Changes of metabolic conditions around calving affect oxidative stress and acute phase protein in pluriparous dairy cows

The study aimed te evaluate the relationships between the variation of metabolism during the post partum and the inflammatory conditions and oxidative stress in dairy cows. For this purpose, two commercial farms were selected and 30 pluriparous Friesian cows for each farm were identified on the basis of expected date of calving. Blood was sampled from cows every fortnight starting from 14 days before calving and until 70 days postpartum (7 samples). At the same time of blood sampling, fat thickness of pelvic region was measured with an ultrasound scanner equipped with a 5 MHz transducer. Blood was analysed for acute phase response (ceruloplasmin, haptoglobin, albumin aad zinc), metabolic (b-OHB, glucose, NEFA, cholesterol,urea, haemoglobin, total proteins and cortisol) and oxidoreductive status (paraoxonase, SOD, GPx and glutathione). Data were analysed with a factorial model (GLM) with fixed effects for time (7 levels), farm (2 levels) and their interaction. Correlation coefficients between the analysed parameters and the levels of significance were calculated with 2 tails Pearson test. Statistical analysis allowed to separate the markers influenced by time of sampling from that influenced by farm, and to select the best predictors of metabolic and oxidative stress around parturition, i.e. total proteins, urea, haptoglobin, cholesterol, BOHB, NEFA, paraoxonase and SOD. The present work also allowed to underline the relationships between stress post partum and oxidoreductive status. Animals presenting impaired body conditions at the beginning of lactation showed an highest probability to develop oxidative stress. In particular the correlation analysis showed significant relationship between fat thickness and albumin, ceruloplasmin, cholesterol, GPx and glutathione.