Three lactating Saanen goats weighing 55-71 kg, producing 1.2-3.6 kg milk/day and fed ad libitum concentrates and hay, were infused via a jugular catheter with 35S-cysteine (35S-Cys) at 9.3 mCi/min for 9 hours. Blood samples were taken hourly and mammary tissue biopsied terminally. Concentrations and specific radioactivities (SRA) of cysteine (Cys) and glutathione (GSH) were determined in whole blood, plasma and mammary tissue. Mean arterial concentrations (nmoles/g±SE) of Cys and GSH in whole blood, plasma and red blood cells were: 71±7, 79±9 and 19±8; and 823±30, 1.6±01 and 3426±124 respectively. Arterial SRA in whole blood at plateau (7-9h) of 35S-Cys (352±13 dpm/nmole) was higher than that for GSH (5.9±0.7 dpm/nmole). However the difference between intracellular SRA for Cys and GSH in mammary gland tissue was much less (231±23 vs 146±13 dpm/nmole). Total uptake of Cys by one half of the mammary gland was 0.5±0.2 g/day. Whole body irreversible loss rate of Cys was 7.3±0.7 g/day, giving a percentage utilisation of whole body Cys by the mammary gland of 13.6±4.3.
Proceedings of the New Zealand Society of Animal Production, Volume 54, , 103-106, 1994
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