Plasma fructosamine during the transition period and its relationship with energy metabolism and inflammation biomarkers in dairy cows

Plasma concentration of fructosamine (Fr) has been proposed as a way to monitor retrospective undernutrition in dairy cows during the transition period. The objective of this study was to evaluate, under standard feeding conditions, the variation of plasma Fr in dairy cows during the transition phase and its relationship with biomarkers of energy metabolism and inflammatory conditions. The trial was carried out with 24 Italian Friesian dairy cows from the last month of pregnancy through the first 2 months of lactation. Diet characteristics and dry matter intake (DMI) were continuously monitored, and energy balance was evaluated on a weekly basis. Milk yield, body weight, body condition score and health status were also monitored. Blood samples were taken two times a week throughout the experimental period and daily in the week before and after calving. Concentrations of Fr together with biochemical indicators related to energy, protein and mineral metabolism; markers of inflammation; and liver enzymes were measured in plasma. Cows were categorized into three groups according to the average concentration of plasma Fr observed at 28, 35 and 42 days in milk (DIM) (cows with lowest [LF], intermediate [IF] and highest [HF] concentrations of Fr, respectively). The LF cows reached an average maximum milk yield (MY) of 51.7 kg/d, whereas IF and HF cows produced 48.9 and 47.2 kg/d, respectively. During the first month of lactation, the DMI was 17.4, 18.2 and 18.7 kg/d in LF, IF and HF, respectively. In the first month of lactation, Fr was not correlated with MY, but had a positive correlation with DMI (P < 0.05) and energy balance (P < 0.05). In the same period, the average plasma glucose was greater (P < 0.05) in HF (3.71 mmol/L) and lower in LF (3.34 mmol/L). During the first month of lactation, plasma Fr was positively related (P < 0.05) to plasma glucose and albumin concentrations over the previous 1-3 weeks. The Liver Activity Index, used to measure the consequences of inflammation around calving and calculated by using three blood analytes that represent liver-synthesized proteins, indicated greater inflammation in LF cows compared with HF. Our results highlight that plasma Fr during the first 3-4 weeks of lactation summarizes the energy balance during the transition period and that the energy deficit is more influenced by DMI and inflammatory conditions than by MY.