Influence of addition of propionic acid producing bacteria on dry matter digestibility and rumen fermentation profiles in wheat straw containing total mixed ration in vitro

Twelve propionic acid producing bacterial (PAPB) strain were isolated from rumen of cattle and were identified as species of Selenomonas ruminantium (NDRI-PAPB 2, NDRI-PAPB 4, NDRI-PAPB 5, NDRI-PAPB 6, NDRI-PAPB 7 and NDRI-PAPB 8), Megasphaera elsdenii (NDRI-PAPBM), Veillonella parvula (NDRI-PAPBV) andEnterococcus spp. (NDRI-PAPB 1, NDRI-PAPB 11, NDRI-PAPB 12 and NDRI-PAPB 13) based on their morphological, biochemical and genetic characteristics. All the twelve bacterial isolates were screened for IVDMD (%) and rumen fermentation characteristics, using a TMR (60 parts roughage and 40 parts concentrate) as substrate. 200 ± 5mg of diet were incubated for 24 h with 3 ml of each bacterial culture media and 30 ml of buffered rumen fluid at 3 replicates. Among Selenomonas ruminantium isolates, NDRI-PAPB 4 produced lowest gas and methane, and the values were statistically significant than control, however, non significant differences were observed in rumen pH and IVDMD (%) between control and Selenomonas isolates. NDRI-PAPB 4 isolate also produced lowest acetic acid and highest propionic acid. However, no significant difference was observed in butyric acid, isobutyric acid, valeric acid and iso-valeric acid production between control and Selenomonas isolates. Megasphaera isolate significantly(P<0.05) decreased gas and propionic acid than control. But, non significant differences with control in case of methane, pH, IVDMD and acetic, butyric, isobutyric, valeric, iso-valeric acid production were observed. Veillonella isolate also produced significantly higher propionic acid than control, but it had no significant difference in gas production, methane production, IVDMD (%), pH, acetic, butyric, isobutyric, valeric and iso-valeric acid production. Enterococcus isolates had no significant difference with control in relation with gas production, methane production, IVDMD (%), pH and volatile fatty acids.