Activation of innate immunity in transition dairy cows before clinical appearance of milk fever
Milk fever (MF) is a metabolic disease of transition dairy cows associated with calcium imbalance at the onset of lactation. Its pathogenesis and etiology still remain unclear. The objective of this study was to identify alterations in innate immunity reactants and carbohydrate and lipid metabolites in the blood of transition dairy cows with or without MF. One hundred multiparous Holstein dairy cows were involved in the study and the experimental period lasted 16 wks from -8 wk before until +8 wk postpartum. Health status, feed intake, rectal temperature, and milk yield was monitored for each cow during the whole experimental period. Blood samples were collected from the coccygeal vain once per week before the morning feeding and stored until analyses at -80 ºC. Six healthy cows (CTR) and 6 cows that showed clinical signs of MF were selected for intensive blood analyses. Serum concentrations of lactate, non-esterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), haptoglobin (Hp), serum amyloid A (SAA), and lipopolysaccharide binding protein (LBP) were determined. Feed intake, milk production and composition also were collected. Data were processed using the MIXED procedure of SAS 9.2. Results indicated that concentrations of serum lactate, IL-6, TNF-α, SAA, Hp, and LBP were significantly greater in cows with MF than CTR. Most interestingly, serum lactate, TNF-α, SAA, LBP, and Hp in cows with MF were different from CTR cows starting at ~ 4 to 8 wks before diagnosis of disease. Overall feed intake and milk production was lower in MF-affected cows. Interestingly overall milk fat was greater in MF cows vs CTRs. In conclusion cows affected by MF showed alterations of innate immunity reactants and metabolites related to carbohydrate metabolism weeks before clinical appearance of MF. Since innate immunity is a general non-specific host response to sickness these metabolites might be used to indicate general health status of the transition dairy cows ahead of clinical disease event. More research is warranted to validate these data and better understand etiopathogenesis of MF in transition dairy cows.
Keywords: Dairy cow, Innate immunity reactants, Milk fever