Copper levels in liver and brain of dead lambs in relation to breed, age at death and cause of death

Abstract

Copper concentrations were determined in the dry matter of samples of liver and brain taken from the majority of lambs which had died in a grassland flock of sheep between birth and approximately 5 months of age. For liver copper, the data relate to 537 samples collected over a 6-year-period, and for brain, to 453 samples for the last 5 of these years. The flock comprised the Scottish Blackface, the Cheviot and the Welsh Mountain breeds and the crosses among these breeds. Blackface sheep had the lowest and Welsh the highest concentrations of copper in both liver and brain, the difference being approximately 80 parts/million for liver and 3 parts/million for brain. Among the crossbreds, only the Blackface-Cheviot cross had levels of copper significantly above midparental levels. Age at death was grouped into 7 classes—from lambs that were stillborn to those dying after weaning at 15 weeks of age. Concentrations of copper in the liver declined consistently and markedly with age at death by approximately 135 parts/million over this period. For copper in the brain there was no equivalent change with age. Both the age and breed differences remained unchanged when account was taken in the statistical analysis of possible correlated effects through associations between cause of death and copper concentration. Factors recorded on a post mortem examination as contributing to death were grouped into 17 causal categories. Only two of these categories, both fairly vague and unrelated to specific diseases, appeared to be significantly associated with a different level of copper in the liver when the condition was recorded as present than when absent. For brain copper levels, only one of the 17 conditions, cerebrocortical necrosis (polio-encephalomalacia), had a noticeably lower concentration (−3·04±1·58 parts/million) in the 4 lambs where it was found than in dead lambs without this condition.