Good morning, Gentle Spirits and new friends who have found us due to the situation in Rapid City. Let's talk about Refeeding Syndrome.
Severe emaciation, with a BCS less than three, or in animals (including humans) who have not had a steady supply of food in a while, requires a different protocol from rehabbing what most people consider a "skinny" horse.
The majority of equine professionals who deal with emaciation and starvation (BCS of 1s) on a regular basis follow the UC Davis Refeeding Protocol - or a version very close to it. I'll link the study in the comments so you can read it completely - but basically once the animal has used up it's fat stores, the body turns to eating protein, including organs, and even starts stripping the bones. The longer this goes on, and the lower the body condition, the less their body is able to process and eat carbohydrates. So it is critical when rehabilitating a horse like this that you introduce high protein and low carbohydrate/starch food on an extremely limited basis ... and the best is alfalfa.
The basics of refeed are:
1. For the first 2-3 days, feed 1 pound (about 1/6 of a FLAKE) of alfalfa every 4 hours for a total of 1 flake per day. Free choice water and minerals. Vet evaluation.
2. Days 4-10 gradually increase the amount of alfalfa per feeding and reduce numbers of feeding until they are at free choice alfalfa hay between days 10-14.
Supplements, concentrated grains and deworming should not be started until the horse has been through the critical 10 days.
Bloodwork will often show signs of kidney and liver damage in starvation, and a severe heart murmur due to the anemia/thin blood is to be expected, not feared. Both can resolve with a return to health.
We know it is everyone's instinct to provide free choice grass hay immediately so they can fill their bellies and make us feel good, however insulin, which is what processes carbohydrates, will flood the system and draw electrolytes, phosphorous and magnesium from the already depleted body which can lead to kidney, heart and respiratory failure.
This typically happens 3-5 days after refeeding has started, and this is when you see MANY horses in rescues or good hearted people's hands die, but because the horse was being fed you also see rushes of comments about "at least the horse died with a fully belly." Unfortunately, while ultimately the fault is the person who starved the horse, that full belly is commonly what tips the balance for the horse.
We have successfully rehabilitated over 100 horses with a BCS of under 3, and probably another 80 or so with a BCS of 3-4. Every single time is stressful, emotional, and a lot of work and depends on a village of volunteers and donors to get through it, and every one is touch and go.
So, while we know this is controversial to people - it is proven by veterinarians and thousands of horses who have survived it with a much higher percentage of success.