I completely understand your question, there is conflicting advice as the climates we all keep alpacas in varies so much around the world and for us supplementing a,d &e was a learning experience.
We give a,d & e to them all irrespective of gender / age / colour, some years we find we inject more regularly than others - you do develop an eye for spotting when they need a boost. We have bought in alpacas with vitamin deficiencies / rickets from well intentioned caring owners who have believed feed supplements to be sufficient because that’s what they have been told. My feed merchant says it to me regularly too! But, in our experience they all need extra a,d,&e when the days are shorter. Rickets is a painful condition and in my opinion it’s an unnecessary risk. Their bones do straighten out, we’ve had to treat various poorly pacas over the years but it’s not simply necessary to even go there. We have also tried increasing camelibra instead but ours eat such a small supplement daily personally I didnt feel it worked sufficiently well. Ours don’t appear to like camelibra unless it’s mixed with a coarse mix, if the ratio is too strong our alpacas won’t eat it. Camelibra is also relatively expensive, (& gwf do manufacture it.... so they’ve got a vested interest in us using more) - to dose at a,d,& e rates presumably they will excrete other excess nutrients that I’m also paying for? So I’m also I’m not convinced it’s a cost effective solution to their winter nutritional needs. Please don’t misunderstand me - we use it all year around and I think our alpacas do very well on it, but it’s not the right product for us to use to solve their winter needs for additional a, d & e. So, we have found Hipravit works better for us , it isn’t cheap but it targets precisely what they need, it also has a good shelf life, plus by injecting it you know everyone got the appropriate dose and when. Our vet also advises Hipravit to be injected subcutaneously as they advise that’s more effective than intramuscular injections. Likewise I’m also advised by the vet that injecting meds in general is more effective than oral meds in alpacas. The method of administration for us is usually dictated by the situation.
One year we also used camelid drench added to their feed as it was very difficult to obtain a, d & e. I do feel the drench worked fine, but...... the economics of choosing drench / camelibra / paca mix then changed. You don’t need both drench & camelibra so we chose the drench and dosed according to their a d & e needs until the vet could get hold of Hipravit again. We’ve tried a few things over the years until we found what worked for us & I’m sure you will work out what suits you too.
From our experience it is my opinion that all alpacas irrespective of age / colour / gender need a d & e supplementing during the shorter days in the UK, but yes the dosages differ by weight & the frequency differs by age. I’m sure your vet will happily advise on dosage for your alpacas whatever supplement & method you choose.
I hope all if that helps!