Wet brewery spent grains, locally known as brewery waste (bikanja), is the major by-product of the brewing industry.
Brewery spent grains can be fed to cattle, pigs, poultry, fish, rabbits and goats.
The protein content of spent grain is about 24%, with a dry matter content of about 20%.
The metabolisable energy content is 8.8 to 10 mega joules kilogramme of dry matter.
Feeding wet brewery spent grain to dairy cows is a worthwhile opportunity for urban dairy farmers to offer additional rumen undegradable protein and energy to dairy cows, leading to enhanced milk production.
The procedure to be followed during ensiling of wet brewery grain is:
- Dig a trench/pit to store the spent grain (a volume of two cubic metres can store about 1,500kg of spent grain).
- Place plastic sheets inside the trench silo to prevent loss of material. The total amount of polythene sheets required is about 24sq.m.
- Put the spent grain into the trench silo and spread evenly.
- Continue the process until the pit is full and dome-shaped.
- Apply proper tread pressure and complete sealing to prevent air from entering the silo as this results in damage/rotting of the silage.
- Cover the material with a polythene sheet, then cover with soil of at least 1ft (30cm) thickness to further compress the material.
- Storage time can be improved by storing in a shaded or cool place, and by covering the surface with plastic or some other material that minimises surface spoilage.
- Packing and ensiling characteristics can be improved by blending the wet spent grains prior to ensiling with dry materials such as dry forages, cereal bran or hulls, or with a source of carbohydrates such as molasses or cereal grains.
- Adding carbohydrates accelerates fermentation, releasing more acids and results in stable silage.