Composting as a means of disposal of sheep mortalities

Four studies explored the feasibility of year-round composting of lamb and mature sheep mortalities within the arid climate of the Canadian prairies. In all studies, a ratio of 2:1:1 (manure : mortalities : chopped straw) was maintained, although depth of the mortality layer within the bin, number o f layers of mortalities per bin, age of animal (lamb or mature sheep) and t ime of year (summer or winter) were varied. Composting neonatal lambs in th e spring/summer was successful whether a single layer (n=15 lambs, weight 9 9.7 kg) or two, separated layers of mortalities (n=41 lambs, weight 198 kg) were added to a 2.4 m(3) open bin. Residual bone, wool and soft tissues we re negligible after the lamb compost had completed one heating cycle. In co ntrast, composting mature sheep in the fall/winter was more difficult due t o: (1) over wet manure (31% dry matter) resulting in continuous anaerobic d ecomposition of carcasses; (2) fat/grease accumulation when composting a la yer of carcasses 71 cm in depth (weight of sheep 1020 kg). For mature sheep mortalities, 2 heating cycles were required to eliminate soft tissues and wool. As compost in all studies heated in excess of 60 degrees C in the pri mary and/or secondary bin, bacterial isolates taken after the compost compl eted the secondary heating cycle were all innocuous species. Provided that compost is protected from excessive moisture and compost is aerated by turn ing into a secondary bin, a 2:1:1 (manure:mortalities:straw) ratio allowed for year-round composting of lamb and mature sheep mortalities.