“…EIAs have been described for the determination of progesterone in extracts of serum or plasma from animals of several species (Dray, Andrieu & Renaud, 1975; Joyce, Read & Fahmy, 1977;Patricot, Poggi & Revol, 1978; Seeger, Thurow, Haede & Knappe, 1979;Kamonpatana et al, 1979;Johmen, Nakao, Tsunoda & Kawata, 1980) and in extracts of whole milk of cows (van de Wiel, Kamonpatana, Ngramsurijaroy, Koops & Singhajan, 1982), defatted milk (Nakao, Sugihashi, Saga, Tsunoda & Kawata, 1983) and milk fat (Arnstadt & Cleere, 1981). Direct EIA procedures requiring no extraction of progesterone have been described for bovine whole milk (Sauer, Foulkes & Cookson, 1981;Chang & Estergreen, 1984) and cream (Nakao & Kawata, 1980).…”