212 INSEMINATION OF OVUM PICKUP-DERIVED DAIRY COWS RESULTS IN OFFSPRING WITH NORMAL BIRTH WEIGHT

Abstract

Animals derived by ovum pickup-in vitro production (OPU-IVP) have a higher birth weight compared with animals derived by AI (Wagtendonk et al. 2000 Theriogenology 53, 575–597). It has been suggested that this higher birth weight is the result of epigenetic changes such as aberrant methylation and gene expression pattern, which are caused by the presence of serum in the culture medium (Wrenzycki et al. 2004 Anim. Reprod. Sci. 82–83, 593–603). The present study aimed to investigate whether the higher birth weight, possibly caused by epigenetic changes, is a permanent characteristic that is transmitted to the offspring. We therefore monitored the birth weight of calves born after insemination of OPU-IVP-derived animals. Ovum pickup-IVP was performed according to routine procedures. Immature COC were recovered by OPU. The COC were matured in vitro in TCM-199 supplemented with fetal calf serum (FCS)/LH/FSH. Subsequently, matured oocytes were fertilized with frozen–thawed gradient-separated semen and further cultured for 7 days in TCM-199/10% FCS on a BRL monolayer (CoCul group) or in SOFaaBSA (SOF group). First-generation OPU-IVP animals were produced from oocytes collected by OPU of AI-derived animals. The second generation was produced by inseminating OPU-IVP animals. Calves generated by inseminating AI animals were used as a control group. Birth weights of control AI, first-generation, and second-generation calves were analyzed by using restricted maximum likelihood (Genstat 9.1). Model Birth Weight: *Fixed: Parity Recipient + Sex + Gestation Length + Year + Embryo Type (AI, first, or second generation) + Culture System (CoCul or SOF). *Random: Sire + Barn. The results (Table 1) clearly show that the first-generation (OPU-IVP) calves had, on average, a 3.4-kg greater birth weight than the AI calves. The second-generation calves, however, had approximately the same birth weight as the calves in the AI control group. Our results indicated that the high birth weight of OPU-IVP-derived calves is not a permanent characteristic that is transmitted to their offspring. Previous studies have demonstrated that the fertility of OPU-IVP-derived animals is in the normal range (Wagtendonk et al. 2000 Theriogenology 53, 575–597).

Table 1. Birth weight (least squares means ± SE) of AI calves (control), first generation OPU-IVP-derived calves, and second generation AI derived calves from OPU-IVP mothers