Correlations between the abundance of specific ruminal bacteria with milk production and total tract digestibility of dairy cows fed live or killed yeast

Abstract Text:

Ruminal nutrient metabolism and animal performance depend on the abundance and diversity of ruminal bacteria. The objective of this study was to examine the correlation between the abundance of different ruminal bacteria and total tract nutrient digestibility and milk production of dairy cows fed diets supplemented without or with live or killed Saccharomyces cerevisiae. Four ruminally-cannulated lactating cows (284 + 18 DIM) were assigned to 4 treatments arranged in a 4 x 4 Latin square design with four, 21-day periods. Cows were fed a non-acidotic total mixed ration (46.8% corn silage, 8.5% wet brewers’ grain and 44.7% concentrate, DM basis). The diet was not supplemented with yeast or supplemented with a low dose of live yeast (5.7 x 10⁷ cfu/day), a high dose of live yeast (6.0 x 10⁸ cfu/day), or a high dose of killed yeast (6.0 x 10⁸ cfu/day before heating at 80^oC). Ruminal fluid was collected 0, 2, 4, 6, 8 and 10 h after the morning feeding on d 21 and strained through cheese cloth to separate solid and liquid fractions. Microbial diversity was examined by Illumina MiSeq sequencing of the V4 region of the 16S rRNA gene. Data were analyzed using R (R Core Team, 2013). In the ruminal solid fraction, the Fibrobacter abundance was correlated (r = 0.60, P < 0.05) with milk fat concentration. Unknown genera in family Lachnospiraceae and RFP12 were negatively (P < 0.05) correlated with NDF digestibility (r = -0.52 and -0.56, respectively). An unknown genus (UT) in family Paraprevotellaceae was negatively (P < 0.05) correlated with milk fat and protein content (r = -0.56 and -0.52, respectively) and NDF digestibility (r = -0.65), whereas a UT in family Clostridiaceae was negatively correlated with CP digestibility (r = -0.59, P < 0.05). In the liquid fraction, Prevotella was negatively correlated with DMI, milk protein and fat content (r = -0.64, -0.59 and -0.53, respectively, P < 0.05). Unknown genera in family Succinivibrionaceae and Ruminococcaceae were positively correlated (P < 0.05) with ADF digestibility (r = 0.63) and milk yield (r = 0.49), respectively, whereas a UT in family Lachnospiraceae was negatively correlated with DM digestibility (r = -0.56, P < 0.05). This study revealed several uncultured or unknown ruminal bacteria that appear important as candidates for future studies because of their correlation with one or more indices of dairy cow performance.

Keywords: correlation, milk production, rumen bacteria