title: Vitamin B12 status and the effects of vitamin B12 supplementation during the first year of life of spring calves from pasture-fed dairy herds.
abstract: OBJECTIVE
  To determine the vitamin B12 status of dairy calves during their first year of life, and to evaluate the benefits of vitamin B12 supplementation.
  
  
  METHODS
  In Experiment I, 20 17-day-old heifer calves from the AgResearch Flock House herd were monitored until 198 days old. On Days 0 and 90 of the study, half of the animals received an injection of microencapsulated vitamin B12 at 0.12 mg/kg bodyweight. All received colostrum, milk replacer and calf meal, with ad libitum access to pasture. At regular intervals the calves were weighed and serum collected for vitamin B12 measurement. In Experiment II at Flock House and the adjacent Landcorp Tangimoana station, 80 150-day-old heifer calves were monitored until 342 days old. On Days 0 and 97, half of the animals received vitamin B12 as per Experiment I. At regular intervals samples were collected from 12 calves per group, to determine concentrations of vitamin B12 in serum.
  
  
  RESULTS
  Mean concentration of vitamin B12 in milk replacer was 63 (SE 4) µg/kg dry matter (DM). Cobalt concentrations in calf meal were 0.45-1.58 and 0.07-0.28 mg/kg DM in pastures. From 17 to 198 days of age (Experiment I) mean concentrations of vitamin B12 in serum of the control group decreased from 119 (SE 8) to 57 (SE 5) pmol/L. From 150 to 342 days of age (Experiment II), overall mean concentrations of the control groups at Flock House and Tangimoana were 90 (SE 2) and 96 (SE 3) pmol/L, respectively. Vitamin B12 injections increased (p<0.001) serum concentrations for at least 90 days, with peak concentrations of 323 (SE 23) (Experiment I) and 520 (SE 22) (Experiment II) pmol/L reached 28-35 days after each injection. Liveweight gain was not increased by supplementation and there was no difference in final liveweight between groups.
  
  
  CONCLUSIONS
  Concentrations of vitamin B12 in serum of unsupplemented calves prior to weaning indicated their vitamin B12 status was adequate due to the vitamin B12 and Co content of the milk replacer, and calf meal. Concentrations decreased during the transition to a pasture-based diet. Supplementation increased concentrations of vitamin B12 in serum but did not improve liveweight gains.
  
  
  CONCLUSIONS
  Under this calf rearing system, vitamin B12 deficiency is unlikely to occur prior to weaning, and vitamin B12 supplementation is unlikely to increase growth rates of grazing calves when concentrations of vitamin B12 in serum are > 90 pmol/L.
authors.affiliation: a 26 Williams Road, RD4, Palmerston North 4474 , New Zealand.
authors.forename: N D
authors.initials: ND
authors.lastname: Grace
authors.forename: S O
authors.initials: SO
authors.lastname: Knowles
authors.forename: R
authors.initials: R
authors.lastname: Nortjé
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000822:Animal Husbandry; D000818:Animals; D002417:Cattle / Q000097:blood* / Q000254:growth & development / Q000502:physiology*; D003612:Dairying; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D009929:Organ Size; D014805:Vitamin B 12 / Q000008:administration & dosage / Q000494:pharmacology*; D015430:Weight Gain
chemical_list: D014805:Vitamin B 12
keywords: Dairy calves; liver; liveweight gains; long-acting injection; serum; vitamin B12