Resazurin reduction and other tests of semen quality and fertility of bulls

Aim: This study was undertaken to compare the reduction in color of two dyes methylene blue (MBRT) and resazurindye (RRT) with other tests of bull semen quality and to examine their relationship to fertility. Methods: One hundredsixty-four ejaculates from 59 bulls were examined, processed, and used for 30 016 inseminations. Results: Bulls usedin artificial insemination have been selected for high semen quality and fertility, and semen from these bulls averaged80.6 % unstained sperm, only 11% had abnormalities, and fertility ranged from 64 %to 76 %. The MBRT and RRTwere run with standardized sperm numbers to prevent sperm concentration from influencing the dye reduction time. Ashort RRT was correlated with higher fertility ( r = -0.26) but MBRT was not correlated ( r = -0.05, P >0.0,5).The correlations were low, but axe typical and reflect the statistical effect of the large binomial variance associated withpregnancy or nonpregnancy being coded as 1 or O. Conclusion: The fact that the RRT was significant