FR 30. Reproductive response of crossbred heifers (Bos indicus x Bos taurus) used as bovine embryo recipient in venezuelan tropic. II. Heifers recipient selection
This trial was designed to compare the method of recipient selection used traditionally by rectal palpation of the Corpus luteum (CL) versus the progesterone (P4) concentration. Plasma P4 concentrations were determined by Enzyme Linked Immunosorbent Assay (ELISA) in 57 crossbred recipient heifers in a commercial ET program. Forty-seven embryos were transferred to recipients with CL 1 and 2. Recipients with CL3 (n=10) were not transferred. Pregnancy status was confirmed by rectal palpation 45 days after estrus. Pregnancy rates were 38.3 % (18/47) while 61.7 % stayed open. Simple linear regression, one way analysis of variance, chi-square analysis and Fisher test indicated that there were no significantly differences (P>.05) between plasma P4 concentrations of females which remained pregnant and those which did not on either days 0 (estrus) and 7 (ET). The P4 concentrations were not different (P>.05) when CL was evaluated by quality (CL1, CL2 and CL3) by rectal palpation for the day 7. In summary, the analysis of luteal function in recipient cows is useful since it allows the selecton of potential recipients that the rectal palpation discarded (CL3). This increases the number of recipient heifers that the same day and was reduced the maintenance cost of them improving the pregnancy rate.