Serum was separated by centrifugation at
3000 rpm for 20 min and stored at 20 C until assayed.
Validated Food and Agriculture Organisation
(FAO) and International Atomic Energy Agency
(IAEA) progesterone RIA kits were used. Progesterone
concentrations equalling or exceeding 3.18 nmol/
l, were indicative of normal luteal function or pregnancy,
and levels under 3.18 nmol/l, were indicative of
either anoestrous, follicular, or early luteal phase of
the oestrous cycle (Zarkawi, 1997).