Classification of postpartum beef cows as estrous cycling or anestrous through the use of estrus detection patches prior to the start of the breeding season

Two experiments were designed to evaluate use of estrus detection patches (Estrotect Breeding Indi- cators; Hermitage, TN) applied to postpartum cows 24 d before estrus synchronization as a diagnostic tool to clas- sify postpartum beef cows as estrous cycling or anestrous. Estrous cyclicity was de- termined via blood samples (experiment 1) or transrectal ovarian ultrasonography (Experiment 2). In Experiment 1, blood samples were collected from 257 cows 10 d before, and coincident with the start of synchronization. Serum progesterone concentrations were determined via radioim- munoassay; cows were considered cycling if one or both samples exceeded 0.5 ng/mL. Based on progesterone, 55% were cycling at the start of estrus synchronization. Use of activated patches to infer cyclicity resulted in 85% sensi- tivity and 79% specificity. However, 75% of cows presented with missing patches. If missing patches were considered activated, sensitivity was 96% but specificity was 16%, In Experiment 2, estrous cyclicity status was determined for 269 cows via transrectal ovarian ultrasonography coinci- dent with the start of estrus synchronization. Cows were classified as cycling based on the presence of a corpus lu- teum. Based on transrectal ovarian ultrasonography, 59% (161/269) were cycling at the start of estrus synchroniza- tion. Of cows receiving patches, 95% (256/269) retained patches for the full 24-d period. Use of activated patches to infer cyclicity resulted in 89% sensitivity and 68% speci- ficity in Experiment 2. Estrus detection patches are a sensitive tool to classify postpartum cows as cycling before the start of the breeding season; however, patch retention could limit application for this purpose.