1705
Effect of Post-extraction Algal Residue Supplementation on the Rumen Microbiome of Steers Consuming Low-quality Forage
Cattle consuming low-quality forages require protein supplementation to increase forage utilization and ruminal fermentation. Production of algal biomass for biofuel would result in large quantities of post-extraction algal residue (PEAR, 17.9% CP) which has the potential to elicit similar low-quality forage utilization responses to cottonseed meal (CSM, 42.9% CP); however, its effect on ruminal bacterial communities is unknown. Five ruminally and duodenally cannulated Angus steers in a 5 × 5 Latin square had ad libitum access to oat straw (4.5% CP, 80% NDF). Treatments were infused ruminally and consisted of an unsupplemented control (CON), PEAR at 50, 100, and 150 mg N/kg BW, and CSM at 100 mg N/kg BW. Rumen samples were collected 4 h after supplementation on d 14 of each period and separated into liquid and solid fractions. After DNA extraction, amplification of the V4-V6 region of the 16S rRNA gene and 454 pyrosequencing was performed on liquid and solid rumen samples. After denoising, chimera checking, and quality trimming, 8364 ± 2745 sequences were generated per sample. Weighted UniFrac analysis and Morisita-Horn index demonstrated different community composition between liquid and solid fractions. Greater homogeneity was observed within solid samples. At the phyla level, Bacteroidetes characterized more than 75% of sequences in the solid fraction, while relative abundance of Firmicutes in the liquid fraction increased linearly with PEAR supplementation (P = 0.02). Prevotella represented over 25% of sequences in all treatments and decreased in the solid fraction with increasing PEAR provision (linear, P = 0.01). Lachnospiraceae, Ruminococcaceae, and Clostridiaceae increased in the liquid fraction with greater PEAR supplementation (linear, P ≤ 0.03). Fibrobacter and Treponema decreased in the liquid fraction with increasing PEAR (linear, P< 0.10). Bacterial community composition was similar between CON and 100 mg N/kg BW CSM treatments. Results suggest increased forage utilization from PEAR supplementation may be linked to changes within the liquid fraction of the rumen microbiome.
Keywords: microbiome, post-extraction algal residue, supplementation