Strip-dried whole milk sampling technique for progesterone detection in cows by ELISA.

New sampling format of whole cows' milk in strip-dried form was proposed. Few methodological issues of whole milk progesterone ELISA using samples dried on a membrane carrier in a form of strip were investigated and optimized: width of a strip, shape of punched/cut-off part of membrane, sample application method. It was shown that distribution of the hormone along narrow strip was even except the initial part of a strip (the first 0.5 × 0.5cm piece) where recovered concentration of progesterone was higher. Storage stability of progesterone in strip-dried whole cows' milk samples at 4°C, ambient temperature, 37°C and 60°C was investigated. Rising of the detected progesterone concentration over storage period at elevated temperatures was observed predominantly in milk samples with low hormone concentration (from non-pregnant cows). Strip-dried whole milk samples can be used for collection, transportation, storage and ELISA analysis of progesterone level which is correlated with reproductive status of cows.