Mixing Vaccine Brands

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I enjoyed your March 2007 article on vaccinations. It’s obvious, after reading your article, that I’ve been over-vaccinating in some cases and under-vaccinating in others. The one question I have that wasn’t answered is this: If I start with one vaccine that requires a two-dose initial series and switch to another do I need to start the initial two-dose series again' Vets don’t usually ask about previous vaccines and records don’t usually record the manufactures. For example, my horse was initially vaccinated with Prestige V for tetanus, EEE, WEE, rhino and influenza. If I change to Encevac would I have to start the two-dose series again'

Horse Journal Response

The only vaccine we know of that has been validated to be OK to use as a single booster if you had previously given another brand is Merial’s Recombitek. As a general rule, the more different diseases combined in a vaccine, the lower the level of antibody-provoking antigen. Therefore, if going from a vaccine with only one disease to one with multiple, you probably should always do the initial series. If going from a multi-vaccine to a single, or reduced number of diseases vaccine, but by the same manufacturer (so the same type of adjuvant was used), you can stick with the booster dose.

Always follow the initial series recommendations if going from injectable to intranasal, or vice versa. Beyond that we really can’t advise you because to compare between vaccines from different manufacturers would require access to specific titer responses and concentrations that aren’t widely available. Note: Your veterinarian likely does write down the manufacturer and lot number of every vaccine he or she administers. If you’re giving your own vaccines, you should always record that information, in case there’s ever question about that batch’s efficacy or contamination, etc.

Moxidectin Concerns

I have received an e-mail telling people that Quest dewormer (moxidectin) causes liver damage. I have checked around, but I can find no information to confirm this, so I’m turning to you to see if this is garbage or truth. I don’t like to forward e-mails that are frauds.

Horse Journal Response

First, congratulations on being responsible and not spreading unsubstantiated rumors. To our knowledge, there has never been a report of moxidectin, the active ingredient in Quest, causing a problem with liver toxicity in any species or at any dose. Toxicity studies done for the FDA, as well as clinical experience with moxidectin, show neurological signs are the symptoms of toxicity.

Of the 1,261 FDA-listed adverse-event reports for horses involving moxidectin, only nine listed elevated liver enzymes. However, it’s important to realize that the FDA’s adverse-event reports aren’t all cases conclusively proven to be caused by the drug. The symptoms of moxidectin overdose and extensive liver disease are actually similar, and it could easy to confuse the two.

 For future reference, anyone who wants to learn details like this about a drug, it’s available on the FDA’s web site, www.fda.gov/cvm. To see adverse event reports, select this from the ”hot topics” bar on the home page, then ”cumulative reports” from the adverse-event home page. All you need to know is the active drug name, or even the brand name. Instructions are easy to follow.

 To see the original efficacy and safety testing that led to a drug’s approval, select ”Freedom of Information” on the FDA home page, then click ”FOI summaries.” To access these, you need the NADA (New Animal Drug Application) number for the drug. You can find this by doing a simple Internet search using the two terms NADA and whatever the drug name is. You can also get it on the FDA site by selecting Green Book on the home page, then Green Book online and open the trade name file under Section I. This lists the NADA numbers beside the trade names.

Carbs In Hay

I am considering starting to feed my horses Matua hay. It is a form of bromegrass hay but is higher in protein. My concern is for my 18-year-old Arab gelding who has problems with laminitis. Is this hay too high in carbohydrates for him'

Horse Journal Response

While there are some hays that you should avoid because they are virtually guaranteed to be high, like oat hay, the starch and sugar content of any grass hay is going to be highly variable. The only way to know for sure if it’s safe for your horse is to have it tested. When it comes to laminitis, it’s foolish to take chances.

Psyllium and Impaction

I treated my horse with psyllium for one week, and she developed an impaction and spent three days in the intensive care unit at the University of California, Davis, veterinary clinic. Are there reports of psyllium hardening in the gut' There’s a new product on the market that claims not to harden in the gut. For the past six years she has only had one other colic, related to the stress of moving, which did not require going to Davis.

Horse Journal Response

Psyllium is no more likely to harden than anything else your horse eats. In fact, it’s probably less likely since most of the fiber is in water-soluble form and easy for the intestinal organisms to ferment. Unless there’s damage to a section of intestine that interferes with its ability to move a sand collection or enterolith, impactions are caused by lack of sufficient water intake. Impaction due to insufficient water intake is extremely common in the winter, when water freezes over or is too cold to encourage good drinking. Many people also forget to keep salt available or add it to meals so that the horse drinks normally. A drop in activity level due to bad weather or less riding is another risk factor, as is a change in type of hay. As far as we know, psyllium has never been implicated as a cause of impaction colic.

Cooking Flax

Do you have to cook or boil the flax seed to remove harmful ingredients'

Horse Journal Response

Intact flax seeds aren’t inherently poisonous, as long as the seed isn’t damaged. It contains cyanogenic glycosides and the enzyme capable of releasing prussic acid/hydrogen cyanide from them, but in separate compartments. The cyanogenic glycosides themselves aren’t harmful.

Boiling flax does two things. It releases any hydrogen cyanide that may be present in damaged seeds, and it inactivates the enzyme capable of causing the production of hydrogen cyanide from the cyanogenic glycosides. In the early stages of the boiling, as the seeds are softening in hot water but before temperatures get too high, it’s likely that the enzymes are still active in producing some hydrogen cyanide, which is why boiling for a prolonged period, usually an hour, is recommended to make sure all the cyanide gas is vaporized off.

Mature, golden flax seeds don’t need to be subjected to the time-consuming boiling, especially considering the small amounts typically fed to horses. Preformed cyanide is low/absent in mature, intact seeds. We’ve found no recorded case of cyanide poisoning from flax in horses. Plus, boiling for prolonged periods can destroy the fragile omega-3 fatty acids you’re feeding the flax seed to get.