Seminal traits, suitability for semen preservation and fertility in the native Portuguese horse breeds Puro Sangue Lusitano and Sorraia: Implications for stallion classification and assisted reproduction

Abstract

The Puro Sangue Lusitano (PSL) is the major national breed of horse in Portugal, but no studies exist on its seminal characteristics, or on the possibility of conserving semen for future use. The aim of this study was to evaluate semen parameters, fertility and the aptness to semen preservation in Lusitano Stallions. In order to compare characteristics defined by a single or by multiple semen collections per stallion 152 ejaculates obtained from 152 Lusitano stallions presented at an annual breeding soundness examination as well as data related to 371 ejaculates obtained from 9 PSL were analyzed. These latter samples were also evaluated in terms of their possible use in assisted reproduction and were compared with 113 ejaculates obtained from 4 Sorraia horses, a rare and endangered Portuguese breed. The percentage of motile spermatozoa (PMS) was assessed after collection (AC), after semen dilution (AD) and at 24h of cool-storage. Mean values obtained for sperm motility and morphology and semen pH observed after semen collection differ significantly (P<0.05) between single collection/multiple stallions and multiple collections/limited stallions, and no age related effects were detected. Overall, Lusitano semen quality was comparable to that of related breeds, while Sorraia stallions had very poor semen quality. The response to cool-storage of diluted semen samples differed among stallions and breeds, and the best results for progressive motile sperm cells at 24h were in a range of 35-53% for PSL stallions and were lower for Sorraia stallions. Fertility rates obtained with artificial insemination (AI) averaged at 85% for PSL. With the exception of PMS AC, sperm vitality and semen pH no other seminal trait seemed to influence fertility rates in the Lusitano breed.

Impact of inbreeding on fitness-related traits in the highly threatened Sorraia horse breed

“…The mean annual fertility rate of 46.74% obtained for Sorraia stallions in our study is lower than that obtained by Davies Morel and Gunnarsson (2000) for Icelandic stallions (67.7%), by Rho et al (2004) for the Jeju pony stallions (60%), and by Barbosa and Abreu (1986) for Lusitano and Arab stallions (62.4% and 61.6%, respectively). This result might be due to the extremely high levels of inbreeding of Sorraia stallions that have been shown to lower semen quality (Gamboa et al, 2009). The fertility of mares (35.79%) is slightly lower than that of stallions and is also lower when compared to 65% in Jeju pony mares (Rho et al, 2004), 72.6% in Finnish Standardbred Trotters and 66.3% Finnhorses (Sairanen et al, 2009), 62% in Lusitano mares and 61.56% in Arabian mares (Barbosa and Abreu, 1986).…”

“…With respect to stallions, because breeding is done extensively and stallions stay up to four months with the herd having (6 M several opportunities to cover the mares during that period and produce offspring, this could result in the overestimation of the stallions' fertility rate due to the effect of compensatory mating. A study done in Sorraia stallions by Gamboa et al (2009) has revealed overall very poor semen quality, sperm motility and vitality, when compared to other horse breeds, as well as poor preservation ability, possibly due to inbreeding. In our study, there was a significant negative relationship (P¼ 0.003) between inbreeding and fertility rates in Sorraia mares.…”

Stallion Sperm Selection: Past, Present, and Future Trends

“…As the semen quality in these animals may be poor because of lack of selection for fertility [43], SLC before AI could be of considerable benefit for conservation breeding. 6.…”

Fertility Assessment in Sorraia Stallions by Sperm‐Fish and Fkbp6 Genotyping

“…), in turn, has resulted in low fertility (mean fertility rate 46.7%) and bad sperm quality of Sorraia stallions compared to other Portuguese, as well as non‐Iberian horse breeds (Gamboa and Ramalho‐Santos ; Gamboa et al. ; Kjöllerström et al. ).…”