216
Influence of dry-rolled corn processing and distillers grain inclusion rate on rumen pH, VFA and NH3 concentration and in vitro methane production

Tuesday, March 17, 2015: 3:45 PM
308-309 (Community Choice Credit Union Convention Center)
Faithe E. Doscher , North Dakota State University, Fargo, ND
Megan C. Ruch , North Dakota State University, Fargo, ND
James D. Kirsch , North Dakota State University, Fargo, ND
Carl R. Dahlen , North Dakota State University, Fargo, ND
Shafiqur Rahman , North Dakota State University, Fargo, ND
Md S. Borhan , North Dakota State University, Fargo, ND
Marc L. Bauer , North Dakota State University, Fargo, ND
Kendall C. Swanson , North Dakota State University, Fargo, ND
Abstract Text:

Increased DDGS inclusion and decreased corn particle size have been shown to lower ruminal pH and reduce methanogenic bacteria and hydrogen production.  Objectives were to determine the effects of dry-rolled corn processing and DDGS inclusion rate on ruminal pH, VFA and NH3 concentration, and in vitro methane production.  Eight ruminally cannulated Holstein steers (526 ± 3.6 kg) were assigned to treatments in a 2 × 2 factorial arrangement with factors including 1) Particle size (coarse-rolled corn (2.5 mm) or fine-rolled corn (1.7mm)) and; 2) DDGS inclusion level (20 or 40%).  Diets were formulated to meet or exceed NRC recommendations and were offered ad libitum.  The experiment was designed as a 4 × 4 Latin square with 7 d of diet adaptation and 7 d of sample collection.  Ruminal pH was measured using wireless pH sensors (Kahne Ltd.) with measurements taken every 5 min from d 3 to 5 of the collection period.  To determine VFA and NH3 concentration, approximately 200 mL of ruminal fluid were sampled from d 3 to 5 in a manner to represent every other hour in a 24-h cycle. Gas production was examined on d 1 and 7 of the collection period using 4 replicates per treatment.  Approximately 0.375 g of each of the 4 dietary substrates was added to 250-mL flasks with 175 mL of McDougall’s buffer and 37.5 mL of ruminal fluid. The flasks were flushed with CO2, fitted with pressure monitor caps and placed in an oscillating waterbath at 39°C for 24 h.  A gas pressure monitoring system (ANKOM) was used to measure the changes in pressure relative to atmospheric pressure as a consequence of gas produced during fermentation.  Data were analyzed using the Mixed procedure of SAS (SAS Inst. Inc., Cary, NC) with statistical significance declared at P ≤ 0.05.  Ruminal pH was not affected (P ≥ 0.07) by treatment while NH3 concentration was greater (P = 0.02) in steers fed 20% DDGS.  Steers fed fine-rolled corn had greater (P = 0.02) concentrations of butryric acid.  Total gas production and methane concentration were not influenced (P ≥ 0.08) by particle size or DDGS inclusion level.  Urea was supplemented in diets containing 20% DDGS to meet DIP requirements which likely accounted for the increase in NH3.  Despite a rise in ruminal butyric acid, acetate and propionate were not affected (P ≥ 0.20) possibly reducing the likelihood of hydrogen capture and subsequent methane mitigation.  

Keywords: bovine, corn, distillers, rumen