RBC and WBC counts in lactating dairy cows affected by subacute ruminal acidosis

The influence of subacute ruminal acidosis (SARA) on ruminal microbiology has received considerable attention, but less is known about systemic manifestations that arise from SARA probably because it is well known that variables such as breed, stage of growth, reproductive status, and stage of lactation have an influence on many blood parameters. The aim of this study was to investigate possible changes in some haematological parameters in dairy cows affected by SARA. During autumn 2007 the study was carried out on 12 highly productive farms, stationed in different zones throughout northern Italy. In all farms, 12 cows in early lactation, in good body condition and without clinical signs of disease were selected randomly from each herd, to perform rumenocentesis and obtain rumen fluid. Blood samples for hematological profiles were obtained from the same cows that had rumenocentesis performed by jugular venipuncture. The herds were divided into 3 groups depending on the mean rumen pH: group A farms with pH>5.8 (normal), group B pH between 5.6 and 5.8 (critical) and group C, pH<5.6 (acidosis). Data were statistically analyzed by analysis of variance to verify the effect of the group. The 3 groups were homogeneous for average dry matter intake and all the animals were on absence of external clinical signs of disease. Day in milk (DIM) and body condition score (BCS) were not statistical different (p<0.05) in 3 groups: in particular dairy herds show an average of 35±19, 28±16 and 32±18 of DIM and an average of 3.02±0.29, 3.07±0.22 and 3.06±0.18 of BCS for group A, B and C, respectively. RBC counts, HGB, HCT, RDW, PLT and MPV were not significantly different in three groups, whereas the concentration of total WBC increased statistically (6.62±1.73, 6.84±1.91 and 8.73±1.98 103/µl) in group A, B and C, respectively. In particular dairy herds show an average differential WBC counts of 2.8±0.94, 3.4±1.01 and 3.8±0.96 103/µl of neutrophils, 2.4±0.64, 2.6±0.71 and 2.9±0.69 103/µl of lymphocytes and 0.34±0.02, 0.23±0.01 and 0.22±0.01 103/µl of basophils for group A, B and C, respectively. These data suggest that modifications of some haematological parameters can be observed and in particular the total and differential WBC count were significantly higher in the dairy cows belonging to the farms affected by SARA.