THE USE OF RAPID ON-FARM MILK PROGESTERONE TESTS AS AN AID TO REPRODUCTIVE MANAGEMENT IN DAIRY-CATTLE

A field study was conducted in 11 commercial dairy herds to test the accuracy and ease of use of a rapid enzyme-linked immunosorbent assay (ELISA) kit for on-farm milk progesterone analysis. Milk samples were collected at milking following detection of estrus and on day 21 postbreeding. Progesterone was measured on-farm by producers using an ELISA kit and by a technician in the laboratory using a radioimmunoassay (RIA). Of the 256 samples collected at suspected estrus, estrual concentrations of progesterone (less-than-or-equal-to 2 ng mL-1) were detected in 246 samples by the farmer and in 253 samples by laboratory analysis. Nonestrual concentrations (> 2 ng mL-1) were detected in 10 samples by the farmer and in three samples by RIA. At 21 d, there was 94% agreement between the two methods in detecting high (> 2 ng mL-1) milk progesterone concentrations (n = 149). The corresponding figure for low (less-than-or-equal-to 2 ng mL-1) milk progesterone was 88% (n = 73). Seventy-two percent of the cows with high milk progesterone (by RIA) at 21 d were subsequently diagnosed pregnant by rectal palpation. The overall agreement between ELISA and RIA was 96.6% (453/469 samples). No significant differences were observed among farmers in their ability to perform ELISA tests on-farm. The results indicate that the ELISA kits can be used with ease by producers and are comparable in accuracy to RIA performed in the laboratory for detection/confirmation of estrus and diagnosis on nonpregnant/possibly pregnant cows at 21 d postbreeding.