The effect of in vitro treatment of bovine embryos with IGF-1 on subsequent development in utero to Day 14 of gestation.

Culture of bovine embryos with insulin-like growth factor-1 (IGF-1) can improve development to the blastocyst stage and embryo survival following transfer to heat-stressed, lactating dairy cows. Two experiments were conducted to determine whether IGF-1 could improve embryo survival and development at Day 14 after ovulation. In Experiment 1, non-lactating Holstein cows (n=58) were selected as recipients following synchronization for timed-embryo transfer. Embryos were produced in vitro and cultured with or without 100ng/mL IGF-1. At Day 7 after expected ovulation (Day 0), groups of 7-12 embryos were randomly transferred to each recipient. Embryos were recovered at Day 14. Embryo length and the presence or absence of an embryonic disc was recorded. Recovered embryos were cultured individually for 24h to determine interferon-tau (IFN-tau) secretion. There was no effect of IGF-1 on embryo recovery rate, embryo length or IFN-tau secretion. In Experiment 2, non-lactating (n=56) and lactating (n=35) Holstein cows were selected as recipients following synchronization for timed-embryo transfer. Embryos were produced as described in Experiment 1. At Day 7 after expected ovulation (Day 0), a single embryo was randomly transferred to each recipient. Embryos were recovered at Day 14. Embryo length and IFN-tau secretion were determined as in Experiment 1. Recovery rate at Day 14 tended (P=0.1) to be higher for recipients that received IGF-1 treated embryos compared to control embryos (43.2% versus 26.1%, respectively). There was no effect of IGF-1 on embryo length or IFN-tau secretion. In conclusion, results suggest that exposure to IGF-1 through Days 7-8 of development does not enhance capacity of embryos to prevent luteolysis. Results of the single embryo-transfer experiment suggested that IGF-1 treatment might affect embryo survival post-transfer as early as Day 14 after ovulation. Further experimentation is warranted to verify this finding.

Embryonic disc development and subsequent viability of cattle embryos following culture in two media under two oxygen concentrations.

Bovine embryos were produced in vitro using a 2 x 2 design of modified medium (KSOM or SOF) and oxygen concentration (5% or 20%). Day 7 blastocysts were transferred in bulk (n = 11, on average) to recipient heifers and recovered non-surgically at Day 14. In two replications of a Latin square, eight heifers received embryos from each combination of factors. Recovered embryos were evaluated for trophoblast length and width, as well as the presence and diameter of an embryonic disc (ED). An ED was detected in a higher percentage of embryos that had been cultured in KSOM than SOF (72% v. 46%, respectively; P < 0.05). The aim of a second series of experiments was to associate Day 14 morphology with subsequent developmental capacity. In vitro-produced blastocysts were transferred (n = 17-20) on Day 7 to each of eight heifers and recovered at Day 14. Thirty-eight blastocysts were retransferred to heifers following morphological evaluation. Embryos in which an ED with no signs of degeneration had been detected maintained more pregnancies than other embryos in which an ED had either shown signs of degeneration or had not been detected (5/8 v. 2/30, respectively; P < 0.01). Further investigation into ED integrity at the elongating stage may contribute to our understanding of pregnancy establishment and maintenance.