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Heat stress and rumen-protected methionine alter whole-blood mRNA abundance of transsulfuration and antioxidant pathway genes.

D. N. Coleman

Events

06-23-2020

Abstract:

210
Heat stress and rumen-protected methionine alter whole-blood mRNA abundance of transsulfuration and antioxidant pathway genes.
D. N. Coleman*1, M. G. Lopes1,2, M. Vailati-Riboni1, R. T. Pate1, D. Luchini3, F. C. Cardoso1, J. J. Loor1. 1Department of Animal Sciences, University of Illinois Urbana, IL, 2Universidade Federal de Pelotas Pelotas, Rio Grande do Sul, Brazil, 3Adisseo Alpharetta, GA.

The objective was to investigate the effects of rumen-protected Met (RPM) during a heat stress (HS) challenge on whole blood mRNA abundance of genes related to immune and antioxidant responses and the transsulfuration pathway. 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 per period. During phase 1 (9 d), all cows were in thermoneutral conditions (TN; THI = 60 � 3) and fed ad libitum. During phase 2 (9 d), group 1 (n = 16) was exposed to HS using electric heat blankets. Group 2 (n = 16) remained in TN but was pair-fed to HS counterparts. After a 14-d washout and 7-d adaptation period, the study was repeated (period 2) and environmental treatments were inverted relative to phase 2 in period 1, while the dietary treatments were the same. Blood was collected from the coccygeal vein approximately 4 h postfeeding on d 8 of phase 2. Data were analyzed using PROC MIXED in SAS. An Env � diet interaction was observed for mRNA abundance of cytathionine β synthase (CBS; P = 0.03); with RPM cows having greater CBS during TN compared with HS. The same Env � diet interaction was detected for the mRNA abundance of superoxide dismutase (SOD) 1 (P = 0.01) and cysteine dioxygenase type 1 (CDO1; P = 0.02). A tendency for an interaction was observed for the expression of toll-like receptor 2 (P = 0.09) due to an increase in abundance in CON cows during HS compared with TN. Regardless of diet, mRNA abundance of CDO1 and cystathionine gamma-lyase was downregulated by HS (P < 0.05) and glutathione synthase tended to be downregulated (P = 0.08). Overall, preliminary evaluation suggests that supplying RPM may enhance the antioxidant responses in whole blood. Results also highlight the negative effect of HS on whole blood transsulfuration pathway and antioxidant responses.

Keywords: amino acid, immune response.