Regulation of Nutritional Metabolism in Transition Dairy Cows: Energy Homeostasis and Health in Response to Post-Ruminal Choline and Methionine

Abstract

This study investigated the effects of rumen-protected methionine (RPM) and rumen-protected choline (RPC) on energy balance, postpartum lactation performance, antioxidant capacity and immune response in transition dairy cows. Forty-eight multiparous transition cows were matched and divided into four groups: control, 15 g/d RPC, 15 g/d RPM or 15 g/d RPC + 15 g/d RPM. Diet samples were collected daily before feeding, and blood samples were collected weekly from the jugular vein before morning feeding from 21 days prepartum to 21 days postpartum. Postpartum dry matter intake (DMI) was increased by both additives (P < 0.05), and energy balance values in supplemented cows were improved after parturition (P < 0.05). Both RPC and RPM decreased the plasma concentrations of non-esterified fatty acids (NEFA), β-hydroxybutyric acid (BHBA), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) (P < 0.05), but increased the plasma levels of glucose, very-low-density lipoprotein (VLDL) and apolipoprotein B100 (ApoB 100, P < 0.05). The supplements improved milk production (P < 0.05), and increased (P < 0.05) or tended to increase (0.05 < P < 0.10) the contents of milk fat and protein. The post-ruminal choline and methionine elevated the blood antioxidant status, as indicated by total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px) activity and the vitamin E concentration (P < 0.05), and reduced the plasma malondialdehyde (MDA) level (P < 0.05). Furthermore, RPM and RPC elevated the plasma interleukin 2 (IL-2) concentration and the CD4+/CD8+ T lymphocyte ratio in peripheral blood (P < 0.05). Alternatively, the levels of tumor necrosis factor-α (TNF-α) and IL-6 were decreased by RPM and RPC (P < 0.05). Overall, the regulatory responses of RPC and RPM were highly correlated with time and were more effective in the postpartum cows. The results demonstrated that dietary supplementation with RPC and RPM promoted energy balance by increasing postpartal DMI and regulating hepatic lipid metabolism, improved postpartum lactation performance and enhanced antioxidant capacity and immune function of transition dairy cows.

Fig 1. Dynamic effects of dietary RPC and RPM supplementation on the intakes of dry matter, net energy for lactation and metabolizable protein in transition dairy cows.

^{a, b} Values with different superscript letters at the same time point are significantly different (P < 0.05).

Fig 2. Prepartal and postpartal energy balance (as Mcal/d or %requirements) of transition dairy cows in response to supplementation of rumen-protected choline (T_C), rumen-protected methionine (T_M) or both (T_CM).

^{a, b} Values with different superscript letters at the same time point are significantly different (P < 0.05).

Fig 3. Dynamic effects of supplementation with rumen-protected choline (T_C), rumen-protected methionine (T_M) or both (T_CM) on plasma levels of non-esterified fatty acids (A), β-hydroxybutyric acid (B) and glucose (C) in transition dairy cows.

^{a, b, c} Values with different superscript letters at the same time point are significantly different (P < 0.05).

Fig 4. Plasma concentrations of total cholesterol (TC), very-low-density lipoprotein (VLDL) and apolipoprotein B100 (ApoB 100) in response to dietary supplementation of rumen-protected choline (T_C), rumen-protected methionine (T_M) or both (T_CM) during periods of prepartum, calving day and postpartum in transition dairy cows.

^{a, b, c} Values with different superscript letters at the same time point are significantly different (P < 0.05).

Fig 5. Plasma concentrations of total bilirubin (TBIL), alkaline phosphatase (ALP) and urea nitrogen in response to dietary supplementation of rumen-protected choline (T_C), rumen-protected methionine (T_M) or both (T_CM) during periods of prepartum, calving day and postpartum in transition dairy cows.

^{a, b, c} Values with different superscript letters at the same time point are significantly different (P < 0.05).

Fig 6. Plasma total antioxidant capacity (T-AOC) and levels of malonaldehyde (MDA) and vitamin E in response to dietary supplementation of rumen-protected choline (T_C), rumen-protected methionine (T_M) or both (T_CM) during periods of prepartum, calving day and postpartum in transition dairy cows.

^{a, b, c} Values with different superscript letters at the same time point are significantly different (P < 0.05).

Fig 7. Plasma levels of interleukin 2 (IL2) and tumor necrosis factor α (TNF-α) in response to dietary supplementation of rumen-protected choline (T_C), rumen-protected methionine (T_M) or both (T_CM) during periods of prepartum, calving day and postpartum in transition dairy cows.

^{a, b, c} Values with different superscript letters at the same time point are significantly different (P < 0.05).

Fig 8. Effects of supplementation with rumen-protected choline (T_C), rumen-protected methionine (T_M) or both (T_CM) on proportions of T lymphocyte subtypes in peripheral blood of transition dairy cows.

(A) and (B) present the output images from flow cytometry. (C) displays the effects of each treatment over the three weeks before calving, on calving day, and over the three weeks after calving. ^{a, b, c} Values with different superscript letters at the same time point are significantly different (P < 0.05).