Variability of reduced glutathione levels in Massese ewes and its effect on daily milk production

The variability of the erythrocyte concentration of the tripeptide glutathione was studied in four flocks of Massese sheep. A relationship was found between glutathione level and stage of lactation in which the second month showed the lowest content. Genotype at transferrin and haemoglobin loci was associated with glutathione levels. Homozygotes at the transferrin locus yielded higher levels, while the D allele at the same locus was associated with lower concentrations. Animals with haemoglobin AA showed higher contents of glutathione. Also, a negative correlation was found between daily milk production and glutathione level.