Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2012
Publication Date: 7/1/2012
Citation: Soder, K.J., Brito, A.F., Rubano, M.D., Dell, C.J. 2012. Effect of incremental flaxseed supplementation of an herbage diet on methane output and ruminal fermentation in continuous culture. Journal of Dairy Science. 95(7):3961-3969. DOI: 10.3168/jds.2011-4981. Interpretive Summary: The aim of this study was to evaluate incremental flax supplementation of an herbage-based diet on ruminal fermentation and methane output in continuous culture fermentation. Treatments included 0, 5, 10, or 15% dry matter of flaxseed supplementation to a pasture-based diet. Dry matter digestibility decreased with increasing flaxseed supplementation. Increasing flax supplementation also resulted in corresponding decreases in methane output, which is desirable in reducing greenhouse gas emissions by ruminants. However, this potential environmental benefit came at the cost of decreased nutrient digestibility which, at the cow level, could result in decreased dry matter intake and milk production.
Technical Abstract: A 4-unit dual-flow continuous culture fermentor system was used to assess the effect of increasing flax supplementation of an herbage-based diet on nutrient digestibility, bacterial N synthesis and methane output. Treatments were randomly assigned to fermentors in a 4 x 4 Latin square design with 7 d for diet adaptation and 3 d for data and sample collection. Treatments were: 0, 5, 10 and 15% ground flaxseed (Linum usitatissimum) supplementation of an orchardgrass (Dactylis glomerata L.) herbage diet (70 g total dry matter (DM) fed daily). Samples were collected from the fermentors 4 times daily at feeding (0730, 1030, 1400 and 1900 h) on d 8 to 10 of each of 4, 10-d periods and analyzed for pH, NH3-N, and volatile fatty acids. Gas samples for methane analysis were collected immediately before, and 1 and 2 h after the 0730-h feeding on days 8, 9 and 10 and at the 1400-h feeding on days 7, 8 and 9 of each period. Effluents were analyzed for DM, organic matter, crude protein and neutral detergent fiber for determination of nutrient digestibilities, and for total purines concentration for estimation of bacterial protein synthesis. Apparent DM, organic matter and neutral detergent fiber digestibilities decreased linearly with increasing supplemental flaxseed, while true DM and organic matter digestibilities were not significantly affected by treatments, averaging 77.6 and 79.1%, respectively. Mean ruminal pH was not significantly affected by increasing the dietary concentration of flaxseed, averaging 6.68 across treatments. Total volatile fatty acid concentrations were not significantly affected by treatments. However, molar proportions of acetate and propionate increased linearly while butyrate and valerate decreased linearly with increasing flaxseed supplementation. Methane output decreased linearly as supplemental flaxseed increased from 0 to 15% of diet DM. However, both the NH3-N concentration and the apparent crude protein digestibility did not differ significantly with flaxseed supplementation, averaging 17.0 mg N/dL and 89.9% across treatments, respectively. Similarly, efficiency of bacterial N synthesis was not affected by treatments. Incremental ground flaxseed supplementation of an herbage-based diet resulted in a corresponding decrease in methane output in a dual-flow continuous culture fermentor system. However, nutrient digestibility also decreased with flaxseed supplementation, which, at the cow level, could result in decreased DM intake and milk production.