Feeding incremental amounts of ground flaxseed: Effects on diversity and relative abundance of ruminal microbiota and enteric methane emissions in dairy cows

Authors: KLEVES, ALMEIDA - University Of New Hampshire; RESENDE, TALES - Universidade Federal De Minas Gerais; SILVA, LUIS - Western Kentucky University; DORICH, CHISTOPHER - Colorado State University; PEREIRA, ANDRE - University Of New Hampshire; Soder, Kathy; BRITO, ANDRE - University Of New Hampshire

Submitted to: Journal of Dairy Science Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2023
Publication Date: 5/29/2023
Citation: Kleves, A., Resende, T., Silva, L., Dorich, C., Pereira, A., Soder, K.J., Brito, A. 2023. Feeding incremental amounts of ground flaxseed: Effects on diversity and relative abundance of ruminal microbiota and enteric methane emissions in dairy cows. Journal of Dairy Science Communications. 7(1):1-8. https://doi.org/10.1093/tas/txad050.
DOI: https://doi.org/10.1093/tas/txad050

Interpretive Summary: Oilseeds such as flaxseed are fed to dairy cows to improve milk production, increase proportions of milk fatty acids that may have human health benefits, and decrease methane produced during ruminal fermentation. However, oilseeds also may have negative impacts on ruminal fermentation due to toxicity to rumen microbes, but the effect on specific microbial populations has not been evaluated. Four levels of whole flaxseed (0, 5, 10, and 15% of diet dry matter) were fed to cows consuming a forage and grain diet. Results showed that feeding increasing amounts of flaxseed decreased the abundance of ruminal bacteria populations that digest fiber which may be associated with the observed tendency for decreased methane production. However, the tradeoff may be that fiber digestion is decreased, resulting in reduced milk production.

Technical Abstract: We evaluated the effects of incremental amounts of ground flaxseed (GFX) on diversity and relative abundance of ruminal microbiota taxa, enteric CH4 emissions, and urinary excretion of purine derivatives using 16 Jersey cows averaging (mean ± SD) 184 ± 60 days in milk and 421 ± 35 kg of body weight in the beginning of the study. Twelve were used for ruminal microbiota analysis and all 16 for enteric CH4 measurements. Cows were blocked by days in milk or parity and, within block, randomly assigned to treatment sequences in a replicated 4 × 4 Latin square design. Each experimental period lasted 21 d with 14 d for diet adaptation and 7 d for data and sample collection. Diets (63:37 forage:concentrate ratio) were formulated by replacing corn meal and soybean meal with incremental amounts of GFX (0, 5, 10, and 15% of the diet dry matter). Ruminal fluid samples obtained via stomach tubing were used for DNA extraction and MiSeq sequencing. Enteric CH4 production was measured using the hexafluoride tracer technique. Diets had no effect on ruminal microbiota a-diversity indices (operational taxonomic units, Shannon, and Faith). Principal coordinate analysis of unweighted and weighted dissimilarities showed no overall unifying differences in the ruminal microbiota of cows fed GFX. Similarly, the relative abundance of ruminal archaea genera was not affected by diets. In contrast, GFX reduced the relative abundance of the phylum Firmicutes linearly and increased that of Bacteroidetes linearly. The relative abundance of the ruminal bacteria genera Ruminococcus and Clostridium decreased linearly, and that of Prevotella and Pseudobutyrivibrio increased linearly with feeding GFX. A tendency for a linear reduction in enteric CH4 production was observed in cows fed increasing amounts of GFX. However, diets did not change CH4 yield and CH4 intensity. Overall, feeding incremental amounts of GFX decreased the relative abundance of ruminal bacterial genera involved in cellulose degradation (i.e., Ruminococcus, Clostridium), which may be associated with the linear reduction tendency in CH4 production.