Preovulatory evaluation of the superovulatory response in donor cattle.

Dairy cows and heifers (n = 134) were induced to superovulate with exogenous gonadotrophins. In 103 animals, peripheral plasma concentrations of progesterone (P4) and luteinizing hormone (LH) were measured during the preovulatory period. On the basis of these measurements, normal and deviating profiles of P4 and LH were defined. A high degree of correlation existed between the normality of the two profiles; when the P4 profile was normal, the probability for the LH profile also to be normal was greater than 10:1. This relationship was utilized to evaluate donors based on four preovulatory measurements of P4. When used on 31 animals used for collection of eggs, a superior superovulatory response was encountered in animals with normal vs deviating P4 profiles (eggs recovered: 7.2 +/- 1.1 vs 0.5 +/- 0.3, P < 0.001; transferable embryos: 4.4 +/- 0.9 vs 0.3 +/- 0.2, P < 0.01). It is concluded that evaluation of donors by measurements of progesterone in plasma at four preovulatory sampling points allows for the early exclusion of donors with inferior embryo yield.