This study used the Oxford Nanopore (ONT) MinION to provide long-read sequencing of amplicons from bovine IgM and IgG B cell receptors from colostrum and blood. Blood mononuclear cells (BMC, n=7) and colostral cells (n=8) were isolated from Holstein dairy cows. BMCs were magnetically sorted to capture B cells. Colostral cells were harvested by centrifugation without magnetic sorting. RNA was extracted from cells, cDNA was produced, and IgM and IgG transcripts were amplified using polymerase chain reactions. Amplicons were sequenced using the ONT Native barcoding kit 24 V14 and MinION with R10.4 flow cells. This study aimed to characterize colostral B cell populations and, for the first time, identify a subset with ultralong CDR3s and compare with blood B cell repertoires.