Effect of sodium formate and lactic acid bacteria treated rye silage on methane yield and energy balance in Hanwoo steers

This study was performed to evaluate the effects of rye silage treated with sodium formate (Na-Fa) and lactic acid bacteria (LAB) inoculants on the ruminal fermentation characteristics, methane yield and energy balance in Hanwoo steers. Forage rye was harvested in May 2019 and ensiled without additives (control) or with either a LAB inoculant or Na-Fa. The LAB (<i>Lactobacillus plantarum</i>) were inoculated at 1.5 × 10¹⁰ CFU/g fresh matter, and the inoculant was sprayed onto the forage rye during wrapping at a rate of 4 L/ton of fresh rye forage. Sixteen percent of the Na-Fa solution was sprayed at a rate of approximately 6.6 L/ton. Hanwoo steers (body weight 275 ± 8.4 kg (<i>n</i> = 3, group 1); average body weight 360 ± 32.1 kg (<i>n</i> = 3, group 2)) were allocated into two pens equipped with individual feeding gates and used in duplicated 3 × 3 Latin square design. The experimental diet was fed twice daily (09:00 and 18:00) during the experimental period. Each period comprised 10 days for adaptation to the pen and 9 days for measurements in a direct respiratory chamber. The body weights of the steers were measured at the beginning and at the end of the experiment. Feces and urine were collected for 5 days after 1 day of adaptation to the chamber, methane production was measured for 2 days, and ruminal fluid was collected on the final day. In the LAB group, the ratio of acetic acid in the rumen fluid was significantly lower (<i>p</i> = 0.044) and the ratio of propionic acid in the rumen fluid was significantly higher (<i>p</i> = 0.017). Methane production per DDMI of the Na-FA treatment group was lower than that of the other groups (<i>p</i> = 0.052), and methane production per DNDFI of the LAB treatment group was higher than that of the other groups (<i>p</i> = 0.056). The use of an acid-based additive in silage production has a positive effect on net energy and has the potential to reduce enteric methane emissions in ruminants.