Neeti Lakhani1, Ravi Prakash Pal2 and S N Abedin3
1ICAR- Research Complex for Eastern Region, Patna
2ICAR- CAZRI, Jodhpur
3ICAR- Indian Veterinary Research Institute, Mukteshwar
INTRODUCTION
Silage is a fermented feed produced by preserving high-moisture crops such as grasses, green fodder, and crop residues under anaerobic conditions in a structure called a silo. The process, known as ensiling, involves tightly packing green fodder to exclude air and prevent aerobic spoilage. Under air tight conditions, beneficial microorganisms ferment the fodder, producing organic acids mainly lactic acid along with acetic and formic acids which lower the pH and inhibit the growth of undesirable spoilage organisms, thereby ensuring effective preservation.
SILAGE ADDITIVES
Silage additives are natural or industrial substances applied to forage at the time of ensiling to improve fermentation efficiency and preservation quality. Their primary role is to support rapid lactic acid production, minimize nutrient losses, enhance aerobic stability, and ensure that the silage retains as much nutritional value as possible from the fresh forage.
Silage additives are especially useful under unfavorable ensiling conditions, such as:
- Wet or unpredictable weather
- Low sugar content in forage
- High residual fertilizer levels
- Risk of soil contamination
Even under ideal conditions, the use of additives can further improve silage quality, leading to higher feed intake, better animal performance, and improved farm profitability (Merry, 1993). An ideal silage additive should be safe to use, cost-effective, nutritionally beneficial, and capable of improving animal productivity (Yitbarek and Tamir, 2014).
Types of Silage Additives (Based on Mode of Action)
| Type of Additive | Mode of Action | Examples |
| Fermentation Stimulants | Promote rapid dominance of homofermentative lactic acid bacteria, resulting in faster pH decline and stable fermentation | Microbial inoculants: Lactic acid–producing bacteria Enzymes: Cellulases, amylases, pectinases, proteases Sugars: Molasses, glucose, sucrose, citrus pulp |
| Fermentation Inhibitors | Increase silage acidity directly, suppress undesirable microorganisms, and limit excessive fermentation | Aerobic preservatives: Acetic acid, propionic acid, sorbic acid, caproic acid Anaerobic acids: Formic acid, mineral acids, lactic acid, benzoic acid. |
| Nutrient Additives | Supply additional nutrients or nitrogen and inhibit spoilage microorganisms | Non-protein nitrogen sources: Urea, ammonia |
EVALUATION OF SILAGE ADDITIVES
1. FITNESS VALUE – Fitness value is used to assess the effect of different silage additives on silage quality as compared to control (silage with no additives). Different silage additives were selected by screening them for desirable characteristics in the laboratory and then small scale; full term ensilage experiments were performed. The main disadvantage of these experiments was that they are labor intensive and only a few additives can be tested in each experiment. To avoid this, the silage fermentation with additives was determined using a fitness value relative to control silage (without any additives).
The best samples were selected with the help of fitness equation on the basis of following parameters:
- Minimum dry matter loss
- Low Ammonia Nitrogen
- Low pH and higher LA content
Where wtg is weighting, ctrl is control silage, lac is lactate content, and aa is amino acid content.
Changes in these three parameters were expressed as ratios relative to the control silage. The fitness parameters have sufficient interactions in between; lactic acid level is closely related to the decrease in pH, influencing the extent of protein breakdown. Lactate accumulation can be measured accurately and the parameter shows greatest change. Therefore, the weighting given to the lactate level was 4, the weighting given to the decrease in pH was 2.5 and weighting given to the free amino acid level was 3.5.
MODIFIED FITNESS VALUE – The fitness value was modified to remove the cost parameter and weighting was adjusted accordingly for different parameters.
where wtg is weighting and ctrl is control. The weighting for different parameters is pH: 4; DM loss: 3 and Ammonia–N: 3.
CONCLUSION:
Silage additives are valuable tools for improving the efficiency of the ensiling process by promoting desirable fermentation, minimizing nutrient losses, and enhancing aerobic stability. Their judicious use, particularly under challenging ensiling conditions, helps produce high-quality silage that supports higher feed intake, better nutrient utilization, and improved livestock productivity.