Heritability of semen traits in German Warmblood stallions.

This study examines the genetic factors influencing semen quality in German Warmblood stallions, noting the correlation between certain traits and their heritability. It suggests the use of breeding values (EBVs) to improve semen quality in future generations, due to the significant impact of individual stallion genetic variance on these traits.

Study Objective and Methodology

• The goal was to determine genetic parameters for semen quality traits in German Warmblood stallions widely used for artificial insemination. A total of 241 stallions owned by the Celle and Warendorf National Studs in Germany were used for the study.
• The researchers analysed specific semen traits such as gel-free volume, sperm concentration, total number of sperm, progressive motility, and the total number of progressively motile sperm.
• Data from 63,972 ejaculates collected between the years 2001 and 2014 was used in this study. The team utilised a multivariate linear animal model to estimate additive genetic and permanent environmental variances among the stallions and their breeding values for semen traits.

Results and Findings

• The highest heritability was found for gel-free volume (h(2)=0.28), while the lowest was for the total number of progressively motile sperm (h(2)=0.13). Heritability indicates the proportion of observed variations in a particular trait that can be attributed to inherited genetic factors. In these cases, it means that these specific traits are more prone to be affected by genes rather than environment.
• A significant negative additive genetic correlation was found between gel-free volume and sperm concentration (rg=-0.76), suggesting that an increase in one trait tends to result in a decrease in the other.
• The average reliabilities of breeding values were between 0.37-0.68 for the stallions included in the study.
• The individual stallion’s variance explained between 33 and 61% of the trait variance, indicating that the individual stallion’s genetic makeup has a significant impact on the semen quality traits being studied.

Implications and Recommendations

• The study recommends the recording of semen traits from stallions used in artificial insemination, citing that estimated breeding values achieve sufficient accuracies to improve semen quality in future generations.
• Furthermore, due to the favorable genetic correlations observed, it suggests that sperm concentration, total number of sperm, and total number of progressively motile sperm can be simultaneously increased.
• These findings could significantly enhance the breeding process, directing selection towards stallions with better genetic traits related to semen quality, thereby improving the genetic quality of future generations.