Comparison of dried and liquid direct-fed microbial (MYLO) on liveweight gain and carcass performance in feedlot...

Direct-fed microbials (DFMs) are increasingly being used as supplements to support productivity and gut health in ruminants. One supplement available commercially is MYLO^® (Terragen, Coolum Beach, Australia), a liquid DFM supplement ('Liquid') (Terragen, Coolum Beach, Australia), that contains three bioactive microbial strains: Lacticaseibacillus paracasei, Lentilactobacillus buchneri, and Lacticaseibacillus casei. To determine equivalence of the commercially-available Liquid MYLO DFM supplement ('Liquid') to a new dried MYLO formulation, a study was undertaken using purebred Angus steers (n = 264) fed a high-grain diet supplemented with 1 × 10¹⁰ Colony Forming Units (CFU/hd/day, X1 MYLO), 2 × 10¹⁰ CFU/hd/day (X2 MYLO), or liquid MYLO (Liquid) compared to a control diet containing no DFM (Control). Steers were fed a total mixed ration (TMR) with increasing grain inclusion (starter ration, 58% grain; intermediate, 68% grain) with all steers on finisher ration (78% grain) by day 21. Steers were grain fed for 106 days prior to slaughter at a commercial processing plant. Steers were allocated to pens (22 head/pen, 3 pens/treatment) using a randomised block design, and production, health, and carcass data were analysed. Data were analysed using generalised mixed linear models with pen as the experimental unit. Liveweight gain, feed efficiency, health and carcass parameters were compared between MYLO groups and an untreated control cohort. Results showed that steers supplemented with X2 MYLO dried formulation showed a trend towards an increased liveweight with significance at 82 and 106 DOF (P = 0.014 and 0.032, respectively). No difference was observed in overall Average Daily Gain (ADG) (P = 0.997) or Gain to Feed Ratio (G : F) (P = 0.760) between treatments despite X2 MYLO trended towards greatest G : F ratios (Control G : F, 0.160; X2 MYLO, 0.163; liquid MYLO, 0.165). Hot standard carcass weight (HSCW) trended higher in X2 MYLO steers, resulting in an increased carcass value of $41 Australian Dollars (AUD)/head. Longissimus dorsi eye muscle area, as measured between the 12-13^th rib, was increased in X2 and Liquid MYLO DFM groups compared to controls (P = 0.037 and 0.008 respectively). Overall, the Lactobacillaceae-based X2 MYLO dried supplement showed increases in liveweight gain, carcass weight, and muscle area compared to low-dose dried or liquid formulations.