Effects of supplementation of iodixanol to semen extender on quality and fertilization ability of frozen-thawed Thai native bull sperm.

This study investigates the effects of iodixanol supplementation in varied concentrations to Tris egg yolk (TEY) extender on the quality and fertilization ability of frozen-thawed sperm of Thai native bulls. Each ejaculate was divided into four different groups, as follows: sperm were treated with TEY extender (control group) and TEY extender supplemented with three different concentrations of iodixanol (1.25%, 2.50% and 5.00%). Semen straws were frozen in liquid nitrogen vapor. After thawing, sperm motility characteristics, viability, plasma membrane integrity and acrosome integrity were determined. Also, frozen-thawed spermatozoa from all groups were used for in vitro fertilization and artificial insemination (AI) in natural estrus Thai native cows. The results showed that the post-thaw quality of the 2.50% iodixanol group was superior to the other iodixanol groups (P < 0.05). However, iodixanol had no beneficial effect on post-thaw sperm in vitro fertilization ability and pregnancy rate after AI (P > 0.05). It can be concluded that the supplementation of 2.50% iodixanol extender significantly improves the progressive motility, viability, plasma membrane integrity and acrosome integrity of cryopreserved semen from Thai native bulls, but it has no beneficial effect on in vitro fertilization ability and pregnancy rate after AI.

Comparison of three superovulation protocols with or without GnRH treatment at the time of artificial insemination on ovarian response and embryo quality in Thai native heifers.

To optimize the superovulation protocol in Thai native cattle, the present research was designed to (1) compare three different protocols designed to induce superstimulation and (2) study the effect of gonadotropin-releasing hormone (GnRH) administration at insemination time (to induce ovulation) on ovarian follicular activities in terms of the number of large follicles, corpora lutea (CLs) and unovulated follicles, and the number and quality of ova/embryos recovered in Thai native heifers. Initially, the estrous cycles of animals (n = 36) at unknown stages were synchronized by two prostaglandin F2α (PGF2α) injections at an interval of 12 days. Follicular development of heifers was randomly superstimulated with one of three different treatment protocols: treatment A-a total of 100 mg of pituitary-derived FSH (pFSH; Folltropin®-V) administered in eight decreasing doses; treatment B-a single dose of 100 mg pFSH dissolved in 30% (w/v) polyvinylpyrrolidone; or treatment C-ablation of all follicles ≥5 mm with a single dose of pFSH. All heifers received PGF2α 48 h after the initiation of FSH treatment to induce luteolysis from the previous cycle, and they were twice inseminated at 12 and 24 h after the onset of estrus. Heifers in each treatment were assigned to be injected or not with GnRH at the time of first insemination with frozen/thawed semen to induce ovulation. About 7 days after artificial insemination (AI), ova/embryos were collected and classified. The numbers of large follicles at the onset of estrus were not statistically significantly different; meanwhile, the maximum diameters of follicles at the time of first insemination in treatment C were smaller compared with the other treatment groups (p < 0.001). The administration of GnRH at the first insemination time resulted in a greater number of CLs and fewer unovulated follicles at the time of ova/embryo collection (p = 0.001), which subsequently resulted in a higher number of total ova/embryos recovered (p = 0.030). Among heifers treated with different superstimulation protocols, the ablation of all follicles ≥5 mm in diameter before superstimulation (treatment C) resulted in significantly higher quality of fertilized ova and transferable embryos (p = 0.001). In summary, it could be inferred that GnRH treatment improved ovarian function rather than embryo quality. Dominant follicle ablation prior to superstimulation is preferable for collecting a greater number of transferable embryos.

Superstimulation of follicular growth in Thai native heifers by a single administration of follicle stimulating hormone dissolved in polyvinylpyrrolidone.

This study was undertaken to determine whether a single i.m. injection of FSH dissolved in 10 ml of 30% (wt/vol) polyvinylpyrrolidone (PVP; MW=40,000) to form FSHp would induce follicular growth in Thai native heifers and to determine its optimal dose. In Group 1, heifers (n=4) were given multiple i.m. injections of FSHp every 12 h for 3 days at decreasing doses, for a total of 100 mg (control). In Groups 2, 3 and 4, heifers (n=4 in each group) were given single i.m. injections of FSHp at 50, 100 and 150 mg. All heifers received a single injection of 750 µg PGF2α 48 h after the initiation of exogenous FSH treatment. Ovaries of treated heifers were examined by transrectal ultrasonography every day until they showed estrus. Group 3 showed significantly higher numbers of ovulation follicles, significantly higher growth rates of follicles per day and significantly larger diameters of follicles and corpora lutea than groups 1 and 2 but not Group 4 (P<0.05). Group 4 showed significantly higher numbers of large follicles (≥5 mm in diameter), unovulated follicles and ovulations, a significantly higher growth rate of follicles per day, and significantly larger diameters of follicles and corpora lutea (P<0.05) than those of the other groups. This indicates a state of overstimulation of ovaries in this group. Besides, the plasma levels of FSH in Group 4 were significantly higher (P<0.05) than in the other group and were maintained in the range of 2.2-0.7 ng/ml over a period of 6 to 66 h after the FSHp injection. Meanwhile, the plasma levels of P4 and E2 did not differ in any of the groups in the period of 0 to 96 h during the superstimulation program. In conclusion, it was demonstrated that a single i.m. injection of 100 mg FSHp was the most effective dose for superstimulation of follicular growth in Thai native heifers under the experimental conditions in this study.