82 Compensation of the Growth and Development of Individually Transferred Bovine Bisected Embryos

Abstract

Embryo bisection has been used in cattle for decades to multiply embryos. Recent articles assert that each bisected hemi-embryo continues its growth and differentiation without regenerating the original number of cells, producing smaller embryos. This size difference has been verified until Day 17, when the embryo has already elongated. The objective of this research was to evaluate fetal morphometric differences between embryos and hemi-embryos during the intrauterine period and at birth. For this purpose, 6 Angus cows were superovulated using the FSH/LH protocol (Pluset®, Hertape Calier, Minas Gerais, Brazil) and all were artificially inseminated with the sire ‘Las Lilas 1931 Líder Max’. At Day 7 post-AI, 45 embryos were recovered using a non-surgical technique. In the laboratory, 30 of them were bisected under a stereoscopic magnifier using a portable micromanipulator with a microscale attached. Each hemi-embryo (N = 60) and the remaining integer embryos (N = 15, used as controls) were immediately transferred individually to a recipient. The growth of the fetuses was evaluated ultrasonographically using a Esaote Aquila Pro vet ultrasound (Esaote SpA, Genoa, Italy). Transrectal measurements were performed at 60 and 90 days, recording femur length (only at 60 days), biparietal distance, and abdominal and umbilical cord diameter. At birth, animals were weighed, measured for length and height, and the circumferences of the skull, thorax, abdomen, and metatarsus were recorded. Data were analysed by the t-test implemented in InfoStat Version 1.1 software (https://www.infostat.com.ar/). Table 1 shows the average and standard deviation of all measurements performed. No significant differences (P < 0.05) were observed between hemi-embryos and control at any stage, except for biparietal diameter on Day 90 of gestation, which was not reflected in skull circumference at birth. In conclusion, individually transferred hemi-embryos generated 60-day fetuses with almost no differences in growth and development compared with the control embryos. The compensation phenomenon should have occurred before Day 60 of gestation.

Table 1.  Mean and standard deviation of all measurements performed on hemi-embryos and control embryos at 60 and 90 days and at birth