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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2008-1066v1 86/9/2126    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Miles, J. R. Articles by Zuelke, K. A. PubMed PubMed Citation Articles by Miles, J. R. Articles by Zuelke, K. A.

Conceptus development during blastocyst elongation in lines of pigs selected for increased uterine capacity or ovulation rate^1,2

J. R. Miles^*,3, B. A. Freking^*, L. A. Blomberg, J. L. Vallet^* and K. A. Zuelke

^* USDA-ARS, US Meat Animal Research Center, Clay Center, NE 68933; and USDA-ARS, Beltsville Area Research Center, Beltsville, MD 20705; and and USDA-ARS, National Animal Disease Center, Ames, IA 50010

³ Corresponding author: Jeremy.Miles{at}ars.usda.gov

Lines of pigs selected for increased uterine capacity have improved conceptus survival, whereas pigs selected for increased ovulation rate have decreased conceptus survival relative to an unselected control line. The objective of this study was to evaluate conceptus development during blastocyst elongation as a potential contributing factor to differences in conceptus survival rate among these pig lines. Conceptuses were recovered from pregnant control, uterine capacity, and ovulation rate line gilts at d 10 and 12 of gestation. At d 10 of gestation, conceptus morphologic diversity was assessed by comparing within-litter average conceptus diameter and the standard deviation of conceptus diameters. At d 12 of gestation, conceptus morphologic diversity was assessed by comparing blastocyst populations obtained from individual gilts. Real-time PCR analyses for transcripts involved in steroidogenesis, cellular differentiation, and immune responsiveness were performed on spherical, ovoid, and filamentous conceptuses recovered from these selection lines. Uterine flushings were also assayed for total protein and estradiol-17β at d 10 and 12 of gestation. Morphological data were analyzed using ANOVA with the fixed effects of line, farrowing season, and their interactions. Conceptus mortality, uterine flushing, and real-time PCR data were analyzed using ANOVA with the fixed effects of line, day or blastocyst morphology, farrowing season, and their interactions. Conceptus mortality, measured as the ratio of conceptus recovery to ovulation rate, was not different between the lines on d 10 and 12 of gestation. There were no significant line effects for conceptus morphologic diversity at d 10 and 12 of gestation. Expression of transcripts associated with steroidogenesis (steroidogenic acute regulatory protein, cytochrome P450 side chain cleavage, and aromatase), cellular differentiation (cytokeratin-18 and vimentin), and immune responsiveness (interleukin-1β) in spherical, ovoid, and filamentous conceptuses was not different between the lines. Furthermore, protein and estradiol-17β in uterine flushings at d 10 and 12 of gestation were not different between the selection lines. These findings indicate limited, if any, deviations between these lines of pigs in conceptus development during blastocyst elongation and suggest that mechanisms involved in generating line differences in survival rate likely are manifested later in gestation.

Key Words: blastocyst elongation • estradiol • gene expression • pig • ovulation rate • uterine capacity