TECHNOLOGY FEED & ADDITIVE MAGAZINE September 2025 71 BRIX CHANGES DURING NORMAL FERMENTATION Before ensiling, high Brix values indicate plentiful fermentable sugar. As fermentation progresses, sugars are consumed and Brix declines. A rapid early drop often signals active LAB growth, particularly in inoculated silage (Table 2). WHEN BRIX CAN MISLEAD: POORLY PRESERVED SILAGE A falling Brix reading is only a sign of good fermentation when the silage is well compacted, sealed promptly, and kept airtight. If oxygen enters, due to poor packing, delayed covering, or damaged plastic, aerobic microorganisms (yeasts, molds, aerobic bacteria) can dominate. These organisms also consume sugars, but instead of producing lactic acid, they generate heat, carbon dioxide, and ethanol. As a result, pH stays high, fermentation fails, and nutrient losses mount. Early sugar depletion can look similar in good and poor silage, but the cause is different. Without a rapid pH drop below 4.2, protein breakdown accelerates, heating develops (>35–40 °C), and molds appear quickly (Table 3). SAMPLING & MEASUREMENT PROTOCOL To get accurate readings: • Collect representative samples across the field, avoiding extreme patches. • For fresh grass, freeze for about 6 h, then thaw to release juice. Early-cut ryegrass Mid-season ryegrass Alfalfa Maize (corn) whole plant Wet, overly mature grass 12 – 18 8 – 12 6 – 10 8 – 14 3 – 6 Excellent Good Moderate Good–Excellent Poor Forage Type Typical Brix (%) Fresh-Cut Fermentation Potential Notes Table 1. Typical Brix ranges in fresh forage High sugar content, very suitable for rapid fermentation. Adequate for inoculant use; rapid wilting preserves sugars. Lower sugars, higher buffering capacity; benefits greatly from inoculants. Starch adds additional fermentable energy. Risk of slow fermentation and spoilage may require molasses addition. Time After Ensiling Inoculated Silage Brix (%) Untreated Silage Brix (%) Interpretation Table 2. How Brix levels change during fermentation with and without inoculants Both have excellent fermentation potential. Inoculated batch showing faster sugar consumption, suggesting more active fermentation. Greater decline in inoculated batch likely linked to faster lactic acid production. Both nearing stable phase; differences reflect inoculant activity. Pre-ensiling (0 h) 24 h 48 h 7 days 12 8 5 4 12 10 8 6
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