Influence of Sample Preparation, Staining Procedure and Analysis Conditions on Bull Sperm Head Morphometry using the Morphology Analyser Integrated Visual Optical System

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Abstract
The importance of standardizing the procedures of sample and slide preparation for computer‐assisted morphologic analysis has been emphasized in human and veterinary andrology. The purpose of this study was to optimize slide preparation (dilution grade and sperm washing), staining procedures and analysis conditions (colour of light source and objective magnification) for the morphometric analysis of bull spermatozoa using the Hamilton Thorne morphology analyzer integrated visual optical system (IVOS). For experiment 1, one ejaculate was collected from one bull and diluted to 200 000–300 000 spermatozoa/μl. Slides were prepared and stained using seven different procedures: rapid Papanicolaou (PAP), rapid Papanicolaou with prolonged staining times (PAP+), Diff‐Quik (DIF), haematoxylin (HEM), Farelly (FAR), Spermac (SPER) and the modified GZIN (MGZIN) staining. All slides were analysed using a Hamilton Thorne Morphology Analyser IVOS equipped alternatively with a red, green or blue light source, and a 40× or 100× oil immersion objective. Recognition and digitization errors as well as morphometric parameters were determined. The IVOS was unable to detect DIF‐stained spermatozoa. The GZIN and the SPER staining as well as the blue light source led to unsatisfactory results. Among the staining methods examined, the FAR, HEM, PAP+, and PAP staining, preferably in combination with the green light source, and the 40× objective yielded optimal results concerning sperm recognition and digitization. The 100× objective did not allow reliable analysis of the sperm heads because of a frequently appearing digitization error. For experiment 2, three ejaculates were collected from each of three bulls and diluted to five dilution grades (100 000–500 000 spermatozoa/μl). An aliquot of each dilution grade was washed additionally. The percentage of correctly digitized sperm heads decreased with increasing spermatozoal concentration. However, the evaluation speed increased. The range of 200 000–300 000 spermatozoa/μl appeared to be a reasonable compromise for both criteria. Sperm washing failed to further improve the analysis results. Sperm head dimensions were influenced significantly by all variations of the methods in both experiments. In conclusion, using the proposed methods, the IVOS allows precise and reliable morphometric analyses of bull spermatozoa. The consistent application of these procedures may lead to an inter‐laboratory standardization and to further establishment of generally accepted morphometric criteria used in human andrology (e.g. World Health Organisation or strict criteria).