Evaluation of a feed additive mixture of pre- and probiotics, enzymes and yeast on in vitro true digestibility of feeds

Abstract Text:

Two in vitro experiments were conducted to determine effects of feeding a proprietary formula containing pre- and probiotics, enzymes and yeast (FORMULA) for 21 d (ADAPTED) and/or incubating with or without FORMULA inclusion (ADDITIVE) on in vitro true digestibility (IVTD) of forage (Experiment 1) and concentrate (Experiment 2) samples.  Two cannulated lactating dairy cows underwent a 21-d adaptation period consisting of daily intra-cannula dosing of either 2 g of FORMULA (ADAPT) or dried distillers grains with solubles (DDGS; NADAPT).  Feed samples (8) representing mature (MGH) and late-bud (LBGH) grass hay, and fresh range grass (FRG; Experiment 1) or corn silage (CS), dry rolled corn (DRC) and DDGS (Experiment 2) were incubated in ANKOM F57 filter bags for 48 h in each of four incubator jars in two replicate incubations (ANKOM DAISY^II) within experiment.  Proportion of non-NDF (100 – NDF) fraction remaining in bags after 48 h represented IVTD.  Rumen fluid from either ADAPT or NADAPT was mixed with buffer at a 1:4 ratio, and filter bags containing 0.5-g samples were suspended in each incubator.  While preparing incubations, FORMULA (ADD) or DDGS (NADD) was added at 0.02 g/incubator.  Therefore, all possible combinations of rumen fluid source and additive inclusion were represented for a 2 X 2 split plot factorial (ADAPTED X ADDITIVE) experiment where ADDITIVE effect was nested within ADAPTED.  Incubating forage samples in ADAPT led to greater (P < 0.05) IVTD in MGH (34.0 vs 37.2%) and FRG (56.0 vs 59.0%) but not (P > 0.05) in LBGH (64.6 vs 64.9%).  Adding FORMULA the day of incubation of forage samples resulted in greater (P < 0.05) IVTD (52.0 vs 53.3%).  When concentrate samples were incubated in ADAPT, IVTD was greater (P < 0.05) regardless of concentrate sample (84.3 vs 87.8%).  In vitro evaluation of effects of long-term ruminal adaptation to FORMULA on digestibility demonstrated potential to improve digestibility of forages and concentrates in vivo.  Specific situations for which digestibility improvements may not occur need to be determined in additional studies.  Future in vitro studies must be conducted using rumen fluid of cattle adapted to FORMULA for at least 21 d. 

Keywords: in vitro digestibility, forage, concentrate