensively processed. Six ruminally cannulated heifers (average body weight, 715 ± 29 kg) were used in a 6 × 6 Latin square design with three PI (65%, 75%, and 85%) × 2 uNDF concentration (low and high; 4.6% vs. 5.6% of DM) factorial arrangement. The heifers were fed ad libitum a total mixed ration consisting of 10% barley silage (low uNDF), or 5% silage and 5% straw (high uNDF), 87% dry-rolled barley grain, and 3% mineral and vitamin supplements. Interactions (P < 0.01) of PI × uNDF were observed for DM intake, ruminating and total chewing time, and DM digestibility in the total digestive tract. Intake of DM, organic matter (OM), starch, and crude protein (CP) did not differ (P > 0.14) between low and high uNDF diets, but intakes of NDF and acid detergent fiber were greater (P = 0.01) for high uNDF diets regardless of barley PI. Heifers fed high uNDF diets had longer (P = 0.05) eating times (min/d or min/kg DM) and tended (P = 0.10) to have longer total chewing times (min/kg DM) than those fed low uNDF diets. Additionally, heifers sorted (P = 0.01) against long particles (>19 mm) for high uNDF diets but not for low uNDF diets. Altering PI of barley grain did not affect (P > 0.12) total volatile fatty acid (VFA) concentration, molar percentages of individual VFA, or duration of ruminal pH < 5.8 and <5.6. Total VFA concentration was less (P = 0.01), acetate percentage was greater (P = 0.01), and duration of ruminal pH < 5.8 and <5.6 was less (P = 0.05) for high compared with low uNDF diets. Digestibility of DM, OM, and CP was greater (P = 0.02) for low vs. high uNDF diets with PI of 65% and 75%, with no difference between low and high uNDF diets at PI of 85%. Blood metabolites and gastrointestinal tract barrier function were not affected (P ≥ 0.10) by the treatments. These results suggest that increasing dietary uNDF concentration is an effective strategy to improve ruminal pH status in finishing cattle, regardless of the extent of grain processing, whereas manipulating the extent of barley processing did not reduce the risk of ruminal acidosis.

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