Transcript abundances associated with fertility in a case-control design including Angus and Holstein heifers

We carried out an experiment to test the hypothesis that differences in gene transcript abundance due to fertility fitness would be shared between heifers of different breeds. We produced transcriptome data from peripheral white blood cells from 22 heifers (purebred Angus heifers (n=12), purebred Holstein (n=10) heifers). We identified two genes whose transcript abundance differed (eFDR = 0.002) between the two groups (Fertile and Sub-Fertile), namely Adipocyte Plasma Membrane Associated Protein (APMAP, 1.16 greater abundance in the Fertile group) and Dynein Axonemal Intermediate Chain 7 (DNAI7, 1.23 greater abundance in the Sub-Fertile group). Overall design: We collected blood samples from purebred Angus heifers (n=12), averaging 14 months in age, at the time of their first artificial insemination (AI) service. Heifers were subjected to a 7-Day Co-Synch + CIDR estrus synchronization protocol prior to breeding. Additionally, we collected blood samples from purebred Holstein (n=10) heifers, averaging 12 months in age, at the time of the first AI service. Heifers were identified as either Fertile (Holstein, n=5; Angus, n=5) or Sub-Fertile (Holstein, n=5; Angus, n=7) based on their pregnancy outcome. Fertile animals were identified as those who became pregnant and subsequently delivered a calf following the first insemination service. Angus heifers were categorized as Sub-Fertile after failing to achieve pregnancy following two insemination services and exposure to a bull for natural breeding. Holsteins were identified as Sub-Fertile after receiving four or more inseminations before achieving pregnancy or not becoming pregnant.