Abstract
The objective of this study was to determine the effects Saccharomyces cerevisiae fermentation product (SCFP, NaturSafe®, DiamondV) on ruminal fermentation and site and extent of feed digestion in beef heifers. Five ruminally and duodenally cannulated beef heifers (BW=561 ± 11.7 kg) were used in a 5 × 5 Latin square design with 28-d periods (21-d adaption and 7-d data collection). Five treatments were: 1) control diet (10% barley silage and 90% barley concentrate, DM basis); 2) control diet supplemented with antibiotics (ANT; 330 mg/d monensin and 110 mg/d tylosin); 3) ruminal (top dress) delivery of SCFP (rSCFP; 18 g/d SCFP); 4) duodenal delivery of SCFP (dSCFP; 18 g/d SCFP); and 5) combination of rSCFP and dSCFP (rdSCFP; 18 g/d rSCFP and 18 g/d dSCFP). Data were analysed using MIXED procedure of SAS with model including fixed effect of treatment and random effects of heifer and period. Intake of DM tended (P<0.10) to be greater with rdSCFP than control (13.0 vs. 12.2 kg/d). Heifers fed rSCFP vs. control diet showed greater (P<0.05) minimum ruminal pH (5.30 vs. 5.02), shorter (P<0.10) duration of ruminal pH (5.6 vs. 11.6 h/d) and greater (P<0.10) acetate proportion (51.8% vs. 47.2%). Truly fermented OM was greater (P<0.03) with rdSCFP (7.2 kg/d) than other treatments (5.9 kg/d). Treatment with rSCFP and rdSCFP vs. control showed greater(P<0.05) ruminal digestibility of OM (63.8 vs. 53.1%) and NDF (52.7 vs. 41.3%). Total tract digestibility of OM (P<0.07) and NDF (P<0.01) was greater with rSCFP (80.7 and 67.7%) and rdSCFP (81.7 and 66.1%) than control (77.2 and 56.2%) and ANT (77.4 and 55.1%). These results demonstrate that supplementation of SCFP improved ruminal pH status and ruminal digestibility of OM and NDF, with limited effects on nutrient digestibility in the intestine and suggest the SCFP could serve as natural alternative for antibiotics for beef cattle.