Equine in vitro fertilization (IVF) is still inconsistent. In the present work, we studied how modified Whitten's (MW) medium and Tissue Culture Medium 199 (TCM) added with Foetal Bovine Serum (FBS; 10% v/v) or Bovine Serum Albumin (BSA; 7 mg/ml) affected equine gametes to subsequently run IVF trials. Compact (Cp) and expanded (Ex) cumuli equine oocytes were matured and placed in TCM or MW supplemented with BSA or FBS for 18-20 h (no sperm added). In Ex oocytes, TCM-199 added with FBS or BSA resulted in higher metaphase II (MII) rates (75.7% and 62.7%, respectively) than MW added with BSA (54%) or FBS (52.2%; p < 0.05); this was not observed for Cp oocytes. Equine sperm were capacitated in the same media at 10 × 10(6) sperm/ml for 4 h at 37°C; total motility and protein tyrosine phosphorylation (PY) were evaluated. While motility remained unchanged, TCM or MW added with FBS enhanced the number of sperm showing PY-stained tails (25 ± 4.8% and 31 ± 6.6%; mean ± SEM, respectively) over BSA supplemented media (3 ± 1.2% and 11.7 ± 1.1%) for TCM and MW (p < 0.05). In view of the previous results, sperm were capacitated in TCM + FBS and MW + BSA (control); IVF trials were run in the same media supplemented with 200 ng/ml of progesterone, but no fertilization occurred. Our results show that TCM + FBS enhances Ex equine oocyte's meiotic competence over MW + BSA and TCM or MW added with FBS successfully induce equine PY over media supplemented with BSA.
The use of sexed semen in dairy and beef farms ensures the production of animals of the desired sex, resulting in a reduction of costs and an improvement of environmental sustainability. Several methods have been developed over the years, but most of them were abandoned due to their limited efficacy. Currently, the only commercially available method for the separation of X‐ and Y‐chromosome‐bearing sperm is fluorescence‐activated cell sorting. However, this technique is expensive and has limited usefulness for the industry, considering that it cannot produce doses of sexed semen with the desired number of sperm for artificial insemination. Immunological methods have emerged as an attractive alternative to flow cytometry and proteomic knowledge of X‐ and Y‐sperm could be useful to the development of a new method. In this review, we identify the main applications of sexed semen, describe the existing methods and highlight future research opportunities in the field. We consider that immunological methods, based on sperm cell's surface proteins differentially expressed between X‐ and Y‐sperm, could be an interesting and promising approach to semen sexing.
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