|Abstract:||Many factors influence fetal growth and development throughout pregnancy. During this critical time maternal nutrition is one of the most important factors that can affect offspring health and performance. Methionine, besides being the first limiting amino, is an important precursor of antioxidants and methyl donor. Therefore, our objectives were to investigate if increasing methionine (Met) supply during late-pregnancy affects developmental, metabolic, and immune parameters of the calf at birth and during the neonatal period. Calves born to Holstein cows individually-fed a basal control [CON; 1.47 Mcal/kg dry matter (DM) and 15.3% crude protein] diet with no added Met or CON plus rumen-protected Met (MET; Mepron® at 0.09% of diet DM) during the last 28 ± 2 d of pregnancy were used. A total of 39 calves were in CON and 42 in MET. At birth, calves were randomly allocated considering dam treatment and colostrum as follows: 1) calves from CON cows and colostrum from CON cows (n = 21); 2) calves from CON cows and colostrum from MET cows (n = 18); 3) calves from MET cows and colostrum from MET cows (n = 22); and 4) calves from MET cows and colostrum from CON cows (n = 20). Liver biopsies were harvested at 4, 14, 28, and 50 d of age and used for metabolomics via GS-MS and activity of hepatic 1-carbon metabolism enzymes. Liver samples at day 4 were used for RNA sequencing, protein expression, and global DNA methylation. Blood for biomarker analyses and innate immune function assays was harvested at birth (before colostrum feeding), 7, 21, 42 and 50 d of age. Whole blood was challenged with enteropathogenic bacteria (E. coli 0118:H8), and phagocytosis and oxidative burst of neutrophils and monocytes quantified by flow cytometry. Despite greater daily DM intake pre-partum in cows fed MET (15.7 vs. 14.4 0.12 kg/d, P < 0.05), colostrum quality and quantity were not affected by maternal diet. At birth, MET calves had greater (P ≤ 0.05) body weight (BW, 44.1 vs. 42.1 ± 0.70 kg), hip height (HH, 81.3 vs. 79.6 ± 0.53 cm) and wither height (WH, 77.8 vs. 75.9 ± 0.47 cm). In contrast, concentrations of His, Lys, and Asn in plasma were lower (P ≤ 0.05) in MET calves. Regardless of colostrum source, the greater BW, HH, and WH in MET calves at birth persisted through 9 wk of age resulting in average responses of +3.1 kg BW, +1.9 cm HH, and +1.8 cm WH compared with CON. Average daily gain during the 9 wk was (P < 0.05) 0.72 ± 0.02 kg/d in MET compared with 0.67± 0.02kg/d in CON calves. Despite similar rates of daily DMI, maternal supplementation with Met led to greater (P ≤ 0.05) overall hepatic concentrations of the 1-carbon metabolism intermediates adenosine, betaine, choline, glycine, and N,N-dimethylglycine in liver tissue. Among transsulfuration pathway metabolites, concentrations of cystathionine, cysteinesulfinic acid, hypotaurine, serine, and taurine were greater (P ≤ 0.05) in MET calves. There was a treatment day effect for the activity of betaine-homocysteine S-methyltransferase (BHMT), methionine synthase (MTR), and cystathionine-beta-synthase (CBS) in liver tissue. The activity of BHMT and CBS increased in MET calves between d 4 and 14, with a peak at 28 d. Despite a linear increase from d 4 to 28, the activity of MTR in MET calves was lower on d 4 and 50. In vitro phagocytosis in stimulated neutrophils was greater overall (P ≤ 0.05) in MET calves. At day 4 of life, MET calves have greater global DNA methylation comparing to CON calves along with a greater ratio of EBP1: EBP1 and p-AKT:AKT protein expression. Overall, our results indicate that the enhanced post-ruminal supply of methionine to cows during late-pregnancy benefits calf growth in part through alterations in hepatic metabolism and innate immune response.