The effect of parenteral vitamin B12 on the growth rate of dairy calves over the summer and autumn on seven farms from the Central Plateau, New Zealand.

Aims: To investigate the effect of parenteral vitamin B₁₂ supplementation on the growth rate of dairy heifer calves over the summer and autumn on seven farms from the Central Plateau of New Zealand, an area historically associated with low cobalt levels in grazing pasture.

Methods: This was a controlled clinical trial conducted on a convenience sample of seven farms with young female calves randomly assigned to three vitamin B₁₂ treatment groups and followed through a grazing season. Two treatment groups received either monthly SC injections of a short-acting (SA) B₁₂ formulation or 3-monthly injections of a long-acting (LA) B₁₂ formulation and the third group received no treatment (NT). No additional parenteral vitamin B₁₂ was given; however, all calves received additional cobalt (0.04-0.4 mg Co/kg liveweight) in the mineralised anthelmintic drenches given orally every month. Liveweight was recorded in December/January and at the end of the trial in May/June/July depending on farm. Pasture cobalt concentrations (mg/kg DM) were measured every month using 500-g herbage samples from 100-m transects in the area about to be grazed by the trial groups.

Results: There was evidence for a difference in growth rate between groups with mean final weight of 228 (95% CI = 212-243) kg for the LA groups, 224 (95% CI = 209-239) kg for the SA groups and 226 (95% CI = 211-241) kg for the NT groups respectively, (global p-value = 0.014). Calves given SA vitamin B₁₂ were 3.77 (95% CI = 0.71-6.82) kg lighter than calves given LA vitamin B₁₂ (p = 0.011). There was no evidence for a change in pasture cobalt concentrations (p = 0.32).

Conclusions and clinical relevance: The results of this trial raise the question as to whether the routine use of vitamin B₁₂ supplementation in young cattle from areas traditionally thought to be cobalt deficient is necessary, and further raise the possibility that vitamin B₁₂ supplementation by repeated injection of SA products may negatively impact growth rates.