Ruminal Acidosis Conditions

Th is study evaluated the reliability of various blood parameters to assess the ruminal acidosis in cattle. Six whole heifers were fed three experimental rations in a 3 x 3 Latin square design. Th e diets had diff erent starch levels: high (HS), medium (MS) or low (CT). Ruminal pH values were continuously measured using wireless sensors. To evaluate the severity of ruminal acidosis, the amount of time per day that the pH was below 5.8, 5.5 and 5.0 was recorded. Blood samples were analyzed for complete blood count, venous blood gas and biochemical profi le at 8:00 and 12:00 h. Th e data were analyzed according to a mixed model. Feeding on CT, MS and HS led to signifi cant diff erences in DMI (7.7 vs. 6.9 vs. 5.1 kg/d; P < 0.01) which modifi ed the amount of time per day that the pH was below 5.0 (0 vs. 12 vs. 92 min; P < 0.10). Feeding MS and HS diets led to infl ammation as indicated by the signifi cant increment of white blood cells when compared to the CT ones and to blood concentration due to the osmotic pressure at ruminal level. Furthermore a signifi cant decrease of bicarbonate level, CO2 partial pressure and oxyhemoglobin was observed as consequence of the activation of metabolic processes aimed to prevent metabolic acidosis. No diff erences were observed on blood sampling time, suggesting that one daily blood sample was enough to evaluate the metabolic variations related to ruminal acidosis.