Nonreturn Rate and Embryonic Mortality from Inseminations by Bulls with Vibrio fetus

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Abstract
Data were obtained from an experiment with 91 bulls and 119,896 services to compare 3 different treatments involving antibacterial agents with a control. Seven bulls were infected with pathogenic Vibrio (V. fetus) as evidenced by cataslase tests. Breeding results from these bulls were compared with bulls believed to be carrying only non-pathogenic Vibrio or with the other bulls in the experiment. There was a markedly greater embryonic mortality and a lower nonreturn rate among cows bred to bulls infected with V. fetus when no antibacterial agents were in the extender. Results for these bulls were comparable with the others when antibacterial agents were in the extender. Five bulls with V. fetus had services on the 1st and 2d days after collection. Without antibacterial agents the nonreturn rate increased from the 1st to the 2d day in contrast to the usual decline as observed with these same bulls when antibacterial agents were included in the extender or with any of the 4 treatments with 52 other bulls not known to have V. fetus and with services on the 1st and 2d days. These data suggest the possibility that V. fetus, while in vitro at refrigeration tempera-tures above freezing, tend to undergo some reduction in ability to cause infection, even in the absence of antibiotics.