After months of anticipation finally your foal arrives. You carefully selected a sire that would complement your mare with the goal of producing a foal with the perfect conformation to succeed in the discipline of your choice. However, as the foal stands to take its first wobbly steps you realize something is less than perfect. The fetlocks are buckled over in front so that the foal gives the appearance of standing on tiptoes and being very over at the knee. You realize the foal has contracted tendons, a form of flexural deformity.
Angular and flexural limb deformities in foals come in a variety of forms. There are deformities that are present at birth (classed as perinatal or congenital) resulting in a toed out or toed in appearance or contraction similar to the one described above and others such as physitis and club feet that develop as the foal ages (classed as developmental deformities). All have the potential to negatively impact future soundness if swift action is not taken.
Causes of perinatal deformities include; trauma to soft tissue prior to birth, lack of strength in the soft tissues surrounding joints, placentitis in the dam during pregnancy, uterine poisoning, rapid in utero growth, genetics, being one of a twin or being born premature. These situations lead to either incomplete ossification of joints, a looseness in the soft tissues that support the joints causing uneven loading and compression to, or atrophy of, precursor cartilage, or hyperflexion and in rare cases hyperextension.
While exact causes for these conditions is often unclear, developmental deformities do appear to share some common mismanagement issues. In particular, unbalanced nutrition, excessive exercise and of course those unfortunate accidents that do happen resulting in joint trauma.
Luckily, therapeutic options do exist for foals with both perinatal and developmental deformities. The therapies themselves can be broken into two approaches: non-surgical and surgical. Non-surgical options include corrective trimming/shoeing and rest. However, severe deformities are not considered to be good candidates for such conservative approaches. The joint that is impacted in combination with the age of the foal will also have implications on the chosen therapy as eventually growth plates will close leaving little room for improvement. For these reasons, expert veterinary advice should always be sought as soon as an angular or flexural deformity is noticed.
Due to the wide range of possible factors that can lead to these deformities it is impossible to remove all risk factors. However, as a nutritionist, I am particularly keen to avoid deformities that appear to result from poor nutritional management. With careful management and knowing what to avoid you can reduce the chances of nutritionally induced developmental deformities. Below are some key considerations that will reduce the chances of nutrition being the cause.
Excess energy intake
While historically excess protein was thought to be the culprit of some developmental deformities it was actually excess energy intakes that were to blame. Foals consuming calories greater than their requirement grow at excessive rates and or become fat, neither of which are good for joint health. Excessive growth rates can lead to orthopedic disease such as osteochondrosis which in turn can result in irregular growth at the physis or epiphysis resulting in angular deformity. Carrying excess weight may crush the physis leading to early closure. This crushing of the growth plates is a concern when foals exercise excessively. Excessive exercise is a greater risk when foals are kept in relatively confined spaces but granted infrequent access to turn-out increasing their desire to blow off steam and potentially overdo it when they do get out. The risk to joints is compounded if they are also over weight. Orthopedic disease or trauma to joints leading to pain may cause foals to change their stance and way of moving. If this altered stance is maintained flexural deformities can result.
Some producers find themselves over feeding foals so that they will be larger and more impressive for yearling sales and futurities. The problem with this approach is that extra condition is due to fat build up not muscle. But how can you generate muscle on a foal if exercise is bad? It is not that exercise is bad but rather excessive exercise that is a potential problem. There is no reason why a sensible conditioning program can't be utilized to prepare weanlings for sale. However, this does require more work on the part of the management than simply feeding more grain.
An area that perhaps leads managers to unknowingly overfeed foals is that condition scoring foals less than a year old is different than scoring mature horses. Foals lay down fat at the withers and behind the shoulder first followed by moving back and down over the rib cage. Appropriately conditioned foals should have a slight crease or valley down their spine over the loin but an outline of 3 or 4 ribs should be visible for a condition score of 5. This differs from mature horses where ribs are not visible for the same score. Data from Kentucky Equine Research showed that in a study of Thoroughbred breeding farms, those with the heaviest weanlings (115% of normal weight for age) had the highest incidence of OCD versus no OCD on the farm where weanlings were on average 97% of normal weight. This should serve as motivation not to over feed and to manage body condition correctly.
Ideally a foal’s growth should track a steady curve with no significant deviations. Sudden rapid increases in growth or slumps in growth rate followed by a period of rapid compensatory growth when conditions are more favorable can lead to developmental deformities especially epiphysitis. Flexural deformities appear to occur in the coffin joint between 1 and 4 months of age and in the fetlock joint between 12 and 14 months of age. In the coffin joint this leads to a more upright or club foot or in less severe cases a dishing of the front wall of the hoof.
In all these cases the goal is to return growth to a steady curve by either decreasing or slowly increasing calorie intake depending on whether growth needs to be slowed or stimulated. This is most easily achieved if the manager has an idea of what the foals projected growth curve should be and whether the foal is staying on track. Curves can easily be created by frequently calculating body weight and graphing measurements over time. I recommend taking measurements at birth and then every 2 weeks thereafter at least until weaning. Changes in growth rate are then easy to identify and hopefully correct before they are manifested as limb deformities.
Weaning stress can be a cause for a decrease in growth rate especially if foals have not previously been introduced to their post-weaning diet. For this reason post-weaning diets should be introduced at least 2 weeks prior to weaning. If the foals growth has been tracked to the point of weaning measurements post weaning will easily identify if growth rate has in fact decreased allowing for corrections to be made.
Figure 1 (above right) and Figure 2 (below right) give examples of how tracking growth data can be used to identify changes in growth rate. Both figures show foals of similar expected mature size through 4 months of age. Both graphs show predicted growth curves for 3 potential mature weights as well as each foal’s actual weight based on calculations using equations published in the 2007 NRC Nutrient Guidelines For Horses. Data for the foal in Figure 1 were not collected very frequently and the owner became motivated to re-measure their foal when the foal developed physitis. The measurement taken at that point showed what appeared to be a fairly dramatic deviation from the original curve although the accuracy would be greater had more data been collected. The owner of the foal in Figure 2 took frequent measurements and the foal tracked fairly evenly along the projected curve and has had a clean bill of health.
Calcium, phosphorous and magnesium play a critical role in bone development and must be present in amounts that will both meet the foal’s requirement as well as be in the correct proportions to each other in order to maximize absorption and utilization. Less considered but perhaps just as important in bone health is trace mineral balance. Copper is necessary for forming the collagen matrix that is at the center of bones and other tissues necessary for joint function. The level of trace minerals such as copper and zinc in mare’s milk are relatively low such that the foal must build stores of these minerals while in utero that will last the first few months after birth. In fact, research has shown that in some cases the numbers of cases of OCD are reduced in foals whose mothers were fed adequate amounts of copper during pregnancy. Also of interest is that poor mare trace mineral nutrition could not be corrected by supplementing the foal shortly after birth. Correct mare nutrition is therefore an important part of managing potential limb deformities in foals.
Other data shows that foals fed diets with poor mineral balance but adequate or excessive calorie provision show good bone growth as far as bone length but poor bone quality. This is a major compounding factor for foals fed large amounts of traditional unfortified grain feeds as these grains have inverted calcium phosphorous ratios and poor trace mineral levels.
Sometimes in trying to reduce or maintain growth rates managers reduce the amounts of fortified feeds being fed to foals so as to reduce calorie intake and regulate growth. However, it is not just calories that are being removed but sources of amino acids and minerals that are vital for maintaining the quality of growth. In these situations, and also when managing foals who do not require many more calories than forage alone provides, use of a high protein ration balancer is critical. While quality pasture or hay can provide adequate calories, protein and macrominerals, certain amino acid and trace mineral levels may be low and are often unbalanced. Ration balancers are heavily fortified and pack a big punch nutritionally even though daily serving sizes are small and will improve the balance of an otherwise all forage ration. Utilizing such feeds will insure that while calories are not provided in excess other nutrients critical for correct growth are still provided.
Source of Calories
Another strike against traditional grains and some compounded commercial growth feeds is the high starch levels resulting in a high glycemic index. Kentucky Equine Research have shown that incidence of OCD increased almost linearly with an increase in dietary glycemic index. Feeds that utilize ingredients such as wheat mill run, wheat middlings, beet pulp, soybean hulls, rice bran and vegetable oil rather than grains such as oats, corn and barley will typically have a lower glycemic index and be a safer option. However, they will only provide the necessary supplemental minerals if fed per the manufacturers recommendations. If condition is being maintained with amounts lower than recommended a ration balancer should be used as well or instead to insure a balanced ration.
While some causes of angular and flexural deformities are out of a managers control others such as nutrition can be managed to reduce potential risk. If you have concerns about how to feed to reduce the risk of these conditions or you have had foals in the past with developmental angular or flexural issues it would be a good investment to seek the services of a qualified equine nutrition professional.
Dr. Clair Thunes, PhD, is an equine nutritionist who owns Clarity Equine Nutrition, based in Gilbert, Arizona. She works as a consultant with owners/trainers and veterinarians across the United States and globally to take the guesswork out of equine nutrition and provides services to select companies. As a nutritionist she works with all equids, from WEG competitors to Miniature donkeys and everything in between. Born in England, she earned her undergraduate degree at Edinburgh University, in Scotland, and her master’s and doctorate in nutrition at the University of California, Davis. Growing up, she competed in a wide array of disciplines and was an active member of the U.K. Pony Club. Today, she serves as the district commissioner for the Salt River Pony Club. Dr. Thunes is available for personal consultations either by phone, email or in person. You can find her online at her website www.clarityequine.com or on Facebook by searching for ClarityEquineNutrition.