Comparative assessment of Bull fertility based on Semen characteristics and In vitro Embryo Development

Abstract

The goal of a contemporary dairy farmer is to maximise the efficiency of milk production. The major component of efficient dairy production is sound reproductive efficiency of the cow and the bull. Reproductive efficiency of the bull is dependent upon potential fertility as always judged using semen characteristics such as ejaculate volume, spermatozoal motility, sperm morphology and concentration. At times, subjective judgement of bull semen characteristics may not correlate to the actual ability of such semen to fertilize oocytes, with the latter determining its fertility status. Based on reduced results of pregnancies and or calving, some farmers in Kenya had doubts on the potential fertility status of bull semen passed for use in AI. Therefore, the need arose to compare how the current semen evaluation methods used would correlate with spermatozoal morphological evaluation, a method not routinely used in Kenya and cleavage and blastocyst formation rates in in vitro embryo production. Room temperature (RTS) and deep frozen semen (DFS) samples from six bulls of selected three dairy breeds were used. The ejaculate volume, spermatozoal motility, concentration, morphology, in-vitro cleavage, blastocyst formation parameters were assessed. Correlation analysis was done between cleavage and blastocyst formation rates with motility, concentration and sperm morphology. Differences in ejaculate volume, motility, concentration, morphology, cleavage and blastocyst formation rates were observed between breeds as well as between individual bulls within the same