286 - Effects of Supplementation of Quebracho Extract Supplementation on Ruminal Ph of Growing Beef Steers

Rumen acidosis is a common metabolic disorder occurring when organic acid production exceeds clearance capacity, reducing ruminal pH. Acidosis occurrence has been directly correlated to the ratio of concentrate to forage in the diet. However, the rates of substrate fermentation and acid absorption vary at different locations in the rumen. The objective of this study was to determine the pH in different locations of the rumen using 16 rumenally- cannulated steers (309 ± 43 kg) receiving quebracho extract (QT; Schinopsis balansae) within a grower-type diet [25:75 forage-to-concentrate, dry matter (DM) % basis]. Animals were randomly assigned to one of four dietary treatments (n = 4): QT at 0, 1, 2, and 3% of DM (QT0, QT1, QT2, and QT3). Animals were adapted to the basal diet (QT0) for 12-d before being introduced to predetermined treatments for four weeks, with feed provided twice daily to allow ad libitum intake. Weekly measurements of ruminal fluid pH and redox potential (Eh) were taken four h post-feeding using a portable pH and redox meter probe in four locations of the rumen (cranial sac, ventral sac, dorsal sac, and reticulum). Data were analyzed using a random coefficients model with the pen as a random effect and week as repeated measures. The DM intake was included as a covariate. There was no interaction among diet, location, and week (P ≥ 0.925) on pH. Overall, ruminal pH was lower for QT0 and QT1 compared to QT3 (P < 0.001). Ruminal pH in the cranial sac and reticulum was greater than in the dorsal sac (5.98, 6.03, and 5.87, respectively; P = 0.001). Redox potential was lower for QT0 in week 1 than all other treatments (P = 0.042). This study indicated that pH differs among locations of the rumen regardless of QT supplementation level and days on feed.