Decline in Fertility of Bull Semen with Increase in Storage Time as Influenced by Dilution Rate

Summary Three experiments involving 6,607 services have been conducted to compare rate of decline in nonreturn rate from day of collection to the next day with semen extended 1:100 and 1:300. The average nonreturn rate for semen diluted 1:100 was 68.2% and for semen diluted 1:300, 62.4%. The difference of 5.8 percentage units is highly significant. The average nonreturn rate with semen used on the day of collection was 68.4% and on the next day was 62.5%. This difference of 5.9 percentage units is also highly significant. The average decline from day of collection to the next day with 1:100 was 3.6%) and with 1:300 was 8.2%. The differences in decline with 1:100 and with 1:300 were quite consistent in the three experiments. The interaction of age and dilution level was short of significance (P = 0.1), however. The breeding results parallel motility observations reported in the literature and support other work which indicates that high dilutions have a direct, detrimental effect upon spermatozoa.