|Chase, Chadwick - Chad|
|Cushman, Robert - Bob|
|PERRY, GEORGE - South Dakota State University|
|TENLEY, SARAH - University Of Nebraska|
|WOOD, JENNIFER - University Of Nebraska|
|CUPP, ANDREA - University Of Nebraska|
Submitted to: Reproduction, Fertility and Development
Publication Type: Abstract Only
Publication Acceptance Date: 8/4/2016
Publication Date: 12/1/2016
Citation: Chase, C.C., Cushman, R.A., McNeel, A.K., Wright-Johnson, E.C., Perry, G.A., Tenley, S.C., Wood, J.R., Cupp, A.S., Vallet, J.L., Miles, J.R. 2017. Effect of antral follicle count in beef heifers on in vitro fertilization/production [abstract]. Reproduction, Fertility and Development. 29(1):180.
Technical Abstract: Our objective has been to compare the in vitro fertilization (IVF) and production (IVP) of embryos from low and high antral follicle count (AFC) heifers. This is the 4th year of the study with years 1 to 3 reported individually. For this report, we add data for the 4th year and present a combined analysis (years 1 to 4) for the first time. Each year, AFC was determined on approximately 120 Angus heifers using transrectal ultrasonography. Ten heifers with the lowest AFC and 10 heifers with the highest AFC with evidence of estrous cyclicity were synchronized with two injections of PGF2a and half were harvested on d 5 to 6 and half on d 15 to 16 of the estrous cycle. The IVF procedure for media and sperm separation was slightly modified each year. For year 4, the IVF procedure included protocols for semi-defined media and was as described (IVP Protocol, P.J. Hansen’s Laboratory, University of Florida). Cumulus-oocyte complexes (COCs) from follicles less than 8 mm in diameter were cultured in maturation medium (5% CO2; 38.5°C) for 24 h. Matured COCs were fertilized using thawed frozen semen from a bull that was purified using Isolate. Motile spermatozoa were added to COCs in fertilization medium at a final concentration of 1x106 spermatozoa per mL. About 24 h later, presumptive zygotes were placed in micro drops of development medium under oil, and cultured (5% CO2; 5% O2; balance N2; 38.5°C). On d 3 and 8 after fertilization, cleavage and blastocyst development rates, respectively, were assessed. Data were analyzed using the MIXED procedure of SAS and the model included the effects of year (1 to 4), group (high or low AFC), and their interaction. The year x group interaction was not significant (P > 0.10). Low AFC heifers, compared to high AFC heifers, had fewer numbers of COCs (P < 0.0001; 12.8 ± 1.83 vs. 31.9 ± 1.86), fewer numbers of COCs that cleaved (P < 0.0001; 8.0 ± 1.38 vs. 21.6 ± 1.40), and fewer numbers of COCs that developed to the blastocyst stage (P < 0.0001; 1.7 ± 0.58 vs. 5.7 ± 0.58). Year affected the numbers of COCs that cleaved (P < 0.003) and the numbers of COCs that developed to the blastocyst stage (P < 0.0001). Year also influenced the percentage of COCs that cleaved (P < 0.0002) and the percentage of COCs that developed to blastocysts (P < 0.0001). Group (AFC) did not influence (P > 0.19) the percentage of COCs that cleaved (61.2 ± 2.83 vs. 66.4 ± 2.83%, for low vs. high AFC, respectively). Low AFC heifers had a lower (P < 0.002) percentage of COCs that developed to blastocysts (10.3 ± 1.52%) than high AFC heifers (17.6 ± 1.52%). These results indicate that high AFC heifers, compared to low AFC heifers, have more COCs recovered, more COCs cleaved, and more COCs developed to the blastocyst stage. The percentage of COCs cleaved did not differ between AFC groups; however, the percentage of COCs that developed to the blastocyst stage was greater for high than low AFC heifers. This suggests a potential advantage in maternal to embryonic transition for high compared to low AFC heifers.