(1) Eight groups of newly weaned lambs were given diets containing 15, 30, 45 or 60% dried poultry waste (DPW) from battery or broiler units in a 4x2 factorial experiment lasting 16 weeks. The Cu content of the diets increased from 12·7 to 35·5 and from 16·1 to 47·1 mg/kg DM with increasing levels of battery and broiler waste, respectively.
(2) As inclusion rates increased, final liver Cu concentrations were 269, 318, 379 and 441 with battery waste and 686, 1009, 877 and 874 mg/kg DM with broiler waste. Total liver Cu accumulation, though higher on broiler than on battery waste, was not proportional to inclusion rate and reached a plateau at the 30% level for both sources.
(3) Mean hepatic Cu retention was constant at 4·8 % of Cu intake with battery waste but decreased from 8·3 to 3·2% as level of broiler waste increased.
(4) Plasma asparate amino transferase (PAAT) levels were highest in groups given broiler waste and final PAAT concentrations were correlated with liver Cu concentration, reaching levels associated with Cu toxicosis in some individuals. The effect of DPW on PAAT was not proportional to inclusion rate.
(5) The factors responsible for the observed variations in liver Cu accumulation between sources and inclusion rates and the possibility of Cu toxicity occurring in sheep given DPW are discussed.