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In the last 30 years, encapsulation technology has been applied to different species to minimize the loss of spermatozoa after artificial insemination. In particular, the vehiculation of boar sperm cells in barium alginate membrane has proved a valid strategy to reduce the risk of polyspermy and optimize in vivo fertilizing yields. Controlled release of male gametes into the female genital tract has reduced the minimum fertilizing dose of spermatozoa. Notwithstanding these results, encapsulation has not yet reached commercial application, largely due to the additional costs of production. However, encapsulation could be useful in advanced reproductive technology, such as sex sorting, to store sorted boar semen. The controlled release of flow cytometrically sorted spermatozoa could be a promising strategy to reduce the number of cells necessary for each insemination and hence allow the widescale use of sex sorting in this species.

A boar sperm encapsulation technology in barium alginate has been developed to enhance reproductive performances and spermatozoa preservation time; aim of this work was to evaluate the effect of in vitro sperm encapsulation on polyspermy as a function of storage time at 18 degrees C. A total number of 40 in vitro fertilization (IVF) tests were performed using encapsulated or diluted spermatozoa (20 IVF each treatment). Overall, 1288 in vitro matured oocytes were fertilized with spermatozoa stored at 24, 48 or 72 h at 18 degrees C for both treatments polyspermy and normospermy, and the non-penetration rates were assessed by optical microscopy. Results indicate a significant reduction in risk of polyspermic oocytes when spermatozoa are preserved in barium alginate membranes (incidence risk ratio: 0.766 with respect to diluted); such enhancement could be explained by lesser damage of sperm membranes achieved by encapsulation technology.

Little information is available on the quality of stallion spermatozoa after sex sorting. The objectives of the present study were to assess the quality of sex-sorted stallion spermatozoa and determine its fertilizing ability after hysteroscopic low dose insemination. Ejaculates from four stallions were collected and sorted by a MoFlo SX flow cytometer/sperm sorter. Before and after sorting, spermatozoa were evaluated for motility by Computer Assisted Sperm Analysis, viability (SYBR 14-propidium iodide), mitochondrial function (JC-1) and acrosomal status (fluorescein isothiocyanate Pisum sativum agglutinin conjugated). A fertility trial was carried out on four mares (seven oestrous cycles) by hysteroscopic insemination, depositing 5 x 10(6) X-bearing spermatozoa. Sex sorting resulted in a significant decrease (p < 0.001) in all motility characteristics. Sperm viability and percentage of spermatozoa with functional mitochondria were not affected by the sorting process, while the percentage of reacted spermatozoa was higher (p < 0.01) for non-sorted than sorted spermatozoa. Pregnancy rate was 28.6% (2/7) after low dose hysteroscopic insemination. Only one pregnancy was carried to term with the birth of a healthy filly. In conclusion, despite the reduction in sperm motility, sex sorting did not impair stallion sperm viability and mitochondrial activity immediately post-thaw; moreover, the sexed spermatozoa retained the ability to fertilize in vivo.

Leptin is active in both metabolism and reproduction. In fact, it seems to exert an inhibitory action on gonadal functions by reducing testosterone production. The presence of leptin in human and boar seminal plasma and in human spermatozoa has been demonstrated; recently, leptin receptors (Ob-R) have been localized in human spermatozoa, thus suggesting a possible action of this hormone even on these cells. Our aim was to verify whether leptin receptor [the long form (Ob-Rb)] is present in boar spermatozoa. Immunofluorescence and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques were employed. RNA was extracted from boar spermatozoa and a specific band (382 bp) for Ob-Rb was detected after RT-PCR. Ob-Rb was detected on acrosome, subequatorial area and either on the midpiece or on the whole tail. These localizations were maintained even in semen washed twice to eliminate seminal plasma. We conclude that Ob-R is present in boar spermatozoa where seminal plasma leptin can exert its effects.