Short communication. Evaluation of a commercial kit based on acridine orange/propidium iodide to assess the plasma membrane integrity of ram sperm

This study was designed to develop a semiautomatic computer assisted methodology to evaluate the membrane integrity of ram spermatozoa using a commercial kit based on acridine orange/propidium iodide (AO/PI) labelling and ImageJ software. The study was divided into two experiments. In the first trial, the new computer-assisted method was validated by mixing fresh semen samples with different volumes of freeze killed spermatozoa to determine proportions of damaged spermatozoa in the final samples. The proportion of damaged spermatozoa in each sample determined by the automated procedure where highly correlated (R2=0.97, p<0.001) with the predicted theoretical values. In the second trial, the new method was compared with a previously validated method of membrane integrity assessment based on phase-contrast/propidium iodide (PH/PI) methodology. Measurements by AO/PI were, on average, 4.0% larger than measurements by PH/PI (SD=7.02%) and 1.79% smaller than measurements of sperm motility determined by CASA (SD=4.83). The AO/PI method was also more repeatable than the PH/PI. The double staining methodology coupled with the routine for image analysis allowing automatic determination of sperm membrane integrity means a reduction in processing time of 75% compared to the previously developed method using a single fluorochrome (3 vs 12 min on average if the incubation period was included). This facilitates its use when a large number of samples are analysed. Our results validate the new computer assisted method for assessing sperm membrane integrity in sheep. The new method developed, in addition to being a free tool, allows quick automatic determination of sperm viability, which facilitates its use in routine semen analysis

Role of Antioxidants in Cooled Liquid Storage of Mammal Spermatozoa

Cooled preservation of semen is usually associated with artificial insemination and genetic improvement programs in livestock species. Several studies have reported an increase in reactive oxidative species and a decrease in antioxidant substances and sperm quality parameters during long-term semen storage at refrigerated temperatures. The supplementation of antioxidants in extenders before refrigeration could reduce this detrimental effect. Various antioxidants have been tested, both enzymatic, such as superoxide dismutase and catalase, and non-enzymatic, such as reduced glutathione, vitamins E and C and melatonin. However, the problem of oxidative stress in semen storage has not been fully resolved. The effects of antioxidants for semen-cooled storage have not been reviewed in depth. Therefore, the objective of the present study was to review the efficiency of the supplementation of antioxidants in the extender during cooled storage of semen in livestock species