Variation in the concentration of copper in the blood plasma of Finnish Landrace and Merino sheep and their crosses with reference to reproductive performance and age

Abstract

SUMMARYConcentrations of copper in blood plasma were determined in January and in February 1971 and in February and March 1972 in a grassland flock of sheep comprising the Finnish Landrace and (Tasmanian) Merino breeds and their reciprocal crosses. Numbers of animals ranged from 30 to 100. The unadjusted mean copper levels of the flock varied from 63 to 81 μg/100 ml. The Finnish Landrace had a markedly lower plasma copper concentration than did the Merino, the mean difference after adjustment for other factors varied from 16 to 54 μg/100 ml. First crosses had levels halfway between those of the parental breeds. Copper concentration fell in the 4-week period between February and March 1972 when most of the ewes were pregnant. This fall was greatest for the Finnish Landrace which started with the lowest level and least for the Merino.Neither the breed differences in the change in level nor the actual concentration appeared to be related to the number of lambs (0 to 4) carried by the ewes. Variation in copper level associated with the age of ewe, significant for the two bleedings in 1972, was largely attributable to the higher level among the youngest age class, approximately 10 months old when bled. The stage of pregnancy at the time of blood sampling, as reflected by date of lambing, did not significantly affect plasma copper concentration in this flock.