Blood serum vitamin B12 concentration in dairy cows during early lactation

Objective: To describe the characteristics of the blood serum vitamin B-12 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 B-12 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 B-12 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 B-12 concentration in the morbid cows compared to the healthy cows (p <= 0.05). Conclusions and clinical relevance: The vitamin B-12 concentration is significantly dynamic during lactation and displays a close relationship with the GGT activity and the parameters of energy metabolism. Vitamin B-12 may act as an indicator for increased lipolysis and cholestasis. Higher vitamin B-12 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 B-12 concentration. The close correlations of vitamin B-12 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.