A comparative study on equine sperm chromatin using the Sperm Chromatin Structure Assay and the Sperm-Halomax kit®

Abstract

Breeding stallions tend to be selected based upon desirable traits and should, therefore, undergo extensive breeding soundness exams to ensure that they are capable of passing such traits onto future offspring. While it is well understood that environmental and others stresses can induce DNA damage which often leads to infertility or birth defects. Traditional standard semen evaluations excluded a sperm DNA analysis. A number of recent studies have assessed the effects of excessive heat load on chromatin damage in stallions and suggested extreme heat loads do induce significant DNA fragmentation. However, none appear to have assessed such damage due to seasonal heat loads. Therefore the objective of the present study was to determine the effects of season heat chromatin structure using two tests, the Sperm Chromatin Structure Assay (SCSA) and Sperm- Halomax® kit (Halo), to assess DNA damage. Stallion semen was collected after a period of excessive heat load (October 2011; average temperature = 31.05°C; temperatures ranged between 23.41°C and 36.18°C) and compared to semen collected at lower ambient temperatures (March 2012; average temperature = 14.26°C; temperatures ranged between 9.20°C and 20.69°C) to assess chromatin damage due to ambient heat stress caused in the testes. The collected data suggest that there exists no correlation between the SCSA and Halo techniques (r = .182 and F = .479). Furthermore, in regard to natural heat stress during the October and March collections, no correlation was observed for any of the applied techniques—SCSA, Halo, and live: dead staining (P = 0.2682, 0.4628, and 0.0377, respectively). The results suggest ambient heat load play little role in chromatin damage. However, other factors, such as relative humidity and heat index were beyond the control of this study and need to be assessed in the future.