Modulation of fat mobilization and adipose tissue gene expression in Holstein cows supplemented with omega-3 fatty acids and N-acetyl-tryptophan during the transition period.

The transition period is critical for dairy cows, characterized by negative energy balance (NEB), excessive adipose mobilization, and metabolic challenges. This study investigated the effects of dietary omega-3 fatty acids (O3) and N-acetyl-tryptophan (NAT) on blood metabolites and adipose tissue gene expression in Holstein cows. Forty-eight multiparous cows were assigned to four groups (control, O3, NAT, O3+NAT) from -21 to +42 days relative to calving. Body weight (BW) and body condition score (BCS) were recorded, and plasma non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), insulin, and glucose were measured at -21, 0 (calving), +21, and +42 days. Adipose biopsies at +21 and +42 days postpartum were used to perform qPCR analysis of lipogenesis-related genes (Acetyl-CoA carboxylase alpha (ACACA), peroxisome proliferator-activated receptor gamma (PPARγ), lipoprotein lipase (LPL)), fatty acid oxidation (Acyl-CoA oxidase 1 (ACOX1)), lipolysis (hormone-sensitive lipase (LIPE), adipose triglyceride lipase (ATGL)), and adiponectin receptors (AdipoR1, AdipoR2). Statistical analysis used two-way ANOVA with repeated measures. Cows supplemented with O3+NAT maintained higher BW (p<0.05) and BCS (p<0.05), exhibited lower NEFA and BHBA (p<0.05), and had increased insulin (p<0.05) and tended to have higher glucose (p=0.08) compared with controls. PPARγ, LPL, and adiponectin receptors (AdipoR1, AdipoR2) were upregulated in all supplemented groups compared to controls (p<0.05). ACOX1 was downregulated in O3, NAT, and O3+NAT groups compared to control (p<0.05). Network analysis revealed strong positive correlations between insulin and AdipoR1/2 (r>0.7) and positive correlations between NEFA/BHBA and LIPE/β2AR (r>0.75) at d 21. These results demonstrate that O3 and NAT act via complementary mechanisms to attenuate lipolysis, promote lipid storage, and enhance metabolic homeostasis during the transition period.