Effects of Probiotic Supplementation from Dry-Off Through Early Lactation on Serum Protein Indices and Free Amino Acids in Dairy Cows: A Randomized Field Study

The transition from late gestation to lactation is accompanied by marked changes in protein and amino acid metabolism in dairy cows. This randomized field study evaluated whether oral multi-strain probiotic supplementation from dry-off to 12 weeks postpartum affected serum protein indices and circulating free amino acids. Twenty multiparous cows were allocated 1:1 to a control group (CON) or a probiotic-supplemented group (PRO). The longitudinal hematology and serum biochemistry subcohort comprised five cows per group, whereas free amino acids were measured at 7–8 weeks postpartum in 9 CON and 10 PRO cows. At 3–4 weeks postpartum, PRO cows had higher total protein (83.86 vs. 73.98 g/L; p = 0.009) and globulin (40.20 vs. 32.80 g/L; p = 0.024). At 7–8 weeks postpartum, PRO cows had lower asparagine (13.30 vs. 20.11 μmol/L; p = 0.004) and glutamine (280.90 vs. 363.44 μmol/L; p = 0.019), and higher aspartic acid (24.80 vs. 6.56 μmol/L; p = 0.008) and tryptophan (26.60 vs. 16.67 μmol/L; p = 0.045). Probiotic supplementation was associated with differences in selected serum protein indices and amino acids, although the underlying mechanisms remain to be established.