1545
Rumen-protected methionine and choline supplementation during the transition period enhance the proinflammatory cytokine response of whole blood
The immune system of dairy cows declines in responsiveness during the transition period. In spite of this, there are several factors that can stimulate immune cells and induce the production of proinflammatory cytokines (PIC). The objective of this study was to investigate the effect of supplementing rumen-protected methionine or choline on the production of the proinflammatory cytokine IL1-beta by whole blood challenged with E. Coli lipopolysacharide (LPS). Twenty-four multiparous Holstein cows were dried off at -50 d from parturition (DFP) and allocated to 1 of 3 treatment groups (n = 8/group) starting on -24 DFP; control (CON; fed a basal diet with a 3.4:1 Lys:Met), methionine (MET; basal diet plus Smartamine M with a 2.9:1 Lys:Met), and choline (CHO; basal diet plus ReaShure, 60 g/d). Blood samples for LPS challenge were collected on -15, -7, 2, 7 and 20 DFP into evacuated tubes containing lithium-heparin and kept at 38 °C. An ex vivo whole blood (1 mL) stimulation assay was performed within 30 min using LPS at three different doses, 0 (negative control, CTR), 0.01, and 5 µg/mL blood. Samples were incubated for 3.5 h. At the end of incubation the plasma was collected after centrifugation and used to analyze IL-1beta concentration via ELISA. The data were analyzed as a factorial design with repeated measures using PROC MIXED in SAS. There was an overall diet effect (P < 0.05) associated with greater IL1-beta in cows fed MET and CHO (1,812 pg/mL) compared with CON (1,043 pg/mL). Similarly, there was an overal LPS effect (P < 0.05) with control incubations averaging 52 pg IL1-beta/mL compared with 1,621 and 3,013 pg IL1-beta/mL in response to 0.01 and 5 µg LPS. The three-way interaction (P < 0.05) revealed that the high LPS dose induced a marked response in IL1-beta in both MET or CHO regardless of DFP. In contrast, whereas the high dose of LPS induced a similar response (1,500-2,000 pg IL1-beta) in CON on -15, -7, 7, and 20 DFP, the response on 2 DFP was markedly greater to the point that IL1-beta concentration was similar for CON, MET, and CHO. Overall, results confirmed the responsiveness of blood cells to an inflammatory challenge even in a period of immune suppression. More importantly, data revealed that supplemental methionine or choline during the transition period enhances the PIC response, hence, potentially enhancing the responsivennes to invading pathogens.
Keywords: inflammation, transition period, nutrition