The use of the serum progesterone strip test as a clinical tool for assessing reproductive status in replacement...

Identifying the reproductive status of replacement gilts at the appropriate age can improve mating efficiency and reduce non-productive days. This study aimed to evaluate the reproductive status of gilts and assess the accuracy of a serum progesterone strip test. A total of 112 Landrace × Yorkshire gilts, aged 196-238 days, were enrolled. Estrus detection was performed daily from 189 days of age using the back-pressure test with fence-line boar exposure. Blood samples were collected from all gilts, and serum progesterone levels were determined using both ELISA and a progesterone lateral flow assays (LFAs) strip test. Puberty was defined by an ELISA-based serum progesterone concentration ≥5.0 ng/ml. The LFAs employed a competitive assay using a monoclonal antibody against progesterone. A single test line indicated a 'positive' result (pubertal), while two lines indicated 'negative' (prepubertal). To perform the test, 2-3 drops of serum were applied to the strip, with results read after 15 min. Based on ELISA, 51.8 % of gilts were pubertal and 48.2 % were prepubertal. Pubertal gilts had significantly higher serum progesterone levels than prepubertal gilts (30.8 ± 11.4 vs. 0.8 ± 0.8 ng/ml; P < 0.001). The LFAs correctly identified 98.2 % of pubertal gilts and 94.4 % of prepubertal gilts, yielding a sensitivity of 98.2 % and specificity of 94.4 %. In conclusion, the progesterone strip test demonstrated high accuracy and shows strong potential for on-farm use in identifying pubertal gilts based on serum progesterone concentration.