By Dr Jolly Kabirizi and Joshua Kato
Brewers’ spent grain is the major by-product of the brewing industry which remains largely unutilized despite its nutritional quality. It makes up about 85% of the by-products produced in the brewing process. On average, for every 100 litres of beer produced, approximately 20kg of brewery spent grain by-product will also be produced.
The crude protein content of spent grains ranges from 25 to 34%. The fibre content is about 70%. Most of the starch present in regular barley is not present in brewery spent grain since it is removed during the mashing phase of the brewing process. The protein and fibre present in barley is more concentrated in the brewer’s spent grain by-product. The concentration of rumen degradable protein ranges from 28 to 43% with a mean of 35%, indicating that brewer’s spent grains is good sources of rumen undegradable or “by-pass protein.” By-pass’ or ‘Rumen escape’ protein is simply “a protein that is less likely to be digested by rumen microbes”.
Cows need nutrients to produce milk. The bacteria in the rumen provide them with both energy and protein as they digest grass.
Brewer’s spent grains are low in calcium and potassium, similar to other cereal grains. Therefore, more phosphorus is supplied relative to calcium from brewery spent grains. A well-balanced mineral supplement should be supplied when using wet brewery grains in livestock diets to avoid the negative effects of decreased growth performance experienced when this ratio is not properly balanced.
Brewer’s spent grains from sorghum contains high levels of anti-nutrients such as tannins which are very dangerous to animals if consumed in high quantitates (over 10 kgs/day).