Lactobacillus plantarum as feed additive to improvement in vitro ruminal biofermentation and digestibility of some tropical tree leaves

Aim: This study was performed to investigate the effects of Lactobacillus plantarum (LP) on the in vitro gas production (GP) kinetics and ruminal fermentation parameter of three species of tropical forage Ziziphus mauritiana, Acacia victoriae and Moringa oleifera. Methods and Results: Treatments were (i) Z. mauritiana (Z) without LP (−ZLP), (ii) Z. mauritiana (Z) with LP (+ZLP), (iii) A. victoriae (A) without LP (−ALP), (4) A. victoriae (A) with LP (+ALP), (5) M. oleifera (M) without LP (−MLP) and (6) M. oleifera (M) with LP (+MLP). The LP was used at 0·5 Mcfarland (1·5 × 10⁸ colony-forming unit per millilitre (CFU per ml)). Kinetic of GP (GP from the fermentable fraction [b], GP rate [c] and lag phase [L]) and GP were affected (P < 0·05) by plant species and LP. The highest value of b, c and GP were observed in +MLP treatment compared with other treatments. The lowest value of L was observed for the +ZLP treatment compared with other treatments. The GP and fermentation parameter included organic matter digestibility (OMD), metabolizable energy (ME) content, microbial CP (MCP) and truly degraded substrate (TDS) were affected by plant species and LP supplementation. The highest OMD, ME, TDS and MCP values were observed in +MLP treatment. At different incubation times, the highest amount of ammonia-N was observed in treatment +MLP compared with other treatments. Under the influence of experimental treatments (effect of plant species and LP), the highest concentrations of total volatile fatty acids, acetate and acetate to propionate ratio were observed in treatments +MLP, +ALP and +ALP, respectively. Concentrations of propionate, iso-butyrate, n-valerate and iso-valerate were affected by plant species, and the highest levels were observed in −ZLP, +MLP, −MLP and +MLP tretments, respectively. Conclusions: The use of LP as a microbial additive had a positive effect on the in vitro digestibility and ruminal fermentation of tannins-rich tropical plants. Results suggest that dietary LP inclusion could be an option to improve ruminant energy utilization efficiency of tannins-rich tropical plants. Significance and Impact of the Study: Regardless the effect of the forage species, the use of LP as a microbial additive improved GP and kinetics and also increased OMD, TDS, MCP and enhanced the total in vitro ruminal VFAs production.