RESUMO
Proinflammatory cytokines are involved in regulating several reproductive processes that occur during the periovulatory period, including ovulation, corpus luteum formation, and preimplantation embryo development. The objective of this study was to determine whether stimulation of proinflammatory cytokines through administration of mycobacterium cell wall fraction (MCWF; Amplimune, NovaVive) could improve embryo development following superovulation in dairy heifers. A total of 34 independent embryo recovery procedures were performed using nulliparous Holstein heifers (n = 20; age 12-18 mo) as donors. For superovulation, dominant follicle removal was performed and an intravaginal progesterone device was inserted on d -6. Thirty-six hours later, on d -4, FSH (420 IU total) was administered in a decreasing dose regimen consisting of 8 injections given twice daily at 12-h intervals. Prostaglandin F2α was administered in conjunction with the fifth and sixth injections of FSH on d -2 and the intravaginal progesterone device was removed on the morning of d -1. Twenty-four hours later, on d 0, donors received their randomly assigned treatment (sterile saline or MCWF, 5 mL, i.m.) and gonadotropin-releasing hormone was administered to induce ovulation. Donors were artificially inseminated with frozen-thawed semen at 12 and 24 h after induced ovulation. Nonsurgical embryo recovery procedures were performed on d 7. Recovered structures were evaluated using a stereomicroscope to assess embryo development. There was no effect of MCWF treatment on the numbers of total structures, unfertilized oocytes, degenerate embryos, transferable embryos, or blastocysts. However, there was a trend for donors treated with MCWF to have a greater proportion of blastocysts out of total structures recovered. Overall, the efficacy of superovulation in virgin dairy heifer donors was not improved by administration of MCWF during the peri-ovulatory period, but results indicate that MCWF treatment may enhance embryo developmental kinetics.
RESUMO
An experiment was conducted to determine whether administration of mycobacterium cell wall fraction (MCWF; Amplimune, NovaVive) could enhance embryo developmental competence following in vitro embryo production (IVP) and pregnancy establishment after embryo transfer (ET). Nulliparous, Holstein heifers (n = 40; age 8-15 months) were submitted to two rounds of ovum pick-up (OPU) and IVP in a crossover design. Thirty-six h after follicle wave synchronization, treatments (saline or MCWF, 5 mL, im) were administered in conjunction with a single dose of follicle stimulating hormone (175 IU) and OPU was performed 48-52 h later. Recovered cumulus-oocyte complexes were used for IVP to assess embryo development. For ET, nulliparous, Holstein heifers (n = 225; age 12-18 months) were used as recipients. At 12-24 h after detection of spontaneous estrus, recipients were randomly treated with either saline or MCWF (5 mL, im). The effect of MCWF on pregnancy per ET (P/ET) was assessed in a 2 × 2 factorial design with recipients treated with or without MCWF receiving a fresh IVP embryo from a donor treated with or without MCWF at day 7 or 8 after detected estrus. Blood samples were collected from a subset of donors (n = 8) and recipients (n = 26 to 33 per treatment) prior to treatment and at 6 and 24 h post-treatment to determine serum concentration of interleukin (IL)-1ß, IL-6, tumor necrosis factor-α, and interferon-γ. Blood samples were also collected from a group of recipients (n = 31 to 39 per treatment) to assess serum concentration of progesterone at days 4, 7, and 16 post-treatment. Pregnancy status was determined at days 40 and 100 of gestation. Donor treatment with MCWF tended (P < 0.07) to increase the proportion of oocytes that developed into transferable embryos, but there was no effect of MCWF on other parameters of embryo development. The P/ET at days 40 and 100 of gestation and pregnancy loss were not affected by donor treatment or recipient treatment with MCWF and there was no interaction. Serum concentration of proinflammatory cytokines among donors and recipients and serum concentration of progesterone among recipients were not increased by treatment with MCWF. Results of the present study indicate that treatment of donors with MCWF has minimal impact on subsequent embryo development following IVP. Moreover, regardless of whether donors or recipients were treated with MCWF, there was no effect on P/ET following transfer of IVP embryos.