The effect of selection for fertility of frozen-thawed semen on spermatozoa oxygen uptake, motility and concentration, and ejaculate volume in the chicken

The response to 3 generations of selection for duration of fertility of frozen-thawed semen on fertility and hatchability of fresh and frozen-thawed semen, spermatozoa oxygen uptake, motility and concentration, and ejaculate volume was measured in a broiler line of chickens. The selected line, as compared to the control, had significantly higher levels for all fertility traits of frozen-thawed semen but not hatchabilities. For fresh semen, the lines differed only for duration of fertility. The only difference in semen quality traits was in oxygen uptake by spermatozoa of frozen-thawed semen. The differences between lines for the other parameters were not significant but were in a direction that supported the hypothesis that selection had resulted in improved reproductive capacity. All estimates of fertility within an ejaculate were positively correlated (P < 0.01). Correlations between corresponding fertility estimates of fresh and frozen-thawed semen were positive, low and generally non-significant. The proportion of variation as determined by stepwise regression, in fertility estimates accounted for by the measurements of oxygen uptake and motility of fresh and frozen-thawed spermatozoa, ejaculate volume and spermatozoa concentration ranged from 12 to 19 percent.