|Chase, Chadwick - Chad|
|AMUNDSON, OLIVIA - South Dakota State University|
|Cushman, Robert - Bob|
|PERRY, GEORGE - South Dakota State University|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 10/31/2014
Publication Date: 12/15/2014
Citation: Chase, C.C., Amundson, O.L., Cushman, R.A., Freetly, H.C., McNeel, A.K., Wright-Johnson, E.C., Perry, G.A., Sypherd, D.D., Miles, J.R. 2015. Effect of increased systemic concentrations of urea nitrogen in crossbred heifers on in vitro fertilization (IVF)[abstract]. American Society of Animal Science, Southern Section, January 31-February 3, 2015, Atlanta, GA. p. 30.
Technical Abstract: Elevated levels of dietary N and hence systemic concentrations of urea-N have been shown to have a deleterious effect on reproductive processes. The objective of this study was to determine the effect of feeding pubertal crossbred heifers diets with moderate (M-N; 64.8% corn silage, 30.0% alfalfa hay-chopped, 5.0% corn, and 0.2% salt; 2.2% N) or high (H-N; 64.3% corn silage, 29.8% alfalfa hay-chopped, 5.0% soybean meal, 0.7% urea, and 0.2% salt; 3.0% N) levels of N on IVF. From a pool of 150 heifers, 30 heifers (15 M-N and 15 H-N) were used in this portion of the study. Heifers were fed treatment diets for at least 90 d. Heifers were synchronized using one or two injections of PGF2a and sacrificed over 2 d; on d 4 of the estrous cycle. Twenty-six heifers (n=12 M-N and n=14 H-N) were at the appropriate stage of the estrous cycle. Ovaries were collected and transported to the laboratory. The IVF procedures and media were as described (P.J. Hansen’s Laboratory, IVP Protocol). 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 crossbred bull that was purified using Percoll separation procedures. Motile spermatozoa were added to COCs in fertilization medium at a final concentration of 1 x 106 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; 38.5°C). On d 3 and 8 after fertilization, cleavage and blastocyst development, respectively, were assessed. Data were analyzed using the MIXED procedure of SAS and the model included the effects of collection d, treatment, and the interaction. Contemporary heifers fed H-N had higher plasma urea N concentrations than heifers fed M-N (11.0 vs. 6.2 ± 0.17 mg/dL, respectively). Neither collection d nor the interaction differed (P > 0.2). Likewise, treatment (M-N vs. H-N) did not affect (P > 0.3) the number of COCs collected per heifer (12.0±2.20 vs. 14.7±2.04), oocytes that cleaved (9.3±2.02 vs. 11.9±1.87), and developed to blastocysts (3.0±0.97 vs. 4.4±0.90). Additionally, there were no treatment differences (P > 0.9) in the percentage of COCs per heifer that cleaved (76.0±4.21 vs. 75.9±3.89%) or that developed to blastocysts (27.7±5.25 vs. 27.5±4.85%). Inclusion of a relatively high N level in the diet to growing pubertal heifers did not negatively impact oocyte competence.