Effects of administration of mycobacterium cell wall fraction during the periovulatory period on embryo development following superovulation in virgin dairy heifers

Abstract

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 F_2α 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.

Summary: The objective of this study was to evaluate the effects of stimulating proinflammatory cytokines during the periovulatory period on embryo development using superovulation as a model. Animals submitted to a superovulation protocol received either a control treatment (sterile saline) or mycobacterium cell wall fraction (MCWF, Amplimune) on the day of induced estrus. Seven days after artificial insemination, embryos were recovered through nonsurgical recovery, and the number and development of each collected structure were evaluated. There were no statistical differences in any of the measures evaluated except for a trend in animals receiving MCWF having a greater proportion of blastocysts recovered (P < 0.10).

Figure 1

Schematic depiction of the experimental schedule, including superovulation, treatment, and embryo recovery. Controlled internal drug-releasing device (CIDR), mycobacterium cell wall fraction (MCWF), dominant follicle removal (DFR). Created with BioRender.com.