Classification of agro-industrial byproducts
Based on their nutrient content agro-industrial byproducts can be divided into:
1. Feed low in fiber and low in protein. These are usually byproducts of food processing for human consumption and include products such as molasses and citrus pulps and potato peels.
2. Feeds low in fiber and high in protein. These include mainly oilseed meals.
3. Feeds high in fiber and low in nitrogen. These include milling byproducts such as oat hulls and pea hulls.
4. Feeds high in fiber and high in protein content. These include distillers’ and brewers’ grains and several oilseed meals.
Some agro-industrial byproducts such as feed grade cereal and legume seeds do not fit within any of the above groups. Byproducts, which result from cleaning of cereal grains and oilseed usually, contain high proportions of dust, chaff and weed seeds. Consequently they are high in ash and fibre contents. They also contain moderate levels of starch or fat depending of the source of the parent material. Feed grade peas and beans are high in starch and protein but low in fiber. Due to the great differences in chemical composition, the energy content of unconventional feed varies considerably among unconventional feeds. Information pertinent to a few of the common unconventional agro-industrial byproducts has been discussed hereafter, though not strictly in order of their utilization.
Attempts have been made to replace the high quality oilseed meal such as soybean meal or groundnut cake with other medium/low quality oilseed meals to reduce the cost of feeding. In India, exhaustive efforts have been made to evaluate the feeding value of various such by-products. A few important and common unconventional agro- industrial byproducts along with their availability, nutritive value, levels of incorporation and anti-nutritional factors have been presented in the Table 7b.2. The approach, motivated essentially by the scarcity of the feedstuffs, is commendable since it generates efficiency in feeding and management, minimum loss of potentially useful feedstuffs and economic production. The potential availability of byproducts is calculated from production or utilization data of the primary commodity. Quantities theoretically available may differ greatly from those actually usable for animal feeding, owing to alternative uses and constraints such as irregular supply, and minor or excessive volumes, high transportation costs relative to product value, rapid spoilage and lack of preservation facilities. Although it is proved that complete replacement of the protein of high quality meals with other protein sources in the ration of dairy animals is not possible, yet partial replacement is possible. Some of the unconventional agro-industrial byproducts which can be exploited are discussed hereunder.