Mitragyna speciosa Korth Leaf Pellet Supplementation on Feed Intake, Nutrient Digestibility, Rumen Fermentation, Microbial Protein Synthesis and Protozoal Population in Thai Native Beef Cattle

SIMPLE SUMMARY: The leaves of Mitragyna speciosa Korth contain phytogenic compounds, including total phenolics, flavonoids and mitragynine. The objective of this study was to evaluate the effects of Mitragyna speciosa Korth leaf pellets (MSLP) on feed intake and nutrient digestibility in Thai native beef cattle. The findings suggest that supplementation of MSLP at 10–30 g/hd/d significantly increased nutrient digestibility, VFA concentration, and especially propionic acid and microbial protein synthesis while decreasing protozoal populations and estimated CH(4) production. ABSTRACT: This experiment evaluated the use of Mitragyna speciosa Korth leaf pellets (MSLP) on feed intake and nutrient digestibility in Thai native beef cattle. Four Thai native beef cattle steers were randomly assigned according to a 4 × 4 Latin square design to receive four dietary treatments. The treatments were as follows: control (no supplementation), MSLP supplement at 10 g/hd/d, MSLP supplement at 20 g/hd/d and MSLP supplement at 30 g/hd/d, respectively. All animals were fed a concentrate mixture at 0.5% body weight, while urea lime-treated rice straws were fed ad libitum. Findings revealed that feed intakes were increased by MSLP, which also significantly increased the digestibility of dry matter (DM), organic matter (OM) and neutral detergent fiber (NDF). Ruminal total volatile fatty acid (TVFA) concentration and propionate (C(3)) proportion were increased (p < 0.05) with MSLP supplementation, whereas ruminal ammonia-N (NH(3)-N), plasma urea nitrogen (PUN), acetate (C(2)), C(2):C(3) ratio and estimated methane (CH(4)) production decreased (p < 0.05). Total bacterial, Fibrobacter succinogenes and Ruminococus flavefaciens populations increased (p < 0.05) at high levels of MSLP supplementation, while protozoal populations and methanogenic archaea reduced (p < 0.05). Supplementation of MSLP also increased the efficiency of microbial nitrogen protein synthesis. Supplementing beef cattle with MSLP 10–30 g/hd/d significantly increased rumen fermentation end products and nutrient digestibility by mitigating protozoal populations and estimated CH(4) production.