Effects of Synbiotics on Rumen Fermentation

A metabolism study was conducted to evaluate the effects of synbiotics on ruminal fermentation in steers fed high grain diets. Three synbiotics (hydrolyzed yeast/live yeast (LYHY)), Celmanax (prebiotics)/live yeast (CLY) and Synerall (a commercial pre- and probiotics product, SYN) were selected for a rumen fermentation study. Prior to this, seven different synbiotics were evaluated using the batch culture technique to measure in vitro gas production, DM disappearance and VFA concentrations. There was no difference in asymptotic gas volume and VFA concentrations but LYHY, SYN and CLY had numerically higher DM disappearance values compared with the other treatments. For the ruminal fermentation study, treatments consisted of these three synbiotics and a control. Four rumen cannulated steers were randomly assigned to the following 4 dietary treatments: 1) Control – high grain finishing diet, 2) Control + CLY, 3) Control + LYHY, 4) Control + SYN. Cannulated steers had ad libitum access to the dietary treatments. Steers were housed individually and fed once daily in a 4 × 4 Latin Square design with 4 periods of 21 days. In each period, the steers were adapted to the diet for 14 days and ruminal fluid samples were collected from day 15 to 21 to determine pH, lactic acid and volatile fatty acid (VFA) concentrations. Addition of synbiotics had no effect (P > 0.05) on ruminal pH although values for the synbiotics treatments were numerically higher compared with the control treatment. For beef cattle in the feedlot, higher pH is desirable to minimize incidences of acidosis. Typically, ruminal pH of 5.6 is regarded as the reference point for chronic acidosis. Ruminal pH value for the control treatment was below this reference point (5.56) compared with higher pH values (5.62) for the synbiotics treatments. With the exception of valeric and isovaleric acid concentrations, no difference were noted in total and individual VFA concentrations. Inclusion of synbiotics resulted in greater (P = 0.019) acetate-to-propionate ratio compared with the control (1.41 vs. 1.23). The LYHY treatment had the lowest numerical acid load (total VFA + lactic acid) compared with the other treatments. Considering that LYHY had the highest numerical in vitro DM digestibility, a lower acid load could be interpreted as LYHY partitioning more energy into microbial mass which will benefit the animals. The LYHY treatment was selected based on lower acid load compared with the other treatments and is currently being used in a feedlot finishing study.