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 two 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 days, blood samples and the BW of each animal were collected, and animals were transferred to the headbox style respiratory chamber. Following a 24-hour adaptation, respiratory data were recorded for 48 hours. 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-day feeding period (7.42 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 body weight (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.