I have just read an article in the latest edition of Alpaca World (a UK alpaca magazine) regarding vitamin D dosing to prevent rickets. It is written by an Australian alpaca breeder. In the article she advocates doses of up to 18,000 IU/kg using pure vitamin D3. She does not justify the use of these very high doses except to say that if they're fine for a cow to be given just before calving then they must be fine for alpacas.... She is apparently aware of the concern for vitamin D toxicity but states that she has "not heard of, or seen any ill effects" - although she does not include any mention of the clinical signs or pathology so I'm not sure that she would recognise them if they occurred.
I am very concerned that alpaca breeders reading this article, potentially your clients, may think that this is a good idea. I am aware of some breeders already recommending this protocol, mostly those with Australian connections. Please be advised that, for prevention or treatment of hypovitaminosis D in camelids (obviously including rickets in growing animals), the recommended doses are 1000-2000 IU/kg - parenterally (SQ) this can be given every 2 months during the winter, or orally every 4-6 weeks. These recommendations are made on the basis of known and published pharmacokinetics - there is no justification for higher doses which may in fact depress normal function via feedback mechanisms.
Please can you ensure that your clients are using the appropriate doses of vitamin D supplementation (follow the link below) and are not following the unsubstantiated recommendations of other alpaca owners. Fortunately I don't believe Vitamin D3 is available in the UK any more (unless anyone else knows differently!) but owners have been known to import (and sell) their own drugs from outside the UK without knowing this is illegal.
Claire E Whitehead BVM&S MS MRCVS
Diplomate ACVIM (Large Animal)
Camelid Veterinary Services
Vitamin D, used for prevention or treatment of rickets in camelids, is no longer easy to source in the UK.