Effect of Sprouted Barley Grain Supplementation of an Herbage or Haylage Diet on Ruminal Fermentation and Methane Output in Continuous Culture

Abstract Text: A 4-unit dual-flow continuous culture fermentor system was used to assess the effect of supplementing 7-d sprouted barley (SB) or barley grain (BG), with a pasture (orchardgrass) or haylage diet, on nutrient digestibility, VFA production, bacterial protein synthesis, and methane production. Treatments were randomly assigned to fermentors in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments using 7 d for diet adaptation and 3 d for sample collection. Treatments were: 1) pasture+SB, 2) pasture+BG, 3) haylage+SB, and 4) haylage+BG. Feedings (60 g of DM) occurred 4 times daily (0730, 1030, 1400, 1900 h) throughout four 10-d periods. Gas samples for methane analysis were collected 6 times daily (0725, 0830, 1000, 1355, 1530, 1630 h). Samples for pH, ammonia-N, and VFA analysis were taken on d 8, 9, and 10 and analyzed for DM, OM, CP, NDF, and  ADF for determination of nutrient digestibilities, and estimation of bacterial protein synthesis. Data were analyzed using the MIXED procedure of SAS with period and treatment as fixed effects and fermentor as random. Orthogonal contrasts were tested using haylage vs. pasture and BG vs. SB treatments. Apparent and true DM digestibility was not affected by forage type. True DM digestibility was greater (P = 0.05) for diets supplemented with SB. Apparent and true digestibilities of OM and apparent CP were not affected by treatment (68, 83, and 89%, respectively). Apparent NDF and ADF digestibilities of pasture diets were greater (P < 0.05) compared to haylage diets (79 vs. 72% and 76 vs. 73%, respectively); however, supplement did not affect fiber digestibility. Diets supplemented with SB had greater (P < 0.05) mean and minimum pH than BG. Haylage diets produced greater (P < 0.01) concentrations of total VFA compared with pasture diets (72 vs. 61 mmol/L). Supplementation with BG produced a greater (P = 0.03) concentration of total VFA compared to diets supplemented with SB (68 vs. 64 mmol/L). Haylage diets produced greater (P < 0.05) concentrations of daily methane compared with pasture diets (35 vs. 27 mmol) but supplementation did not affect methane production. Bacterial efficiency was greater (P< 0.05) for pasture diets compared with haylage diets with no effect of supplementation. Supplementation with SB increased true DM digestibility of pasture and haylage diets, but did not impact fiber and CP digestibility, methane production, or microbial efficiency, compared to BG.

Keywords: sprouted barley, pasture, methane