title: Influence of Wheat Straw Pelletizing and Inclusion Rate in Dry Rolled or Steam-flaked Corn-based Finishing Diets on Characteristics of Digestion for Feedlot Cattle.
abstract: Eight Holstein steers (216±48 kg body weight) fitted with ruminal and duodenal cannulas were used to evaluate effects of wheat straw processing (ground vs pelleted) at two straw inclusion rates (7% and 14%; dry matter basis) in dry rolled or steam-flaked corn-based finishing diets on characteristics of digestion. The experimental design was a split plot consisting of two simultaneous 4×4 Latin squares. Increasing straw level reduced ruminal (p<0.01) and total tract (p = 0.03) organic matter (OM) digestion. As expected, increasing wheat straw level from 7% to 14% decreased (p<0.05) ruminal and total tract digestion of OM. Digestion of neutral detergent fiber (NDF) and starch, per se, were not affected (p>0.10) by wheat straw level. Likewise, straw level did not influence ruminal acetate and propionate molar proportions or estimated methane production (p>0.10). Pelleting straw did not affect (p≥0.48) ruminal digestion of OM, NDF, and starch, or microbial efficiency. Ruminal feed N digestion was greater (7.4%; p = 0.02) for ground than for pelleted wheat straw diets. Although ruminal starch digestion was not affected by straw processing, post-ruminal (p<0.01), and total-tract starch (p = 0.05) digestion were greater for ground than for pelleted wheat straw diets, resulting in a tendency for increased post-ruminal (p = 0.06) and total tract (p = 0.07) OM digestion. Pelleting wheat straw decreased (p<0.01) ruminal pH, although ruminal volatile fatty acids (VFA) concentration and estimated methane were not affected (p≥0.27). Ruminal digestion of OM and starch, and post-ruminal and total tract digestion of OM, starch and N were greater (p<0.01) for steam-flaked than for dry rolled corn-based diets. Ruminal NDF digestion was greater (p = 0.02) for dry rolled than for steam-flaked corn, although total tract NDF digestion was unaffected (p = 0.94). Ruminal microbial efficiency and ruminal degradation of feed N were not affected (p>0.14) by corn processing. However, microbial N flow to the small intestine and ruminal N efficiency (non-ammonia N flow to the small intestine/N intake) were greater (p<0.01) for steam-flaked than for dry rolled corn-based diets. Ruminal pH and total VFA concentration were not affected (p≥ 0.16) by corn processing method. Compared with dry rolled corn, steam-flaked corn-based diets resulted in decreased acetate:propionate molar ratio (p = 0.02). It is concluded that at 7% or 14% straw inclusion rate, changes in physical characteristics of wheat straw brought about by pelleting negatively impact OM digestion of both steam-flaked and dry-rolled corn-based finishing diets. This effect is due to decreased post-ruminal starch digestion. Replacement of ground straw with pelleted straw also may decrease ruminal pH.
authors.affiliation: Veterinary School, Autonomous University of Baja California, Mexicali 21283, México.
authors.forename: O M
authors.initials: OM
authors.lastname: Manríquez
authors.affiliation: Veterinary School, Autonomous University of Baja California, Mexicali 21283, México.
authors.forename: M F
authors.initials: MF
authors.lastname: Montano
authors.affiliation: Veterinary School, Autonomous University of Baja California, Mexicali 21283, México.
authors.forename: J F
authors.initials: JF
authors.lastname: Calderon
authors.affiliation: Veterinary School, Autonomous University of Baja California, Mexicali 21283, México.
authors.forename: J A
authors.initials: JA
authors.lastname: Valdez
authors.affiliation: Veterinary School, Autonomous University of Baja California, Mexicali 21283, México.
authors.forename: J O
authors.initials: JO
authors.lastname: Chirino
authors.affiliation: Veterinary School, Autonomous University of Baja California, Mexicali 21283, México.
authors.forename: V M
authors.initials: VM
authors.lastname: Gonzalez
authors.affiliation: Veterinary School, Autonomous University of Tamaulipas, Cd. Victoria, 87078, México.
authors.forename: J
authors.initials: J
authors.lastname: Salinas-Chavira
authors.affiliation: Department of Agricultural and Animal Production, Autonomous Metropolitan University, Xochimilco 04960, México.
authors.forename: G D
authors.initials: GD
authors.lastname: Mendoza
authors.affiliation: Department of Animal and Range Sciences, New Mexico State University, Las Cruces NM 88007, USA.
authors.forename: S
authors.initials: S
authors.lastname: Soto
authors.affiliation: Department of Animal Science, University of California, Davis CA 95616, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Zinn
keywords: Cattle; Corn Grain; Digestion; Processing; Wheat Straw