Pelleting of compounds with a high proportion of by-products [cattle compounds]

The aim of the experiments was to find methods for packaging cattle compounds with a high proportion of by-products into pellets with suitable physical properties - at the lowest possible costs. For the experiments we used compounds with a high proportion of beet molasses, alkali-treated straw pellets and animal fat together with ground barley and cotton-seed meal. In addition, the effect of several other by-products and other cattle feed ingredients was examined: Dried beet pulp, wheat brans, grass- and lucerne pellets, barley malt culms, dried citrus pulp and various oilseed meals and cakes. The experiments were carried out on a semi-technical scale at a pilot plant at Biotechnical Institute. The main technical variables examined were the effect of steam addition and fineness of meal for pressing in combination with varying content of molasses and cold long time conditioning between addition of molasses and pelleting. The experimental results are accumulated by multiple regression into equations by which may be predicted the effect of changes on the technical variables. The production rate of pellets related to the consumption of electric power was at a high level during the main part of the experiments. Cold long-term conditioning between addition of molasses and pelleting showed a positive effect on both specific capacity (kg/kWh) and on reduction of the formation of fines - at least in compounds with a high proportion of fibrous by-products, such as alkali-treated straw. As expected, fine grinding resulted in a low formation of fines. However, fine grinding may consume unnecessary energy. In addition, it thoroughly decreases the physical structure of the final productswhich is demanded by many dairy farmers. The pelleting properties of compounds containing dried beet pulp, barley malt culms and dried citrus were better than for ground barley. Lower capacity and higher formation of fines than for grain were recorded for straw pellets, grass pellets and coconut cakes, lucerne pellets and wheat brans