PSXVI-5 Rumen Parameters and Microbial Population Changes in Fattening Holstein Heifers fed with Nitrate-Contaminated Water

Abstract The aim of this study was to evaluate the effect drinking water nitrate concentration on rumen parameters and its microbial population that may affect greenhouse gases in fattening cattle. Holstein heifers (n = 24; 161 ± 19.9 kg initial BW, 183 25.3 d age) were housed individually fed ad libitum. Animals assigned 4 treatments according water: 1) Control (n=6), without NO3-; 2) Low with 44 mg/L 3) Moderate 110 NO3-, 4) High 220 NO3-. After 14 168 days ruminal content sampled determine pH, volatile fatty acids (VFA), nitrite concentration, microbiota (except for Moderate). To assess microbiota, DNA-based qPCR total bacterial (16S rRNA), dissimilatory sulfate-reducing prokaryotes (aprA), ammonia-oxidizing bacteria archaea (amoA-AOB amoA-AOA), typical complete denitrifiers (nosZ-clade I linked transformation N2O N2), anammox (hzo) determined. Rumen VFA, analyzed a mixed effects model. populations statistically treated by analysis variance applying pairwise comparisons (Fisher's least). not affected water; however, concentrations greater (P < 0.01) than (32.1 vs. 6.3 4.20 mg/L, respectively). Nitrate did populations, except complete-denitrifying I) which slightly (P=0.01) 168. In conclusion, nitrate-contaminated show significant impact but increased denitrifying potential after long term, could decrease emissions accumulation heifers.