The evaluation of sewage sludge as protein source for growing pigs.
The utilization of sewage sludge (28% CP) as a protein source in pig growth diets was investigated. Fish meal was replaced by sewage sludge at three levels (0%, 25% and 50%) on a mass basis in growth diets formulated to be equal in nitrogen, lysine and DE content. The inclusion of sewage sludge significantly decreased the dry matter, nitrogen and energy digestibility of the diets. Nitrogen retention (g per day and % of N intake) was also significantly (P < 0,05) decreased. Nitrogen retention (% of digested N) was, however, not affected. No difference In dry matter intake could be detected between diets. Sewage sludge had a negative effect on live mass gains and feed utilization but not on DE (MJ/kg gain) or digestible N (g/kg gain) utilization. The C + K and P2 back fat measurements on the carcasses of pigs, fed sewage sludge-containing diets, were lower than the measurements of the control diet pigs.