Hyperglycaemia in transition dairy cows: Effects of lactational stage and conjugated linoleic acid supplementation on glucose metabolism and turnover.

Supplementing conjugated linoleic acid (CLA) is supposed to spare glucose due to the milk fat-depressing effect of the trans-10, cis-12 CLA isomer, and allows repartitioning nutrients despite an energy deficiency in early lactation. However, there is still a lack of knowledge in terms of the dynamic pattern of the glucose turnover in transition dairy cows. We hypothesized that dairy cows supplemented with CLA have an altered rate of glucose turnover and insulin sensitivity during early lactation. We conducted three consecutive hyperglycaemic clamps (HGC) in weeks -2, +2 and +4 relative to parturition in Holstein cows supplemented daily either with 70 g of lipid-encapsulated CLA (6.8 g trans-10, cis-12 and 6.6 g of the cis-9, trans-11 CLA isomer; CLA; n = 11) or with 56 g of control fat (CON; n = 11). From week -3 up to week +4 relative to parturition, milk yield and dry matter intake (DMI) were recorded daily, while body weight (BW) and milk composition were obtained once weekly. Blood samples were taken once weekly and every 30 min during the HGC. Plasma was analysed for concentrations of glucose, fatty acids (FFA), beta-hydroxybutyrate (BHB), insulin, triglycerides and cholesterol. The CLA supplementation did not affect performance and metabolic parameters except for BHB and cholesterol. Furthermore, insulin concentrations and insulin sensitivity were affected by treatment. During the HGC in early lactation, insulin response was lower and decrease in FFA and BHB greater compared with the HGC in week -2 although glucose target concentration achieved during the steady-state period was similar for all three HGC. Our findings in terms of insulin and cholesterol suggest that body reserves are preserved through CLA feeding without restraining animal's performance. Furthermore, CLA effects on cholesterol and triglyceride concentrations indicated beneficial effects on hepatic lipid export contributing to an improved efficiency of prevailing metabolites in circulation.