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Rumen-protected methionine supply to cows during heat stress alters liver tissue protein abundance of mechanistic target of rapamycin.

D. N. Coleman

Events

06-23-2020

Abstract:

209
Rumen-protected methionine supply to cows during heat stress alters liver tissue protein abundance of mechanistic target of rapamycin.
D. N. Coleman*1, P. Totakul1,2, N. Onjai-Uea1,3, M. Vailati-Riboni1, R. T. Pate1, D. Luchini4, F. C. Cardoso1, J. J. Loor1. 1Department of Animal Sciences, University of Illinois Urbana, IL, 2Department of Animal Science, Faculty of Agriculture, Khon Kaen University Khon Kaen, Thailand, 3Institute of Agricultural Technology, Suranaree University of Technology Nakhon Ratchasima, Thailand, 4Adisseo Alpharetta, GA.

The objective was to investigate effects of rumen-protected Met (RPM) during a heat stress (HS) challenge on protein abundance of mechanistic target of rapamycin (mTOR), insulin, and antioxidant signaling in liver tissue. Thirty-two multiparous, lactating Holstein cows (184 � 59 DIM) were randomly assigned to 1 of 2 environmental (Env) treatment groups, and 1 of 2 dietary treatments [TMR with RPM (Smartamine M; Adisseo Inc., France; 0.105% DM as top dress) or TMR without RPM (CON)] in a crossover design. The study was divided into 2 periods with 2 phases. During phase 1 (9d), all cows were in thermoneutral conditions (TN;THI = 60 � 3) and fed ad libitum. During phase 2 (9d), group 1 was exposed to HS using electric heat blankets. Group 2 remained in TN but was pair-fed to HS counterparts. After 14d washout and 7d adaptation period, the study was repeated (period 2) and environmental treatments were inverted relative to phase 2, but dietary treatments were the same. Liver biopsies were performed at the end of each period. Tissue was incubated in Dulbecco's modified eagle medium for 2h and protein extracted. Data were analyzed using PROC MIXED in SAS. An Env � diet was detected for CUL3, an inhibitor of nuclear factor erythroid 2 like 2 (NFE2L2), due to upregulation in CON cows during HS vs. TN. Abundance of CUL3 did not differ due to RPM during HS or TN and tended to be lower than CON, suggesting that RPM alleviated HS-induced oxidative stress. An Env � diet was detected for phosphorylated (p) mTOR (P = 0.001); compared with CON, RPM led to greater abundance under TN conditions. However, p-mTOR decreased with RPM but increased with CON in HS. These effects suggested a potential shift in protein synthesis with RPM supply during HS. There was also an interaction for p-AKT (P < 0.001); HS cows on the CON diet had greater abundance than all other treatments. This response in CON cows was similar to CUL3, suggesting altered insulin signaling. Overall, preliminary evaluation indicates that RPM supplementation may help cows maintain hepatic homeostasis in mTOR, insulin, and antioxidant signaling in liver during a HS challenge.

Keywords: amino acid, lactation.