Genotype as a source of variation in selenium concentration and glutathione peroxidase activity of whole blood from grazing sheep and cattle

Abstract

Selenium and glutathione peroxidase activities in whole blood were measured in a herd of 213 cattle containing Bos indicus and Bos taurus heifers and their crosses grazed at Rockhampton, Qld, and in a herd of 125 pregnant cows containing Hereford, Friesian x Hereford, Brahman x Hereford, and Simmental x Hereford genotypes, which was grazed at Grafton, N.S.W. Similar measurements were made on a flock of 18 Suffolk and 24 Cheviot lambs, and on a flock of 358 ram and ewe lambs of the Dorset Horn, Merino and Corriedale breeds and their reciprocal crosses. All lambs grazed at Armidale, N.S.W. Genotype was a significant source of variation in blood composition in all herds and flocks; there were differences between Bos indicus and Bos taurus cattle, between Bus indicus x Bos taurus cattle and Bos taurus cattle, between breeds of sheep and between sire groups within breeds. Heterosis was identified in blood selenium concentrations and glutathione peroxidase activities of blood from Dorset-Merino lambs. Other significant sources of variation were nematode and tick infestation in cattle and single versus twin births in sheep.