Analysis of 18 RNA-seq libraries from three bovine calves at day 0, 7, 14 and 28, together with their dams (day 0 and 7) revealed a significant shift in neonatal transcriptome within first week post-birth. At this time point, a set of 717 genes is up-regulated. Global pathway analysis of the transcriptome showed 110 differentially expressed (DE) immune-related genes at birth as compared to day 7. These include immune related genes, such as, complement, MHCII, chemokine receptors, defensins and cytokines. As compared to adults, IGKC is expressed at higher levels in the neonates, despite predominant IGLC expression at birth. Two members of IGKV2 family, IGKV10 and IGKV12, are preferentially expressed in neonatal B cells. As for IGLV1 family, IGLV1b.1 and IGLV1x.1 are most expressed in neonatal B cells. Another member, IGLV3.4, of rarely expressed IGLV3 family is preferentially used in neonatal B cells. The IGHM and IGHD transcripts are expressed at birth and IGHM achieves adult levels by day 7. This is followed by IGHA and IGHG transcripts 14-28 days post birth. Interestingly, most 3 ́ IGHV1S1(BF4E9) gene, known to encode antibodies with exceptionally long CDR3H, is preferentially expressed in neonatal B cells. In parallel, single longest IGHD2(DH2) gene that encodes such an atypical CDR3H is expressed at high levels at birth. It seems that IGHV1S1(BF4E9) gene has an important functional role in the development and expansion of bovine neonatal B-cell repertoire. To conclude, the bovine neonate acquires IgM levels similar to adult by day 7 and is immunocompetent by four weeks of life. [Supported by NSERC Canada Discovery Grant]