Effects of Saccharomyces cerevisiae fermentation-derived postbiotic on methane production and plasma metabolome of fattening Holstein steers fed a high-grain diet.

This study assessed the effects of feeding Saccharomyces cerevisiae fermentation-derived postbiotic (SCFP) on methane production and plasma metabolome of Holstein steers on a finishing diet. Twelve Holstein steers (n = 6 per treatment) were enrolled in a randomized complete block design and blocked into 3 groups based on their initial body weight (BW: 294 ± 12.7 kg). Steers within each block were randomly assigned to 2 treatments: CON (Control, basal diet only), or SCFP (basal diet, top dressed with 12 g/d SCFP, NaturSafe, Diamond V, Cedar Rapids, IA). The diet consisted of 20% corn silage and 80% concentrate on a DM basis. After 29 d, blood samples and the BW of each animal were collected, and animals were transferred to the headbox-style respiratory chamber. Following a 24-h adaptation, respiratory data were recorded for 48 h. The GLIMMIX procedure of SAS 9.4 and Metaboanalyst 6.0 were used to conduct data analyses. Overall dry matter intake (DMI) was greater (P = 0.05) in steers fed SCFP. Compared to the control, SCFP steers had greater DMI both during the 29-d feeding period (7.43 vs. 7.08 kg/d) and during the respiratory measurement (6.58 vs. 5.45 kg/d). Feeding SCFP did not affect total methane production per day (P = 0.91), per kg of metabolic BW (P = 0.94), or per kg of DMI (P = 0.46). Similarly, O2 consumption and CO2 production were unaffected (P ≥ 0.34 and 0.30, respectively). Supplementation of SCFP enriched plasma pathways of 'Ubiquinone and other terpenoid-quinone biosynthesis' (P = 0.02) and 'Phenylalanine, tyrosine, and tryptophan biosynthesis' (P = 0.03). In summary, SCFP improved intake and enriched metabolic pathways associated with protein and energy metabolism and may support antioxidant capacity without affecting methane emissions in steers fed high-concentrate diets.