PSV-A-12 - The Influence of Calcium Dose and Olive Meal on in-vitro Rumen Fermentation Characteristics

Abstract: Rumen fluid from three beef steers (480 ± 10 kg), fitted with rumen canulae, were used to investigate the impact of Ca dose and olive meal on in vitro rumen fermentation characteristics. Steers were fed a high concentrate finishing diet for 21d, and rumen fluid was collected from each steer 2h post-feeding. A 2 x 4 factorial arrangement of treatments was used for this experiment. Factors included: 1) 0 or 5% olive meal and 2) Ca dose: 0, 0.02, 0.04, and 0.08% Ca from CaCl₂. A McDougall’s buffer-rumen fluid mixture (1:1; 30 mL) was added to conical tubes containing 0.5g of the ground basal diet and incubated at 39°C for 0, 4, 8, and 12h (5 replicates per treatment per time point). After incubation, supernatant was removed for VFA analysis and the remaining digesta was dried to determine DM disappearance (DMD). At 4 and 8h post incubation digestion tubes containing 0.04% Ca had greater (P < 0.001) DMD when compared to all other Ca doses. At 12h post incubation, DMD was greater (P < 0.001) in digestion tubes containing 0.02% and 0.08% Ca compared to all other Ca doses. At 8h post incubation, molar proportions of acetic acid were greater (P < 0.03) in digestion tubes containing olive meal compared to no olive meal and were greater (P < 0.001) in digestion tubes containing 0.08% Ca compared to all other Ca doses. At 12h post incubation, isobutyric acid (P < 0.01) and butyric acid (P < 0.02) were greater in digestion tubes containing 0.02% and 0.04% Ca compared to all other Ca doses. Butyric acid was lesser (P < 0.02) with olive meal inclusion at 12h. Total VFA concentrations were similar across treatments. These data suggest that Ca and olive meal can impact in vitro fermentation characteristics.