Effect of an injectable microencapsulated Vitamin B-12 On serum and liver Vitamin B-12 concentrations in calves

Aim: To evaluate the efficacy of a long-acting injectable microencapsulated formulation of Vitamin B-12 in dairy calves. Method: Fifty calves, average liveweight 110kg, were randomly allocated to 5 groups of 10 animals and injected subcutaneously in the anterior neck wit h 0.12, 0.18, 0.24 and 0.3 mg Vitamin B-12/kg liveweight using a formulatio n of microencapsulated Vitamin B-12 in a lactide : glycolide copolymer. The untreated calves were injected with the same vehicle, without Vitamin B-12 . Subsequent changes in serum and liver Vitamin B-12 concentrations were fo llowed for 244 days. Results: The microencapsulated Vitamin B-12 significantly increased, then m aintained serum and liver Vitamin B-12 concentrations higher than those of untreated controls for at least 110 days. Conclusions: Injection of the microencapsulated Vitamin B-12 at dose rates of 0.12 to 0.24 mg/kg liveweight will increase and maintain the Vitamin B-1 2 status of calves for at least 110 days.