STUD NOTES

YOU CAN'T BEAT MOTHER'S MILK

Colostrum and Immunoglobulin

So great is the importance of colostrum to the newborn foal we regard it as liquid gold. If the foal does not receive adequate levels within the correct time frames, then the foal is left extremely vulnerable to illness and disease. Colostrum is the source of their antibodies and their custodian to good health early in life.

Many people know that they should send their pregnant mare off to stud about one month prior to foaling, and probably don’t even know all the reasons why. Certainly travelling the pregnant mare has a bit to do with it, especially over distances; and yes it is helpful to the studmaster to get to know your mare’s behaviour patterns and idiosyncrasies, and it does allow the mare to ‘settle in’. But none of these factors are anything like as important as protecting your newborn foal from disease for the first period of its life.

Every farm has its own individual microbial environment with a community of infective organisms. This is normal. Exposing the mare to this environment for about a month allows her to build up antibodies associated with these local antigens. A passive immunity to potential disease and illness is passed on to the foal via the mare’s colostrum. This is the primary reason to get your mare to the breeding farm in good time prior to foaling.

Accordingly, this provides us an opportune time to enhance the foal’s early protection from strangles and tetanus. In the normal situation the foal needs to be about six weeks old before receiving its own vaccination course, so this added protection in the interim is most helpful. Please note however, these vaccinations do not provide 100% protection. To give the mare her tetanus and strangles booster vaccination approximately one month prior to foaling, however, is good policy and helps boost their immune system and produce specific antibodies for these diseases in her colostrum.

Passive Transfer and IgG levels
A foal is born without immunities (antibodies or immunoglobulins) so at that point is exposed to any undesirable infectious or bacterial pathogens. Passive Transfer is the transfer of antibodies from the mare’s colostrum to the foal’s bloodstream.

The foal’s intestinal tract is designed to have the ability to absorb proteins into the bloodstream from the mare’s colostrum, including the immunoglobulins. However, there is only a short widow that this passive transfer can take place. The highest rate of absorption is in the first three or four hours, with excellent levels experienced for about 12 hours after birth.

After 12 hours and the rate of successful transfer tapers significantly until closure at about 20-24 hours. This demonstrates very clearly that we do not have long to ensure that the foal has the desired levels of immunoglobulins.

We can now measure immunoglobulin (IgG levels) very effectively with the right equipment. To use the lingo, the minimum desired IgG level, and the level that insurance companies will accept is 800mg/dl. There is a school of thought that levels a little below 800 mg/dl are still ok, but I do not accept this on the farm. It does not take much of a challenge from the ‘nasties’ for the foal to use up these antibodies in defence, hence dipping their level even further.

In fact, I would prefer to get our levels at or over 950 mg/dl for a couple of reasons. Firstly, stud farms are high traffic areas of horses (therefore higher risk of elevated infectious agents) and secondly, I just like the comfort of a buffer zone of significance if the foal is challenged.

In the bank - the Robin Hood approach
All large farms will work very hard on building a bank of colostrum so that we can supplement foals that have not reached their desired IgG levels. We pretty much steal from the rich to give to the poor. Mares with ample quantities of high quality colostrum will be targeted as potential donors. What we do not always know is which mares have high quality colostrum. Working backwards, we will discount certain mares immediately. The following mares will not be considered as potential colostrum donors:

• Mares that have been running milk (in fact we probably will be supplementing their foals)
• Maiden mares - there are very few that have the quantities required to steal extra above their own foals needs and we have no history
• Aged mares - quality and quantity seem to decrease with age
• Mares we know historically have lower quality colostrum or not great milkers

We do have methods by which we can grade colostrum quality: the two most common are the refractometer and DVM Rapid Test. Of course, there are many out there, including myself, find that the thicker and creamier the colostrum is, the more likely it is to be of good quality. Without any scientific backup apart from collecting, using the refractometer and accurately knowing IgG results from mares over a vast sample group over many years, I think this is more than fair comment. Interestingly, provided the mare does not run milk, those that have given excellent IgG levels on their foals historically are extremely likely to be a great donor candidate in the years ahead.

To supplement a foal with colostrum would require a minimum of 250 ml of high quality colostrum right up to 1500 ml or so in extreme cases. Most foals that are supplemented as a ‘top up’ to get them well over the desired 800mg/dl line will receive 250-600 ml depending on the circumstances.

It must be remembered antibody levels are not only calculated in terms of quantity of colostrum, but also the quality, so there is a certain amount of weighing up to do to get this right. Given that a mare will donate about 250- 400 ml depending on the individual, and that a large percentage of our pregnant mare population will not have sufficient residual stocks after meeting their own foal’s requirements, building and maintaining a colostrum bank is not easy.

Foals likely to require colostrum supplementation
Rick and I come from a farming background and it’s amazing how often we compare what we do here now compared with the old farming days. At times we feel that this industry is glorified farming in a very scientific and intensive manner, but still essentially farming. This brings me to make a statement that applies to what we are discussing here - the quality and volumes of milk production of the horse.
With sheep, beef cattle and pigs for example, which were my previous areas of expertise (before meeting a very handsome neighbour!), we culled those animals that were not able to nurture and provide the appropriate nutrition to their youngsters and maintain their own body weight at the same time. With thoroughbreds we are breeding athletes for the sole purpose of becoming racehorses. We do not cull for poor milking ability or low grade colostrum to give the foals a great start. Instead we have many ways around this: fancy IgG testing, colostrum banks, plasma stocks and, if all else fails, we will at great expense use a foster mare to bring up a foal.

Essentially, foals that are at a higher risk at not receiving enough colostrum can be broken up into the following groups. A number of these foals may not need colostrum sourced from our bank - it may be just a matter of pinching it from mum and manually giving it to the foal by either stomach tubing or bottle feeding.

•  Mare not supplying large enough volumes and or poor quality

• Mares that run milk prior to foaling
• Aged mares
• Some maiden mares
• Mares that historically give us unsatisfactory IgG results, indicating poor quality colostrum is part of her makeup
• Stress related foaling - eg. the mare may foal earlier than they are supposed to, so the milk production is not at its true potential

•  Weak foals

• Those that have health issues at birth such as septic foals, dummy foals
• Dysmature or premature foals
• Foals from maiden mares will quite often be on the weaker side and slow to get to the nipple

•  Foals with early conformation/other issues

• Very contracted tendons, being well over in the knees or extremely upright on fetlocks
• Tendon laxity such as very down on fetlocks or windswept (unstable asymmetry through hocks)
• Retained meconium, causing pain and abdominal colic, will prevent the foal from wanting to nurse

•  Behavioural (mare)

• Maiden mares: no one told them the sport they had 11months prior, resulted in this! They can be over fussy, continually wanting to keep the foal under her nose, hence swinging the udder out of reach. They also don’t like the feel of a foal nursing, so may squeal, give little kicks and so on, resulting in the foal losing confidence to continue attempts to nurse.
• Foaling in the paddock with other mares - if a mare foals with horses in the paddock, the disturbances created by curious mares, or worse - baby pinchers - can impact heavily on the foal’s opportunity to nurse.
• Nervous mares or just plain “nutters”!
• Foal rejection - it does happen, more likely if the mare foals within a group and often a maiden mare. They can have their foal and just get up and walk away. I have had one mare foal in a stable environment under full supervision, that just did not look at her foal and wanted absolutely nothing to do with it right from the word go. She became aggressive towards it once it wanted to nurse. This foal had to be fostered.

•  Nipples on the mares -

• These can be extremely large and when stimulated with a foal trying to nurse, swell even more, then run milk. The foal may struggle to get a hold on them and then when they do, avoid gagging due to high flow rates. Much colostrum can simply run away.
• Maiden mares in particular can have very small nipples with the first foal. Some older mares are pre disposed with small nipples throughout their breeding life - just a genetic thing. These can be very difficult for the foal to identify where the milk bar is firstly, and then latch on.
• Mastitis or other blockages eg. tumours. It is not unusual to see mares with only one operative side of the udder

So yep, the colostrum bank is like storing gold - precious to the needy foal, difficult to source in desired quantities in its natural state, it needs careful handling to change its storage shape (freezing) and maintain value (viability) and when we want to liquidate.
And, after all that, the bank keeps getting robbed!