Plasma progesterone levels from oestrus through day 7 after A.I. in heifers carrying embryos with normal or deviating...

Twenty-five dairy heifers, 11 repeat breeder and 14 virgin heifers, were used. Blood samples were taken twice a day (9 a.m. and 3 p.m.) from day of A.I. to 7 days later when embryo collection was made. One series of blood samples were taken from 16 heifers and two and three, respectively, from 6 and 3 heifers. Analysis of progesterone was performed by radioimmunoassay. The embryos were classified in 3 groups: normal blastocysts, morphological deviators, and degenerated embryos. Analysis of variance and a discriminant analysis was performed. The discriminant analysis was made to predict embryonic morphology, using daily progesterone values as predictors. No significant relationship between embryonic morphology and progesterone levels was found. The discriminant analysis showed that 64.9 % of progesterone curves were correctly classified, with individual groups ranging from 50 % (degenerated) to 76.5 % (normal embryos). It was concluded that abnormal embryonic development occurs with normal lateal function and that normal bovine embryo does not exhibit luteotrophic activity 7 days after mating.