Effects of organic acid salts on ruminal biogas production and fermentation kinetics of total mixed rations with different maize silage to concentrate ratios

Abstract

Ruminants are one of the major generators of methane, a greenhouse gas (GHG) with a global warming potential, 25-fold that of carbon dioxide. Methane production by ruminants also reduces the gross feed energy intake utilization by about 2–12%. The present study aimed to test the effects of different levels of a ruminal fermentation modulator (RFM) on in vitro ruminal fermentation and GHG production of five total mixed rations (TMR) with different silage (S) to-concentrate (C) ratios (0S:100C, 25S:75C, 50S:50C, 75S:25C, and 100S:0C). The RFM contained mainly calcium propionate and malate, and monopropylene glycol. The rumen inoculum was collected from a Brown Swiss cow fed a TMR of concentrate and alfalfa hay (1:1 dry matter (DM)) ad libitum. Gas production (GP) measurements were recorded up to 72 h of incubation. There were interactions (P < 0.05) between ration type and RFM dose for GP until 18 h and for partitioning factor and gas yield at 24 h of incubation. The 100S:0C TMR had the highest asymptotic GP (linear and quadratic effects; P < 0.05) compared with other TMR. The 0S:100C TMR had the lowest GP rate (linear effect; P = 0.003). Ration type and RFM inclusion had no effect (P > 0.05) on methane production. The DM digestibility increased (linear effect; P = 0.003) as silage level increased. Overall, increasing silage in the TMR lowered the asymptotic GP and DM digestibility. The asymptotic GP was higher with the addition of the RFM without any effect on fermentation kinetics. These results suggest that the RFM can be used as an environmental cleaner product in animal farming due to its ability to improve ruminal fermentation of feedstuffs and to reduce methane emissions.