SERUM METABOLOMICS ASSESSMENT OF ETIOLOGICAL PROCESSES PREDISPOSING KETOSIS IN WATER BUFFALO THROUGH THE 1H-NMR SPECTROSCOPY

A negative energy balance is still one of the major concerns that may decrease the productivity in buffaloes and predispose to other disorders as ketosis which is characterized by elevated concentrations of β-hydroxybutyrate (BHB). Nevertheless, a specifically BHB threshold for dairy buffaloes was not establish and dairy cows’ reference are often used [1]. The aim of this study was to use 1H-NMR to assess the metabolomic profile of Mediterranean buffaloes in early lactation to investigate the metabolic changes associate with different levels of energy deficit. This study received the approval by the Ethical Animal Care and Use Committee of the University of Napoli (protocol number 0099607/2017). Sixty-two Italian Mediterranean Buffaloes (MBs) were selected from a single dairy farm located in Campania, Italy, in early lactation (32±12 days in milk (DIM)). All animals received a clinical examination and BCS evaluation on a 9-point scale. Blood samples were collected by clinical healthy subjects into clot activator tubes to obtain serum. According to serum BHB concentration, MBs were divided into two groups [2]: healthy group (Group H; 37 MBs; BHB<0.70 mmol/L) and group at risk of hyperketonemia (Group K; 25 MBs; BHB≥0.70 mmol/L). The differences between groups were assessed by one-way ANOVA for normally distributed data, and Wilcoxon Test for not normally distributed. The significance threshold was sept at p-value ≤ 0.05. Parameters that presented a p- value between 0.05 and 0.1 were considered as trend to significance. A total of fifty -seven molecules was characterized in MBs serum samples. Six of the quantified metabolites were different between groups: glycerol, taurine, and creatinine reduced in group K, while acetone, acetate and 3-hydroxybutyrate increased in the same group. Additionally, other six metabolites were tended to significance: methanol, proline, and glycine reduced in group K, whereas formate, citrate, glutamate increased in the same group. An increment of body resources mobilization was evidenced by the reduction of glycerol and creatinine. Glycerol may be used for gluconeogenesis or for an increase in milk fatty acids synthesis, a characteristic of ketosis; whereas creatinine derives from muscular metabolism and can be used to supply energy. The altered concentration of acetate, methanol, and formate suggested an alteration of ruminal microbial population and fermentation according to BHB [3]. The reduction of proline, glycine, and taurine may suggest an initial alteration of urea cycle other than a potential state of oxidative stress due to the increased use of glutathione and hypotaurine systems. Furthermore, glutamate and taurine changes may be related to the thyroid hormone synthesis [4]. The reduced concentration of proline and glycine may also suggest a potential alteration of Krebs cycle according to the progressive increment of BHB, even if glutamate and citrate were increased in group K [3]. In conclusion, the increment of BHB below the cut-off of dairy cows revealed different relationships with an early development of ketosis by a metabolomic approach.