Prediction of first season stallion fertility of 3-year-old Dutch Warmbloods with prebreeding assessment of percentage of morphologically normal live sperm.

Abstract

In the selection procedure to acquire a breeding licence, 3-year-old Dutch Warmblood stallions have to undergo a breeding soundness test It is questioned whether this evaluation is predictive of the stallion's fertility results in the first breeding season. Therefore, semen parameters at the beginning of their first breeding season were evaluated and correlated to nonreturn at first cycle and foaling rate of mares bred by stallions (n = 13). The total number of mares inseminated with chilled semen from those stallions was 1055. Semen parameters were recorded on 2 ejaculates, collected 1 h apart. Percentage progressive sperm motility, % morphologically normal from unstained spermatozoa (MNA), % sperm cells with abnormal acrosomes and the total number of spermatozoa were correlated with first cycle nonreturn rate and foaling rate. Mean motility at evaluation was 72 +/- 6%. Mean MNA was 62 +/- 13%. Mean first cycle nonreturn rate and foaling rate were 58 +/- 15% and 69 +/- 12%, respectively. A significantly positive correlation (P<0.05) was found between the MNA and first cycle nonreturn rates. Foaling rates were not significantly correlated with semen characteristics and first cycle nonreturn rates. In conclusion, the breeding soundness test is of predictive value for the breeding results in the breeding season following the test. First cycle nonreturn rates reflect fertilising capacity better than foaling rates.