Effects of mycobacterium cell wall fraction on embryo development following in vitro embryo production and pregnancy rates following embryo transfer in virgin dairy heifers

Abstract

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)-1β, 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.

Keywords: Cattle; Embryo transfer; In vitro fertilization; Mycobacterium cell wall fraction.