Red blood cell glutathione as a marker of milk production in Finn sheep.

Reduced glutathione (GSH) levels of erythrocytes were determined in high (GSHH) and low (GSHh) types of Finn sheep. The blood samples were drawn parallelly from jugular and mammary veins before and after milking to calculate arteriovenous differences across the mammary gland. Erythrocyte GSH levels were higher in jugular veins compared with respective mammary veins. This difference was markedly higher in high-GSH ewes. The arteriovenous difference was highest after milking. The ewes showing higher arteriovenous differences in erythrocyte GSH (high-GSH sheep) produced more milk during the first eight weeks of lactation. The results clearly indicated that erythrocyte GSH is involved in milk synthesis.