Livestock (cattle, sheep, rabbits, goats and pigs) provide: food, cash income, insurance and savings, draft power, energy and social capital, among other things. Households that include livestock in their enterprise mix tend to perform better socially and economically. Improved livestock production is a function of genetic and several management factors but poor nutritional status is considered the most challenging constraint. This is due to inadequate (quality and quantity) feed availability and unimproved practices used by farmers in the utilization of available local feed resources. The major part of the feed supplied thus goes just to satisfy maintenance requirements. Poor animal nutrition leads to high susceptibility to diseases and parasites. These cause exceedingly high losses in animal productivity. New feeds and feed management technologies offer many opportunities for innovations in animal feed and nutrition.
Agro-industrial by-products are mostly derived from agricultural processing industries such as cereal grain milling, oilseed extraction, brewery, malt production, fruit and vegetable processing. These represent a vast potential source of animal feed, which are currently not fully exploited. Although the nutritional value of most agro-industrial by-products is widely known, their utilisation is hindered by several factors such as poor control of processing techniques, fluctuating supply, limited access to available suppliers, poor marketing channels, difficulty in transferring existing technologies and lack of legislation on their trade and use.
Agro-industrial by- products have several advantages, such as: (a) relatively cheap or no cost, (b) feed shortage during periods of scarcity and uneven distribution, (c) they do not compete for human food resources, (d) they have comparable values to the crop they are derived.
Sustainability: Recovery and Reuse of Brewing-Derived By-Products
Among all industrial processes, the brewing process has one of the greatest impacts on the environment due to the huge amount of waste such as: brewer’s spent grain and brewery spent yeast solution, also known as residual yeast. Landfill for solid wastes and disposal via sewage for liquid wastes are unsustainable and expensive options. For this reason, most brewing industries have adopted disposal options for their waste streams that are within their financial and geographical reach, often favouring their use as animal feed. Industries are interested in new solutions, and they are been adopting technological advances to reduce the amount of waste produced and to generate useful materials from brewing-derived by-products.
Brewer’s Spent Grains (Spent Grains)
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.
Nutritional Value of Spent Grains
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).
Preserving and Storing Brewer’s Spent Grains
The high moisture content of brewery spent grains (80 to 85%) together with polysackcharide and protein makes it particularly susceptible to microbial growth and subsequent spoilage in a short period of time (7 to 10 days). Where storage may be required for downstream processing of brewery spent grains, then deterioration through microbial activity is perceived as a potential problem, unless the brewery spent grains can be stabilized post-production. Wet brewery grains can be preserved through: (a) silage making and; (b) dehydration/drying.