[Blood serum vitamin B12 concentration in dairy cows during early lactation]. / Vitamin-B12-Konzentration im Blutserum von Milchkühen in der Frühlaktation.

OBJECTIVE: To describe the characteristics of the blood serum vita- min B12 concentration of dairy cows post partum (p. p.) and to investigate its relationship with metabolic parameters, the erythrogram and the health status of the cows. MATERIAL AND METHODS: Blood samples from 157 Holstein-Friesian-cows were obtained for metabolic analysis at 2-6 days p. p. and at 4-5 weeks p. p. In addition, clinical findings were compiled to evaluate the health status (healthy/morbid). RESULTS: In all animals a decline in the vitamin B12 concentration (p ≤ 0.05) at 4 weeks p. p. was observed. Animals of both groups (healthy/morbid) had higher values for the erythrocyte count, haematocrit and haemoglobin concentration 2-6 days p. p. when compared to 4 weeks p. p. In all cows, gamma-glutamyl transferase (GGT) activity was closely correlated to the vitamin B12 concentration (p ≤ 0.01). Furthermore, all animals displayed elevated concentrations of beta-hydroxybutyrate, non-esterified fatty acids and bilirubin (p ≤ 0.05) at 2-6 days p. p. as a consequence of partus-dependent increased lipolysis. There was a smaller decrease in the vitamin B12 concentration in the morbid cows compared to the healthy cows (p   ≤   0.05). CONCLUSIONS AND CLINICAL RELEVANCE: The vitamin B12 concentration is significantly dynamic during lactation and displays a close relationship with the GGT activity and the parameters of energy metabolism. Vitamin B12 may act as an indicator for increased lipolysis and cholestasis. Higher vitamin B12 concentrations may indicate clinical problems. A relationship with haematopoiesis is recognizable from the red cell readings. Decreasing red cell readings associated with reduced performance could be related to a low vitamin B12 concentration. The close correlations of vitamin B12 with GGT activity and bilirubin concentration may indicate cholestatic metabolic stress in dairy cows at blood serum concentrations ≥ 227 ng/l (3rd quartile 2-6 days p. p. healthy group). Morbid cows can already be identified at the subclinical stage.