Document Type : Research Paper

Authors

• Parvaneh Hashemi ¹
• Leila Taherabadi ²
• Farokh Kafilzadeh ³

¹ Department of Animal Science, Faculty of Agriculture, Razi University, Kermanshah, Iran. E-mail: hashemi.pa@razi.ac.ir

² Corresponding Author, Department of Animal Science, Faculty of Agriculture, Razi University, Kermanshah, Iran. E-mail: taherabadi.le@razi.ac.ir

³ Department of Animal Science, Faculty of Agriculture, Razi University, Kermanshah, Iran. E-mail: Kafilzadeh@razi.ac.ir

Abstract

Objective: Ensilage is one of the methods of preserving forage plants for livestock feeding. The use of carbohydrate sources in  silage preparation can improve the quality of anaerobic fermentation by increasing the concentration of lactic acid. Aerobic stability of silage after exposure to air is one of the quality parameters of silages. Heterofermentative lactic acid bacteria are among the additives that have been used to improve the aerobic stability of silages. However, there is no information on the use of the Lactobacillus fermentum on the aerobic stability of Napier grass silage with or without the use of carbohydrate sources. Therefore, this research was conducted to study the effect of Lactobacillus fermentum 92069 and molasses on fermentation properties, aerobic stability and in vitro digestibility of Napier grass silage as a new forage source (introduced for the first time) in the country.
Methods: Napier grass was cultivated in the research farm of the Faculty of Agriculture, Razi University on May 2021. To prepare silage, the forage was harvested, chopped and treated with 0, 3 or 6 percent molasses with or without 0, 1× 10⁶ cfu or 2×10⁶ cfu of Lactobacillus Fermentum 92069 per gram of fresh forage and then  ensiled in laboratory silos with four replicates. After 90 days of ensiling, the chemical composition and fermentation products of the silages such as lactic acid, butyric acid, acetic acid, ammonia nitrogen and in vitro digestibility were determined. The fungal population of the silages including yeast and mold was also determined. During the aerobic fermentation process, aerobic stability of the silages and changes in pH and the population of fungal in the silages were also measured.
Results: Increasing the level of molasses was associated with an increase in dry matter and soluble carbohydrates in silage. The lowest pH values ​​ (3.90 to 3.97) with higher production of lactic acid concentration (47.9 to 53.3 g/kg dry matter) were observed in silages containing the high level of molasses with or without bacterial inoculant. The addition of Lactobacillus fermentum increased acetic acid production, but had no effect on the aerobic stability of the silage. There was no difference in the fungi population of silages among treatments. Dry matter and organic matter digestibility, as well as metabolizable energy, were higher in silages containing molasses with or without bacterial inoculants. 
Conclusion: The results of the present study showed that Napier grass silage without additives was of good quality. However, the use of molasses resulted in improved anaerobic fermentation and digestibility. The aerobic stability of Napier grass silages in spite of an increase in acetic acid was not affected by the addition of the Lactobacillus fermentum up to 2 ×10⁶ cfu/ g fresh forage.

Keywords

• Aerobic stability
• Bacterial additive
• Fermentation quality
• Napier grass
• Silage