Bovine semen thermoresistance tests and their correlation with pregnancy rates after fixed-time artificial insemination

ABSTRACT The objective of the study was to determine whether or not there is a correlation between thermoresistance tests (TT) after semen thawing and pregnancy rate (PR) after fixed-time artificial insemination (FTAI). Four different TT were performed on ten samples used for AI; a rapid test (RTT) (30min / 46°C) and three slow tests (STT): STT1 (60min/38°C), STT2 (180min/38°C), and STT3 (300min/38°C). Two hundred and fifteen multiparous crossbred cows were submitted to FTAI under the following protocol: on day zero (d0) the animals received a P4 device +EB; on d7 PGF2α; on d8 P4 was removed and eCG+EC were administered; IATF was performed on d10. Three gestational diagnoses (G D) were performed on d40, d70 and d120. The mean sperm motility (%) in RTT and STTs were 19.84±6.13, 28.55±10.48, 17.62±5.87 and 8.63±3.46, respectively, and TP in the three DG 61.86%, 57.67%, and 55.81%, respectively. Through Person test a significant negative correlation (P< 0.05) was found between STT2 and PR at 60 days (r= -0.644) and between STT3 and all TPs (r= -0.774, -0.752, 0.748). It was concluded that TT parameters are not able to determine correlation between semen quality and TP.