Tannins in sal seed ( Shorea robusta) and sal seed meal limit their utilization as livestock feeds

Abstract

The availability of sal seed meal (SSM), a by-product of the sal seed fat industry in India, is of the order of 5 million tons per annum. Based on results of numerous feeding trials, recommendations have been made for its extensive utilization as an ingredient of concentrate feeds for cattle, pigs and poultry. The dry matter of sal seeds contains 10–16% fat, 6–9% crude protein and 7–12% tannins. Fat extraction lowers the ether extract content of SSM to 4–8%. The nitrogen-free extract content of the meal, though comparable to that of maize grain, includes a high proportion of tannins and lignin. As a protein-low material it has no value as a protein supplement, and the presence of tannins adversely affects the utilization of other feed proteins. Attempts to remove tannins from SSM are neither effective nor practicable. Critical evaluation of the results of feeding experiments shows that the available energy in the meal, represented by total digestible nutrients, is comparable to that in poor quality roughages. The invariable absence of a negative control in the experimental designs has led to incongruous interpretation of results, which mask the harmful effects of SSM as a feed ingredient. It is concluded that in the interest of welfare of the livestock industry, the use of SSM in livestock rations should be discontinued.