Indices of multiple sperm defects applied to dog semen

The morphological evaluation of dog semen is based on the assessment of the percentage of normal and abnormal spermatozoa. In the conventional analysis, sperm abnormalities are divided into primary/secondary or major/minor defects. When a spermatozoon is affected by more than a single alteration it is classified according to the “most important” abnormality. This implies the knowledge on its effect on fertility and masks other defects. The WHO guidelines for human semen examination suggest a multiple-entry system to record all the abnormalities of a single spermatozoon and the calculation of three indices: the Multiple Abnormalities Index (MAI: mean number of anomalies, excluding cytoplasmic droplets, per abnormal spermatozoon), the Teratozoospermic Index (TZI: similar to MAI, but including a maximum of 4 anomalies) and the Sperm Deformity Index (SDI: number of defects divided by the total number of spermatozoa). These are diagnostic and prognostic tools allowing to establish the fertility potential of human semen. In this study MAI, TZI and SDI were applied to dog semen with the aim of testing their contribution to a more objective sperm morphological evaluation. Materials and methods. Forty-seven dog semen samples were evaluated according to WHO guidelines. Undiluted samples were stained with a rapid Giemsa-Wright stain (Diff-Quick, Merck, Germany). In each sample a total of 200 spermatozoa was evaluated to obtain MAI, TZI and SDI indices. Based on the proportion of MNS (morphologically normal spermatozoa; 3) the samples were classified into three categories: MNS ≥ 70% (15 samples), from 50% to 69% (14 samples) or ≤ 49% (18 samples). Data are reported as mean ± SD and significant differences (P<0.05) were determined by ANOVA and Tukey’s Studentized Range (HSD) test. Results. Data show that MAI and TZI were similar in the samples characterized by different proportions of normal spermatozoa, whereas SDI significantly increased. Conclusions. These results evidence that the spermatozoa were seldom affected by multiple and associated abnormalities as the values of TZI and MAI are approximately 1 or below 1, respectively. Consequently, SDI reflects the increase of the proportions of abnormal spermatozoa in the different categories. Not being these information revealed by the conventional analysis, the indices of multiple sperm defects provide a more objective evaluation of the morphological quality of the semen. However, the use of these indices in clinical practice as prognostic values for the estimation of fertility require the analysis of their potential correlation with in vitro and in vivo fertility outcomes.