Supplemental Smartamine M in higher-energy diets during the prepartal period improves hepatic biomarkers of health and oxidative status in Holstein cows

Background： Feeding higher-energy prepartum is a common practice in the dairy industry. However, recent data underscore how it could reduce performance, deepen negative energy balance, and augment inflammation and oxidative stress in fresh cows. We tested the effectiveness of rumen-protected methionine in preventing the negative effect of feeding a higher-energy prepartum. Multiparous Holstein cows were fed a control lower-energy diet（CON, 1.24 Mcal/kg DM; high-straw） during the whole dry period（-50 d）, or were switched to a higher-energy（OVE, 1.54 Mcal/kg DM）, or OVE plus Smartamine M（OVE ＋ SM; Adisseo NA） during the last 21 d before calving.Afterwards cows received the same lactation diet（1.75 Mcal/kg DM）. Smartamine M was top-dressed on the OVE diet（0.07% of DM） from -21 through 30 d in milk（DIM）. Liver samples were obtained via percutaneous biopsy at -10, 7 and 21 DIM. Expression of genes associated with energy and lipid metabolism, hepatokines, methionine cycle, antioxidant capacity and inflammation was measured.Results： Postpartal dry matter intake, milk yield, and energy-corrected milk were higher in CON and OVE ＋ SM compared with OVE. Furthermore, milk protein and fat percentages were greater in OVE ＋ SM compared with CON and OVE. Expression of the gluconeogenic gene PCK1 and the lipid-metabolism transcription regulator PPARA was again greater with CON and OVE ＋ SM compared with OVE. Expression of the lipoprotein synthesis enzyme MTTP was lower in OVE ＋ SM than CON or OVE. Similarly, the hepatokine FGF21, which correlates with severity of negative energy balance, was increased postpartum only in OVE compared to the other two groups. These results indicate greater liver metabolism and functions to support a greater production in OVE ＋ SM. At 7 DIM, the enzyme GSR involved in the synthesis of glutathione tended to be upregulated in OVE than CON-fed cows, suggesting a greater antioxidant demand in overfed cows. Feeding OVE ＋ SM resulted in lower similar expression of GSR compared with CON. Expression of the methionine cycle enzymes SAHH and MTR, both of which help synthesize methionine endogenously, was greater prepartum in OVE ＋ SM compared with both CON and OVE, and at 7 DIM for CON and OVE ＋ SM compared with OVE, suggesting greater Met availability. It is noteworthy that DNMT3A, which utilizes S-adenosylmethionine generated in the methionine cycle, was greater in OVE and OVE ＋ SM indicating higher-energy diets might enhance DNA methylation, thus, Met utilization.Conclusions： Data indicate that supplemental Smartamine M was able to compensate for the negative effect of prepartal energy-overfeeding by alleviating the demand for intracellular antioxidants, thus, contributing to the increase in production. Moreover Smartamine M improved hepatic lipid and glucose metabolism, leading to greater liver function and better overall health.