RESUMEN
New rapid method of lateral flow enzyme immunoassay (LFEIA) for progesterone detection in whole cows' milk was developed. The test system utilized horseradish peroxidase as a label along with the substrate solution containing 3,3',5,5'-tetramethylbenzidine and dextran sulfate to obtain an insoluble blue colored product of the enzyme reaction on a surface of analytical membrane (test and control lines). Several aspects of LFEIA were optimized: time of the signal detection, membrane materials and assay conditions. Resulting competitive LFEIA can be performed within 15 minutes with the limit of progesterone detection of 0.8 ng/ml. Progesterone concentration in whole milk samples was determined by LFEIA and enzyme-linked immunosorbent assay (ELISA). The results obtained were in good correlation (R=0.97, n=46). Thus new sensitive LFEIA can be successfully used for on-site monitoring of oestrus status of cows' reproductive system and for early none-pregnancy detection. The method is fast, easy to perform and needs no preliminary sample preparation.