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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #322299
Title: Effect of starchy or fibrous carbohydrate supplementation of orchardgrass on ruminal fermentation and methane output in continuous culture

Author
item Soder, Kathy
item BRITO, ANDRE - University Of New Hampshire
item HAFLA, AIMEE - Agri-King, Inc
item Rubano, Melissa

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2016
Publication Date: 6/1/2016
Citation: Soder, K.J., Brito, A., Hafla, A.N., Rubano, M.D. 2016. Effect of starchy or fibrous carbohydrate supplementation of orchardgrass on ruminal fermentation and methane output in continuous culture. Journal of Dairy Science. 99:4464-4475.

Interpretive Summary: Due to its sugar content, beet pulp may provide a better source of energy to grazing dairy cows than barley grain, which contains starch. We looked at supplementing a pasture diet with either barley grain or beet pulp at two levels of supplementation. Feeding beet pulp improved protein digestibility, but decreased fiber digestibility of the diets compared to supplementation with barley grain. However, methane output was greater for diets supplemented with beet pulp, which may have negative environmental impacts and must be weighed against potential benefits. More research is needed to evaluate the economic and environmental sustainably of supplementing pasture diets with alternative energy sources such as beet pulp.

Technical Abstract: A 4-unit dual-flow continuous culture fermentor system was used to assess the effect of supplementing an orchardgrass (Dactylis glomerata L.) herbage diet with 2 levels [5 and 10% of total dry matter (DM) fed] of starchy (barley grain; BAR) or fibrous (beet pulp; BP) carbohydrates on nutrient digestibility, volatile fatty acid (VFA) production, bacterial protein synthesis, and CH4 production. Treatments were randomly assigned to fermentors in a 4 × 4 Latin square design with a 2 × 2 factorial arrangement using 7 d for diet adaptation and 3 d for sample collection. Treatments included: 1) 57 g DM herbage + 3 g DM barley grain; 2) 54 g DM herbage + 6 g DM barley grain; 3) 57 g DM herbage + 3 g DM beet pulp; or 4) 54 g DM herbage + 6 g DM beet pulp. Feedings occurred at 0730, 1030, 1400 and 1900 h throughout 4, 10-d periods. Gas samples for CH4 analysis were collected 6 times daily at 0725, 0830, 1000, 1355, 1530, and 1630 h. Fermentor samples for pH, ammonia-N, and VFA analysis were taken on d 8, 9, and 10 and analyzed for DM, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber 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 for carbohydrate type (starchy vs. fibrous) and level of supplementation (5 versus 10%). Apparent and true DM and organic matter digestibilities were not affected by supplement source. Apparent neutral and acid detergent fiber digestibilities were greater for BAR-supplemented diets compared with BP-supplemented diets. Conversely, apparent crude protein digestibility was greater for BP-supplemented diets. Mean and maximum pH tended to be greater for BAR-supplemented diets. Minimum pH was greater at the lower level (5%) of supplementation. Barley diets produced a greater concentration of total VFA and molar proportions of acetate compared with diets supplemented with BP. Beet pulp-supplemented diets had greater outputs of daily CH4 and greater CH4 output compared with BAR-supplemented diets. There was a significant supplement type by level interaction for efficiency of bacterial protein synthesis. Overall, supplementing herbage-based diets with BP marginally improved crude protein digestibility, reduced fiber digestibility and had reduced VFA and increased CH4 output compared with BAR-supplemented diets.