Chaste tree berry


I am curious about the chaste berry, It has been recommended for PPID horses I am wondering if it has any positive effect on IR horses? 
I’m new to this forum so please let me know if I’m doing this Thanks

Jann Gardner
Located in Portland, Oregon  
joined summer 2022

Bobbie Day

Hello Jan and welcome to the group! What will follow below is your welcome message that is sent out to new members upon their first post. 
There is a lot to read so when your able if you could read it and keep it handy for future reference it will help you with other questions that may come up.
I'm assuming since you're asking about Chasteberry that you have an IR horse?
I'm going to do my best to answer your question but also include some links that may help. 
PPID and IR are two different things as you know, PPID is (only) controlled by Pergolide, not chasteberry. Medication is needed to keep the pituitary tumor under control, I know it's sometimes recommended for PPID, but it won't do anything but maybe help your horse to shed his or her coat. PPID is a progressive, age-related disease and only controlled by medication not herbs.
IR is a metabolic in nature which is more common in thrifty breeds, the only thing we have found to help this from progressing is a strict diet and exercise which you can read about in your message below.
IR cannot cause PPID, but uncontrolled PPID can cause a horse to tip over the other direction with IR and thus possibly laminitis. 
I could not find anything directly linking Chasteberry to IR as a treatment other than what I have included below but hopefully Dr.Kellon or our other mods will have some input as well. 

There is absolutely no solid evidence at all to suggest that pergolide is of use in treatment of insulin resistance related to genetic predisposition, obesity, diet or any other nonpituitary cause. Anecdotal reports of a positive response to pergolide in IR horses are flawed by either failure to test for/rule out Cushing's as a factor and/or the institution of dietary changes simultaneously with giving the pergolide. Pergolide is a dopamine agonist, which means it increases the activation of dopamine receptors. Dopamine is a neurotransmitter in the brain as well as peripheral tissues, although there are a variety of dopamine receptor types and pergolide may not work equally on all of them. In the brain though, the effect is to mimic higher levels of dopamine. There is no evidence at all in any species of a link between low brain dopamine and insulin resistance. 
[-- (
Insulin Resistance and Pergolide.pdf (

Now on to your welcome message, please let us know if you have any other questions!


Welcome to the group! 

The ECIR Group provides the best, most up to date information on Cushing's (PPID) and Equine Metabolic Syndrome (EMS)/Insulin Resistance (IR). Please explore our website where you'll find tons of great information that will help you to quickly understand the main things you need to know to start helping your horse. Also open any of the links below (in blue font) for more information/instructions that will save you time.

Have you started your Case History? If you haven't done so yet, please join our case history sub-group. We appreciate you following the uploading instructions so your folder is properly set up with the documents inside. Go to this CH message with info on how to use various devices and forms. If you have any trouble, just post a message to let us know where you are stuck.

Orienting information, such as how the different ECIR sections relate to each other, message etiquettewhat goes where and many how-to pages are in the Wiki. There is also an FAQs on our website that will help answer the most common and important questions new members have. 

Below is a general summary of our DDT/E philosophy which is short for Diagnosis, Diet, Trim and Exercise.


DIAGNOSIS: There are two conditions dealt with here: Cushings (PPID) and Equine Metabolic Syndrome (EMS)/Insulin Resistance (IR). These are two separate issues that share some overlapping symptoms. An equine may be either PPID or EMS/IR, neither or both. While increasing age is the greatest risk factor for developing PPID, IR can appear at any age and may have a genetic component. Blood work is used for diagnosis as well as monitoring the level of control of each.

PPID is diagnosed using the Endogenous ACTH test, while EMS/IR is diagnosed by testing non-fasting insulin and glucose.

The fat-derived hormone leptin is also usually abnormally elevated in insulin resistance but because there are many other things which can lower or increase leptin ECIR is not recommending routine testing for this hormone. Leptin is the hormone that says "stop eating".

In Europe, adiponectin is tested instead of leptin. Adiponectin helps regulate glucose and fat burning, and maintain insulin sensitivity. Low levels are associated with EMS. It has come to be preferred over leptin because it is not influenced by things like weight or exercise, and also because it was the only factor other than insulin levels that predicted laminitis risk

*Before calling your vet to draw blood for tests, we suggest saving time and wasted money by reading these details and then sharing them with your vet so that everyone is on the same page regarding correct testing and protocols.

*Please remember to request copies of the results of all the tests done rather than just relying on verbal information. Your vet should be able to email these to you. If you have previous test results, please include those as well. All should go in your CH, but if you are having any trouble with the CH, just post in the messages for now. 

Treatment: EMS is a metabolic type - not a disease - that is managed with a low sugar+starch diet and exercise (as able). The super-efficient easy keeper type breeds such as minis, ponies, Morgans, Arabs, Rockies are some of the classic examples. PPID is a progressive disease that is treated with the medication pergolide. Some, but not all, individuals may experience a temporary loss of appetite, lethargy and/or depression when first starting the medication. To avoid this "pergolide veil" (scroll down for side effects), we recommend weaning onto the drug slowly and the use of the product APF. The best long term results are seen when the ACTH is maintained in the middle of the normal range at all times, including during the annual seasonal rise. To accomplish this, the amount of medication may need to increase over time. Neither condition is ever "cured", only properly controlled for the remainder of the equine's life. If your partner is both PPID and IR then both medication and diet management will be needed. 

DIET: Almost all commercial feeds are not suitable - no matter what it says on the bag. Please see the International Safe Feeds List for the safest suggestions.

No hay is "safe" until proven so by chemical analysis. The diet that works for IR is:

  • low carb (less than 10% sugar+starch)
  • low fat (4% or less) 
  • mineral balanced  

We use grass hay, tested to be under 10% ESC + starch, with minerals added to balance the excesses and deficiencies in the hay, plus salt, and to replace the fragile ingredients that are lost when grass is cured into hay, we add ground flax seed and Vitamin E. This diet is crucial for an EMS/IR horse, but also supports the delicate immune system of a PPID horse. 

*Until you can get your hay tested and balanced we recommend that you soak your hay and use the emergency diet (scroll down for it).  The emergency diet is not intended for long term use, but addresses some of the most common major deficiencies. Testing your hay and getting the minerals balanced to its excesses and deficiencies is the best way to feed any equine (look under the Hay Balancing file if you want professional help balancing). If you absolutely cannot test your hay and balance the minerals to it, or would like to use a "stop gap" product until you get your hay balanced, here's a list of "acceptable" ration balancers

There is a lot of helpful information in the start here folder so it is important you read all the documents found there. The emergency diet involves soaking your untested hay for an hour in cold water or 30 minutes in hot water. This removes up to 30% of the sugar content, but no starch. Starch is worse than sugar since it converts 100% to glucose while sugar only converts 50%, so starch causes a bigger insulin spike. Make sure you dump the soaking water where the equine(s) can't get to it. 

What you don't feed on the EMS/IR diet is every bit as, if not more important than, what you do feed! No grass. No grain. No sugary treats, including apples and carrots. No brown/red salt blocks which contain iron (and sometimes molasses) which interferes with mineral balancing, so white salt blocks only. 

No products containing molasses. No bagged feeds with a combined sugar and starch of over 10% or starch over about 4%, or fat over about 4%. Unfortunately, even bagged feeds that say they are designed for IR and/or PPID equines are usually too high in sugar, starch and/or fat. It’s really important to know the actual analysis and not be fooled by a name that says it is suitable for EMS/IR individuals.

We do not recommend feeding alfalfa hay to EMS/IR equines as it makes many of them laminitic. Although it tends to be low in sugar, many times the starch is higher and does not soak out. Additionally, protein and calcium are quite high, which can contribute to sore footedness and make mineral balancing very difficult.

TRIM: A proper trim is toes backed and heels lowered so that the hoof capsule closely hugs and supports the internal structures of the foot. Though important for all equines, it's essential for IR and/or PPID equines to have a proper trim in place since they are at increased risk for laminitis. After any potential triggers are removed from the diet, and in PPID individuals, the ACTH is under control, the realigning trim is often the missing link in getting a laminitic equine comfortable. In general, laminitic hooves require more frequent trim adjustments to maintain the proper alignment so we recommend the use of padded boots rather than fixed appliances (i.e. shoes, clogs), at least during the initial phases of treatment.

Sometimes subclinical laminitis can be misdiagnosed as arthritis, navicular, or a host of other problems as the animal attempts to compensate for sore feet. 

You are encouraged to make an album and post hoof pictures and any radiographs you might have so we can to look to see if you have an optimal trim in place. Read this section of the wiki for how to get a hoof evaluation, what photos are needed, and how to get the best hoof shots and radiographs.

EXERCISEThe best IR buster there is, but only if the equine is comfortable and non-laminitic. An individual that has had laminitis needs 6-9 months of correct realigning trims before any serious exercise can begin. Once the equine is moving around comfortably at liberty, hand walking can begin in long straight lines with no tight turns. Do not force a laminitic individual to move, or allow its other companions to do so. It will begin to move once the pain begins to subside. Resting its fragile feet is needed for healing to take place so if the animal wants to lay down, do not encourage it to get up. Place feed and water where it can be reached easily without having to move any more than necessary. Be extremely careful about movement while using NSAIDs (bute, banamine, previcox, etc.) as it masks pain and encourages more movement than these fragile feet are actually able to withstand. Additionally, NSAIDs (and icing) do not work on metabolic laminitis and long term NSAID use interferes with healing. Therefore, we recommend tapering off NSAIDs after the first week or so of use. If after a week's time your equine's comfort level has not increased, then the cause of the laminitis has not been removed and keeping up the NSAIDs isn't the answer - you need to address the underlying cause.


There is lots more information in our files and archived messages and also on our website. It is a lot of information, so take some time to go over it and feel free to ask any questions. If you are feeling overwhelmed, don't worry, you will catch on, and we are always here to help you! Once you have your case history uploaded, we can help you help your equine partner even better.

For members outside North America, there are country specific folders in the files and many international lists in the wiki to help you find local resources.

If you have any technical difficulties, please let us know so we can help you. 


Bobbie and Maggie 
Desi (over the rainbow bridge 7/21) 
Utah, Nov 2018
NRC Plus 2020, NAT, C&IR March 2021
ECIR Group Primary Response


A PPID horse really should be on the proper medication such as Pergolide or Prascend rather than the chaste berry. Having said that, my horse is on 1/2 mg of Prascend during Spring and Summer and then I add Vitex Gold Plus which is herbal including the chaste berry during the fall rise.  My vet recommended it and it seems to help him a lot, without having to increase his Prascend. I understand that horses on high doses of the Prascend should not take the Chaste Berry because it can interfere with the Prascend and actually reduce the efficacy of the drug.
October 2020, Mendocino County, CA

Case History:
Jacob's Photo Album:


Kirsten Rasmussen

Hi Jann,

You're doing this right! 

Unless the IR is caused by underlying PPID, chastetree berry is unlikely to help.  And even if the IR is caused by PPID, the chastetree berry doesn't actually lower ACTH, which is one of the hormones that ultimately increases insulin.  That's why we do not recommend chastetree berry for PPID horses: because it doesn't address the cause and, as Angie mentioned, it can block the effects of pergolide.  It does provide some symptomatic relief, most notably with coat changes, but does not actually control the disease.

Kirsten and Shaku (IR + PPID) - 2019
Kitimat, BC, Canada
ECIR Group Moderator
Shaku's Case History
Shaku's Photo Album

Eleanor Kellon, VMD


You are fortunate in that his insulin, at least the only one in your file, is very low so laminitis risk is low. However, even baseline ACTH shows PPID is not being controlled and the Vitex may be making that even worse. At some point, you may end up with high insulin and laminitis. We cannot recommend using Vitex in PPID horses during the seasonal rise.

Vitex agnus-castus has reliable effects on abnormal PPID coats, on abnormal temperature regulation, on udder enlargement (all of these are hypothalamic effects, not pituitary) and it is also an "upper" for horses because it has an opioid effect in the brain.
Eleanor in PA 
EC Owner 2001