Abstract
INTRODUCTION: Microbial fermentation effectively addresses the issue of rice bran rancidity also enhances its nutritional value as animal feed. This study aimed to explore the effects of dietary microbially fermented rice bran feed (MFRB) supplementation on lactation performance, nutrient digestibility, plasma biochemical indicators, rumen fermentation parameters and microbiota of lactating dairy cows. METHODS: Thirty Holstein cows with similar milk yield (38.1 ± 1.0 kg/d), days in milk (282.8 ± 2.2 d) and parity (2.37 ± 0.1) were randomized into two groups: (1) CON (Control group, fed a basal diet); (2) MFRB (2.6% of pelleted corn was replaced with MFRB). The experiment consisted of a 7-day adaptation period followed by a 30-day experimental period. RESULTS: As a result, despite a lower dry matter intake, dairy cows fed MFRB achieved significantly higher milk yield, feed efficiency, milk fat yield, milk protein percentage, fat-corrected milk, and energy-corrected milk (P < 0.05). Apparent neutral detergent fiber digestibility was also significantly increased (P < 0.05), with trends toward increased dry matter and crude protein digestibility (0.05 < P < 0.1). Rumen fermentation shifted to a propionate-dominant pattern, with significantly higher levels of propionate, ammonia-N, microbial protein, and Prevotella abundance (P < 0.05). plasma triglycerides and glucose levels were increased, while alanine aminotransferase and aspartate aminotransferase activities decreased (P < 0.05). DISCUSSION: In conclusion, these integrated changes demonstrate that MFRB enhanced rumen fermentation performance, nutrient utilization, and metabolic health, ultimately optimizing lactational performance.