A retrospective study on semen quality parameters from four different Dutch horse breeds with different levels of inbreeding.

The research investigates the effect of high inbreeding levels on semen quality in different Dutch horse breeds. Existing evidence suggests a significant negative impact on semen quality in Friesian horses and Shetland ponies due to inbreeding, and this study extends the research to the Dutch Warmblood horse breed.

Study Background and Hypothesis

• The Dutch Warmblood horse breed comprises two primary populations: the KWPN-Riding horses, which constitute an open studbook or breeding register, and the KWPN-Harness horses, an almost closed studbook due to their smaller gene pool.
• The research’s hypothesis is based on previous studies indicating a negative impact of inbreeding on semen quality, suggesting that the increased inbreeding levels observed in the KWPN-Harness horses might adversely affect their semen quality.

Research Methodology

• The study was retrospective, indicating that it used existing data rather than collecting new data through experimentation or surveys.
• It compared semen quality parameters across four different horse breeds (Friesian Horses, Shetland Ponies, KWPN-Riding horses, and KWPN-Harness horses), each with different inbreeding levels.
• Several parameters were examined in the analysis, including semen concentration, percentages of motile (capable of movement) sperm cells, and morphologically normal sperm cells (cells with normal shapes and sizes). It also included the total number of morphologically normal, progressively motile sperm cells per ejaculation (TNM) over a 15-year period, with 2832 semen evaluations used in the study.

Key Findings

• The study found that KWPN-Harness horses had significantly lower sperm concentration, motility, and viability than KWPN-Riding horses.
• However, both KWPN subpopulations showed higher percentages of motile and morphologically normal spermatozoa, as well as a higher TNM, than the Friesian horses and Shetland ponies.
• Results suggest that the lower semen quality in KWPN-Harness horses could be a result of higher inbreeding levels.

Implications and Recommendations

• The study identified a potential early-warning sign for breeders, suggesting that increased inbreeding levels could potentially reduce semen quality.
• Breeders and studbooks were encouraged to carefully monitor inbreeding levels to avoid further degradation of semen quality, as observed in the Friesian and Shetland pony breeds.