RELATIONSHIP BETWEEN SEMEN CHARACTERISTICS OF YOUNG AND ADULT BULLS IN THE NORMANDE BREED

Semen production and semen quality of Normande bulls in performance te st station and in two AI centers were studied. In station data from 26 77 bulls between 12 and 15 months of age, exhibited large differences between 5 groups corresponding to an overall classification given by a technician. Correlations between variables corrected for environmenta l factors showed a high relationship between all measures of semen qua lity and number of doses per ejaculate. In the AI centers, trimestral (for the first year) or annual means (for years 2 and 3) of 387 bulls were calculated from monthly means and were analyzed with a mixed mode l, treating the bull effect as random. Best linear unbiased prediction s of the bull effect considering the two periods separately were stron gly correlated (0.57 to 0.79). Correlations between corrected data col lected in station and bull effect estimates in AI studs were quite hig h for volume and concentration, and moderate for motility and number o f doses per ejaculate or per month. The correlations calculated are un derestimates of the true ones, as bulls with undesirable semen charact eristics were culled before entering AI. Nevertheless, among the remai ning bulls, important differences (40%) in semen output were observed between extreme groups, as classified by the technician.