Miles J R, Freking B A, Blomberg L A, Vallet J L, Zuelke K A
USDA-ARS, US Meat Animal Research Center, Clay Center, NE 68933, USA.
J Anim Sci. 2008 Sep;86(9):2126-34. doi: 10.2527/jas.2008-1066. Epub 2008 May 9.
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-17beta 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-1beta) in spherical, ovoid, and filamentous conceptuses was not different between the lines. Furthermore, protein and estradiol-17beta 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.
为提高子宫容量而选育的猪群，其着床前胚胎的存活率有所提高；而与未选育的对照品系相比，为提高排卵率而选育的猪群，其着床前胚胎的存活率有所降低。本研究的目的是评估囊胚伸长期间着床前胚胎的发育情况，作为这些猪品系着床前胚胎存活率差异的一个潜在影响因素。在妊娠第10天和第12天，从妊娠的对照、子宫容量和排卵率品系的后备母猪中回收着床前胚胎。在妊娠第10天，通过比较同窝内着床前胚胎平均直径和着床前胚胎直径的标准差来评估着床前胚胎形态多样性。在妊娠第12天，通过比较从个体后备母猪获得的囊胚群体来评估着床前胚胎形态多样性。对从这些选择品系中回收的球形、卵形和丝状着床前胚胎进行实时PCR分析，检测参与类固醇生成、细胞分化和免疫反应的转录本。在妊娠第10天和第12天，还检测子宫冲洗液中的总蛋白和雌二醇-17β。形态学数据采用方差分析，固定效应包括品系、产仔季节及其交互作用。着床前胚胎死亡率、子宫冲洗液和实时PCR数据采用方差分析，固定效应包括品系、天数或囊胚形态、产仔季节及其交互作用。以着床前胚胎回收率与排卵率的比值衡量的着床前胚胎死亡率，在妊娠第10天和第12天各品系之间没有差异。在妊娠第10天和第12天，各品系着床前胚胎形态多样性没有显著的品系效应。球形、卵形和丝状着床前胚胎中，与类固醇生成（类固醇生成急性调节蛋白、细胞色素P450侧链裂解酶和芳香化酶）、细胞分化（细胞角蛋白-18和波形蛋白）和免疫反应（白细胞介素-1β）相关的转录本表达在各品系之间没有差异。此外，在妊娠第10天和第12天，各选择品系子宫冲洗液中的蛋白质和雌二醇-17β没有差异。这些发现表明，在囊胚伸长期间，这些猪品系着床前胚胎发育的差异（如果有的话）有限，这表明导致品系存活率差异的机制可能在妊娠后期才表现出来。
