Abstract

The conservation of endangered wildlife species depends on the development of assisted reproductive technologies and has been focusing on epididymal sperm conservation for several years. Epididymides from sexually mature Southern lechwes (Kobus leche, n=15 individuals) and springboks (Antidorcas marsupialis, n=11 individuals) kept in captivity at the Réserve Africaine de Sigean (France) were collected soon after death and stored at +4°C. Epididymal sperm collection was performed using a 25-ga needle mounted on a 1-ml syringe previously filled with 0.5 ml of a sterile isotonic liquid, and by catheterizing the epididymal duct in the cauda epididymis, as previously described.⁴ Sperm motility, viability, and morphology were regularly examined at different time intervals. Individual motility was assessed subjectively by light microscopy at 100x magnification on at least five fields, with a minimum of 200 spermatozoa per examination, previously gradually warmed to 37°C. Morphology was evaluated under optic light microscopy at a 400x magnification, on at least five fields, with a minimum of 200 sperm per examination; the morphologic differences found were grouped as follows: normal spermatozoa, spermatozoa with a head abnormality, with an abnormal flagellum, tailless spermatozoa, sperm with a cytoplasmic droplet (proximal or distal). Epididymal sperm vitality was approached by assessing the percentage of live and dead gametes using an eosin-nigrosin staining.

In this managed collection, Southern lechwes and springboks are highly seasoned with respectively 58% and 87% of births taking place in a 4-mo period (respectively, April to July, and March to June). Sperm cell parameters were then compared between reproductive and non-reproductive periods.

Considering the peaks of births, and the length of gestation in these two species, reproductive season was considered from August to November in Southern lechwes, and from September to December in springboks. To compare the characteristics of epididymal sperm between reproductive and non reproductive seasons, a trend line, regression curve type, was obtained from the data collected, determining all the following parameters: mean expected longevity, mean expected vitality at death, mean expected motility at death, mean expected immobility of all sperm cells, mean expected percentage of normal morphology, mean decay in vitality over time, and mean decay of motility over time. There were no statistically significant differences (Chi square test, p>0.05) for these parameters between reproductive and non reproductive periods in Southern lechwes and springboks, leading to the following conclusion: there is no statistically significant difference in the quality and longevity of sperm cells retrieved by post mortem epididymal aspiration in these two species, in the conditions of this study. As a result, this technique may be used year round for assisted reproduction technologies of these two species.

In a previous study conducted on wild bovids in the same conditions, no statistically significant difference was shown in the decrease in total sperm motility and vitality over time between two seasons: autumn/winter, and spring/summer; nevertheless, this work was conducted on several species, seasoned or not.⁴ The influence of season on sperm quality has been studied in Cervidae; motility and sperm without morphologic abnormality are maximal during the breeding season.^1,2,5 Ghosh and Fischer found that most samples collected on fallow deers (Dama dama) by electro-ejaculation in June–July are azoospermic.³ In wild Bovidae, knowledge is more limited and sometimes contradictory between publications. The diameter of the seminiferous tubules or testes, sperm count per ejaculate and sperm motility appear lower outside the breeding season in free-ranging springboks, blesboks (Damaliscus pygargus), impalas (Aepyceros melampus), greater kudus (Tragelaphus strepsiceros), blue wildebeests (Connochaetes taurinus), hartebeests (Alcelaphus caama) and African buffaloes (Syncerus caffer), but the difference is not always statistically significant.^6,7

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