175 CONSEQUENCES OF IN VITRO PRODUCTION OF EMBRYOS WITH OR WITHOUT COLONY-STIMULATING FACTOR 2 IN CULTURE MEDIUM ON MORPHOMETRIC FEATURES OF THE BOVINE CONCEPTUS AT DAY 86 OF GESTATION

In vitro production (IVP) of embryos can disrupt fetal and placental development and increase risk of abnormal fetal growth. Maternal factors play a role in developmental programming of the early embryo. Colony-stimulating factor 2 (CSF2) is present in the oviduct and endometrium and has improved competence of the pre-implantation embryo to establish pregnancy in cattle. The objective was to determine whether CSF2 during embryo culture alters fetal development and alleviates abnormalities associated with IVP. Holstein oocytes were matured and fertilised in vitro with X-sorted semen from a Holstein bull. Putative zygotes were cultured in SOF-BE1 at 5% CO2 and 5% O2 for 5 days and then randomly assigned to receive vehicle (IVP-control) or 10 ng mL–1 CSF2 (IVP-CSF2). Grade I blastocysts were transferred on Day 7 to Holstein recipients that were previously randomised to receive an IVP-control or an IVP-CSF2 embryo. A third group of cows included in the randomization was assigned to be artificially inseminated on Day 0 using the same bull as for IVP (AI). Pregnancy was terminated on Day 85 or 86. Statistical analysis was performed by analysis of variance using the GLM procedure of SAS with contrasts for AI v. (IVP-control+IVP-CSF2) (contrast 1; C1) and IVP-control v. IVP-CSF2 (contrast 2; C2). Results are least squares means ± s.e.M. A total of 23 morphometric measurements of placenta and fetus were made on 9 AI, 12 IVP and 7 CSF2 female singletons. Conceptuses derived by IVP (IVP-control and IVP-CSF2) differed from those derived by AI for 4 characteristics including fetal bodyweight (142.9 ± 4.7, 157.2 ± 4.4, and 162.6 ± 6.1 g for AI, IVP-control and IVP-CSF2, respectively; C1, P = 0.0237), eviscerated weight (102.9 ± 3.4, 113.6 ± 3.2, and 112.2 ± 4.4 g; C1, P = 0.0602), crown-rump length (CRL) (13.7 ± 0.2, 14.0 ± 0.2, and 14.7 ± 0.3 g; C1, P = 0.0434; C2, P = 0.0631) and umbilical cord diameter (0.85 ± 0.08, 1.1 ± 0.08, and 0.91 ± 0.1 cm; P = 0.0519). Note that while IVP-CSF2 conceptuses were generally similar to those for IVP-control, CRL tended to be highest for IVP-CSF2. Also, umbilical cord diameter for IVP-CSF2 was similar to AI and lower than IVP-control. Data from 1 fetus in the IVP-CSF2 group was excluded from analysis because it had a phenotype consistent with large offspring syndrome. Bodyweight (354 g) was 2-fold larger than other fetuses (average = 155 g) and placental weight was 7-fold greater (1505 v. 211 g). In addition, organs were enlarged and severe ascites and hemorrhagic cotyledons were observed. In conclusion, IVP resulted in increased fetal size and umbilical cord diameter without other significant effects on placental morphometry. CSF2 did not alleviate adverse effects of culture on fetal growth, exacerbating effects on CRL, but did reduce effects of IVP on umbilical cord diameter. Gene expression analysis may be useful for further characterisation of effects and elucidation of mechanisms involved. This project was supported by USDA NIFA Grant 2011–67015–30688.