Abstract #457

# 457
Rumen-protected methyl donors during the transition period: 3. Hepatic one-carbon metabolism flux in response to supplemental Smartamine M or ReaShure.
Z. Zhou*1, T. A. Garrow1, M. Vailati Riboni1, F. C. Cardoso1, D. N. Luchini2, J. J. Loor1, 1University of Illinois at Urbana-Champaign, Urbana, IL, 2Adisseo NA, Alpharetta, GA.

Nutrients such as methionine (MET), choline (CHO), folate, and betaine are vital for provision of methyl groups required by various cellular pathways in tissues such as liver. In the context of dietary methyl-donors, the peripartal dairy cows are characterized by negative MET and CHO balance, both of which can play a role in allowing cows to achieve optimal performance while maintaining good health. Although studies of 1-carbon metabolism and MET cycle in ruminant liver already were performed in sheep, similar data are not available for high-producing Holstein dairy cows. Objectives were to measure activity of enzymes governing S-adenosyl MET formation (methionine adenosyltransferase 1), the transsulfuration pathway (Cystathionine β synthase), and endogenous synthesis of MET via CHO (betaine homocysteine S-methyltransferase, BHMT). Forty multiparous Holstein cows were used in a randomized complete block design with 2 × 2 factorial arrangement of MET and CHO level (with or without). Treatments (10 cows each) were control (CON), no MET or CHO; (SMA), CON+Smartamine M, Adisseo NA; (REA) CON+ReaShure, Balchem Inc.; and (MIX) CON+SMA+REA. From −50 d to −21 d before expected calving, all cows received the same diet (1.24 Mcal/kg DM) with no MET or CHO. From −21 d to calving, cows received the same close-up diet (1.54 Mcal/kg DM) and were assigned randomly to each treatment. From calving to 30 d, cows were on the same postpartal diet (1.69 Mcal/kg DM) and continued to receive the same treatments through 30 d. MET supplementation was adjusted daily at a rate of 0.08% (DM basis) of diet and CHO was supplemented at 60 g/cow/d. Liver samples were harvested at −10, 10, 20 and 30 d relative to calving. Compared with −10 d, liver BHMT activity increased (P < 0.01) by 2-fold postpartum regardless of treatment and remained high through at least 30 d. CHO supplementation had no affect (P > 0.05). Although no main effect of MET was detected (P > 0.05), a significant MET × Time interaction (P < 0.01) occurred due to higher BHMT activity in MET vs. CON cows on d 20. Data underscore the high demand for endogenous MET synthesis and increased flux through the MET cycle during early lactation.

Key Words: methionine, choline, betaine homecysteine S-methyltransferase (BHMT)