Transcript:

[0:00]

Hi everyone, welcome back to Mad Barn Academy, and if this is your first time tuning in, then welcome — we hope to earn your subscription today. I’m Dr. Fran Rowe, one of the veterinary nutritionists here at Mad Barn, and today I wanted to piggyback off of last week’s video about post-foaling benchmarks and dive a little bit deeper into the importance of colostrum for foals. If you haven’t seen the video on post-foaling benchmarks yet, I’ve included a link in the description below. Be sure to check that out, especially if you have a mare that’s ready to foal in the coming months or you’re planning on foaling out next year.

[0:39]

Okay, let’s get started on our deep dive today: colostrum and why it’s so important for the newborn foal. Colostrum is the first milk that the mare produces; over about 24 to 48 hours, that colostrum will transition into true milk. The composition and appearance of colostrum is very different than milk — it’s thick, yellow, and really sticky if you get it on your hands, whereas milk is thinner, white, and still a little sticky if you get it on your hands, but much less so. Colostrum is much higher in proteins, certain vitamins and minerals, sugars, and fats compared to milk, and most notably, it’s concentrated with immunoglobulins, also called antibodies.

[1:33]

Antibodies, or immunoglobulins, are protective proteins produced by the immune system. Their job is to circulate around the bloodstream and identify foreign substances — harmful pathogens like bacteria, fungi, parasites, etc. They bind to these substances, generally called antigens, and stimulate the immune system to come and destroy them, thus protecting the body from infection. You can think of every antigen as a unique key, where there will be a matching antibody lock that the key fits into.

[2:12]

Sometimes we’re exposed to brand new pathogens that we’ve never seen before — that antigen key doesn’t fit into any antibody lock. This stimulates an immune response where our body fights off the foreign invader, and eventually the body produces a specific antibody to remember that antigen for next time. This process describes active immunity, where the body is actively generating new antibodies in response to novel pathogens. This is how many vaccines work and why we’re immune to certain diseases after having been sick — the body remembers.

[2:57]

Under certain conditions, it’s possible to transfer those protective antibodies from one individual to another, and this is termed passive immunity. One of the best examples of the transfer of passive immunity is intake of colostrum by the newborn foal. Foals are born with a naive immune system, meaning their immune system is basically a blank slate. Passive transfer of immunity through colostrum essentially provides a surrogate immune system for the foal until it can develop its own immune system. Passive transfer of immunity provides immediate but short-term protection — in horses, maternal antibodies begin to wane at about four to six months of age.

[3:41]

When a newborn foal consumes colostrum, those immunoglobulins are absorbed from the small intestine. However, the gut is only open to absorb these large molecules during the first 24 hours of life, and in fact, most absorption occurs in the first 12 hours, with absorption rates decreasing by about 80% after 12 hours. After that 24-hour mark, the gut is officially closed and no immunoglobulins will be absorbed.

[4:16]

Foals need to consume a lot of colostrum within this critical window to confer adequate passive immunity. Those that do not meet this threshold are considered to have failure of passive transfer, or FPT. We assess passive transfer of immunity by measuring IgG levels in the foal’s blood. IgG is the most abundant immunoglobulin in colostrum and in the body, so it’s a good marker to measure. We aim for IgG levels of 800 milligrams per deciliter or higher. Foals that are less than 800 would be considered to have FPT, which can be further classified as partial or complete failure depending on the level.

[5:04]

There are several different tests to measure IgG nowadays, and measuring IgG is the standard protocol at a foal’s first wellness exam at about 24 hours old. Some different tests include SRID, which is the gold standard and very accurate but takes about 24 hours to receive results; several agglutination tests, such as zinc sulfate turbidity and latex agglutination; and ELISA tests such as the SNAP IgG Foal Test. The SNAP test, pictured here, has become popular with veterinarians because it’s rapid and stall-side, so it can be done right there on the farm while you’re examining the foal. In this picture, this foal’s test has come back as adequate, or greater than 800, as indicated by the dark blue middle dot.

[6:10]

The reason all of this matters — and why we ensure foals are nursing and measure their IgG — is because foals with failure of passive transfer are at significant risk of life-threatening infection. These foals can become very sick, very rapidly, just days after being born if they do not have those protective antibodies circulating in their bloodstream. Some of the most common illnesses these foals suffer from include severe GI infection and diarrhea, pneumonia, umbilical infection, joint sepsis, and generalized sepsis. Without aggressive medical intervention, many of these foals will not survive.

[6:56]

So, what are some of the key factors that influence passive transfer of immunity with regards to colostrum and the newborn foal? The two main parties involved in passive transfer are the mare and the foal. The mare has to produce enough colostrum for the foal, and the foal has to be able to ingest it. If something goes wrong with either party, then adequate passive transfer will not take place.

[7:25]

Factors that we can attribute to the dam include the quantity and quality of the colostrum produced. If the mare does not produce enough high-quality colostrum, then passive transfer to the foal will be inadequate. Factors that we can attribute to the foal include the foal’s ability — or potential lack thereof — to consume enough colostrum during the necessary window. So, let’s break down each of these factors a little bit more.

[7:55]

With regards to the quantity produced by the mare — or the quantity available to the foal — the good news is that the vast majority of mares will produce an adequate amount of colostrum for their foal. There are a few scenarios that may negatively impact or affect milk yield and thus colostrum production, such as if the mare is young, maiden, or in poor body condition prior to foaling. Maiden mares are first-time mothers, while multiparous mares have had one or more foals in their lifetime.

[8:37]

Two other scenarios worth mentioning include premature lactation and agalactia, which are abnormal situations with regards to the mare’s milk production and lactation. The first refers to when the mare develops an udder abnormally early and may even begin leaking milk well in advance of foaling. In some cases, these mares will leak out all of their colostrum, leaving none for the foal by the time it’s born. This is a common complication in mares with placentitis, for example. The second, agalactia, refers to a mare that develops no udder and fails to produce any milk at all. This is a common complication in cases of fescue toxicosis, in which mares graze on endophyte-infected fescue pasture or hay. I’ve included links to both of these conditions in the description below if you’d like to read more about them specifically, but it would be too much to go into for today.

[9:43]

When we talk about colostrum quality, we’re usually talking about the level of immunoglobulin in that colostrum. Most mares will produce good quality colostrum, but remember: the antibodies in that colostrum will mirror the mare’s own immune system. In order to improve colostrum quality, it’s standard that mares receive pre-foaling vaccines about a month prior to foaling. This stimulates antibody production to those pathogens — the ones you’re vaccinating against — which will load the colostrum with extra antibodies.

[10:19]

Core vaccines for all horses in North America include rabies, tetanus, West Nile virus, Eastern equine encephalitis virus, and Western equine encephalitis virus. There are also risk-based vaccines that depend on your area of North America and the likelihood of exposure to certain pathogens, so it’s important to chat with your veterinarian to determine what vaccines make the most sense for that mare — and subsequently for that foal.

[10:50]

Colostrum quality will also depend on the mare’s overall nutrition during pregnancy, particularly in late pregnancy when she’s getting ready to transition into lactation. During this time, she’ll need extra energy and protein to supply the growing fetus and prepare for lactation. Ensuring balanced vitamin and mineral intake for the mare ensures that her milk will also be highly fortified to support the foal. Additionally, research has shown that supplementing the mare with yeast, probiotics, and DHA — an omega-3 fatty acid — during gestation is beneficial to the foal as well.

[11:31]

The last factor to consider, and the one most people tend to focus on, is ensuring that the foal consumes enough colostrum during that critical time frame. A healthy, normal foal should be up and suckling within two hours of birth, and they must consume about two to three liters of colostrum within the first 12 hours of life — the window in which the gut is open to absorb antibodies into the bloodstream.

[11:56]

There are many reasons why a foal may not meet this benchmark. Examples include premature birth, foals that are slow to stand and suckle, foals that are unable to do so at all, foals with an abnormal or weak latch and suckle reflex, and foals that have been rejected by the mare or orphaned.

[12:25]

At the end of the day — or night, since most mares foal in the middle of the night — if you’re concerned about your foal’s ability to get enough colostrum, call your vet for assistance. Prompt intervention is key for the foal’s health and survival. Your vet will determine the best treatment plan using a combination of history, physical exam of the foal, and testing IgG levels.

[12:52]

Foals that are less than 12 hours old are still good candidates to receive passive transfer of immunity from colostrum because their gut is still open. Your vet may tube the foal with donor colostrum or frozen colostrum that’s been thawed. If the foal is greater than 12 hours old, then administration of protective antibodies will come in the form of hyperimmunized plasma, given through an IV catheter.

[13:19]

Alrighty, you guys — here are the references for today, and thanks so much for listening. Don’t forget to like and subscribe, and explore the other videos on our channel. We’ve got lots coming out all the time on various topics, and don’t forget to check out the additional links I’ve provided in the description below if you want to learn more about foaling, colostrum, and managing the pregnant and lactating mare. Alright — until next time.