Relation Between Organic Acids in Total Mixed Ration and Rumen Volatile Fatty Acids

The present study investigated relationship between organic acid contents in total mixed ration (TMR) and rumen volatile fatty acid production. TMR for lactating dairy cow was used. Organic acid production in TMR was modified by inoculation of different starter cultures. Five lactic acid bacteria (LAB) were used as starter culture and 12 different blends of those strains were designed based on Plackett-Burman experimental design. TMRs with different inoculants were fermented for 3 days at room temperature and organic acid profiles (lactate, aetate, propionate, butyrate and valerate) were examined. Fermented TMR was then air-dried at 60ºC and ground for in vitro rumen fermentation. Rumen fluid from cannulated Holstein cow was mixed with McDoughal solution. In vitro rumen fermentation with TMR was performed for 24 hours and volatile fatty acid (VFA) production was measured. Significant effects of LAB were found at lactate, propionate and butyrate of TMR (p<0.05). On lactate, L. paracasei HNB34 showed significant positive effect (PE) (p<0.05). Significant PE on propionate was detected at L. paracasei HNB31 (p<0.05). On butyrate, HNB34 and L. parabuchneri HNB35 showed significant PE (p<0.05). Significant alterations of nutrients (DM, CP, EE, NDF and ADF) in TMR by LAB were not found. Then, correlation between volatile fatty acid profiles from in vitro rumen fermentation with TMRs and organic acids in used TMR was investigated. Lactate in TMR showed significant positive correlation (PC) with propionate in the rumen fluid (p<0.05). Ruminal propionate was found to be negatively correlated with acetic acid in TMR, significantly (p<0.05). Propionate in TMR showed significant correlation with all ruminal VFAs (p<0.05). All ruminal VFAs, except valerate, showed PC with propionate in TMR. Butyrate in TMR showed significant PC with valerate (p<0.05) and significant negative correlations with acetate and propionate (p<0.05). As a conclusion, propionate and butyrate were detected as influencing factors toward rumen VFAs profiles. More propionate and less butyrate production in TMR could be beneficial in terms of more propionate production in the rumen.