Abstract
Effect of factors affecting the embryo production of superovulated Holstein cows were evaluated. Data were obtained from 455 superovulation-collections using 84 donors. For all of the hormonal treatment, FSH and PGF2α were used. Season (every 12 month), year (1988, 1989, 1990), age at calving (3, 4, 5, 6, ≥7 years old), time after calving (1st, 2nd, ≥3rd year), interval of treatment (1st treatment, 21-90, 91-150, ≥151 days) and interaction (season×year, age×time) were evaluated by analysis of variance for number of total ova/embryos (NT), number of fertilized ova (NF), number of normal embryos (NN) fertilization rate (%F) and normal rate (%N), and time after calving within each flush were evaluated by another model. The effects of season on NT, NF and NN, age at calving on NT, NF, %F and %N, and time after calving on NF, NN, %F and %N were significant (P<0.05), while effects of year, interval of treatment, season×year and age×time were not. Seasonal effects suggested the influence of heat. Effects of age at calving indicated a lag of peaks between NT (3 years) and %N (5 years), and no difference was observed among 3-6 years in NN. Influence of time after calving without the effect of repeated treatment was observed, and embryo production during the 3rd year or over was worse as compared with the 1st and 2nd year.
