PMID- 27136015 OWN - NLM STAT- MEDLINE DCOM- 20170531 LR - 20181202 IS - 1525-3163 (Electronic) IS - 0021-8812 (Linking) VI - 94 IP - 4 DP - 2016 Apr TI - Effects of quebracho tannin extract on rumen fermentation and yield and composition of microbial mass in heifers. PG - 1561-75 LID - 10.2527/jas.2015-0061 [doi] AB - To determine the effects of incremental quebracho tannin extract (QTE) infusions on rumen fermentation and yield and composition of microbial mass, a study was conducted that consisted of 1 control period (Control I) without QTE dosing; 4 periods when all animals received 1, 2, 4, or 6% QTE of the diet (DM basis); and a second control period (Control II). Each period consisted of 9 d of adaptation, 6 d of urine collection, and 1 d of rumen sampling. Three rumen-fistulated heifers (495 kg BW [SE 14]) were offered 2.6 kg/d grass hay, 2.6 kg/d concentrates, and 60 g/d mineral-vitamin premix (as fed) in 2 equal meals. Half the daily QTE dosage was intraruminally administered at every meal. Urine and rumen fluids were analyzed for purine derivatives and short-chain fatty acids, respectively. Nitrogen and purine base (PB) concentrations were determined in liquid-associated microbes in rumen fluid (LAMF), liquid-associated microbes in the solid phase (LAMS), and particle-associated microbes (PAM). Increasing QTE dosages linearly increased propionate and butyrate proportions in rumen fluid ( = 0.37, = 0.004 and = 0.51, < 0.001, respectively). Instead, proportions of acetate ( = 0.75, < 0.001), isobutyrate ( = 0.66, < 0.001), and isovalerate ( = 0.49, < 0.001) and urinary purine derivatives excretions ( = 0.66, < 0.001) linearly decreased with increasing QTE infusions. Inconsistent differences were observed for LAMF, but concentrations of PB in LAMS (